Abstract:
A small machine that can be removably mounted on a wall and may be used while sitting or standing to provide aerobic exercise without requiring the use of the legs. The machine simulates the action of a kayak by using an alternating power strokes from the arms, with an inertial component and adjustable retarding forces created by frictional and various speed-dependent mechanisms. A unidirectionally-rotating flywheel simulates the mass of the kayak plus operator, while friction pads, an eddy current generator and air vanes operating on the flywheel provide additional retarding forces. Various ways to grip the ends of the cord are provided, including individual hand grips and a single long shaft with or without paddles at either end.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the field of exercise machines, and particularly to those machines that simulate the action of a kayak, thereby providing aerobic exercise generated by the upper body. 
     2. Description of Related Art 
     There is a wide range of exercise machines and devices that provide aerobic exercise, that is, exercise that improves respiratory function by increasing the consumption of oxygen. Treadmills, stair stepping machines and cross-country ski simulators all provide effective aerobic exercise. However, these machines all require the use of the user&#39;s legs, either to stand while exercising or to operate the machine. Individuals who cannot use their legs, such as those with an injury, chronic conditions such as arthritis, or who must exercise from a wheelchair, cannot use these machines. There are also those who are able to use their legs while exercising, but do not wish to commit the space required of the existing machines and would like a smaller machine, especially for home use. 
     The present invention arose out of the need of individuals to have an aerobic exerciser that did not require the use of the individual&#39;s legs. Because of its alternating power stroke, continuous action and focus on exercising muscles of the upper body, a kayak provides an excellent aerobic exercise. However, using an actual kayak for exercise it is inconvenient for most people, because of the need for storage space and a suitable body of water. However, the simulation of a kayak provides a useful form of exercise. 
     A complete simulation of the action of a kayak calls for having components of mass as well as frictional and speed-dependent retardation forces, just as occur in any water craft. The present invention has all of these components. 
     The present invention includes a small, rigid base plate on which the operating mechanisms are mounted. This plate is in turn removably attached to a fixed surface such as a wall. The user can sit on a chair or wheelchair, or even stand in front of the machine while exercising. Because there is no large, heavy and unwieldy apparatus to take up floor or storage space, when the exercise is competed the machine can easily be demounted and stored. 
     The machine includes a continuous cord that passes through the machine, around a rotatable drum that translates the alternating linear movement of the cord into a rotation, and out the other side. The user grasps one end of the cord with one hand, and the other end with the other hand. Individual hand grips can be used to facilitate the grip, or in the best simulation of a kayak, each end of the cord attaches to an end of a shaft, with or without paddles at either end. In either example, a spring clasp or other similar device is used to removably attach the grip to the cord ends. 
     The retarding force and hence the aerobic exercise, derive from the mechanisms attached to the drum around which the cord wraps. One of these is a rotating mass or flywheel that simulates the mass of the kayak and paddler that must be propelled through the water against the retarding forces. In addition, there are retarding forces caused by a set of variably-spring-loaded friction pads that press against the flywheel, a permanent magnet that induces electrical eddy currents in the moving flywheel that in turn react with the magnetic field of the magnet, and a multitude of air-disturbing vanes mounted on the outer perimeter of the flywheel. The machine can employ some or all of these force mechanisms. 
     One of the unique aspects of this exercise machine is a conversion device that translates the back and forth rotation of the drum into a unidirectional rotation of the flywheel. The device allows a free-wheeling coasting of the flywheel between power strokes that is an accurate representation of the action of a kayak in the water between paddle strokes. Yet, the retarding forces remain in effect at all times, also accurately simulating the action of a real kayak. 
     Prior art for upper body aerobic exercise machines is of several varieties including lever-operated weight machines, cross-country or alternating arm type, kayak, canoe and rowing simulators. Unlike the present invention, nearly all of these machines consist of a large structure that contains both the part of the machine that generates the inertial and lossy retarding forces, and a part on which the user sits. Also unlike the present invention, others involve separate power and return strokes (e.g. Lo U.S. Pat. No. 5,076,573, Jonas U.S. Pat. No. 4,880,224, Kolomayets U.S. Pat. No. 4,714,244, Ware U.S. Pat. No. 4,469,325, Coffey U.S. Pat. No. 4,940,227), the use of levers to cause motion, rather than a cord (e.g. Hickman U.S. Pat. No. 5,803,876, Larsson U.S. Pat. No. 4,687,197, Chininis U.S. Pat. No. 4,717,145, and Rawls U.S. Pat. No. 5,565,002), lifting weights as the primary work mechanism (e.g. Hanagan U.S. Pat. No. 4,336,934, Jones U.S. Pat. No. 5,135,449 and Koenig U.S. Pat. No. 5,957,817) or when cord is used to actuate the work mechanism, the machine is large and self-contained (e.g. Grinblat U.S. Pat. No. 4,709,918, Street U.S. Pat. No. 4,625,962 and Sleamaker U.S. Pat. No. 5,354,251). Deluty U.S. Pat. No. 4,114,875 and Dudley U.S. Pat. No. 4,557,480 describe small exercise machines that are contained within housings and can be mounted on a fixed surface, but unlike the present invention, both involve a single cord with separate power and return strokes and only one form of retarding force. The closest prior art to the present invention is Englehart U.S. Pat. No. 5,624,357, since it uses a cord and paddle shaft that can be manipulated in three-dimensional space. However Englehart&#39;s invention is shown with an integral seat and uses only frictional resistance, thereby not providing a realistic simulation of an actual kayak. 
     In most cases, the result is a machine that is large, heavy and ungainly. Further, most such machines simulate the rowing action of a boat where both arms work together, first with a power stroke and then a return stroke. Further, they are usually designed to require the use of the legs, an aspect intentionally avoided in the present invention. In the present invention, the exercise machine is small enough to be mounted to a wall for support and easily removed for storage. It also accurately and realistically simulates the action of and forces encountered in paddling a kayak, where the arms work freely in three-dimensional space with alternating power strokes with inertial, frictional and various speed-dependent retarding forces all without requiring the use of the user&#39;s legs. 
     Until the present invention, there was no practical, cost-effective means available of providing a simple, practical, unique, yet different aerobic exerciser that had a frictional retarding force, speed-dependent retarding forces, a single inertial mass or flywheel rotating in one direction and did not require the use of the individual&#39;s legs. 
     SUMMARY OF THE INVENTION 
     In use, the individual applies a force to one end of the cord, say at the right end of the machine, pulling it out and away from the machine. Since the cord is wrapped around the drum at least once and the drum can be coated with or made from a high-friction material, the linear force is converted into a rotational force without slippage between cord and drum. The opposite end of the cord is automatically pulled into the machine by virtue of being part of a continuous cord. 
     The cord enters the machine through the conical throat of a cord port made from low-friction material such as Teflon or nylon. The purpose of the port is to accept the varied angles of approach of the cord that result from simulation of the action of a kayak paddle. After exiting the narrow output end of the port, the cord makes a 90 degree turn around a grooved pulley as it heads toward a drum used to convert the linear motion of the cord to rotational motion of the flywheel. 
     To assure that the cord remains within the concave periphery of the pulley, a spring-loaded idler made of a softer material such as rubber presses against the outside surface of the cord as it lies in the groove of the pulley. In addition, the cord on the return side is not under tension and is thus kept from slipping from the groove. There are other means of assuring this contact between cord and pulley, such as a fixed, curved piece that follows the curve of the pulley for about 90 degree of its periphery. 
     As the cord is pulled, the friction between the cord and drum causes the drum to rotate. That rotation causes the position of the turn(s) on the drum to slowly “walk” or move toward one end of the drum. When the drum reverses direction, the turns will move towards the other end. The position of the turn(s) continues to move until the cord has reached the end of its stroke. There is generally a small angle between where the cord exits the pulley and the shortest distance to the drum from that point. That angle creates a small component in the force in the cord that lies along the axis of the drum in the direction of the center of the drum and tends to keep the turns together. That force increases as the cord turns move toward the end of the drum. 
     Additionally, because of the restoring effect of the angle in the cord, after several full cycles, the set of turns will oscillate between extremes centered about the center of the drum, even if their initial position when the cord was at its midpoint was offset from the center. In case the turns begin their movement too close to one end of the drum and continue to move in that direction, the drum has end caps on both ends that serve to prevent the turns from falling off the ends. 
     The total stroke of the cord, say six feet, divided by the circumference of the drum, say 6.5 inches, determines the number of turns of the drum during each power stroke. Typically, this will be about 11 turns (6 ft×12 in./ft/6.5 in.). If the diameter of the cord is ⅛″, then cord will move 1⅜″ (11 T/⅛ in.) during that full stroke. During the next power stroke, during which the drum rotates in the opposite direction, the turn(s) of the cord will move the same distance in the opposite direction on the drum. This action then requires a drum of length only somewhat greater than the 1⅜″ movement of the turns per stroke. 
     The drum is fixedly mounted on a drive shaft for the purpose of transmitting power. Also mounted on this drive shaft is a spur gear and a toothed timing belt pulley. Both the gear and the pulley are in turn fixed to their own one-way clutch. Each of these clutches is designed to transmit power in opposite directions. That is, when the gear is transmitting power from the drive shaft through its one-way clutch and then to the gear itself, the timing belt pulley&#39;s clutch that is mounted on the same drive shaft is free-wheeling. The reverse is also true. That is, when the drive shaft is rotating in the opposite direction, the one-way clutch attached to the timing belt pulley now transmits power from the drive shaft, through the clutch and hence to the other pulley. On the other hand, the clutch mounted to the spur gear, also on the same drive shaft, is now disengaged and is free-wheeling. 
     As the drum rotates during this first pull, it causes either the one-way clutch attached to either the gear or the timing belt pulley to accept that power. Whether it is the gear or pulley which transfers power, depends on which one-way clutch is mounted with its power mode in that direction. For the purposes of this discussion, we will assume that the cord is moving to the right as the user pulls with her right arm in a power stroke, and that the drum thus rotates counter-clockwise. 
     Since it is the gear which accepts power in this case, then its mating gear attached to the output shaft will rotate clockwise, or in the opposite direction from the drive shaft. The ratio of the number of teeth of these two gears will determine the relative rate of rotation of the output shaft. 
     The output shaft will then cause a flywheel that is also fixedly attached to the output shaft to rotate. The purpose of the flywheel is to simulate the weight of the paddler and kayak through its rotational inertia. The flywheel can be constructed from a single molded or machined piece of metal, or from a disk with an annular cylinder attached to the outer periphery of the disk. As a practical matter, to achieve the largest inertia in the smallest diameter, the outer portion of the flywheel should be a metal such as iron with a high mass density. Regardless of the material used or its construction, the flywheel should have a non-magnetic annular disk outer portion for the generation of eddy current retarding forces, as will be described. 
     Even though the total weight of a kayak and paddler might easily exceed 200 pounds, it is not necessary to provide that same weight in this machine to properly simulate the operation of an actual kayak. Because the cord wraps around a drum of modest size, say one inch in radius, and the radius of gyration of the flywheel is much greater, say five inches, there is a significant multiplication of the inertia of the flywheel, reflected back to the driving cord. In addition, if the conversion device driving the flywheel provides an increase in rotational speed compared to that of its input shaft, the net effect is a further increase in the effective inertia of the flywheel. Typically, with a two inch diameter drum, a multiplication of 40% of output shaft speed in the direction conversion device compared to input shaft speed, and a flywheel of only 10 pounds weight and 10 inches in diameter, a 10-15 pound stroke force will be necessary to maintain a steady machine speed. This is equivalent of a several mile per hour cruising speed for a 200 pound loaded kayak. 
     Opposing spring-loaded friction pads can be mounted on the base to apply a retarding force to opposite sides of the flywheel, most conveniently to its disk portion. The arms on which these pads are mounted can be hinged at their opposite ends and be drawn together by the spring, thus creating equal and opposite normal forces on the disk portion. If the arms are slotted and the spring is mounted on bushings that slide in the slots, then movement of the spring in the slots will provide a variation in normal force and resulting frictional retarding force. This retarding force will generally not be a function of rotational speed, and simulates the mostly speed-independent frictional force between the kayak and the water. 
     There is also a retarding force generated when any water craft such as a kayak displaces water and creates waves when it moves through the water. This force generally varies with speed in a complex way. To simulate this force, a non-magnetic annular disk portion of the flywheel passes through a magnetic field that is perpendicular to the disk and whose strength is greatest near the disk&#39;s outer perimeter. This motion induces electric currents, called eddy currents, whose strength is a function of the rotational speed of the flywheel. These currents react with the magnetic field that caused them, resulting in an additional retarding force. The simulation of wave action forces is not exact, but does provide a speed-dependent force component. Because the force exerted on the disk is perpendicular to its radius and is in the plane of the disk, there is no net force on the bearing of the disk that could lead to bearing failure or require the use of a more robust bearing than otherwise would be necessary. 
     The magnet used for the purpose of creating eddy currents in the mon-magnetic disk can in principle be either an electromagnet or permanent magnet. As a practical matter, a permanent magnet will be assumed, since ones of sufficient magnetic field intensity are easily obtainable, and avoid having any requirement for electrical current. 
     To achieve a measure of variability in the eddy current retarding forces, the support for the magnet can be designed to move along a radial path of the flywheel without changing the perpendicularity of the magnetic field with respect to the flywheel. Thus, as it moves away from the disk, the number of field lines cutting the moving metallic disk are reduced. The eddy currents also reduce, thus decreasing the reaction force. 
     Another form of speed-dependent retarding force can be implemented by adding vanes to the outer perimeter of the flywheel. These vanes project into the air as the flywheel rotates and disturb the air. The faster the rotational speed of the flywheel, the greater the retarding force they produce. The vanes also serve to dissipate the heat losses created by the friction pads and eddy currents. These vanes could be variably isolated from the air stream by a movable shield to provide a control on the force they create. 
     When the full power stroke is complete and the user&#39;s right arm is fully drawn back, the stroke can then be reversed such that the left arm now pulls on the cord to provide the power stroke. Inside the machine, the drum is now rotating in the opposite direction from the first power stroke. As a result, the one-way clutch attached to the gear is now free-wheeling, since it was installed to transfer power in the original direction. On the other hand, the clutch attached to the toothed timing belt pulley is now engaged and thus causes the pulley to turn. The power is transmitted smoothly to the output shaft via the timing belt that engages a second toothed pulley mounted to the output shaft. 
     As a result of this combination of two power transmission methods, each designed to transmit power during a different rotational direction of the drive shaft, the output shaft always rotates in the same direction and always transmits power to the flywheel and retarding force mechanisms, regardless of the direction of rotation of the drive shaft. When the user ceases to pull on the cord, the flywheel will coast, but still under the influence of the retarding forces, further simulating the action of a real kayak. Because of the coasting action of the direction conversion device, there is no large force at the end of each power stroke that would otherwise occur if the rotational direction of the flywheel were also reversed. 
     The ratio of output to drive teeth in both the gear and timing belt pulleys governs the output shaft speed relative to the drive shaft speed. In order to assure that the output shaft rotates at the same speed regardless of the direction of the drive shaft, these ratios must be close in value. 
     As the user exercises with the present invention, operating the paddle shaft in three dimensional space and unconstrained by any system of rigid levers, she can move the paddle shaft in a realistic simulation of actual kayak paddling, performing all the usual maneuvers, including paddle twisting as the shaft changes from one hand power stroke to the other. Further, the machine can be mounted low enough on the rigid support (e.g. a wall) such that the force exerted by the cord on the paddle shaft is at a downward angle, as it would be in the case of an actual kayak, thus further enhancing the simulation. 
     When in operation, the force exerted on the cord during a power stroke and the rate of strokes is such that the machine generates an amount of heat that is easily dissipated by the rotation of the flywheel, particularly if air vanes are installed. Typically at a continuous force of 10 lbs and a stroke of five feet every second, the power generated by the user&#39;s efforts is: 
      Power=10 lbs×[5 ft/1 sec]×1.36 Watts/ft-lb-sec=68 Watts 
     The base plate to which all the machine&#39;s mechanisms are mounted must be attached to a rigid support during operation. One way to accomplish this end is to have a set of mechanical connectors that removably attaches the base plate to a support plate. The support plate can then attache permanently to a wall. If the attachment is such that the cords exit the machine at a level of about two feet off the floor, then the machine can be used while sitting down, making it suitable for individuals in a wheelchair or seated on a chair, preferably of the armless variety. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     An embodiment of the invention is described in more detail with reference to the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of a user seated at the exercise machine. 
     FIG. 2 is an overhead view of the machine base plate containing the mechanisms for transmitting power and exerting retarding force. 
     FIG. 3 is a cross-sectional view of a portion of the machine showing the gear train and its one-way clutch. 
     FIG. 4 is a cross-sectional view of a portion of the machine showing the timing belt train and its one-way clutch. 
     FIG. 5 is a cross-sectional view of the drum. 
     FIG. 6 is a rear view of a portion of the machine showing the flywheel, friction pad and magnet structures. 
     FIG. 7 is a cross-sectional view of a portion of the machine showing the grooved pulley and rubber idlers. 
     FIG. 8 is a cross-sectional view of the cord port. 
     FIG. 9 is a cross-sectional view of the friction arm tensioning spring and its control bracket and arm. 
     FIG. 10 is an cutaway view of a portion of the flywheel showing an alternate form of the flywheel. 
     FIG. 11 is a cutaway view of a portion of the flywheel showing air vanes. 
     FIG. 12 is an end view of the paddle shaft showing a spring clasp and cord end. 
     FIG. 13 is a side view of the base plate, wall support and support bracket. 
     It will be recognized that some or all of the preceding Figures do not necessarily show all the elements required to construct the depicted preferred embodiment, or accurately reflect their relative sizes or positions. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is a front view of a user  19  seated at a chair  77  facing the exercise machine while holding a simulated kayak paddle consisting of a shaft  22  and paddles  29  and  62 . Removably attached to the ends of the shaft at points  63  and  64  are the left and right ends of cord  68 . Assuming that the user is shown in a power stroke with the right hand, then the cord  68  will exit the machine at right-hand port  70 , while the left hand releases the cord  68  to enter the machine at left-hand port  69 . 
     A safety cover  114  protects the user from the mechanisms. Raised portions  14  and  15  of the cover  114  protect protruding internal mechanisms such as the flywheel and conversion device respectively. The mechanisms are mounted on a rigid base plate  21  which in turn is removably mounted to the support plate  16  by a mechanical connector means (not visible in this view). The support plate is attached to a wall  20  by suitable lag bolts  17 . 
     FIG. 2 is a top view of the base plate  21  and the mechanisms mounted on it. The base plate  21  is removably attached to a support plate  16  (not shown in this view) by mechanical connectors such as  18 . As previously described, the cord  68  is entering the left-side port  69  while exiting right-hand port  70  on a power stroke of the right hand. On the left-hand side of the machine, the grooved pulley  38  with a central sintered bearing  101  is mounted to the base  21  on a shoulder screw  102 . The rubber idler  35  mounted on an arm  36  tensioned by a spring  37  anchored at point  86  and pivoted at point  81  serves to apply pressure on the cord  68  to prevent it from coming off the pulley  38  during the current low-tension return stroke. The cord then makes a 90 degree turn and exits the pulley  38  in the direction of the drum  33  as shown by the arrow. 
     The cord  68  then wraps around the cylindrical drum  33  at least one full turn, and then is directed toward the right-hand side grooved pulley  110 , where it is held in place by rubber idler  109  and finally exits the right-hand side port  70 . 
     Drum  33  is attached to the drive shaft  105  by end caps  56  at either end of the drum, the disks having hubs with set screws for securing them in place against rotation. Drive shaft  105  is supported by shaft hangers  48  and  104  having press-fit sintered bearings  34  and  100 . 
     Also mounted on drive shaft  105  are spur gear  32  and timing belt pulley  30 , each of which contains a press-fitted one-way clutches (not visible in this view). Each of these clutches is mounted such that their power-transmitting direction is opposite from each other. Spacers  40  and  44  maintain gear  32  and timing belt pulley  30  in their proper position on the shaft. 
     Engaged with spur gear  32  is spur gear  41 , fixedly mounted on output shaft  98 . Also fixedly mounted on the same output shaft  98  is timing belt pulley  42  and flywheel  80 . Output shaft  98  is supported at either end by shaft hangers  97  and  96 , each with press-fit sintered bearings  95  and  94 . 
     As the cord moves from left to right, the drum  33  will rotate counter-clockwise as viewed from the front of the machine. If the one-way clutch mounted to the spur gear  32  is oriented such that it transmits power when the drive shaft  105  rotates counter-clockwise as viewed from the front of the machine, then the spur gear  32  will transmit power to its mating spur gear  41  which will then cause the output shaft to rotate in the opposite direction, namely clockwise. 
     When the cord reverses direction, the drum  33  and attached drive shaft  105  also reverse direction to a clockwise direction. Since the one-way clutch attached to the spur gear  32  is now in the free-wheeling condition, the drive shaft will not transmit power to the spur gear  32 . Instead, the one-way clutch attached to the timing belt pulley  30  will now cause the timing belt pulley  30  to transmit power to its mating timing belt pulley  41  through the timing belt  73 . In the reverse direction now being described, the timing belt then causes the output shaft  98  to rotate in the same clockwise direction as the drive shaft  105 . 
     Thus, regardless of the direction that the drum  33  and its connected input shaft  105  rotate, the output shaft  98  will always rotate in the same direction, namely clockwise. Conversely, by reversing the direction of both one-way clutches, the direction of rotation of the output shaft would then be counter-clockwise. 
     As the cord  68  leaves the drum  33 , it passes around a grooved pulley  110  where it is constrained by the rubber idler  109  mounted on arm  82  pivoted at point  59  and tensioned by spring  83  anchored at point  84 . Pulley  110  is held in place on base  21  by shoulder screw  87  and sintered bearing  88 . Cord  68  then passes through port  70  as it moves in the direction of the user who is pulling on it during the power stroke. 
     As the user reverses direction of the cord, the rotational direction of the drum  33  will change, but the rotation direction of the output shaft and flywheel  80  will remain the same. 
     The flywheel may be made of molded or machined construction. As depicted, the flywheel is constructed from a mass  24  having the form of an annular cylinder and attached to a disk  23  that is supported on the output shaft by a hub  93  (not visible in this view). Only partially visible are two of a multiplicity of vanes  78  that provide a speed-dependent retarding force due to their generation of turbulent air flow. 
     A set of two slotted arms  46  mounted on hinges  71  and brackets  52  are forced together by a tensioning spring  28 . Both ends of the spring  28  are attached to bushings  49  that slide in slots (not shown) in the arms  46  on low-friction washers  51 . The spring  28  is engaged by a u-shaped bracket  43  that in turn is fixedly attached to control arm  39  and slotted sliding bracket  47 . Motion of bracket  47  and hence control arm  39  is constrained to left and right by shoulder screws  45 . Knob  57  on the end of arm  39  thus provides control on the force applied to the friction pads  53  by means of changing the lever arm of arms  46 . As the control knob  57  is moved to the right, the force pulling the arms  46  together, and hence the force applied to the pads  53  increases. The bracket  50  dampens vibrations in arm  46  and retrains them from moving upwards against the influence of rotating flywheel  80 . 
     If the flywheel  80  is formed as a single molded or machined piece rather than from a separate disk  23  and annular cylinder  24  as shown, then the friction pads  53  may instead bear directly on the annular cylinder  24  or on an annular disk attached to the molded flywheel, similar to that depicted in FIG.  10 . 
     A magnet  25  is held in place by a sliding bracket  26 . Motion of bracket  26  is constrained to a left and right direction by the shoulder screws  92  and the slots  60 . The magnet  25  is mounted so that the disk  23  passes with clearance between its two poles  90 . The motion of magnet mounting bracket  26  is controlled by control arm  27  and knob  58 . Bracket  27  is constrained to a small angle of rotation in the plane of the base plate  1  around pivot  91  by shoulder screw  55  and the slot  61 . Moving the knob  58  to the right will move the magnet  25  away from the disk portion  23 , thereby intercepting fewer lines of magnetic force and reducing the eddy current generated retarding force. 
     FIG.  3 . is a cross-sectional view of the spur gear train consisting of drive gear  32  and driven gear  41 . Drive gear  32  is attached to a one-way clutch  31  and the assembly is mounted on drive shaft  105  such that when the drive shaft rotates in one direction the drive gear will transmit power to mating gear  41  and hence to the output shaft  98 , but will not transmit power when rotating in the other direction. Shafts  105  and  98  are supported by shaft hangars  104  and  96 , respectively. The arrows indicate the direction of rotation when the gear  32  is transmitting power. 
     FIG. 4 is a cross sectional view of the timing belt and pulley train, consisting of drive pulley  30 , driven pulley  42  and timing belt  73 . Drive pulley  30  is attached to a one-way clutch  99  and the assembly is mounted on drive shaft  105  such that when the drive shaft rotates in the opposite direction from that engaging the spur gear train, the drive gear will transmit power through the timing belt  73  to the other pulley  42  and hence to the attached output shaft  98 . The arrows indicate the direction of rotation when the timing belt pulley  30  is transmitting power. 
     FIG. 5 is a cross-sectional view of the drum  33 , showing one of the rimmed end caps  56  and cord  68  wrapped around the drum. The end caps  56  are fixedly mounted on drive shaft  105  by hubs  85  with set-screws (not shown in this view). 
     FIG. 6 is a rear-view of a portion of the machine, showing the disk portion  23 , disk mounting hub  93 , drive shaft  98 , annular cylinder  24 , retardant vanes  78 , friction pads  53  and magnet  25 . Friction arms  46  having slots  76 , spring mounting bushings  49 , washer  51  and hinge  71  are supported by brackets  52  mounted to base  1 . Control bracket  50  is attached to base  21  and prevents upward motion of the arms  46 . Control of the spring bushing  49  is effected by bracket  43  and control arm  39 , depicted in greater detail in FIG.  9 . 
     Magnet  25  with poles  90  is attached to bracket  26  and held in place to base  21  by shoulder screws  92  that permit left and right movement. Control arm  27  moves bracket  26 , thereby moving the magnet closer or farther from the disk  23 . 
     FIG. 7 is a cross-sectional view of a portion of the machine, showing the grooved pulley  38  with integral sintered brass bearing  101  and cord  68  passing around grooved edge  103 . The pulley is mounted to base  21  by a shoulder screw  102 . Pressing against cord  68  in groove  103  is rubber idler  35  with sintered bearing  107  and held onto a spring-loaded bracket  36  by shoulder screw  106 . 
     FIG. 8 is a cross sectional view of one of the cord ports  69  consisting of mounting bracket  108  that secures port  68  to base plate  21 . The throat of port  69  (i.e. facing away from the machine) is larger than that on the interior side to allow for variations in angle of approach of the cord  68 . The port can be made of any low friction material, such as nylon or Teflon. 
     FIG. 9 is a cross-sectional view of a portion of the machine showing the control bracket  43  for the friction pad support arm tensioning spring  28 . The bracket  43  is attached to control arm  39 . The structure depicted moves in the directions indicated to vary the tensioning force applied to the friction pads. 
     FIG. 10 is a top view of a portion of the machine showing an alternate construction of the flywheel  80 . In this construction, the flywheel is a single molded or machined piece having a disk-like central portion  75 , vanes  78  and an annular cylindrical portion  72 . Attached to the flywheel is an annular disk  74  that is used in the same way as depicted in FIG. 2 for frictional and magnetic retarding force generation. 
     FIG. 11 is a cross-sectional view of a portion of the machine showing several air vanes attached to the flywheel  80 . In this construction, vanes  78  are attached to the outer periphery of the flywheel disk  23  next to the flywheel mass  24 . The vanes  78  are oriented to intercept the air flow when the flywheel rotates in the direction indicated by the arrow, thereby creating a turbulent, speed-dependent air flow that further contributes to the retarding forces. 
     FIG. 12 is an end view of the paddle shaft  65 , showing the spring clasp  67  that is fixedly mounted to shaft  65  and is used to removably attach the cord  68 . A loop in cord  68  is created and held fast by turns of thread  66 . 
     FIG. 13 is an end view of a portion of the machine showing mechanical screw connector  18  for attaching base plate  21  to nut  112  that is held in place to support bracket  111  by plate  113 . Support bracket  111  in turn is fixedly attached to wall support  16 . 
     Other variants and combinations of the described mechanical components are possible, especially in the mounting and control of movable components such as the friction pads and magnet, all without departing from the scope of the invention. 
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