Abstract:
A human-powered vehicle includes a driven wheel with a cantilevered hub, and a hand-operable crank for vehicle propulsion. In a wheelchair the hand cranks are supported on towers that are lowerable to fit under a desk or table. With the vehicle at rest, cranking motion of the crank in a first rotational direction propels the vehicle forward and cranking motion of the crank in a second rotational direction propels the vehicle backward. With the vehicle in forward motion, cessation of crank rotation allows free rotation of the wheel, and crank torque applied in a sense opposing forward vehicle motion applies a braking force to the wheel. An electric vehicle includes a transmission wheel hub that provides similar functions with an electric drive, such as for a wheelchair.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to U.S. Provisional Application Ser. No. 60/635,383, filed on Dec. 8, 2004, the entire contents of which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD  
       [0002]     This application relates to mobility assistance devices, and more particularly to a hand-operable propulsion system for attachment to a wheeled vehicle for persons with a disability, persons engaged in rehabilitation, as well as able-bodied individuals.  
       BACKGROUND  
       [0003]     Recent advances in the design and development of manual wheelchairs have resulted in significant improvements in propulsion, steering and stability on varying types of terrain and environments, such as the devices disclosed in U.S. Pat. No. 6,902,177, the contents of which is incorporated herein by reference. While these advances have addressed many of the prevailing issues associated with assisted-mobility devices in an outdoor environment, these advances have not addressed the need for a more compact, multiple-gear, bi-directional propulsion system which by design and function, would allow the operator to easily navigate and propel an assisted mobility device in both an indoor and outdoor environment.  
         [0004]     Until now, a push rim wheelchair has prevailed as the most common assisted mobility device for use in an indoor environment. Unfortunately, the design limitations of a push rim wheelchair include several disadvantages: a high incidence of fatigue or strain involving the hand and wrist; an inability to be operated by a rider having limited use of one hand or arm; awkward and inefficient steering and propulsion functions.  
         [0005]     A compact, hand-operable propulsion system for attachment to an assisted-mobility device is desired which satisfies a number of the aforementioned functional limitations.  
       SUMMARY  
       [0006]     According to one aspect of the invention, a human-powered vehicle includes a structural frame, a driven wheel mounted for rotation about an axle secured to a lower portion of the frame, a hand-operable crank manually operable by an operator of the vehicle for vehicle propulsion, and a transmission connecting the crank and wheel, such that motion of the crank is converted to a corresponding motion of the wheel. The axle is affixed to the frame on only one side of the wheel, such that the wheel has a cantilevered hub. Notably, the wheel and crank are interconnected such that with the vehicle at rest, cranking motion of the crank in a first rotational direction propels the vehicle forward and cranking motion of the crank in a second rotational direction propels the vehicle backward, and such that, with the vehicle in forward motion, cessation of crank rotation allows free rotation of the wheel, and crank torque applied in a sense opposing forward vehicle motion applies a braking force to the wheel.  
         [0007]     In some embodiments, the transmission includes a coaster brake assembly contained within the cantilevered wheel hub.  
         [0008]     In some configurations, the hand-operable crank is rotatable about an axis disposed above the driven wheel. In some such configurations, the transmission includes a coaster brake assembly disposed above the driven wheel and adjacent the crank. In other such configurations, the transmission includes a coaster brake assembly contained within the cantilevered wheel hub.  
         [0009]     In some embodiments, the transmission provides multiple gear ratios for propulsion of the vehicle in a forward direction. For example, the transmission may include a planetary gear core disposed within a hub shell connected to the wheel, the gear core engaging the hub shell to drive the hub shell in mutual rotation in only one direction. The hub shell may be disposed above the driven wheel, or the hub shell may be a portion of the driven wheel hub.  
         [0010]     In some instances, the hand-operable crank is a push rim disposed outboard of the driven wheel. In some other instances, the hand-operable crank includes a crank handle disposed above the wheel, and preferably extending horizontally and positioned for grasping by someone seated in a seat of the vehicle.  
         [0011]     Preferably the vehicle includes two hand-operable cranks operably connected to two corresponding driven wheels and independently and simultaneously operable for vehicle propulsion.  
         [0012]     In some embodiments the vehicle includes a seat secured to the frame and positioned to enable the vehicle operator to manually operate the crank while seated in the seat. In some cases, the seat is rotatable and connected to a steerable wheel of the vehicle, such that seat rotation alters a steering angle of the steerable wheel.  
         [0013]     In some embodiments, the transmission includes a brake shoe that bears against a surface of a rotatable transmission shell to drive the shell in one rotational direction for propulsion, and a freewheel bearing that permits rotation of the brake shoe in said one rotational direction. The freewheel bearing also transfers braking loads while preventing rotation of the brake shoe in an opposite rotational direction.  
         [0014]     In some examples, the transmission also includes a brake cone that engages and deflects the brake shoe against the hub shell to rotate the hub shell and drive the wheel in one rotational direction, in response to an associated cranking motion of the crank with the vehicle at rest.  
         [0015]     In some cases the brake shoe is disposed within the cantilevered wheel hub, with the rotatable transmission shell forming a portion of the wheel hub. In such cases the transmission may also include a freewheel bearing cover that transfers the braking loads from the freewheel bearing to the axle, such as by being keyed directly to the outer end of the axle so as to transmit torque.  
         [0016]     In some other cases the brake shoe is disposed within a transmission hub shell that rotates about an axis of rotation of the hand crank, the axis of rotation of the hand crank being above the wheel, for example. In such cases, the freewheel bearing preferably has an inner race rotationally coupled to the brake shoe, and an outer race rotationally coupled to the frame.  
         [0017]     According to another aspect of the invention, a human-powered vehicle includes a structural frame, a driven wheel having a hub mounted for rotation about an axle secured to a lower portion of the frame, a hand-operable crank manually operable by an operator of the vehicle for vehicle propulsion, and a transmission connecting the crank and wheel, such that motion of the crank is converted to a corresponding motion of the wheel. The vehicle also includes a structural crank tower supporting the crank, the crank tower being rotatable about the wheel axle and releasably securable to the frame to lock the tower in an upright position.  
         [0018]     In some embodiments, the crank tower is releasably securable to the frame in multiple rotational positions about the wheel axle. Preferably, the crank is operable to drive the wheel with the tower disposed in each of its multiple rotational positions.  
         [0019]     In some instances the vehicle also includes a seat secured to the frame and positioned to enable the vehicle operator to manually operate the crank while seated in the seat. Preferably, the crank tower is lowerable to a position lower than a seating surface of the seat.  
         [0020]     For vehicle storage or transport, the wheel, crank and crank tower are preferably readily removable from the vehicle frame as a propulsion unit assembly. For example, the propulsion unit assembly may be secured to the vehicle frame by a quick-release connector releasably securing the axle to the frame.  
         [0021]     In some embodiments, the wheel and crank are interconnected such that with the vehicle at rest, cranking motion of the crank in a first rotational direction propels the vehicle forward and cranking motion of the crank in a second rotational direction propels the vehicle backward, and such that, with the vehicle in forward motion, cessation of crank rotation allows free rotation of the wheel, and crank torque applied in a sense opposing forward vehicle motion applies a braking force to the wheel.  
         [0022]     In some configurations, the axle is to the frame on only one side of the wheel, such that the hub is cantilevered.  
         [0023]     According to a third aspect of the invention, a human-powered vehicle has a structural frame and two driven wheels, each mounted for rotation about an axle secured to a lower portion of the frame, with each axle affixed to the frame only inboard of the wheels, such that each wheel has a cantilevered hub. The vehicle has two hand-operable cranks, each rotatable about an axis disposed above the corresponding driven wheel and manually operable by an operator of the vehicle for vehicle propulsion. Transmissions connect each crank with a corresponding wheel, such that motion of each crank is converted to a motion of its corresponding wheel, and structural crank towers support the cranks above the vehicle frame. Notably, the crank towers are releasably secured to the vehicle frame to lock the tower in an upright position, and are movable by the operator sitting in the seat to a lowered position for wheeling a forward portion of the vehicle under a desk, and movable back to their upright position by the operator sitting in the seat, for propulsion.  
         [0024]     According to a fourth aspect of the invention, a vehicle includes a structural frame, a driven wheel having a hub mounted for rotation about an axle secured to a lower portion of the frame, and a brake shoe that bears against a surface of the wheel hub to drive the wheel in one rotational direction for vehicle propulsion. The vehicle also has a freewheel bearing that permits rotation of the brake shoe in that one rotational direction, and transfers braking loads to the frame while preventing rotation of the brake shoe in an opposite rotational direction. A hub driver is rotatable to drive the wheel hub in a first rotational direction, and to drive the brake shoe into torque-carrying engagement with the wheel hub to drive the wheel hub in a second rotational direction. Notably, the axle is affixed to the frame on only one side of the wheel, such that the hub is cantilevered, and braking loads are transferred from the freewheel bearing to the frame through the axle.  
         [0025]     In some embodiments the vehicle has a hand-operable crank operably connected to the hub driver and manually operable by an operator of the vehicle for vehicle propulsion.  
         [0026]     In some embodiments the vehicle has an electric motor, or other power drive, operably connected to the hub driver for vehicle propulsion.  
         [0027]     Preferably, the freewheel bearing and brake shoe are components of a coaster brake assembly connecting the hub driver to the hub such that with the vehicle at rest, rotation of the hub driver in a first rotational direction propels the vehicle forward and rotation of the hub driver in a second rotational direction propels the vehicle backward, and such that, with the vehicle in forward motion, cessation of hub driver rotation allows free rotation of the wheel, and hub driver torque applied in a sense opposing forward vehicle motion applies a braking force to the wheel.  
         [0028]     The various vehicle power transmission systems described herein are useful for driving the wheels of several types of vehicles, but are particularly useful for enabling intuitive manual driving, or simplified powered driving, of a wheeled mobility device, such as a wheelchair. The lowerable crank towers can enable an operator of a wheelchair the benefits of above-wheel hand crank placement while still allowing the forward portion of the vehicle to be wheeled under a desk or table, as in a traditional wheelchair not having above-wheel hand cranks. That these concepts can be embodied in wheelchairs having cantilevered wheel hubs can accommodate wider seating while allowing the operator to maneuver through a standard door width, although the cantilevered hub drive system is also seen as applicable to other types of vehicles.  
         [0029]     Other features and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     DESCRIPTION OF DRAWINGS  
       [0030]      FIG. 1  is a perspective view of a hand-operable propulsion system with cantilevered multi-speed, internal gear hub incorporating a reverse gear.  
         [0031]      FIG. 2  is a front view of a propulsion system with a cantilevered wheel and multi-speed, internal gear hand crank assembly incorporating a reverse drive.  
         [0032]      FIG. 3  is a detailed partial sectional view of one portion of the multi-speed, internal gear hand crank assembly incorporating a reverse drive of the propulsion system of  FIG. 2 .  
         [0033]      FIG. 4  is a detailed partial sectional view of the high helix gear selector of  FIG. 3 .  
         [0034]      FIG. 5  is a detailed partial sectional view of a single speed internal gear hand crank assembly incorporating a reverse drive.  
         [0035]      FIG. 6  is a partial sectional view of a hand operable crank assembly for the propulsions systems of  FIG. 8  and  FIG. 10 .  
         [0036]      FIG. 7  is front view of a propulsion system with a cantilevered wheel and an internal gear wheel hub incorporating a reverse drive.  
         [0037]      FIG. 8  is a partial sectional view of a multi-speed, internal gear wheel hub, a quick release assembly and an adjustable tower pivot clamp.  
         [0038]      FIG. 9  is a detailed partial sectional view of a multi-speed wheel hub and a quick release assembly.  
         [0039]      FIG. 10  is a detailed partial sectional view of a single speed wheel hub and a quick release assembly.  
         [0040]      FIG. 11  is a perspective view of an assisted mobility device including the propulsion system of  FIG. 1 .  
         [0041]      FIG. 12  is a right side view of the propulsion system of  FIG. 1  in an operational position and in a reclined position.  
         [0042]      FIG. 13  is a front view of the right side propulsion system and corresponding attachment points to the frame of the assisted mobility device of  FIG. 11 .  
         [0043]      FIG. 14  is a right side view of the device of  FIG. 11 , depicting the propulsion system an operational position and a reclined position.  
         [0044]      FIG. 15  is a front view of the quick release features of the propulsion system of  FIG. 7  in a detached position.  
         [0045]      FIG. 16  is a front view of the quick release features of the propulsion system of  FIG. 7  in an attached position.  
         [0046]      FIG. 17  is a partial sectional view of a push-rim actuated multi-speed wheel hub incorporating reverse drive with a wheel assembly and a quick release assembly.  
         [0047]      FIG. 18  is a detailed partial sectional view of a push-rim actuated multi-speed wheel hub incorporating reverse drive.  
         [0048]      FIG. 19  is a perspective view of an assisted mobility device including push-rim actuated multi-speed wheel hubs incorporating a reverse drive and a quick release assembly.  
         [0049]      FIG. 20  is a front view of propulsion system with cantilevered wheel and internal gear wheel hub incorporating a reverse drive; with crank arm and handle positioned on the mounting pin side of the propulsion tower.  
         [0050]      FIG. 21  is a perspective view of an assisted mobility device including the propulsion system of  FIG. 1  with the crank arm and the handle positioned on the mounting pin side of the propulsion tower.  
         [0051]      FIG. 22  is a detailed perspective view of a double sprocket assembly with drive chain for rear wheel steering of an assisted mobility device.  
         [0052]      FIG. 23  is a detailed perspective view of a pulley and cable assembly for seat-actuated steering of an assisted mobility device.  
         [0053]      FIG. 24  is a front view of an assisted mobility device depicting one of the two hand crank assemblies in a partial sectional view.  
         [0054]      FIG. 25A  is a detailed partial sectional view of the right side multi-speed, internal gear hand crank assembly of the device of  FIG. 24 .  
         [0055]      FIG. 25B  is a detailed sectional view of the modified coaster brake arm of  FIG. 25A .  
         [0056]      FIG. 26  shows an electric wheel drive, with an electric motor driving a cantilevered wheel hub. 
     
    
     DETAILED DESCRIPTION  
       [0057]     Referring now to  FIGS. 1, 2 ,  3 ,  4  and  11  and in one embodiment, the propulsion system  100  includes a transmission having one or more independent hand-operable multiple-gear crank assemblies  102 , each including a coaster brake assembly  103  operably connected to a corresponding front drive wheel assembly  104  for propulsion and braking of a human powered vehicle  106  in a forward and reverse direction. The hand crank assembly  102  and the front wheel assembly  104  are operably connected by a flexible roller chain  110 , for example, and the assemblies  102 ,  104  are held in position by a propulsion tower assembly  108 .  
         [0058]     With specific reference to  FIG. 3 , the hand-operable multi-gear crank assembly  102  includes a crank handle  112 , a crank arm  114 , a hub driver  116 , a hub axle  120 , a planetary gear core  122 , a brake actuator  124 , an inner brake cone  126 , actuator threads  128 , brake shoes  130 , a brake shoe spring  132 , an outer brake cone  134 , an outer brake cone extension  136 , a freewheel bearing  150  with an inner race  138  and an outer race  140 , a hub housing  142 , retaining bolts  144 , a thrust bearing  146 , an inner axle nut  148 , an outer axle nut  154 , a hub shell  156 , driver ball bearings  160 , brake cone ball bearings  162 , hub housing bearing assemblies  164 , a gear selector assembly  166  and a drive sprocket  168 . As a freewheel bearing, bearing  150  permits relative rotation of its inner and outer races  138 ,  140  in only one direction, such as a roller clutch bearing. In some embodiments, the coaster brake assembly  103  is sized and configured for containment within the hub housing  142 .  
         [0059]     The gear selector assembly  166  includes a gear selector body  170 , a gear selector cap  172 , a ball-nose spring plunger  174 , a push rod  176  and a push rod adjuster  178 .  
         [0060]     The front drive wheel assembly  104  can include a rim  181 , tire  182 , spokes  183 , wheel hub  184 , driven sprocket  185  and wheel hub axle  186 .  
         [0061]     The crank handle  112  is rotatably attached to the crank arm  114 , which is affixed to the hub driver  116  of the internal multi-gear coaster brake bicycle hub  118 . The hub driver  116  rotates about the axle  120  and drives the planetary gear core  122 , which also rotates about axle  120 . Planetary gear core  122  includes pawls (not shown) about its outer circumference that engage and drive hub shell  156  only when rotated in one direction with respect to the hub shell  156 , but otherwise allow the gear core to rotate freely within the hub shell. Those of ordinary skill in the art will understand the components and operation of a standard multi-gear internal hub planetary transmission. In one embodiment, for example, a Shimano Nexus Inter3 Model No. SG-3C41 Internal Gear Coaster Brake Hub can be used. Affixed to the planetary gear core  122  is the brake actuator  124 , which rotates about the axle  120 . The inner brake cone  126  is positioned about the brake actuator  124  and engages the helical block threads  128  of the actuator  124 . The brake shoes  130  are positioned about the inner brake cone  126 . The brake shoes  130  are held in a compressed position by the brake shoe spring  132 . The brake shoes  130  are engaged with the outer brake cone  134  such that the position of the brake shoes  130  relative to the position of the outer brake cone  134  remains constant. The outer brake cone  134  is attached to the outer brake cone extension  136 . The outer brake cone extension  136  is attached to the inner race  138  of freewheel bearing  150 . The outer race  140  of the freewheel bearing is attached to the hub housing  142  with retaining bolts  144 , such that braking loads from brake shoes  130  are transferred through the freewheel bearing to the hub housing and the vehicle frame. The thrust bearing  146  is located about the hub axle  120  and within the cavity defined by the freewheel bearing inner race  138 , positioned between the outer brake cone extension  136  and the inner axle nut  148 . The freewheel bearing  150  is located about the hub axle  120  and within the hub housing  142 . On the coaster brake side  152  of the multi-gear hub  118 , the hub axle  120  is affixed to the hub housing  142  by the outer axle nut  154  and held in position such that the axle  120  is fixed and is unable to rotate. Driver ball bearings  160  are located between the hub shell  156  and the hub driver  116  on the driver side  158  of the hub. Brake cone ball bearings  162  are located between the hub shell  156  and the outer brake cone  134  on the coaster brake side  152  of the hub.  
         [0062]     The multi-gear bicycle hub  118  is rotatably attached within the hub housing  142  and held in position by two hub housing bearing assemblies  164  and affixed to the hub housing  142  by the outer axle nut  154  located on the coaster brake side  152  of the multi-gear hub. A vertical slot  165  is cut into the front and rear lower portion of the hub housing  142  to allow free movement of the flexible roller chain  110 .  
         [0063]     Referring now to  FIGS. 3 and 4 , the internal threads of the gear selector body  190  are attached to the threaded hub axle  120  on the crank arm side of the multi-speed hub  194 . The gear selector body  170  includes right-hand high helix threads  196  located on the circumferential surface of the gear selector body  170 . Two or more detents  198  are located on the crest of the high helix threads  196  of the gear selector body  170 . The internal threads of the gear selector cap  200  are engaged upon the high helix threads  196  of the gear selector body  170 . A ball-nose spring plunger  174  is affixed within the side wall of the gear selector cap  172  and positioned to engage the detents  198  of the gear selector body  170 . The gear selector push rod  176  is located within the hollow cavity of the hub axle  120  at the first end  202  and comes into contact with the push rod adjuster  178  at the second end  204 . The push rod adjuster  178  is a headless hex socket set screw located within a threaded hole  206  in the center of the end wall of the gear selector cap  172  and positioned to engage the second end of the push rod  204 .  
         [0064]     Referring also to  FIGS. 1, 2  and  11 , affixed to the exterior of the multi-gear hub shell  156  is a drive sprocket  168 . Alternative drivers, such as a cog or pulley, for example, can be suitably implemented. Engaged upon the drive sprocket  168  is a chain  110 , cogged belt or cable connecting the hub shell  156  at the upper end to a corresponding driven sprocket  185 , cog or pulley at the lower end. The driven sprocket  185  is affixed to the wheel hub  184 . The wheel hub  184  is rotatably attached to the wheel hub axle  186 , which is affixed to the vehicle frame  208 . The driven front wheel  180  is affixed to the wheel hub  184 . In one example, the gear selector assembly  166  is attached to the multi-gear coaster brake hub axle  120  on the driver side  158  of the multi-gear hub, and is manually operable to move an internal push rod  176  to shift gear engagements within the multi-gear hub  118 .  
         [0065]     In operation, the rider rotates the crank handle  112  and crank arm  114  in a forward direction to propel the vehicle  106  forward. With the vehicle  106  in a stationary position, the rider rotates the crank handle  112  and the crank arm  114  in a rearward direction to propel the vehicle  106  rearward. With the vehicle  106  moving in a forward direction, the rider rotates the crank handle  112  and crank arm  114  in a rearward direction to slow down and brake the vehicle  106 . With the vehicle  106  moving in a rearward direction, the rider rotates the crank handle  112  and the crank arm  114  in a forward direction to slow down and eventually stop the rearward movement of the vehicle  106 . In this way, rotating the crank handle  112  and crank arm  114  in a direction opposite to vehicle motion provides an intuitive means of slowing the vehicle  106 . In one embodiment, partial rotation of the crank handle  112  and crank arm  114  engages the coaster brake function of the multi-gear hub  118 .  
         [0066]     The forward rotation of the crank handle  112  and crank arm  114  rotates the multi-gear hub driver  116 , which rotates the planetary gear core  122 , which engages and rotates the hub shell  156  at a selected ratio with respect to the hub driver  116 . Forward rotation of the hub shell  156  rotates the hub shell drive sprocket  168 , which drives the chain  110 , which rotates the driven sprocket  185  which drives the corresponding front wheel  180 , propelling the vehicle  106  in a forward direction.  
         [0067]     The rider chooses the desired drive gear of the multi-gear hub  118  using the gear selector cap  172  while the vehicle  106  is stationary or moving forward. In operation, the gear selector cap  172  is rotated in a clockwise or counter-clockwise direction to select the desired gear ratio. When the gear selector cap  172  is rotated in a clockwise direction, the push rod adjuster  178  moves the push rod  176  further into the hollow cavity of the hub axle  120 , which causes the planetary gear core  122  to move into a higher gear. When the gear selector cap  172  is rotated in a counter-clockwise direction, the push rod adjuster  178  allows the push rod  176  to move outward from the hollow cavity of the hub axle  120 , which causes the planetary gear core  122  to move into a lower gear.  
         [0068]     When the gear selector cap  172  is rotated in either direction, the ball nose spring plunger  174  located in the side wall of the gear selector cap  172  engages one detent  198  located on the crest of the high helix thread  196 . This engagement holds the gear selector cap  172  in a fixed position, which holds the push rod  176  in a fixed position which maintains the selected gear of the multi-speed internal gear hub  118 . When the push rod adjuster  178  is rotated in a clockwise or counter-clockwise direction, the push rod  176  is repositioned within the cavity of the hub axle  120  to accomplish proper alignment for the selected gear. The function of the gear selector components (not shown) within the planetary gear core  122  of a multi-speed internal gear bicycle hub  118  will be understood by those of ordinary skill in this art.  
         [0069]     In operation, rearward rotation of the crank handle  112  and crank arm  114  while the vehicle  106  is stationary rotates the multi-gear hub driver  116  in a reverse direction, which causes the planetary gear core  122  to rotate in a reverse direction, which causes the brake actuator  124  to rotate in a reverse direction, which causes the inner brake cone  126  to rotate in a reverse direction and move longitudinally along the brake actuator threads  128  away from the crank handle, which causes the inner brake cone  126  to engage the brake shoes  130 , which causes the brake shoes  130  to expand and to engage the hub shell  156 , which causes the hub shell  156  to rotate in a reverse direction. The outer brake cone  134  is engaged with the brake shoes  130  and therefore also rotates in a reverse direction. This reverse rotation of the outer brake cone  134  is possible because the outer brake cone  134  is affixed to the outer brake cone extension  136 , which is affixed to the inner race of the freewheel bearing  138  which rotates within the outer race of the freewheel bearing  140  which is affixed to the crank hub housing  142 .  
         [0070]     When the hub shell  156  rotates in a reverse direction, the hub shell drive sprocket  168  drives the chain  110  in a reverse direction, which rotates the driven sprocket  185  in a reverse direction, which drives the corresponding front wheel  180  in a reverse direction.  
         [0071]     A partial rearward rotation of the crank handle  112  and crank arm  114  while the vehicle  106  is moving forward rotates the multi-gear hub driver  116  in a reverse direction, which causes the planetary gear core  122  to rotate in a reverse direction, which causes the brake actuator  124  to rotate in a reverse direction, which causes the inner brake cone  126  to travel longitudinally on the actuator threads  128 , which causes the inner brake cone  126  to engage the brake shoes  130 , which drives the brake shoes  130  into contact with the outer brake cone  134  which causes the brake shoes  130  to expand and to engage the hub shell  156 , which introduces resistance to the forward rotation of the hub shell  156 . This resistance is transferred from the hub shell  156  to the hub shell drive sprocket  168 , which is transferred to the chain  110 , which then transfers the resistance to the front wheel assembly  104 , which causes the vehicle  106  to slow down or come to a complete stop. In this example, the freewheel bearing  150  prevents the outer brake cone  134  from rotating in a forward direction, which prevents the brake shoes  130  from rotating in a forward direction, which prevents the inner brake cone  126  from rotating in a forward direction, which prevents the planetary gear core  122  from rotating in a forward direction and engaging the multi-gear hub driver  116 , which prevents the crank arm  114  from being driven in a forward direction.  
         [0072]     It can be further noted that when the operator initiates a transition from moving the vehicle  106  in a reverse direction to moving in a forward direction, the freewheel bearing  150  in combination with the outer brake cone extension  136  prevents the outer brake cone  134  from rotating, as does a coaster brake arm in a traditional coaster brake arrangement. In this example, the forward rotation of the brake actuator  124  causes the inner brake cone  126  to slide longitudinally along the actuator threads  128  toward the planetary gear core  122 , causing the inner brake cone  126  to disengage from the brake shoes  130 , which causes the brake shoe spring  132  to return the brake shoes  130  to a compressed position, which causes the brake shoes  130  to disengage from the hub shell  156 .  
         [0073]     This allows the rider to propel the vehicle  106  in a forward direction with a selected gear ratio by rotating the crank handles  112  in a forward direction, freewheel in a forward direction by discontinuing crank rotation, brake the vehicle  106  while moving in the forward direction by partial rotation of the crank handles  112  in a reverse direction, propel the vehicle  106  rearward by rotating the crank handles  112  in a reverse direction, and brake the vehicle  106  while moving in a rearward direction by rotating the crank handles  112  in a forward direction. All of the aforementioned actions are performed while the operator maintains full, uninterrupted contact with the crank handles  112 .  
         [0074]     Referring now to  FIGS. 1, 5 ,  7  and  11  and in another embodiment, the propulsion system  250  includes a transmission having one or more independent hand-operable single speed crank assemblies  252 , each including a coaster brake assembly  103  operably connected to a corresponding front drive wheel assembly  104  for propulsion and braking of a human powered vehicle  106  in a forward and reverse direction. The hand crank assembly  252  and the front wheel assembly  104  are held in position by a propulsion tower assembly  258  and operably connected by a flexible roller chain  110 , for example.  
         [0075]     The hand-operable single speed crank assembly  252  includes a crank handle  112 , a crank arm  264 , a hub driver  266 , a driver-side axle nut  267 , a hub axle  270 , a clutch cone  272 , hub driver threads  274 , brake shoes  276 , clutch cone spring  278 , a brake cone  280 , a brake cone extension  282 , a freewheel bearing  296  with an inner race  284  and an outer race  286 , a hub housing  288 , a freewheel bearing cover  289 , retaining bolts  290 , a thrust bearing  292 , an inner axle nut  294 , an outer axle nut  300 , a hub shell  302 , driver ball bearings  306 , brake cone ball bearings  308 , hub housing bearing assemblies  310  and a drive sprocket  312 . In some embodiments, the coaster brake assembly  103  is sized and configured for containment within the hub housing  142 .  
         [0076]     The front drive wheel assembly  104  can include a rim  181 , spokes  183 , tire  182 , wheel hub  184 , driven sprocket  185  and wheel hub axle  186 .  
         [0077]     The crank handle  112  is rotatably attached to the crank arm  264 , which is affixed to the hub driver  266  of the internal coaster brake bicycle hub  268 . The hub driver  266  rotates about the hub axle  270  and engages the clutch cone  272 . In one embodiment, for example, a KT Internal Gear Coaster Brake Hub Model No. KT305 can be used. Those of ordinary skill in this art will understand the components and operation of a standard single speed internal gear bicycle hub. The clutch cone  272  is positioned about the hub driver  266  and engages the helical block threads of the hub driver  274 . The brake shoes  276  are positioned about the clutch cone  272  on one end. The brake shoes  276  are engaged with the brake cone  280  at the second end such that the position of the brake shoes  276  relative to the position of the brake cone  280  remains constant. The clutch spring  278  is positioned about the hub axle  270  and at the first end is located within the cavity of the clutch cone  272 . At the second end, the clutch spring  278  engages the brake cone  280 . The brake cone  280  of the KT coaster brake hub is modified by removing the internal threads of the brake cone  280 , thereby allowing free rotation of the brake cone  280  about the hub axle  270 . The brake cone  280  is attached to the brake cone extension  282 . The brake cone extension  282  is attached to the inner race  284  of freewheel bearing  296 . The outer race  286  of the freewheel bearing  296  is attached to the freewheel bearing cover  289  with retaining bolts  290 . The thrust bearing  292  is located about the hub axle  270  and within the cavity defined by the freewheel bearing inner race  284 , positioned between the brake cone extension  282  and the inner axle nut  294 . The freewheel bearing  296  is located about the hub axle  270  and within the hub housing  288 . On the coaster brake side  298  of the single speed coaster brake hub, the hub axle  270  is affixed to the hub housing  288  by the outer axle nut  300  and held in position such that the axle  270  is fixed and is unable to rotate. The driver ball bearings  306  are located between the hub shell  302  and the hub driver  266  on the driver side  304  of the hub. The brake cone ball bearings  308  are located between the hub shell  302  and the brake cone  280  on the coaster brake side  298  of the hub.  
         [0078]     The modified single speed internal gear bicycle hub  268  is rotatably attached within the hub housing  288  and held in position by two hub housing bearing assemblies  310  and affixed to the hub housing  288  by the outer axle nut  300  located on the coaster brake side  298  of the single speed hub. A vertical slot  165  is cut into the front and rear lower portion of the crank hub housing  288  to allow free movement of the flexible roller chain  110 .  
         [0079]     A drive sprocket  312  is affixed to the exterior of the single speed hub shell  302 . Alternative drivers, such as a cog or pulley (not shown), for example, can be suitably implemented. Engaged upon the drive sprocket  312  is a chain  110 , cogged belt or cable connecting the hub shell  302  at the upper end to a corresponding driven sprocket  185 , cog or pulley at the lower end. The driven sprocket  185  is affixed to the wheel hub  184 . The wheel hub  184  is rotatably attached to the wheel hub axle  186 , which is affixed to the vehicle frame  208 . The driven front wheel  180  is affixed to the wheel hub  184  with spokes  183 .  
         [0080]     In operation, the rider rotates the crank handle  112  and crank arm  264  in a forward direction to propel the vehicle  106  forward. With the vehicle  106  in a stationary position, the rider rotates the crank handle  112  and the crank arm  264  in a rearward direction to propel the vehicle  106  rearward. With the vehicle  106  moving in a forward direction, the rider rotates the crank handle  112  and crank arm  264  in a rearward direction to slow down and brake the vehicle  106 . With the vehicle  106  moving in a rearward direction, the rider rotates the crank handle  112  and the crank arm  264  in a forward direction to slow down and stop the rearward movement of the vehicle  106 . In this way, rotating the crank handle  112  and the crank arm  264  in a direction opposite to vehicle motion provides an intuitive means of slowing the vehicle  106 . In one embodiment, partial rotation of the crank handle  112  and crank arm  264  engages the coaster brake function.  
         [0081]     In operation, the forward rotation of the crank handle  112  and crank arm  264  rotates the single speed hub driver  266 , which rotates the clutch cone  272 , which is urged longitudinally toward the crank handle to bear against and rotate the hub shell  302 . Rotation of the hub shell  302  rotates the hub shell drive sprocket  312 , which drives the chain  110 , which rotates the driven sprocket  185 , which drives the corresponding front wheel assembly  104 , propelling the vehicle  106 .  
         [0082]     Rearward rotation of the crank handle  112  and crank arm  264  while the vehicle  106  is in a stationary position rotates the single speed hub driver  266  in a reverse direction, which causes the clutch cone  272  to rotate in a reverse direction and travel longitudinally along the hub driver threads  274  away from the crank handle, which causes the clutch cone  272  to engage the brake shoes  276 , which drives the brake shoes  276  into contact with the brake cone  280  which causes the brake shoes  276  to expand and to engage the hub shell  302 , which causes the hub shell  302  to rotate in a reverse direction. The brake cone  280  is engaged with the brake shoes  276  and therefore also rotates in a reverse direction. This reverse rotation of the brake cone  280  is possible because the brake cone  280  is affixed to the brake cone extension  282 , which is affixed to the inner race  284  of the freewheel bearing which rotates within the outer race  286  of the freewheel bearing, which is affixed to the crank hub housing  288 .  
         [0083]     When the hub shell  302  rotates in a reverse direction, the hub shell drive sprocket  312  drives the chain  110  in a reverse direction, which rotates the driven sprocket  185  in a reverse direction, which drives the corresponding front wheel assembly  104  in a reverse direction.  
         [0084]     A partial rearward rotation of the crank handle  112  and crank arm  264  while the vehicle  106  is moving forward rotates the single speed hub driver  266  in a reverse direction, which causes the clutch cone  272  to rotate in a reverse direction and travel longitudinally on the hub driver threads  274  away from the crank handle, which causes the clutch cone  272  to engage the brake shoes  276 , which drives the brake shoes  276  into contact with the brake cone  280  which causes the brake shoes  276  to expand and to engage the hub shell  302 , which introduces resistance to the forward rotation of the hub shell  302 . This resistance is transferred from the hub shell  302  to the hub shell drive sprocket  312 , and then transferred to the chain  110 , and then transferred to the front wheel assembly  104 , which causes the vehicle  106  to slow down or come to a complete stop.  
         [0085]     In this example, the outer race  286  of freewheel bearing  296  is attached to the hub housing  288  with retaining bolts  290  which prevents the brake cone  280  from rotating in a forward direction, which prevents the brake shoes  276  from rotating in a forward direction, which prevents the hub shell  302  from rotating in a forward direction, which prevents the clutch cone  272  from rotating in a forward direction, which prevents the hub driver  266  from driving the crank arm  264  in a forward direction.  
         [0086]     It can be further noted that when the operator initiates a transition from moving the vehicle  106  in a reverse direction to moving in a forward direction, the freewheel bearing  296  in combination with the brake cone extension  282  prevents the brake cone  280  from rotating. In this example, the forward rotation of the hub driver  266  causes the clutch cone  272  to move longitudinally along the hub driver threads  274  toward the hub driver  266 , which causes the clutch cone  272  to disengage from the brake shoes  276 , which causes the brake shoes  276  to disengage from the hub shell  302 . In this example, the clutch cone spring  278  assists in the longitudinal travel of the clutch cone  272  about the hub driver threads  274 .  
         [0087]     This allows the rider to propel the vehicle  106  in a forward direction by rotating the crank handles  112  in a forward direction, freewheel in a forward direction by discontinuing crank handle rotation, brake the vehicle  106  while moving in the forward direction by partial rotation of the crank handles  112  in a reverse direction, propel the vehicle  106  rearward by rotating the crank handles  112  in a reverse direction, and brake the vehicle  106  while moving in a rearward direction by rotating the crank handles  112  in a forward direction. All of the aforementioned actions are performed while the operator maintains full, uninterrupted contact with the crank handles  112 .  
         [0088]     Referring now to the embodiment of  FIGS. 6, 7 ,  8 ,  9  and  11 , propulsion system  350  includes a transmission having one or more independent hand-operable crank assemblies  352 , each including a coaster brake assembly  103  operably connected to a corresponding front drive wheel assembly  354  for propulsion and braking of a human powered vehicle  106  in a forward and reverse direction. The hand crank assembly  352  and the front wheel assembly  354  are held in position by a propulsion tower assembly  356  and operably connected by a flexible roller chain  110 , for example.  
         [0089]     Each hand-operable crank assembly  352  includes a crank handle  112 , a crank arm  358 , a crank arm mounting plate  360 , mounting plate screws  361 , a keyed shaft  362 , a woodruff key  364 , an inner bearing  366 , an outer bearing  368 , a drive sprocket  370 , a crank housing  372 , a shaft retaining nut  374 , a threaded mounting post  376  and a threaded chain tension adjuster  378 .  
         [0090]     Each front drive wheel assembly  354  includes a rim  181 , spokes  183 , a tire  182 , a wheel hub assembly  386  and a driven sprocket  388 .  
         [0091]     Each front wheel hub assembly  386  includes a hub driver  390 , a hub axle  394 , a planetary gear core  396 , a brake actuator  398 , an inner brake cone  400 , actuator threads  402 , brake shoes  404 , a brake shoe spring  406 , an outer brake cone  408 , brake cone extension  410 , a freewheel bearing  422  with an inner race  412  and an outer race  414 , retaining bolts  416 , a thrust bearing  418 , an inner axle nut  420 , a freewheel bearing cover  424 , an outer axle nut  428 , a hub shell  430 , a hub shell extension  432 , driver ball bearings  436 , brake cone ball bearings  438 , and a gear shifter  440 . In some embodiments, the coaster brake assembly  103  is sized and configured for containment within the hub shell  430 .  
         [0092]     Each propulsion tower assembly  356  includes a vertical receiver tube  442  slotted at the upper end, a collar clamp  446 , a tower plate  448  and a horizontal tower mounting pin  450 .  
         [0093]     The crank handle  112  is rotatably attached to the crank arm  358 , which is affixed to the crank arm mounting plate  360  with mounting plate screws  361 . The crank arm mounting plate  360  is affixed to the first end of the keyed shaft  363 . Mounted about the keyed shaft  362  is a drive sprocket  370  with a broached hub and is held in position by a woodruff key  364 . The keyed shaft  362  is rotatably affixed to the crank housing  372  by an inner bearing  366  at the first end  363  and an outer bearing  368  at the second end  369 . The keyed shaft  362  is held in position by a retaining nut  374  at the second end  369 .  
         [0094]     Engaged upon the hand crank drive sprocket  370  is a chain  110 , cogged belt or cable connecting the hand crank assembly  352  to a corresponding driven sprocket  388 , cog or pulley attached to the front drive wheel assembly  354 . The front drive wheel hub assembly  386  is affixed to the propulsion tower mounting pin  450 , which is affixed to the vehicle frame  208 .  
         [0095]     A vertical slot  165  is cut into the front and rear lower portion of the crank housing  372  to allow free movement of the flexible roller chain  110 . Affixed to the lower portion of the hand crank housing  372  is a threaded mounting post  376 . Rotatably attached to the threaded section of the mounting post  376  is a threaded chain tension adjuster  378 .  
         [0096]     The hub driver  390  rotates about the hub axle  394  and drives the planetary gear core  396  of an internal gear coaster brake hub  392 . Planetary gear core  396  includes pawls (not shown) about its outer circumference that engage and drive hub shell  430  only when rotated in one direction with respect to the hub shell, but otherwise allow the gear core to rotate freely within the hub shell. For example, a Shimano Nexus Inter3 Model No. SG-3C41 Internal Gear Coaster Brake Hub can be used. Those of ordinary skill in this art will be familiar with the components and operation of a standard internal gear coaster brake hub. Affixed to the planetary gear core  396  is the brake actuator  398 , which rotates about the hub axle  394 . The inner brake cone  400  is positioned about the brake actuator  398  and engages the helical block threads of the actuator  402 . The brake shoes  404  are positioned about the inner brake cone  400 . The brake shoes  404  are held in a compressed position by the brake shoe spring  406 . The brake shoes  404  are engaged with the outer brake cone  408  such that the position of the brake shoes  404  relative to the position of the outer brake cone  408  remains constant. The outer brake cone  408  is attached to the brake cone extension  410 . The brake cone extension  410  is attached to the inner race  412  of the freewheel bearing. The outer race  414  of the freewheel bearing is attached to the freewheel bearing cover  424  with retaining bolts  416 . The thrust bearing  418  is located about the hub axle  394  and within the cavity defined by the freewheel bearing inner race  412 , positioned between the brake cone extension  410  and the inner axle nut  420 . The freewheel bearing  422  is located about the hub axle  394  and within the hub shell extension  432 . Driver ball bearings  436  are located between the hub shell  430  and the hub driver  390  on the driver side  434  of the hub. Brake cone ball bearings  438  are located between the hub shell  430  and the outer brake cone  408  on the coaster brake side  426  of the hub.  
         [0097]     On the coaster brake side  426  of the multi-gear hub, the outer end of fixed hub axle  394  is keyed to freewheel bearing cover  424 , such that cover  424  is prevented from rotating. In this example, the outer end of the axle has opposing flats and fits within a slot defined in the inner surface of the bearing cover. Thus, braking loads carried by freewheel bearing  422  are transferred through the freewheel bearing cover through the axle to the vehicle frame, without the need for a reaction arm attached to an outer fork as in a traditional brake coaster arrangement. This enables the combination of bidirectional propulsion, braking and coasting with a cantilevered wheel hub.  
         [0098]     The inner end  454  of the hub axle that supports the front drive wheel assembly  354  is a square or hexagonal boss  456  which is received by a corresponding square or hexagonal socket  458  within the first end of the propulsion tower mounting pin  460 . The square or hexagonal boss  456  is affixed to the tower mounting pin  460  with a hardened spring pin  462  or dowel pin. This method of affixing the hub axle  394  to the tower mounting pin  450  prevents the rotation of the hub axle  394 .  
         [0099]     The gear shifter  440  is attached about the hub axle  394  on the driver side  434  of the multi-gear hub, and is manually operable to shift gear engagements within the multi-gear hub  392 .  
         [0100]     In operation, the rider rotates the crank handle  112  and crank arm  358  in a forward direction to propel the vehicle  106  forward. With the vehicle  106  in a stationary position, the rider rotates the crank handle  112  and the crank arm  358  in a rearward direction to propel the vehicle  106  rearward. With the vehicle  106  moving in a forward direction, the rider rotates the crank handle  112  and crank arm  358  in a rearward direction to slow down and brake the vehicle  106 . With the vehicle  106  moving in a rearward direction, the rider rotates the crank handle  112  and the crank arm  358  in a forward direction to slow down and stop the rearward movement of the vehicle  106 . Rotating the crank handle  112  and crank arm  358  in a direction opposite to vehicle motion provides an intuitive means of slowing the vehicle  106 .  
         [0101]     In operation, the forward rotation of the crank handle  112  and crank arm  358  rotates the crank arm mounting plate  360 , which rotates the keyed shaft  362 , which rotates the drive sprocket  370 , which drives the flexible roller chain  110  in a forward direction, which rotates the driven sprocket  388 , which rotates the multi-gear hub driver  390 , which rotates the planetary gear core  396 , which engages and rotates the hub shell  430  in a forward direction at a selected ratio with respect to the hub driver  390 . Rotation of the hub shell  430  rotates the front drive wheel assembly  354 , which propels the vehicle  106  forward.  
         [0102]     The rider can choose the desired drive gear of the multi-gear hub  392  using a standard bicycle gear selector (not shown) while the vehicle  106  is stationary or moving forward. This may be any style of gear selector provided by the multi-gear wheel hub manufacturer or other suppliers.  
         [0103]     In operation, rearward rotation of the crank handle  112  and crank arm  358  while the vehicle  106  is in a stationary position rotates the crank arm plate  360 , which rotates the keyed shaft  362 , which rotates the drive sprocket  370 , which drives the flexible roller chain  110 , which rotates the driven sprocket  388 , which rotates the multi-gear hub driver  390 , which rotates the planetary gear core  396  in a reverse direction, which rotates the brake actuator  398  in a reverse direction, which causes the inner brake cone  400  to travel longitudinally on the actuator threads  402  toward the outer brake cone  408 , which causes the inner brake cone  400  to engage the brake shoes  404 , which causes the brake shoes  404  to expand and to engage the hub shell  430 , which causes the hub shell  430  to rotate in a reverse direction. The outer brake cone  408  is engaged with the brake shoes  404  and therefore also rotates in a reverse direction. This reverse rotation of the outer brake cone  408  is possible because the outer brake cone  408  is affixed to the brake cone extension  410 , which is affixed to the inner race  412  of the freewheel bearing  422 , which rotates within the outer race  414  of the freewheel bearing.  
         [0104]     When the hub shell  430  rotates in a reverse direction, the front drive wheel assembly  354  rotates in a reverse direction, which drives the vehicle  106  in a rearward direction.  
         [0105]     A partial reverse rotation of the crank handle  112  and crank arm  358  while the vehicle  106  is moving forward rotates the drive sprocket  370  in a reverse rotation, which drives the chain  110  in a reverse direction, which rotates the driven sprocket  388  in a reverse direction, which causes the planetary gear core  396  to rotate in a reverse direction, which causes the brake actuator  398  to rotate in a reverse direction, which causes the inner brake cone  400  to travel longitudinally on the actuator threads  402  toward the outer brake cone  408 , which causes the inner brake cone  400  to engage the brake shoes  404 , which causes the brake shoes  404  to expand and to engage the hub shell  430 , which introduces resistance to the forward rotation of the hub shell  430 . This resistance is transferred from the hub shell  430  to the front drive wheel assembly  354 , which causes the vehicle  106  to slow down or come to a complete stop.  
         [0106]     In this example, the outer race  414  of the freewheel bearing is affixed to the freewheel bearing cover  424 , which is affixed to the second end of the axle  466 , which prevents the outer brake cone  408  from rotating in a forward direction, which prevents the brake shoes  404  from rotating in a forward direction, which prevents the hub shell  430  from rotating in a forward direction, which prevents the planetary gear core  396  from rotating in a forward direction, which prevents the hub driver  390  from driving the chain  110  in a forward direction, which prevents the crank arm  358  from rotating in a forward direction.  
         [0107]     It can be further noted that when the operator initiates a transition from moving the vehicle  106  in a reverse direction to moving in a forward direction, the freewheel bearing  422  in combination with the brake cone extension  410  prevents the outer brake cone  408  from rotating. In this example, the forward rotation of the brake actuator  398  causes the inner brake cone  400  to slide longitudinally along the actuator threads  402  toward the planetary gear core  396 , which causes the inner brake cone  400  to disengage from the brake shoes  404 , which causes the brake shoe spring  406  to return the brake shoes  404  to a compressed position, which causes the brake shoes  404  to disengage from the hub shell  430 .  
         [0108]     This allows the rider to propel the vehicle  106  in a forward direction with a selected gear ratio by rotating the crank handles  112  in a forward direction, freewheel in a forward direction by discontinuing crank rotation, brake the vehicle  106  while moving in the forward direction by partial rotation of the crank handles  112  in a reverse direction, propel the vehicle  106  rearward by rotating the crank handles  112  in a reverse direction, and brake the vehicle  106  while moving in a rearward direction by rotating the crank handles  112  in a forward direction. All of the aforementioned actions are performed while the operator maintains full, uninterrupted contact with the crank handles  112 .  
         [0109]     Referring now to  FIGS. 1, 6 ,  7 ,  10 ,  11 ,  20  and  21 , propulsion system  500  includes a transmission having one or more independent hand-operable crank assemblies  352 , each including a coaster brake assembly  103  operably connected to a corresponding front drive wheel assembly  504  for propulsion and braking of a human powered vehicle  106  in a forward and reverse direction. The hand crank assembly  352  and the front drive wheel assembly  504  are held in position by a propulsion tower assembly  356  and operably connected by a flexible roller chain  110 , for example.  
         [0110]     Each hand-operable crank assembly  352  includes a crank handle  112 , a crank arm  358 , a crank arm mounting plate  360 , mounting screws  361 , a keyed shaft  362 , a woodruff key  364 , an inner bearing  366 , an outer bearing  368 , a drive sprocket  370 , a crank housing  372 , a shaft retaining nut  374 , a threaded mounting post  376  and a threaded chain tension adjuster  378 .  
         [0111]     Each front drive wheel assembly  504  includes a rim  181 , spokes  183 , a tire  182 , a wheel hub assembly  508  and a driven sprocket  388 .  
         [0112]     Each front wheel hub assembly  508  includes a hub driver  510 , a hub axle  514 , a clutch cone  516 , hub driver threads  518 , brake shoes  520 , a clutch cone spring  522 , a brake cone  524 , brake cone extension  526 , a freewheel bearing  538  having an inner race  528  and an outer race  530 , retaining bolts  532 , a thrust bearing  534 , an inner axle nut  536 , a freewheel bearing cover  540 , an outer axle nut  544 , a hub shell  546 , a hub shell extension  548 , driver ball bearings  552 , and brake cone ball bearings  554 . In some embodiments, the coaster brake assembly  103  is sized and configured for containment with the hub shell  546 .  
         [0113]     Each propulsion tower assembly  356  includes a vertical receiver tube  442  slotted at the upper end  444 , a collar clamp  446 , a tower plate  448  and a horizontal tower mounting pin  450 .  
         [0114]     The crank handle  112  is rotatably attached to the crank arm  358 , which is affixed to the crank arm mounting plate  360  with mounting screws  361 . The crank arm mounting plate  360  is affixed to the first end of the keyed shaft  363 . Mounted about the keyed shaft  362  is a drive sprocket  370  with a broached hub, which is held in position by a woodruff key  364 . The keyed shaft  362  is rotatably attached to the crank housing  372  by an inner bearing  366  at the first end  363  and an outer bearing  368  at the second end  369 . The keyed shaft  362  is held in position by a retaining nut  374  at the second end  369 .  
         [0115]     Engaged upon the hand crank drive sprocket  370  is a chain  110 , cogged belt or cable connecting the hand crank assembly  352  to a corresponding driven sprocket  388 , cog or pulley attached to the front drive wheel assembly  504 . The front drive wheel hub assembly  508  is affixed to the propulsion tower mounting pin  450 , which is affixed to the vehicle frame  208 .  
         [0116]     A vertical slot  165  is cut into the front and rear lower portion of the hand crank housing  372  to allow free movement of the flexible roller chain  110 .  
         [0117]     Affixed to the lower portion of the hand crank housing  372  is a threaded mounting post  376 . Rotatably attached to the threaded section of the mounting post  376  is a threaded chain tension adjuster  378 .  
         [0118]     The hub driver  510  rotates about the hub axle  514  and engages the clutch cone  516  of a single speed internal gear coaster brake hub  512 . For example, a KT Model No. KT-305 Internal Gear Coaster Brake Hub can be used. Those of ordinary skill in this art will be familiar with the components and operation of a standard internal gear coaster brake hub. The clutch cone  516  is positioned about the hub driver  510  and engages the helical block threads of the hub driver  518 . The brake shoes  520  are positioned about the clutch cone  516  at the first end. The brake shoes  520  are engaged with the brake cone  524  at the second end such that the position of the brake shoes  520  relative to the position of the brake cone  524  remains constant. The clutch cone spring  522  is positioned about the hub axle  514  and at the first end is located within the cavity of the clutch cone  516 . At the second end, the clutch cone spring  522  engages the brake cone  524 . The brake cone  524  of the KT coaster brake hub, for example, is modified by removing the internal threads of the brake cone  524 , thereby allowing free rotation of the brake cone  524  about the hub axle  514 . The brake cone  524  is attached to the brake cone extension  526 . The brake cone extension  526  is attached to the inner race  528  of the freewheel bearing  538 . The outer race  530  of the freewheel bearing is attached to the freewheel bearing cover  540  with retaining bolts  532 . The thrust bearing  534  is located about the hub axle  514  and within the cavity defined by the freewheel bearing inner race  528 , positioned between the brake cone extension  526  and the inner axle nut  536 . The freewheel bearing  538  is located about the hub axle  514  and within the hub shell extension  548 . On the coaster brake side  542  of the single speed hub, the hub axle  514  terminates at a position within the freewheel bearing cover  540 . Driver ball bearings  552  are located between the hub shell  546  and the hub driver  510  on the driver side  550  of the hub. Brake cone ball bearings  554  are located between the hub shell  546  and the brake cone  524  on the coaster brake side  542  of the hub.  
         [0119]     As in the embodiment of  FIG. 9 , the outer end of hub axle  514  is rotationally keyed to the freewheel bearing cover  540 , such that the cover is prevented from rotating. Thus, braking loads carried by freewheel bearing  422  are transferred through the freewheel bearing cover through the axle to the vehicle frame, without the need for a reaction arm attached to an outer fork as in a traditional brake coaster arrangement. This enables the combination of bidirectional propulsion, braking and coasting with a cantilevered wheel hub.  
         [0120]     The other end  570  of the hub axle that supports the cantilevered hub of the front drive wheel assembly  504  is a square or hexagonal boss  572  which is received by a corresponding square or hexagonal socket  458  within the first end  460  of the propulsion tower mounting pin. The square or hexagonal boss  572  is affixed to the tower mounting pin  450  with a hardened spring pin  462  or dowel pin. This method of affixing the hub axle  514  to the tower mounting pin  450  prevents the rotation of the hub axle  514 .  
         [0121]     In operation, the rider rotates the crank handle  112  and crank arm  358  in a forward direction to propel the vehicle  106  forward. With the vehicle  106  in a stationary position, the rider rotates the crank handle  112  and the crank arm  358  in a reverse direction to propel the vehicle  106  rearward. With the vehicle  106  moving in a forward direction, the rider rotates the crank handle  112  and crank arm  358  in a reverse direction to slow down and brake the vehicle  106 . With the vehicle  106  moving in a rearward direction, the rider rotates the crank handle  112  and the crank arm  358  in a forward direction to slow down and stop the rearward movement of the vehicle  106 . Rotation of the crank handle  112  and crank arm  358  in a direction opposite to the vehicle motion provides an intuitive means of slowing the vehicle  106 .  
         [0122]     The forward rotation of the crank handle  112  and crank arm  358  rotates the crank arm mounting plate  360 , which rotates the keyed shaft  362 , which rotates the drive sprocket  370 , which drives the flexible roller chain  110  or cogged belt, which rotates the driven sprocket  388 , which rotates the single speed hub driver  510 , which rotates the clutch cone  516 , which rotates the hub shell  546 . Rotation of the hub shell  546  rotates the front drive wheel assembly  504 , which propels the vehicle  106  forward.  
         [0123]     Rearward rotation of the crank handle  112  and crank arm  358  while the vehicle  106  is in a stationary position rotates the crank arm mounting plate  360  in a reverse direction, which rotates the keyed shaft  362 , which rotates the drive sprocket  370 , which drives the flexible roller chain  110  or cogged belt in a reverse direction, which rotates the driven sprocket  388  in a reverse direction, which rotates the hub driver  510 , which rotates the clutch cone  516  in a reverse direction. This causes the clutch cone  516  to travel on the hub driver threads  518  toward the brake cone  524 , which causes the clutch cone  516  to engage the brake shoes  520 , which causes the brake shoes  520  to expand and to engage the hub shell  546 , which causes the hub shell  546  to rotate in a reverse direction. The brake cone  524  is engaged with the brake shoes  520  and therefore also rotates in a reverse direction. This reverse rotation of the brake cone  524  is possible because the brake cone  524  is affixed to the brake cone extension  526 , which is affixed to the inner race  528  of the freewheel bearing  538 , which rotates within the outer race  530  of the freewheel bearing. In this example, the clutch spring  522  is compressed by the lateral movement of the clutch cone  516  at the first end  562  and the fixed position of the brake cone  524  at the second end  564 .  
         [0124]     When the hub shell  546  rotates in a reverse direction, the front drive wheel assembly  504  rotates in a reverse direction, which drives the vehicle  106  in a rearward direction.  
         [0125]     A partial rearward rotation of the crank handle  112  and crank arm  358  while the vehicle  106  is moving forward drives the chain  110  in a reverse direction, which rotates the driven sprocket  388  in a reverse direction, which causes the hub driver  510  to rotate in a reverse direction, which causes the clutch cone  516  to travel longitudinally on the hub driver threads  518  toward the brake cone  524 , which causes the clutch cone  516  to engage the brake shoes  520 , which causes the brake shoes  520  to expand and to engage the hub shell  546 , which introduces resistance to the forward rotation of the hub shell  546 . This resistance is transferred from the hub shell  546  to the front drive wheel  574 , which causes the vehicle  106  to slow down or come to a complete stop.  
         [0126]     In this example, the outer race  530  of the freewheel bearing  538  is affixed to the freewheel bearing cover  540 , which is affixed to the second end  568  of the axle. The freewheel bearing  538  prevents the brake cone  524  from rotating in a forward direction, which prevents the brake shoes  520  from rotating in a forward direction, which prevents the hub shell  546  from rotating in a forward direction, which prevents the clutch cone  516  from rotating in a forward direction, which prevents the hub driver  510  from engaging the chain  110  in a forward direction, which prevents the crank arm  358  from rotating in a forward direction.  
         [0127]     It can be further noted that when the operator initiates a transition from moving the vehicle  106  in a reverse direction to moving in a forward direction, the freewheel bearing  538  in combination with the brake cone extension  526  prevents the brake cone  524  from rotating. In this example, the forward rotation of the hub driver  510  causes the clutch cone  516  to travel longitudinally along the hub driver threads  518  toward the driven sprocket  388 , which causes the clutch cone  516  to disengage from the brake shoes  520 , which causes the brake shoes  520  to disengage from the hub shell  546 . During this process, the outer edge of clutch cone spring  522 , which is prevented from rotating due to its connection to the brake cone, drags against the inner surface of the clutch cone, assisting to drive the clutch cone along the threads of hub driver  510  toward the sprocket. The operation of the clutch cone spring is as is known in the art of bicycle hub design.  
         [0128]     This allows the rider to propel the vehicle  106  in a forward direction by rotating the crank handles  112  in a forward direction, freewheel in a forward direction by discontinuing crank rotation, brake the vehicle  106  while moving in the forward direction by partial rotation of the crank handles  112  in a reverse direction, propel the vehicle  106  rearward by rotating the crank handles  112  in a reverse direction, and brake the vehicle  106  while moving in a rearward direction by rotating the crank handles  112  in a forward direction. All of the aforementioned actions are performed while the operator maintains full, uninterrupted contact with the crank handles  112 .  
         [0129]     Any of the aforementioned propulsion systems may be attached to a human powered vehicle, and more specifically to an assisted mobility device as described in U.S. Pat. No. 6,902,177.  
         [0130]     Referring to  FIG. 11 , human powered vehicle  106  includes a structural frame  208 , two front wheels  602  mounted to a forward portion of the frame  604  for rotation, a seat  606  secured to the frame  208 , the seat  606  positioned between the front wheels  602  and adapted to pivot about a seat pivot axis  608 , and a steerable rear wheel  610  mounted to the frame  208  behind the seat  606  and defining a rear wheel king pin axis  612 , the rear wheel  610  operably linked to the seat  606  such that pivoting of the seat  606  about the seat pivot axis  608  causes pivoting of the rear wheel  610  about the kingpin axis  612  to steer the vehicle  106 .  
         [0131]     Referring also to  FIGS. 1, 12 ,  13 , and  14 , the propulsion system is rotatably attached to the lower horizontal frame tube  642  of the human powered vehicle  106  at the lower attachment point  615  and attached to the tower adjustment plate  616  at the upper attachment point  617 , such that the propulsion system can be rotated about the pivot axis  618  into multiple positions forward and aft of a vertical position while maintaining the operable connection between the hand crank assembly  620  and the corresponding front drive wheel assembly  624  of any of the aforementioned propulsion systems. In this example the propulsion system is attached to an assisted mobility device as described in U.S. Pat. No. 6,902,177. In some embodiments, the upper portion of the propulsion system can be rotated rearward about the pivot axis  618  to permit an operator seated in the human powered vehicle  106  to roll the forward portion of the vehicle underneath a standard table, desk or work surface  627  (shown in outline), positioned at a height of between about 28 to 34 inches from the floor.  
         [0132]     Each of the aforementioned propulsion systems include a hand operable crank assembly  620 , a propulsion tower assembly  622 , a front drive wheel assembly  624 , a flexible roller chain  110  or cogged belt, a tower adjustment plate  616 , an adjustable clamping handle  626 , a propulsion tower pin receiver  628  and a spring loaded retractable plunger  630 .  
         [0133]     Each of the aforementioned hand operable crank assemblies  620  includes a crank handle  112 , a crank arm  621 , a crank housing  623 , a vertical slot  165 , a mounting post  376  and a chain tension adjuster  378 .  
         [0134]     Each of the aforementioned drive wheel assemblies  624  includes a rim  181 , tire  182 , spokes  183 , wheel hub  625  and driven sprocket  185 .  
         [0135]     The hand operable crank assembly  620  is affixed to the upper end of the propulsion tower assembly  622 . The front drive wheel assembly  624  is affixed to the lower end of the propulsion tower assembly  622 . The flexible roller chain  110  operably connects the hand crank assembly  620  and the front drive wheel assembly  624 . The tower adjustment plate  616  is affixed to a forward portion of the frame of the vehicle  636  and includes a curved slot  640 . The adjustable clamping handle  626  is rotatably attached to a threaded portion of the propulsion tower assembly  638  and located within the curved slot  640  of the tower adjustment plate  616 . The propulsion tower pin receiver  628  is an integral portion of the lower horizontal frame tube  642  of the vehicle frame  208 . The spring loaded retractable plunger  630  is affixed to the lower horizontal frame tube  642 .  
         [0136]     In operation, the propulsion system is secured to the tower adjustment plate  616  with the adjustable clamping handle  626  at the first end and secured to the propulsion tower pin receiver  628  with the spring loaded retractable plunger  630  at the second end.  
         [0137]     The propulsion system is rotatably adjusted in a forward or rearward direction by loosening the adjustable clamping handle  626  and rotating the propulsion system to the desired position. The propulsion system pivots within the propulsion tower pin receiver  628 . Retightening the adjustable clamping handle  626  secures the propulsion tower assembly  622  to the tower adjustment plate  616  in the position advantageous for the vehicle user.  
         [0138]     In operation, the propulsion tower assembly  622  can be rotated in a rearward direction to a position behind and below the seat  606  when such a position may be advantageous to the vehicle user. For example, this may include working at a desk or conference table, or for compact transport of the vehicle  106 .  
         [0139]     Referring now to  FIGS. 15 and 16 , the propulsion system is attached to the tower adjustment plate  616  of the vehicle frame  208  with the adjustable clamping handle  626  at the upper attachment point  617 , and attached to the propulsion tower pin receiver  628  of the vehicle frame  208  with the spring loaded retractable plunger  630  at the lower attachment point  615  such that the propulsion system can be attached and detached from the vehicle frame  208  in a simple operation referred to as “quick release” in bicycle terminology. Each of the aforementioned propulsion systems includes a hand operable crank assembly  620 , a propulsion tower assembly  622 , a front drive wheel assembly  624 , a flexible roller chain  110  or cogged belt, a tower adjustment plate  616 , an adjustable clamping handle  626 , a propulsion tower pin receiver  628  and a spring loaded retractable plunger  630 . The propulsion tower assembly  622  includes a vertical receiver tube  442 , a collar clamp  446 , a tower plate  448 , and a horizontal tower mounting pin  450 . The horizontal tower mounting pin  450  includes a tapered end  654  and a circumferential concave groove  656 .  
         [0140]     The hand operable crank assembly  620  is affixed to the upper end of the propulsion tower assembly  632 . The front drive wheel assembly  624  is affixed to the lower end of the propulsion tower assembly  634 . The flexible roller chain  110  operably connects the hand crank assembly  620  and the front drive wheel assembly  624 . The tower adjustment plate  616  is affixed to a forward portion of the frame  636  of the vehicle  106  and includes a curved slot  640 . The adjustable clamping handle  626  is rotatably attached to a threaded portion of the propulsion tower assembly  638  and located within the curved slot  640  of the tower adjustment plate  616 . The propulsion tower pin receiver  628  is an integral portion of the lower horizontal frame tube  642  of the vehicle frame  208 . The locking retractable spring plunger  630  is affixed to the lower horizontal frame tube  642 . The vertical receiver tube  442  of the propulsion tower assembly  622  is affixed to the tower plate  448 . The tower plate  448  is affixed to the horizontal tower mounting pin  450 . The horizontal tower mounting pin  450  includes a tapered end  654  and a circumferential concave groove  656  which is positioned to receive the retractable spring plunger  630 .  
         [0141]     In operation, each of the aforementioned propulsion systems is secured to the tower adjustment plate  616  with the adjustable clamping handle  626  at the upper attachment point  617  and secured to the propulsion tower pin receiver  628  with the locking retractable spring plunger  630  at the lower attachment point  615 .  
         [0142]     The propulsion system is detached from the vehicle frame  208  by removing the adjustable clamping handle  626  and retracting the locking retractable spring plunger  630 . The propulsion system is then detached from the vehicle frame  208  by sliding the propulsion tower mounting pin  450  out of the propulsion tower pin receiver  628 .  
         [0143]     To reattach the propulsion system, the locking retractable spring plunger  630  is released into the engaged position  658  and the propulsion tower mounting pin  450  is inserted into the propulsion tower pin receiver  628 . This engages the spring plunger  630  with the circumferential groove  656  of the propulsion tower mounting pin  450 . The adjustable clamping handle  626  is reattached to the threaded portion of the propulsion tower assembly  638  to secure the propulsion system to the vehicle frame  208 .  
         [0144]     Retightening the adjustable clamping handle  626  secures the propulsion tower assembly  622  to the tower adjustment plate  616  in the position advantageous for the vehicle user.  
         [0145]     In operation, the propulsion system can be detached from the vehicle frame  208  for the ease and convenience of transport by the rider or an assistant.  
         [0146]     Referring back to  FIG. 1 , a wheelchair-type locking brake  662  is mounted to the propulsion tower assembly  622  for immobilizing the vehicle  106 . When engaged, the brake  662  makes contact with the corresponding front tire  182  of the front wheel assembly  624 , thereby preventing rotation of the front wheel assembly  624 .  
         [0147]     Referring now to  FIGS. 17, 18  and  19 , in another embodiment the propulsion system  666  includes a transmission having one or more hand-operable push rims  668 , each including a coaster brake assembly  103  operably connected to a corresponding drive wheel assembly  670  for propulsion and braking of a hand powered vehicle  672  in a forward and reverse direction. The push rim  668  and the drive wheel assembly  670  are rotatably affixed about a cantilevered axle  674 , which is attached to the vehicle frame  676 .  
         [0148]     Each drive wheel assembly  670  may include a rim  181 , spokes  183 , a tire  182 , a wheel hub assembly  684  and a push rim  668 .  
         [0149]     Each front wheel hub assembly  684  includes a hub driver  686 , a hub axle  674 , a planetary gear core  690 , a brake actuator  692 , an inner brake cone  694 , actuator threads  696 , brake shoes  698 , a brake shoe spring  700 , an outer brake cone  702 , brake cone extension  704 , a freewheel bearing  716  with an inner race  706  and an outer race  708 , retaining bolts  710 , a thrust bearing  712 , an inner axle nut  714 , a freewheel bearing cover  718 , an outer axle nut  722 , a hub shell  724 , a hub shell extension  726 , driver ball bearings  730 , brake cone ball bearings  732 , and a gear selector assembly  734 . In some embodiments, the coaster brake assembly  103  is sized and configured for containment within the hub shell  724 .  
         [0150]     The gear selector assembly  734  includes a gear selector body  736 , a gear selector cap  738 , a ball-nose spring plunger  740 , a push rod  742  and a push rod adjuster  744 .  
         [0151]     The push rim  668  is attached to the hub driver  686  and functions as a hand-operable crank. The hub driver  686  rotates about the hub axle  674  and engages the planetary gear core  690  of an internal gear coaster brake hub  688 . For example, a Shimano Nexus Inter3 Model No. SG-3C41 Internal Gear Coaster Brake Hub can be used. Affixed to the planetary gear core  690  is the brake actuator  692  that rotates about the hub axle  674 . The inner brake cone  694  is positioned about the brake actuator  692  and engages helical block threads of the actuator  696 . The brake shoes  698  are positioned about the inner brake cone  694 . The brake shoes  698  are held in a compressed position by the brake shoe spring  700 . The brake shoes  698  are engaged with the outer brake cone  702  such that the position of the brake shoes  698  relative to the position of the outer brake cone  702  remains constant. The outer brake cone  702  is attached to the brake cone extension  704 . The brake cone extension  704  is attached to the inner race  706  of the freewheel bearing  716 . The outer race  708  of the freewheel bearing is attached to the freewheel bearing cover  718  with retaining bolts  710 . The thrust bearing  712  is located about the hub axle  674  and within the cavity defined by the freewheel bearing inner race  706 , positioned between the brake cone extension  704  and the inner axle nut  714 . The freewheel bearing  716  is located about the hub axle  674  and within the hub shell extension  726 . On the coaster brake side  720  of the multi-gear hub, the hub axle  674  penetrates the freewheel bearing cover  718 . Driver ball bearings  730  are located between the hub shell  724  and the hub driver  686  on the driver side  728  of the hub. Brake cone ball bearings  732  are located between the hub shell  724  and the outer brake cone  702  on the coaster brake side  720  of the hub.  
         [0152]     The first end  746  of the hub axle that supports the drive wheel assembly  670  is a square or hexagonal boss  748 , which is received by a corresponding square or hexagonal socket  750  within the frame mounting pin  752  on the axle side of the mounting pin  752 . The square or hexagonal boss  748  is affixed to the square or hexagonal frame mounting pin  752  with a hardened spring pin  754  or dowel pin. The frame mounting pin  752  is affixed to a square or hexagonal receiver  755 , which is integral to the vehicle frame  676 . This method of affixing the hub axle  674  to the frame mounting pin  752  and affixing the frame mounting pin  752  to the receiver  755  integral to the vehicle frame  767  prevents the rotation of the hub axle  674 .  
         [0153]     The gear selector assembly  734  is attached to the multi-gear coaster brake hub axle  674  on the driver side  728  of the multi-gear hub, and is manually operable to shift gear engagements within the multi-gear hub  688 . Gear selector  734  operates in the same manner as gear selector  166  of  FIG. 4 , discussed above.  
         [0154]     Referring now to  FIGS. 4, 17 ,  18  and  19 , and in operation, the rider rotates the push rim  668  in a forward direction to propel the vehicle  672  forward. With the vehicle  672  in a stationary position, the rider rotates the push rim  668  in a rearward direction to propel the vehicle  672  rearward. With the vehicle  672  moving in a forward direction, the rider rotates the push rim  668  in a rearward direction to slow down and brake the vehicle  672 . With the vehicle  672  moving in a rearward direction, the rider rotates the push rim  668  in a forward direction to slow down and stop the rearward movement of the vehicle  672 . In this way, rotating the push rim  668  in a direction opposite to vehicle motion provides an intuitive means of slowing the vehicle  672 .  
         [0155]     The forward rotation of the push rim  668  rotates the multi-gear hub driver  686 , which rotates the planetary gear core  690 , which rotates the hub shell  724  at a selected ratio with respect to the hub driver  686 . Rotation of hub shell  724  rotates the drive wheel assembly  670 , which propels the vehicle  672  forward.  
         [0156]     The rider can choose the desired drive gear of the multi-gear hub  688  using the gear selector  738  while the vehicle  672  is stationary or moving forward. In operation, the gear selector  738  is rotated in a clockwise or a counter-clockwise direction to select the desired gear ratio. When the gear selector  738  is rotated in a clockwise direction, the internal push rod (not shown) causes the planetary gear core  690  to move into a higher gear. The gear selector assembly  734  is described above and is illustrated in  FIG. 4 .  
         [0157]     When the vehicle is in a stationary position, rearward rotation of the push rim  668  rotates the multi-gear hub driver  686 , which rotates the planetary gear core  690  in a reverse direction, which causes the brake actuator  692  to rotate in a reverse direction, which causes the inner brake cone  694  to travel on the actuator threads  696  toward the outer brake cone  702 , which causes the inner brake cone  694  to engage the brake shoes  698 , which causes the brake shoes  698  to expand and to engage the hub shell  724 , which causes the hub shell  724  to rotate in a reverse direction. The outer brake cone  702  is engaged with the brake shoes  698  and therefore also rotates in a reverse direction. This reverse rotation of the outer brake cone  702  is possible because the outer brake cone  702  is affixed to the brake cone extension  704 , which is affixed to the inner race  706  of the freewheel bearing  716 , which rotates within the outer race  708  of the freewheel bearing, which is affixed to the freewheel bearing cover  718 , which is affixed to the supported end of the axle  674 . When the hub shell  724  rotates in a reverse direction, the front drive wheel assembly  670  rotates in a reverse direction, which drives the vehicle in a rearward direction.  
         [0158]     When the vehicle is moving forward, a partial rearward rotation of the push rim  668  rotates the hub driver  686  in a reverse direction, which causes the planetary gear core  690  to rotate in a reverse direction, which causes the brake actuator  692  to rotate in a reverse direction, which causes the inner brake cone  694  to travel longitudinally on the actuator threads  696  toward the outer brake cone  702 , which causes the inner brake cone  694  to engage the brake shoes  698 , which causes the brake shoes  698  to expand and to engage the hub shell  724 , which introduces resistance to the forward rotation of the hub shell  724 . This resistance is transferred from the hub shell  724  to the drive wheel assembly  670 , which causes the vehicle to slow down or come to a complete stop. In this example, the freewheel bearing  716  prevents the outer brake cone  702  from rotating in a forward direction, which prevents the brake shoes  698  from rotating in a forward direction, which prevents the hub shell  724  from rotating in a forward direction, which prevents the planetary gear core  690  from rotating in a forward direction, which prevents the hub driver  686  from rotating in a forward direction, which prevents the push rim  668  from being driven in a forward direction.  
         [0159]     It can be further noted that when the operator initiates a transition from moving the vehicle in a reverse direction to moving in a forward direction, the freewheel bearing  716  in combination with the brake cone extension  704  prevents the outer brake cone  702  from rotating. In this example, the forward rotation of the brake actuator  692  causes the inner brake cone  694  to slide longitudinally along the actuator threads  696  toward the planetary gear core  690 , causing the inner brake cone  694  to disengage from the brake shoes  698 , which causes the brake shoe spring  700  to return the brake shoes  698  to a compressed position, which causes the brake shoes  698  to disengage from the hub shell  724 .  
         [0160]     This allows the rider to propel forward in a forward direction with a selected gear ratio, freewheel in a forward direction by discontinuing rotation of the push rim  668 , brake the vehicle while moving in the forward direction with a partial rotation of the push rim  668  in a reverse direction, rotate the push rim  668  in a reverse direction for rearward propulsion of the vehicle, and brake the vehicle while moving in a rearward direction by rotating the push rim  668  in a forward direction. All of the aforementioned actions are possible while the operator maintains full, uninterrupted contact with the push rim  668 .  
         [0161]     A hand-activated rear wheel brake (not shown) may also be provided for slowing or stopping the human powered vehicle. This may be a band brake, a caliper brake, a disc brake or a drum brake, for example.  
         [0162]     Referring now to  FIGS. 14 and 22 , a rear wheel driven sprocket assembly  800  may be mounted upon a rear fork steering tube  802  of the vehicle to provide steering of the rear wheel, as described in U.S. Pat. No. 6,902,177. The rear wheel driven sprocket assembly  800  includes an upper sprocket  806  and a lower sprocket  808  of equal diameter. The upper sprocket  806  and lower sprocket  808  are positioned about the fork steerer tube  802  to allow the upper chain  810  to rotate freely without contacting the opposing lower chain  812 .  
         [0163]     In this embodiment, the upper chain  810  wraps approximately two hundred degrees around the upper sprocket  806  in a first direction and terminates at the upper pin  814 , affixing the upper chain  810  to the upper sprocket  806 . The lower chain  812  wraps approximately two hundred degrees around the lower sprocket  808  in a second direction and terminates at the lower pin  816 , affixing the lower chain  812  to the lower sprocket  808 . In operation, the rear wheel steering driven sprocket assembly  800  rotates about the substantially vertical axis  612  of the rear fork steering tube  802 .  
         [0164]     Alternatively, cogs, pulleys, chains or cables may be employed. For example,  FIG. 23  shows a seat steering drive sprocket assembly  818  that may be rotatably attached to the frame of a human powered vehicle. The seat steering drive sprocket assembly  818  includes a double-groove pulley  822 , a hub  824 , an upper cable  826  with a first swaged threaded end  827 , a lower cable  828  with a second swaged threaded end  829 , an upper cable stop  832 , a lower cable stop  834 , and upper and lower adjusting nuts (not shown).  
         [0165]     The upper groove  836  and the lower groove  838  of the pulley  822  are positioned to allow the upper cable  826  to rotate freely without contacting the opposing lower cable  828 . The upper cable  826  wraps approximately two hundred degrees around the upper groove  836  of the pulley  822  in a first direction and passes through the upper cable stop  832 , which is affixed to the pulley  822 . The lower cable  828  wraps approximately two hundred degrees around the lower groove of the pulley  838  in a second direction and passes through the lower cable stop  834 , which is affixed to the pulley  822 . An upper adjusting nut (not shown) is threadably attached to the swaged threaded end of the upper cable  826 . A lower adjusting nut (not shown) is threadably attached to the swaged threaded end of the lower cable  828 . The upper cable  826  and the lower cable  830  are adjusted by the clockwise or counterclockwise rotation of the adjusting nuts (not shown) about the swaged threaded ends of the upper cable  826  and the lower cable  830 . In operation, the seat steering drive sprocket assembly  818  rotates about a substantially vertical axis  608 .  
         [0166]     Referring now to  FIGS. 24, 25A  and  25 B and in another embodiment, the vehicle  900  includes two independent hand-operable multiple-gear crank assemblies  102 . The hand-operable multi-gear crank assemblies  102  include all of the components as described with respect to  FIG. 3  except the gear selector assembly  166  is replaced with a gear selector  920 . Each independent multiple-gear crank assembly  102  is operably connected to a corresponding front drive wheel assembly  904  for propulsion and braking of the vehicle  900  in a forward and reverse direction. The front drive wheel assembly  904  can include the front wheel  906 , the wheel hub  908 , the driven sprocket  910  and the wheel hub axle  912 .  
         [0167]     The gear selector  920  is attached to the multi-gear coaster brake hub axle  120  ( FIG. 25A ) on the driver side  118  of the multi-gear hub  156 , and is manually operable to move an internal push rod (not shown) to shift gear engagements within the multi-gear hub. The rider can choose the desired drive gear of the multi-gear hub  156  using the gear selector  920  while the vehicle  900  is stationary or moving in a forward or reverse direction.  
         [0168]     The hand-operable multi-gear crank assemblies  102  are driven by crank handles  922 , connected to the hub driver  116  by crank arms  114 . Rotation of the crank arm  114  in a first direction rotates the hub shell drive sprocket  168  ( FIG. 25A ), which drives a chain  110 , which rotates the driven sprocket  910 , which in turn, drives the corresponding front wheel  906 , propelling the vehicle  900  in a forward direction. Rotation of the crank arm  114  in a second direction rotates the hub shell drive sprocket  168  ( FIG. 25A ), which drives a chain  110 , which rotates the driven sprocket  910  in a second direction, which in turn, drives the corresponding front wheel  906 , propelling the vehicle  900  in a reverse direction.  
         [0169]     In operation, this embodiment operates identically to the first embodiment of the detailed description illustrated by  FIG. 3 , with the exception noted above regarding the gear selector.  
         [0170]     This allows the rider to propel the vehicle  900  in a forward direction with a selected gear ratio by rotating the crank handles  922  in a forward direction, freewheel in a forward direction by discontinuing crank rotation, brake the vehicle  900  while moving in the forward direction by partial rotation of the crank handles  922  in a reverse direction, propel the vehicle  900  rearward by rotating the crank handles  922  in a reverse direction, and brake the vehicle  900  while moving in a rearward direction by rotating the crank handles  922  in a forward direction. All of the aforementioned actions are performed while the operator maintains full, uninterrupted contact with the crank handles  922 .  
         [0171]     The in-hub transmissions described above are also useful in other types of vehicles. For example,  FIG. 26  shows a portion of a single-speed cantilevered wheel hub  512  (as discussed above with respect to  FIG. 10 ), but with an electric motor  950  disposed about the inner end of the axle  514  and having a rotatable armature  952  keyed to the inner face of a hub driver, to rotate the hub driver  954  about the axle. A stator  956  of the motor is secured within the vehicle frame, and the spring loaded retractable plunger  630  retains the axle and allows for a quick release of the axle and wheel as an assembly. The arrangement shown in  FIG. 26  may be provided in a motorized wheelchair, with either one or two driven wheels. Because the hub configuration mechanically provides the functions of bi-directional propulsion, braking and coasting, the electric motor need only be controlled to generate the torques necessary for such functions. Such torque control may be accomplished by controlling current, without the need for positional feedback. In a wheelchair or assisted mobility vehicle, a joystick control (not shown) may be provided, with current and torque controlled as a function of joystick direction and displacement. Joystick operation is simplified further when steering is provided by seat rotation, as described above.  
         [0172]     This transmission hub arrangement can greatly simplify motor control and reduce power consumption. Rolling forward downhill, for example, the operator need only pull back slightly on the joystick to apply a reverse motor torque to engage the brake shoes  520  for braking, but can otherwise allow the vehicle to coast by releasing the joystick.  
         [0173]     A number of embodiments have been described. Other embodiments are within the scope of the following claims.  
       REFERENCE NUMBERS LIST  
       [0174]      100  Propulsion system with multi-gear transmission in hand crank assembly  
         [0175]      102  Multi-gear crank assemblies  
         [0176]      103  Coaster brake assembly  
         [0177]      104  Front drive wheel assembly  
         [0178]      106  Vehicle  
         [0179]      108  Propulsion tower assembly  
         [0180]      110  Roller chain  
         [0181]      112  Crank handle  
         [0182]      114  Crank arm  
         [0183]      116  Hub driver  
         [0184]      118  Multi-gear coaster brake bicycle hub  
         [0185]      120  Hub axle  
         [0186]      122  Planetary gear core  
         [0187]      124  Brake actuator  
         [0188]      126  Inner brake cone  
         [0189]      128  Actuator threads  
         [0190]      130  Brake shoes  
         [0191]      132  Brake shoes spring  
         [0192]      134  Outer brake cone  
         [0193]      136  Outer brake cone extension  
         [0194]      138  Inner race of freewheel bearing  
         [0195]      140  Outer race of freewheel bearing  
         [0196]      142  Crank Hub housing  
         [0197]      144  Retaining bolts  
         [0198]      146  Thrust bearing  
         [0199]      148  Inner axle nut  
         [0200]      150  Freewheel bearing  
         [0201]      152  Coaster brake side of hub  
         [0202]      154  Outer axle nut  
         [0203]      156  Hub shell (upper)  
         [0204]      158  Driver side of hub  
         [0205]      160  Driver ball bearing retainer  
         [0206]      162  Brake cone ball bearing retainer  
         [0207]      164  Hub housing bearing assemblies  
         [0208]      165  Vertical slot  
         [0209]      166  Gear selector assembly  
         [0210]      168  Drive sprocket  
         [0211]      170  Gear selector body  
         [0212]      172  Gear selector cap  
         [0213]      174  Ball nose spring plunger  
         [0214]      176  Push rod  
         [0215]      178  Push rod adjuster  
         [0216]      180  Front wheel  
         [0217]      181  Rim  
         [0218]      182  Tire  
         [0219]      183  Spokes  
         [0220]      184  Wheel hub  
         [0221]      185  Driven Sprocket  
         [0222]      186  Wheel hub axle  
         [0223]      190  Internal threads gear selector body  
         [0224]      194  Crank arm side of multi-speed hub  
         [0225]      196  High helix thread  
         [0226]      198  Detents  
         [0227]      200  Internal threads gear selector cap  
         [0228]      202  Push rod first end  
         [0229]      204  Push rod second end  
         [0230]      206  Threaded hole (end wall)  
         [0231]      208  Vehicle frame  
         [0232]      210  Gear selector  
         [0233]      250  Propulsion system for Single Speed Transmission in Hand Crank Assembly  
         [0234]      252  Hand crank assembly single speed  
         [0235]      258  Propulsion tower assembly  
         [0236]      264  Crank arm  
         [0237]      266  Hub driver  
         [0238]      267  Driver side axle nut  
         [0239]      268  Modified internal gear bicycle hub  
         [0240]      270  Hand Crank Hub axle  
         [0241]      272  Clutch cone  
         [0242]      274  Hub driver threads  
         [0243]      276  Brake shoes  
         [0244]      278  Clutch cone spring  
         [0245]      280  Brake cone  
         [0246]      282  Brake cone extension  
         [0247]      284  Inner race of freewheel  
         [0248]      286  Outer race of freewheel  
         [0249]      288  Hub housing  
         [0250]      289  Freewheel bearing cover  
         [0251]      290  Retaining Bolts  
         [0252]      292  Thrust bearing  
         [0253]      294  Inner axle nut  
         [0254]      296  Freewheel bearing  
         [0255]      298  Coaster brake side of hub  
         [0256]      300  Outer axle nut  
         [0257]      302  Hub shell  
         [0258]      304  Driver side of hub  
         [0259]      306  Driver ball bearing retainer  
         [0260]      308  Brake cone ball bearing retainer  
         [0261]      310  Hub housing bearing assemblies  
         [0262]      312  Drive sprocket  
         [0263]      324  Clutch cone first end  
         [0264]      326  Clutch cone second end  
         [0265]      350  Propulsion system with multi-gear transmission in wheel hub  
         [0266]      352  Hand crank assembly  
         [0267]      354  Front drive wheel assembly  
         [0268]      356  Propulsion tower assembly  
         [0269]      358  Crank arm  
         [0270]      360  Crank arm mounting plate  
         [0271]      361  mounting plate screws  
         [0272]      362  Keyed shaft  
         [0273]      363  keyed shaft first end  
         [0274]      364  Woodruff key  
         [0275]      366  Inner bearing  
         [0276]      368  Outer bearing  
         [0277]      369  keyed shaft second end  
         [0278]      370  Drive sprocket  
         [0279]      372  Crank housing  
         [0280]      374  Shaft retaining nut  
         [0281]      376  Threaded mounting post  
         [0282]      378  Chain tension adjuster  
         [0283]      386  Wheel hub assembly  
         [0284]      388  Driven sprocket  
         [0285]      390  Hub driver  
         [0286]      392  Multi gear internal bicycle hub  
         [0287]      394  Hub axle  
         [0288]      396  Planetary gear core  
         [0289]      398  Brake actuator  
         [0290]      400  Inner brake cone  
         [0291]      402  Actuator threads  
         [0292]      404  Brake shoes  
         [0293]      406  Brake shoe spring  
         [0294]      408  Outer brake cone  
         [0295]      410  Brake cone extension  
         [0296]      412  Inner race of freewheel bearing  
         [0297]      414  Outer race of freewheel bearing  
         [0298]      416  Retaining bolts  
         [0299]      418  Thrust bearing  
         [0300]      420  Inner axle nut  
         [0301]      422  Freewheel bearing  
         [0302]      424  Freewheel bearing cover  
         [0303]      426  Coaster brake side of hub  
         [0304]      428  Outer axle nut  
         [0305]      430  Hub shell  
         [0306]      432  Hub shell extension  
         [0307]      434  Driver side of hub  
         [0308]      436  Driver ball bearings  
         [0309]      438  Brake cone ball bearings  
         [0310]      440  Gear shifter  
         [0311]      442  Vertical receiver tube  
         [0312]      444  Upper end of vertical tube  
         [0313]      446  Collar clamp  
         [0314]      448  Tower plate  
         [0315]      450  Horizontal tower mounting pin  
         [0316]      454  Hub axle on first end (supporting end)  
         [0317]      456  Square boss  
         [0318]      458  Square socket  
         [0319]      460  Axle side of mounting pin (first end)  
         [0320]      462  Spring pin  
         [0321]      464  Gear selector  
         [0322]      466  Unsupported end of axle  
         [0323]      500  Propulsion System with single speed transmission in wheel hub  
         [0324]      504  Front wheel drive assembly  
         [0325]      508  Wheel hub assembly  
         [0326]      510  Hub driver  
         [0327]      512  Single speed internal bicycle hub  
         [0328]      514  Hub axle  
         [0329]      516  Clutch cone  
         [0330]      518  Hub driver threads  
         [0331]      520  Brake shoes  
         [0332]      522  Clutch cone spring  
         [0333]      524  Brake cone  
         [0334]      526  Brake cone extension  
         [0335]      528  Inner race of freewheel bearing  
         [0336]      530  Outer race of freewheel bearing  
         [0337]      532  Retaining bolts  
         [0338]      534  Thrust bearing  
         [0339]      536  Inner axle nut  
         [0340]      538  Freewheel bearing  
         [0341]      540  Freewheel bearing cover  
         [0342]      542  Coaster brake side of hub  
         [0343]      544  Outer axle nut  
         [0344]      546  Hub shell  
         [0345]      548  Hub shell extension  
         [0346]      550  Driver side of hub  
         [0347]      552  Driver ball bearing retainer  
         [0348]      554  Brake cone ball bearing retainer  
         [0349]      556  First end of keyed shaft  
         [0350]      558  Second end of keyed shaft  
         [0351]      560  Helical threads  
         [0352]      562  Clutch cone first end  
         [0353]      564  Clutch cone second end  
         [0354]      566  Retaining bolts (freewheel cover)  
         [0355]      568  Axle end  
         [0356]      602  Front wheels  
         [0357]      604  Forward portion of frame  
         [0358]      606  Seat  
         [0359]      608  Seat pivot axis  
         [0360]      610  Rear wheel  
         [0361]      612  Rear wheel king pin axis  
         [0362]      614  Frame receiver tube  
         [0363]      615  Lower attachment point  
         [0364]      616  Tower adjustment plate  
         [0365]      617  Upper attachment point  
         [0366]      618  Pivot axis  
         [0367]      620  Hand crank assembly  
         [0368]      621  Crank arm  
         [0369]      622  Propulsion tower assembly  
         [0370]      623  Crank housing  
         [0371]      624  Front drive wheel assembly  
         [0372]      625  Wheel hub  
         [0373]      626  Adjustable clamping handle  
         [0374]      628  Propulsion tower pin receiver  
         [0375]      630  Spring loaded plunger  
         [0376]      632  Upper end of tower assembly  
         [0377]      634  Lower end of tower assembly  
         [0378]      636  Vehicle Frame forward position  
         [0379]      638  Threaded portion propulsion tower assembly  
         [0380]      640  Curved slot  
         [0381]      642  Lower horizontal frame tube  
         [0382]      654  Tapered end of mounting pin  
         [0383]      656  Circumferential groove  
         [0384]      658  Engaged position (plunger)  
         [0385]      660  Disengaged position (plunger)  
         [0386]      662  Wheelchair locking brake  
         [0387]      666  Propulsion system with hand crank comprising push rim  
         [0388]      668  Push rim  
         [0389]      670  Drive wheel assembly  
         [0390]      672  Vehicle-wheelchair  
         [0391]      674  Cantilever axle  
         [0392]      676  Vehicle frame  
         [0393]      684  Wheel hub assembly  
         [0394]      686  Hub driver  
         [0395]      688  Multi gear coaster brake bicycle hub  
         [0396]      690  Planetary gear core  
         [0397]      692  Brake actuator  
         [0398]      694  Inner brake cone  
         [0399]      696  Helical Actuator threads  
         [0400]      698  Brake shoes  
         [0401]      700  Brake shoe spring  
         [0402]      702  Outer brake cone  
         [0403]      704  Brake cone extension  
         [0404]      706  Inner race of freewheel bearing  
         [0405]      708  Outer race of freewheel bearing  
         [0406]      710  retaining bolts  
         [0407]      712  thrust bearing  
         [0408]      714  Inner axle nut  
         [0409]      716  Freewheel bearing  
         [0410]      718  Freewheel bearing cover  
         [0411]      720  Coaster brake side of hub  
         [0412]      722  Outer axle nut  
         [0413]      724  Hub shell  
         [0414]      726  Hub shell extension  
         [0415]      728  Driver side of hub  
         [0416]      730  Driver ball bearings  
         [0417]      732  Brake cone ball bearings  
         [0418]      734  Gear selector assembly  
         [0419]      736  Gear selector body  
         [0420]      738  Gear selector cap  
         [0421]      740  Ball nose spring plunger  
         [0422]      742  Push rod  
         [0423]      744  Push rod adjuster  
         [0424]      746  Hub axle first end (supporting)  
         [0425]      748  Square boss  
         [0426]      750  Square socket  
         [0427]      752  Frame mounting pin first side  
         [0428]      754  Spring pin  
         [0429]      755  Square receiver  
         [0430]      756  High helix threads (gear selector body)  
         [0431]      758  Detent  
         [0432]      760  Internal threads of cap  
         [0433]      762  First end push rod  
         [0434]      764  Second end push rod  
         [0435]      766  Threaded hole  
         [0436]      800  Rear wheel driven sprocket assembly  
         [0437]      802  Rear fork steering tube  
         [0438]      806  Upper sprocket  
         [0439]      808  Lower sprocket  
         [0440]      810  Upper chain  
         [0441]      812  Lower chain  
         [0442]      814  Upper pin  
         [0443]      816  Lower pin  
         [0444]      818  Seat steering drive sprocket assembly  
         [0445]      822  Double groove pulley  
         [0446]      824  Hub  
         [0447]      826  Upper cable  
         [0448]      827  First swaged threaded end  
         [0449]      828  Lower cable  
         [0450]      829  Second swaged threaded end  
         [0451]      832  Upper cable stop  
         [0452]      834  Lower cable stop  
         [0453]      836  Upper groove  
         [0454]      838  Lower groove  
         [0455]      950  Electric motor  
         [0456]      952  Rotatable armature  
         [0457]      954  Hub driver  
         [0458]      956  Stator