Patent Publication Number: US-2013228995-A1

Title: Planetary gear mechanism for a bicycle

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of and claims priority from U.S. non-provisional patent application Ser. No. 12/660,861 filed Mar. 5, 2010. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a planetary gear mechanism for a bicycle, and more particularly to a planetary gear mechanism comprising a first planetary mechanism connected coaxially in series to a second planetary mechanism, which second planetary mechanism is connected coaxially in series to a third planetary mechanism, the second planetary mechanism output is a step up in speed from the first planetary mechanism output, the third planetary mechanism output is a step up in speed from the second planetary mechanism output. 
     BACKGROUND OF THE INVENTION 
     It is known that bicycles may have internal geared transmissions located in rear hubs. For example, the Shimano Company provides a Shimano Nexus™ eight speed transmission. The transmission comprises an internal geared planetary transmission which is located in a bicycle rear wheel hub. Rohloff GmbH of Germany provides a fourteen speed planetary gear transmission, also for use in a bicycle rear wheel hub. 
     The prior art transmissions have common disadvantages including heavy weight and that each is located in the bicycle rear wheel hub. 
     Also representative of the art is U.S. Pat. No. 6,468,178 (2002) to Mohtasham which discloses a rear wheel hub and chainless drive train gear assembly for use on a bicycle having an axle bracket fixed to the frame of the bicycle, a spindle extending axially through the axle bracket and left and right pedal crank arms for rotating the spindle upon application of a pedaling force. A primary drive gear fitted to the spindle drivingly engages carrier gears which operate a planet gear cage housing and a multiple planetary gear and sun gear arrangement according to various gear ratios determined by selective operation of a clutch assembly. Planetary gear groups each include an integral set of planetary gears of varying size which mesh with corresponding sun gear rings. Operation of the clutch assembly serves to selectively engage pawl stops with a corresponding sun gear ring, thereby engaging the corresponding sun gear ring with one of the planetary gears of the planetary gear groups according to a selected gear ratio. The planetary gear groups drive an annular gear ring and an associated annular needle bearing which, in a forward clockwise rotation, engages the hub body to rotate the rear bicycle wheel. Reverse rotation of the annular gear, in a counter-clockwise rotation, results in a freewheeling of the drive train gear assembly relative to the hub body. 
     What is needed is a planetary gear mechanism comprising a first planetary mechanism connected coaxially in series to a second planetary mechanism, which second planetary mechanism is connected coaxially in series to a third planetary mechanism, the second planetary mechanism output is a step up in speed from the first planetary mechanism output, the third planetary mechanism output is a step up in speed from the second planetary mechanism output. The present invention meets this need. 
     SUMMARY OF THE INVENTION 
     The primary aspect of the invention is to provide a planetary gear mechanism comprising a first planetary mechanism connected coaxially in series to a second planetary mechanism, which second planetary mechanism is connected coaxially in series to a third planetary mechanism, the second planetary mechanism output is a step up in speed from the first planetary mechanism output, the third planetary mechanism output is a step up in speed from the second planetary mechanism output. 
     Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings. 
     The invention comprises a planetary gear mechanism comprising an input member ( 22 ), a first carrier ( 100 ) having a first carrier first pinion gear (P 1 ) and a first carrier second pinion gear (P 2 ), each journalled to the first carrier, the first carrier rotationally fixed to the input member ( 22 ), the first carrier second pinion gear (P 2 ) in meshing engagement with sun gear S 1  which is engaged with a first brake (Brake  1 ), a second carrier ( 200 ) having second carrier first pinion gear (P 4 ) and a second carrier second pinion gear (P 5 ), each pinion gear (P 4 ) and (P 5 ) is journalled to the second carrier, the second carrier engaged with a second brake (Brake  2 ), a first ring gear (R 1 ) in meshing engagement with the first carrier first pinion gear (P 1 ), a second ring gear (R 2 ) in meshing engagement with the second carrier first pinion gear (P 4 ), the first ring gear and second ring gear comprise a ring gear member ( 400 ), a third carrier ( 300 ) having a third carrier first pinion gear (P 6 ) and a third carrier second pinion gear (P 7 ), each pinion gear (P 6 ) and (P 7 ) is journalled to the third carrier, a third ring gear (R 3 ) in meshing engagement with the second carrier second pinion gear (P 5 ), the third ring gear fixedly connected to the third carrier ( 300 ), a fourth ring gear (R 4 ) engaged with a third brake (Brake  3 ) and in meshing engagement with the third carrier first pinion gear (P 6 ), a first one-way clutch (CL 1 ) engaged between the first carrier ( 100 ) and the ring gear member ( 400 ), a second one-way clutch (CL 2 ) engaged between the second carrier ( 200 ) and the ring gear member ( 400 ), a third one-way clutch (CL 3 ) engaged between the third carrier ( 300 ) and the fourth ring gear (R 4 ), and an output member ( 44 ) in meshing engagement with the third carrier second pinion gear (P 7 ). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and form a part of the specification, illustrate preferred embodiments of the present invention, and together with a description, serve to explain the principles of the invention. 
         FIG. 1  is a cross-sectional schematic view of the transmission. 
         FIG. 2  is a table of gear ratios. 
         FIG. 3  is a table of brake and clutch positions for each gear. 
         FIG. 4  is a partial side view of a bicycle. 
         FIG. 4A  is a side view of a belt. 
         FIG. 5  is a cross-sectional view of the transmission. 
         FIG. 6  is a perspective view of a brake. 
         FIG. 7  is a cross-section at  7 - 7  in  FIG. 5 . 
         FIG. 8  is a cross-section at  8 - 8  in  FIG. 5 . 
         FIG. 9  is a cross-section at  9 - 9  in  FIG. 5 . 
         FIG. 10  is a cross-section at  10 - 10  in  FIG. 5 . 
         FIG. 11  is a cross-section at  11 - 11  in  FIG. 5 . 
         FIG. 12  is a cross-section at  12 - 12  in  FIG. 5 . 
         FIG. 13  is a cross-section at  13 - 13  in  FIG. 5 . 
         FIG. 14  is an exploded view of the transmission. 
         FIG. 15  is a detail of  FIG. 14 . 
         FIG. 16  is a detail of  FIG. 14 . 
         FIG. 17  is a detail of  FIG. 14 . 
         FIG. 18  is a detail of  FIG. 14 . 
         FIG. 19  is a detail of  FIG. 14 . 
         FIG. 20  is a detail of  FIG. 14 . 
         FIG. 21  is an end view of shift cam ring  600 . 
         FIG. 22  is a side view of the shift cam ring  600 . 
         FIG. 23  is an end view of shift cam ring  600 . 
         FIG. 24  is a perspective view of shift cam ring  600 . 
         FIG. 25  is an end view of shift cam ring. 
         FIG. 26  is a side view of the shift cam ring. 
         FIG. 27  is an end view of shift cam ring. 
         FIG. 28  is a perspective view of the shaft cam ring. 
         FIG. 29  is a perspective view of a shift dog. 
         FIG. 30  is a plan view of a shaft dog. 
         FIG. 31  is a side view of a shift dog. 
         FIG. 32  is a perspective view of a shift dog. 
         FIG. 33  is a perspective view of a shift dog. 
         FIG. 34  is a perspective view of a shift dog. 
         FIG. 35  is a perspective view of a shift dog. 
         FIG. 36  is a perspective view of a shift dog. 
         FIG. 37  is a detail of  FIG. 18 . 
         FIG. 38  is a detail of  FIG. 19 . 
         FIG. 39  is a detail of  FIG. 19 . 
         FIG. 40  is a detail of  FIG. 6 . 
         FIG. 41  is a detail of  FIG. 6 . 
         FIG. 42  is a detail of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  is a cross-sectional schematic view of the transmission. The invention generally comprises a planetary gear mechanism having an input member connected to a first planetary mechanism, the first planetary mechanism connected coaxially in series to a second planetary mechanism, which second planetary mechanism is connected coaxially in series to a third planetary mechanism, the second planetary mechanism output is a step up in speed from the first planetary mechanism output, the third planetary mechanism output is a step up in speed from the second planetary mechanism output, and the third planetary mechanism connected to an output member. 
     The proposed transmission is preferably located in a bicycle bottom bracket, see  FIG. 4 . Crank arms (see  FIG. 4 ) are attached to each end of the input member  22 . Carrier  100  is rigidly connected to the member  22 , and thereby rotates with member  22 . Carrier  100  further comprises a carrier pin or shaft  101 . 
     Three planet pinion gears are journalled to pin  101 , namely, P 1 , P 2 , P 3 . Each pinion gear P 1 , P 2 , P 3  rotates together at the same speed about pin  101 . Pinions P 1 , P 2 , P 3  preferably comprise a single gear component having three different diameters, thereby describing gears P 1 , P 2 , P 3 . 
     Ring gear member  400  comprises a first ring gear R 1  and a second ring gear R 2 . R 1  is in meshing connection with pinion P 1 . Sun gears S 1  and S 2  are in meshing engagement with pinion gears P 2  and P 3  respectively. Sun gears S 1  and S 2  are reaction gears with brake  1  and brake  4 . Brake  1  and brake  4  are connected to a bicycle frame (see  FIG. 4 ). The rotational speed of pinion P 1  is a function of whether brake  1  or brake  4  is engaged or disengaged, see  FIG. 3 . 
     Second planetary mechanism has two pinion gears P 4  and P 5  fixedly connected to a carrier shaft  201 , and therefore gears P 4  and P 5  rotate together with shaft  201 . Ring gear R 2  is in meshing engagement with pinion gear P 4 . Carrier shaft  201  is journalled to carrier  200 . Carrier  200  is a reaction member with and is engaged with brake  2 . 
     A third ring gear R 3  is fixedly attached to the input member of the third planetary mechanism which is carrier  300 . The third planetary mechanism pinion gear P 6  is in meshing engagement with fourth ring gear R 4 . Ring gear R 4  is engaged with brake  3  and one-way clutch CL 3 . One-way clutch CL 3  is engaged with carrier  300  and ring gear R 3 . 
     Pinion gear P 6  and P 7  are each journalled to carrier pin  301 , and therefore rotate together. Pinion gears P 6  and P 7  preferably comprise a single gear component having two different diameters and hence define gears P 6  and P 7 . Pinion gear P 7  is in meshing engagement with output sun gear S 3 . Output sun gear S 3  is fixedly attached to output sprocket  44 . 
     All planetary carrier mechanisms are numbered as a function of increasing speed of their respective output members, that is, the third planetary mechanism causes rotation of sprocket  44 , which in turn rotates faster than the relative rotation of the second planetary mechanism, which in turn rotates faster than the relative rotation of the first planetary mechanism when each planetary mechanism is operating with all one-way clutches dis-engaged, see  FIG. 3  gear  12 . Further, each planetary carrier mechanism is coaxial with the others and each of the planetary carrier mechanisms are connected in series. 
     Each planetary mechanism further comprises a one-way clutch, namely, CL 1 , CL 2 , CL 3 . When engaged each one-way clutch locks each respective planetary carrier mechanism with a gear ratio of 1:1. 
     A low-friction bushing  50  is disposed between input member  22  and sun gear S 1 . A low-friction bushing  51  is disposed between sun gear S 1  and sun gear S 2 . A low-friction bushing  52  is disposed between sun gear S 3  and input member  22 . 
     For ease of reference, the following assemblies may also be generally referred to as the first planetary mechanism, second planetary mechanism and third planetary mechanism.
         First planetary mechanism: carrier  100 ; pinion gears P 1 , P 2 , P 3 ; shaft  101 ; one-way clutch CL 1 ; ring gear R 1     Second planetary mechanism: carrier  200 ; pinion gears P 4 , P 5 ; shaft  201 ; one-way clutch CL 2 ; ring gear R 2 ; ring gear R 3     Third planetary mechanism: carrier  300 ; pinion gears P 6 , P 7 ; shaft  301 ; one-way clutch CL 3 ; ring gear R 4         

       FIG. 2  is a table of gear ratios. Planetary mechanism (carrier)  100  has gear ratios 1, 1.33, and 1.76. Planetary mechanism  200  has gear ratios 1 and 1.15. Planetary mechanism  300  has gear ratios 1 and 2.30. The combined overall gear ratio is noted in column i. 
     The inventive transmission results in very linear steps between each gear ratio averaging approximately 15%. This allows predictable power requirements for each shift as a rider shifts up and down through the gears. 
     Since the inventive transmission increases the speed of the output member front sprocket  44  compared to the speed of input member  22 , the ratio between the front sprocket  44  and a rear sprocket  36  installed on the rear wheel  34  is adjusted accordingly. Hence, for example, front sprocket  44  has  32  teeth and the rear sprocket has  42  teeth. The number of teeth on the front sprocket and rear sprocket may be adjusted as may be required by a user. 
       FIG. 3  is a table of brake and clutch positions for each gear. For example, first gear, the slowest gear, has all planetary mechanisms  100 ,  200 ,  300  at gear ratio 1:1 and all clutches CL 1 , CL 2 , CL 3 , are locked. In first gear all brakes  1 ,  2 ,  3 ,  4  are disengaged. 
     The inventive transmission is about 20%-30% lighter than prior art transmissions. Another advantage of the transmission is better clearance in a bicycle frame since front sprocket is much smaller. 
     The following is provided as an example and is not intended to limit the design parameters which may be used for each component. The diameters are in mm. 
     
       
         
           
               
               
               
               
               
             
               
                   
                   
               
               
                   
                 Pinion Gear 
                 Ring Gear 
                 Diameter 
                 No. of Teeth 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 P1 
                 NA 
                 13.6 
                 17 
               
               
                   
                 P2 
                 NA 
                 18.4 
                 23 
               
               
                   
                 P3 
                 NA 
                 10.4 
                 13 
               
               
                   
                 P4 
                 NA 
                 11.2 
                 14 
               
               
                   
                 P5 
                 NA 
                 13.6 
                 17 
               
               
                   
                 P6 
                 NA 
                 16 
                 20 
               
               
                   
                 P7 
                 NA 
                 10.4 
                 13 
               
               
                   
                 NA 
                 R1 
                 57.6 
                 72 
               
               
                   
                 NA 
                 R2 
                 45.6 
                 57 
               
               
                   
                 NA 
                 R3 
                 48 
                 60 
               
               
                   
                 NA 
                 R4 
                 52.8 
                 66 
               
               
                   
                   
               
            
           
         
       
     
       FIG. 4  is a partial side view of a bicycle. The inventive transmission will be preferably installed in bottom bracket  20 . Crank arms  41  are connected to input member  22 . A rider&#39;s feet engage pedals  42 . A flexible drive member  50  is engaged between sprocket  44  and rear sprocket  36 . Rear sprocket  36  is connected to wheel  34 . A rider (not shown) sits on seat  24 . Wheel  34 , crank arms  41 , bottom bracket  20 , seat  24  are connected to bicycle frame  30 , known in the art. Flexible drive member  50  may comprise a belt or chain. 
       FIG. 4A  is a side view of a belt. Belt  50  comprises a body  98 . Teeth  99  extend from belt body  98 . Teeth  99  extend across the width of the belt and normal to a longitudinal or endless direction. This style of belt is also referred to as a toothed, cogged or synchronous belt as is known in the automotive arts. 
       FIG. 5  is a cross-sectional view of the transmission. Planetary carrier mechanisms  100 ,  200 ,  300  are shown connected in series within bottom bracket or a transmission housing  20 . Carrier  100  is fixedly connected to input member  22 . Carrier  200  is rotatable about member  22  on bearings  1002 ,  1003 . Carrier  300  is rotatable about member  22  on bearings  1003 ,  1004 ,  1005 . Member  22  rotates within bottom bracket  22  on bearing  1001 . Member  22  may be hollow to reduce weight of the transmission. 
       FIG. 6  is a perspective view of a brake. The figure shows sun gears S 1  and S 2 . Brake  1  engages sun gear S 1 . Brake  4  engages sun gear S 2 . The brake mechanisms for shifting the planetary transmission ensures that a compound planetary set cannot engage two gear sets at once and thus become locked. The proposed mechanism is located in the proximity of the sun gears of a compound planetary gear set but could easily be applied to breaking or shifting of a compound planetary gear set with multiple ring gears. 
     The mechanism comprises two levers ( 701 , 702 ) ( 801 , 802 ) configured in a manner such that one physically interferes or prohibits the other lever from engaging its sun gear while the other is engaged with its respective sun gear. When one sun gear is stopped by a brake, the other sun gear will be forced to rotate relative to the stopped sun gear. In the case of a compound set with more than two sun gears, each sun gear will rotate at a different speed than the others. However, if each brake is applied to each sun at the same time the transmission would lock and not rotate. Each lever limits the rotation or brakes their respective sun gear by engaging with a stepped area of the sun gear such that the lever engages the face of a step and limits the rotation of the sun in one direction. The mechanism could engage the sun gears from radially outside or radially inside depending on the configuration required. 
     The shift levers are actuated by a roller  601  that engages a profiled surface  601 B. As the profile changes, the levers are moved to either engage as a brake or open and allow free movement of the respective sun gear. 
     Each brake  1  and brake  4  comprises a shift member  701  and  801  respectively. Shift cam  600  engages shift rollers  601 . Each shift roller  601  engages a compliant pad or member  602 . 
     Each shift member  701  and  801  are pivotally mounted to end cap  205 . Each end  702 ,  802  of each shift member  701 ,  801  engages sun gear teeth  210 ,  211  respectively. 
     In operation, shift cam  600  rotates enabling each shift roller  601  to move radially outward, thereby releasing each complaint pad  602 . Releasing each complaint pad  602  enables each shift member  701 ,  801  to pivot due to the biasing caused by springs  7001  thereby causing shift members  701 ,  801  to engage sun gear teeth  210 ,  211  respectively. Engagement of each shift member  701 ,  801  with the respective sun gear teeth stops rotation of the respective sun gear in a clockwise direction CW. 
     The reaction force caused by engagement of the shift members  701 ,  801  with teeth  210 ,  211  is transmitted through each shift member  701 ,  801  to the end cap  205  and thereby to the bicycle frame. 
     Brake  2  and brake  3  are identical in description and operation to brake  1  and brake  4 . 
       FIG. 7  is a cross-section at  7 - 7  in  FIG. 5 . Pinion gear P 7  has a meshing engagement with sun gear S 3 . Brake  3  shift member  601  engages teeth  213 . Teeth  213  are disposed on an outer perimeter of ring gear R 4 . In the instant embodiment there are three sets of pinion gears P 6 , P 7 . 
       FIG. 8  is a cross-section at  8 - 8  in  FIG. 5 . Pinion gear P 6  is journalled to pin  301 . 
       FIG. 9  is a cross-section at  9 - 9  in  FIG. 5 . Pinion gear P 5  is journalled to pin  201 . Pinion gear P 5  has a meshing engagement with ring gear R 3 . Brake  2  comprises shift member  901  which engages teeth  212 . Teeth  212  are disposed on an outer perimeter of carrier  200 . In the instant embodiment there are three sets of pinion gears P 4 , P 5 . 
       FIG. 10  is a cross-section at  10 - 10  in  FIG. 5 . Pinion gear P 4  has a meshing engagement with ring gear R 2 . 
       FIG. 11  is a cross-section at  11 - 11  in  FIG. 5 . Pinion gear  1  and P 2  are journalled to pin  101 . Pinion gear P 1  has a meshing engagement with ring gear R 1 . In the instant embodiment there are four sets of pinion gears P 1 , P 2 , P 3 , each journalled to a pin  101 . 
       FIG. 12  is a cross-section at  12 - 12  in  FIG. 5 . Sun gear S 1  has a meshing engagement with pinion gear P 2 . Sun gear S 2  has a meshing engagement with pinion gear P 3 . 
       FIG. 13  is a cross-section at  13 - 13  in  FIG. 5 . Pinion gear P 3  has a meshing engagement with sun gear S 2 . 
       FIG. 14  is an exploded view of the transmission. Axis A-A is the axis of rotation. A belt engages sprocket  44  and a rear hub, see  FIG. 4 . 
     Transmission case  20  may be inserted into a bottom bracket in a cartridge manner. Namely, case  20  is inserted into a cylindrical receiver, the cylindrical receiver comprising the bottom bracket. In an alternate embodiment, the seat stay, seat tube and chain stays can be attached directly to case  20 , for example by welding, thereby making the transmission case  20  the bottom bracket. The internals for the transmission would not be changed for either embodiment.  FIG. 15  is a detail of  FIG. 14 . Shift cables  1 ,  2  (known in the art) are connected to the transmission through adjusting grommets  81  and  82  respectively. Shift cables  1 ,  2  are typically connected to shift mechanisms on a bicycle handlebar for example (not shown). Grommets  81 ,  82  are threadably engaged with case  20  at hole  21 ,  22  respectively. Bearing  1006  is disposed between sun gear S 3  and case  20 . 
     Sprocket  44  comprises holes  440  which receive belt teeth (not shown). Further, holes  440  allow dirt and debris thrown up by the wheels to drop through the sprocket, thereby allowing the sprocket to be self cleaning. This prevents debris from accumulating between the belt and the sprocket which would otherwise hinder performance. 
     Bushings  1007  and  1008  engage bearings  1005  and  1006  respectively. 
     Spacer  800  is disposed between bearing  1004  and bearing  1003 . Spacer  801  is disposed between bearing  1003  and bearing  1002 . 
     Nuts  42  attach sprocket  41  to a spider  51  on sun gear S 3 . 
       FIG. 16  is a detail of  FIG. 14 . Each cable  1 ,  2  is fastened to receiver  206 . Receiver  206  is fixed to an end of shift cam ring  600 . By extending or retracting each cable  1 ,  2  the shift cam ring is thereby rotated within the transmission case  20 . The range of rotational movement of shift cam ring  600  is approximately 130°. 
     Surface  601 A engages roller  603  which engages shift dog  702 A and  802 A. Surface  602 A engages roller  603  which engages compliant member  601  and thereby shift dog  720 ,  721 . Surface  603 A engages roller  603  which engages shift dog  702 B,  802 B. Surface  601 B engages roller  603  which engages shift dogs  820 ,  821 . 
     Shift dogs  720  and  721  engage teeth  212 . Shift dogs  820 ,  821  engage teeth  213 . 
     Springs  8001 A,  8001 B,  8001 C,  8001 D bias each shift dog  720 ,  721 ,  820 ,  821  into engagement with teeth  212 ,  213  respectively. Biasing the shift dogs causes the rollers  603  to maintain contact with cam surfaces  601 A,  602 A,  603 A and  601 B. 
       FIG. 17  is a detail of  FIG. 14 . Bushing  1010  engages bearing  1002 . Shift dogs  701 A,  801 A engage teeth  211 . Shift dogs  701 B,  801 B engage teeth  210 . 
       FIG. 18  is a detail of  FIG. 14 .  FIG. 19  is a detail of  FIG. 14 .  FIG. 20  is a detail of  FIG. 14 . Threaded ring  23  attaches end  205  to case  20 . Bushing  1009  engages bearing  1001 . Cap  43  retains crank arms (not shown) to axle shaft  22 . 
     Springs  7001 A,  7001 B,  7001 C,  7001 D bias each shift dog  701 A,  801 A,  701 B,  801 B into engagement with teeth  211 ,  210  respectively. 
       FIG. 21  is an end view of shift cam ring  600 . Shift cam ring  600  comprises member  600 A and  600 B for ease of manufacture and assembly. Member  600 A is cylindrical. Shift cam ring  600  is disposed in the transmission and is radially outermost from the planetary gear sets  100 ,  200 ,  300  and within the transmission case  20 , see  FIG. 5 . 
       FIG. 22  is a side view of the shift cam ring  600 . Member  600 A is shown having a lattice structure in order to reduce weight while maintaining strength. Shift cam ring  600  is rotatable within transmission case  20 . 
       FIG. 23  is an end view of shift cam ring  600 . 
       FIG. 24  is a perspective view of shift cam ring  600 . Each shift circumferential surface  601 A and  602 A is disposed at opposite ends of member  600 A. Each surface  601 A and  602 A comprises a radially inward surface of the shift cam ring  600 . 
     Circumferential surface  601 A comprises a plurality of features each having a differing slope or radius. A radial position of rollers  603  engaging compliant member  601  thereby shift dog  702 A and  802 A is each determined according to which surface of  601 A is engaging rollers  603 . 
     Circumferential surface  602 A comprises a plurality of features each having a differing slope or radius. A radial position of rollers  603  engaging compliant member  601  and thereby shift dog  720  and  721  is each determined according to which surface of  602 A is engaging rollers  603 . 
     Circumferential surface  603 A comprises a plurality of features each having a differing slope or radius. A radial position of rollers  603  engaging compliant member  601  and thereby shift dog  702 B and  802 B is each determined according to which surface of  603 A is rollers  603 . 
     Circumferential surface  601 B comprises a plurality of features each having a differing slope or radius. A radial position of rollers  603  engaging compliant member  601  and thereby shift dog  820  and  821  is each determined according to which surface of  601 B is engaging rollers  603 .  602 . Each surface  603 A and  601 B comprises a radially inward surface of the shift cam ring  600 . 
       FIG. 25  is an end view of shift cam ring. Shift cam ring  600  comprises member  600 A and  600 B for ease of manufacture and assembly. Member  600 B is cylindrical. 
     Shift cam ring  600  is disposed in the transmission outermost from the planetary gear sets and within the transmission case  20 , see  FIG. 5 . The transmission is shifted by rotation of the shift cam ring  600  through extension and retraction of shift cables  1 ,  2  see  FIG. 14 . 
       FIG. 26  is a side view of the shift cam ring. 
       FIG. 27  is an end view of shift cam ring. 
       FIG. 28  is a perspective view of the shaft cam ring. Member  600 B comprises extended members  601 B and  602 B. each member  601 B and  602 B engages a cooperating portion of  600 A, namely, slots  603 A and  604 A. 
       FIG. 29  is a perspective view of a shift dog. Portion  7002  receives member  601 . Member  601  comprises a resilient material which can be compressed and will rebound when the compression is released. 
     Each shift dog  701 ,  801  and  702 ,  802  is identical to the others. For each shift dog  702 ,  802  a member  602  is fixed to portion  7002 . 
       FIG. 30  is a plan view of a shift dog. Receiving portion  760  receives a member  601 . Each shift dog  720 ,  820 ,  721 ,  821  is identical to the others. For each shift dog  720 ,  820 ,  721  and  821  a member  602  is fixed to portion  760 . 
       FIG. 31  is a side view of a shift dog. Receiving portion  760  receives a member  601 . 
       FIG. 32  is a perspective view of a shift dog. Shift dog  820  is pivotally mounted to a dog mount  840 . Dog mount  840  is fastened to case  20  (not shown). A roller  603  is disposed between surface  601 B and member  601 . 
       FIG. 33  is a perspective view of a shift dog. Spring  8001 A biases shift dog  820  toward teeth  213 . 
       FIG. 34  is a perspective view of a shift dog. Shift dog  840  is fastened to case  20 . 
       FIG. 35  is a perspective view of a shift dog. Shift dog  720  is pivotally mounted to dog mount  740 . Spring  8001 A biases shift dog  720  toward teeth  212 . A roller  603  is disposed between a surface  602 A and a member  601 . 
       FIG. 36  is a perspective view of a shift dog. Dog mount  740  is fastened to case  20 . 
       FIG. 37  is a detail of  FIG. 18 . One way clutch dog  920  is pivotally mounted to carrier  300 . Spring  921  biases one way clutch dog  920  against teeth  213  of ring gear R 4 . One way clutch dog  920  allows a reverse rotational movement of ring gear R 4  by disengaging teeth  213 . Depending upon the particular gear that is engaged, the one way clutch is the “free wheel” feature of the transmission which allows a rider to stop pedaling and coast. A second identical one way clutch dog is disposed opposite that shown in  FIG. 37 , thereby forming a pair of one way clutch shift dogs. 
       FIG. 38  is a detail of  FIG. 19 . One way clutch dog  930  is pivotally mounted to carrier  200 . Spring  931  biases one way clutch dog  930  against teeth  401  of ring gear R 1 . One way clutch dog  930  prevents a reverse rotational movement of ring gear R 1  by engaging teeth  401 . One way clutch dog  930  allows a forward rotational movement of ring gear R 1  relative to carrier  200  by disengaging from teeth  401 . Depending upon the particular gear that is engaged, the one way clutch is the “free wheel” feature of the transmission which allows a rider to stop pedaling and coast. A second identical one way clutch dog is disposed opposite that shown in  FIG. 38 , thereby forming a pair of one way clutch shift dogs. 
       FIG. 39  is a detail of  FIG. 19 . One way clutch dog  901  is pivotally mounted to carrier  100 . Spring  902  biases one way clutch dog  901  against teeth  401  of ring gear R 1 . One way clutch dog  901  allows forward rotational movement of ring gear R 1  relative to carrier  100  by disengaging teeth  401 . One way clutch dog  901  prevents a reverse rotational movement of ring gear R 1  by engaging teeth  401 . Depending upon the particular gear that is engaged, the one way clutch is the “free wheel” feature of the transmission which allows a rider to stop pedaling and coast. A second, identical one way clutch dog is disposed opposite that shown in  FIG. 39 , thereby forming a pair of one way clutch shift dogs. 
       FIG. 40  is a detail of  FIG. 6 . Roller  603  engages surface  601 A, thereby pressing upon member  602  which in turn presses shift dog  701 , thereby disengaging shift dog  702  from teeth  210 . 
     Use of resilient member  602  allows the shift cams to rotate while the shift dog is still engaged with the teeth. The cams can rotate and compress the resilient member while the dog is engaged with the teeth and compressively loaded. When a bicycle rider pedals a bicycle, the torque input into the transmission is cyclic as the input shifts from one pedal to the other. Even for the very best cyclists, the input torque drops to zero or near zero during this transfer of input from one pedal the other. Due to the cyclic input loading of a pedaling bicycle rider, when the torque momentarily approaches or reaches zero, the force on the shift dog/tooth interface also drops to zero or near zero, it is at this moment that the shift dog will rotate out of engagement due to the resilient member&#39;s desire to return to a relaxed state. This gives the rider the impression of being able to shift under load while in actuality the shift occurs under near no load conditions. 
     A duplicate set of shift dogs as described in this  FIG. 38  are likewise mounted in area “A”. All shift dogs  701 ,  702 ,  801 ,  802  are pivotally mounted to member  205  at mounting portions  2051 ,  2052 ,  2053 ,  2054  respectively. 
       FIG. 41  is a detail of  FIG. 6 . Shift dog  701  is allowed to move radially outward by a movement of roller  601 , which roller follows surface  601 A as surface  601 A is rotated during a shift by a rider. Shift dog  702  is shown fully engaged with teeth  210 . Shift dog  701  cooperatively engages protrusion  803 , which in turn allows shift dog  702  to pivot and thereby engage teeth  210 . Spring  7001 A urges shift dog  801  into engagement with roller  601 , and thereby said roller  601  into surface  601 A. Shift dogs  802  and  702  are able to pivot independently of each other, but because of the cooperative arrangement of protrusion  803  and shift dog  701 , they cannot both engage with the teeth of their respective sun gears at the same time. If shift dog  702  is engaged with teeth  210 , then the relation of protrusion  803  and shift dog  701  prevents shift dog  802  from engaging teeth  211 . Conversely, if shift dog  802  is engaged with teeth  211 , shift dog  702  cannot pivot to engage with teeth  210 . 
       FIG. 42  is a detail of  FIG. 6 . Since shift dog  701  is fully pressed by roller  603 , shift dog  702  is fully disengaged from teeth  210 . Shift dog  701  cooperatively engages protrusion  803 , which in turn prevents shift dog  702  from pivoting to engage teeth  210 . Protrusion  803  is positioned radially above shift dog  701 . If shift dog  701  rotates to engage teeth  210 , shift dog  802  is held out of engagement with teeth  211  as shown in  FIG. 39 . Shift dog  802  is prevented from engaging teeth  211  by the cooperative arrangement of protrusion  803  and shift dog  701 . 
     When shift dog  802  is engaged with teeth  211  as shown in  FIG. 40  shift dog  702  is prevented from engaging teeth  210  by the arrangement of protrusion  803  and shift dog  701 . Both shift dogs  702  and  802  can be disengaged from teeth  210  and  211  simultaneously. Shift dogs  702 ,  802  are prevented from engaging the teeth simultaneously by the cooperative arrangement of protrusion  803  and shift dog  701 . Each protrusion  703 ,  803  is identical to the other. Protrusion  703  extends from the end of shift dog  701 . Protrusion  803  extends from the end of shift dog  801 . 
     Although a form of the invention has been described herein, it will be obvious to those skilled in the art that variations may be made in the construction and relation of parts without departing from the spirit and scope of the invention described herein.