CA2199997A1 - Tandem bicycle propulsion system utilizing a shared footpedal and crank assembly - Google Patents
Tandem bicycle propulsion system utilizing a shared footpedal and crank assemblyInfo
- Publication number
- CA2199997A1 CA2199997A1 CA002199997A CA2199997A CA2199997A1 CA 2199997 A1 CA2199997 A1 CA 2199997A1 CA 002199997 A CA002199997 A CA 002199997A CA 2199997 A CA2199997 A CA 2199997A CA 2199997 A1 CA2199997 A1 CA 2199997A1
- Authority
- CA
- Canada
- Prior art keywords
- rider
- footpedal
- pedal
- seat
- bicycle
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62K—CYCLES; CYCLE FRAMES; CYCLE STEERING DEVICES; RIDER-OPERATED TERMINAL CONTROLS SPECIALLY ADAPTED FOR CYCLES; CYCLE AXLE SUSPENSIONS; CYCLE SIDE-CARS, FORECARS, OR THE LIKE
- B62K3/00—Bicycles
- B62K3/12—Tandems
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62M—RIDER PROPULSION OF WHEELED VEHICLES OR SLEDGES; POWERED PROPULSION OF SLEDGES OR SINGLE-TRACK CYCLES; TRANSMISSIONS SPECIALLY ADAPTED FOR SUCH VEHICLES
- B62M1/00—Rider propulsion of wheeled vehicles
- B62M1/36—Rider propulsion of wheeled vehicles with rotary cranks, e.g. with pedal cranks
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62M—RIDER PROPULSION OF WHEELED VEHICLES OR SLEDGES; POWERED PROPULSION OF SLEDGES OR SINGLE-TRACK CYCLES; TRANSMISSIONS SPECIALLY ADAPTED FOR SUCH VEHICLES
- B62M3/00—Construction of cranks operated by hand or foot
Abstract
A kit of detachable parts which modify a single rider bicycle such that it accommodates two riders. Each rider applies propulsive force to a common crank-arm and chainwheel assembly by means of two shared footpedal assemblies which transmit both riders' foot pressure onto the same pedal bearing spindles. Each of said footpedal assemblies is comprised of upper and lower footpedal members upon which the front and rear riders respectively apply propulsive foot pressure. The upper (non-rotateable) footpedal member is affixed to the lower (rotateable) footpedal member and extends outwards from the bicycle, thereby permitting either heel or toe pressure to be applied by the front rider. The upper pedal is suspended above the lower pedal by means of compression members disposed such that the rear tandem rider can insert the forepart of each foot between the pedal members to exert foot pressure onto the lower, rotateable footpedal member. Said lower member has a rearward extension used by the rear rider to stabilize the pedal assembly against torque induced by the front rider's eccentric point of pressure application. The rear tandem rider's seat is adjustably affixed onto a support rail assembly at a location behind and substantially lower than the front rider's seat. An adjustable support mechanism permits the front rider's seat to be both raised and advanced with respect to its single rider location such that the legs of the closely coupled riders do not interfere with each other during pedaling activity.
Description
219~97 BACKGROUND AND PRIOR ART:
This invention relates to bicycles and more particularly to a means for modifying a conventional bicycle configuration so as to accommodate two actively pedaling riders.
Heretofore, various efforts have been made to devise means for accommodating tworiders upon the same bicycle such that they can both contribute energy towards propulsion of the vehicle. The prior art reveals three relevant categories of vehicle.
1) The first are those tandem bicycles essentially composed of two conventional, single rider bicycles detachably affixed to each other in a side by side configuration. While no longer a true bicycle, this four wheeled vehicle configuration does have the advantage of permitting two existing, single rider bicycles to be transformed into a tandem rider apparatus. However, the cost of such a vehicle is at least double that of a single rider bicycle and the safety of such a vehicle on public roads is compromised by both its width and its handling characteristics.
This invention relates to bicycles and more particularly to a means for modifying a conventional bicycle configuration so as to accommodate two actively pedaling riders.
Heretofore, various efforts have been made to devise means for accommodating tworiders upon the same bicycle such that they can both contribute energy towards propulsion of the vehicle. The prior art reveals three relevant categories of vehicle.
1) The first are those tandem bicycles essentially composed of two conventional, single rider bicycles detachably affixed to each other in a side by side configuration. While no longer a true bicycle, this four wheeled vehicle configuration does have the advantage of permitting two existing, single rider bicycles to be transformed into a tandem rider apparatus. However, the cost of such a vehicle is at least double that of a single rider bicycle and the safety of such a vehicle on public roads is compromised by both its width and its handling characteristics.
2) The prior art also reveals a second and more prevalent category of tandem bicycle which accommodates its riders, one in front of the other while each rider actuates separate pedal and crank assemblies, said assemblies being rotateably coupled through an auxiliary drive chain. This tandem configuration affords a considerable gain in mechanical efficiency with respect to two riders pedaling separate bicycles. Said efficiencies result from decreased wind resistance on the rear rider as well as the weight and friction economies inherent to sharing wheels, steering components, brakes, some frame components and some transmission components. However, the elongated tandemconfiguration still necessitates the duplication of certain heavy and expensive components: two separate pairs of pedals, crank arms and main bearing assembliestogether with the auxiliary chain required to couple the front and rear drive components.
Furthermore, the elongated frame structure necessitates additional frame members to extend and support the two main triangles which make up a conventional bicycle frame.
These additional frame members also add significantly to the cost and weight of the vehicle. Furthermore, if no second rider is available to contribute pedaling energy, the elongated tandem configuration is too heavy and unwieldy for efficient propulsion by a single rider, thereby limiting the vehicle' s versatility as a means of transportation.
Furthermore, the elongated frame structure necessitates additional frame members to extend and support the two main triangles which make up a conventional bicycle frame.
These additional frame members also add significantly to the cost and weight of the vehicle. Furthermore, if no second rider is available to contribute pedaling energy, the elongated tandem configuration is too heavy and unwieldy for efficient propulsion by a single rider, thereby limiting the vehicle' s versatility as a means of transportation.
3) A third category of prior art exists which is the most relevant to the present invention.
This prior art modifies the conventional single rider configuration by mounting a rear seat over the rear wheel as well as providing specially constructed footpedals which accommodate the feet of both the front and rear riders. In theory, this approach permits the second rider to sit behind the first rider and apply pedaling energy directly to the shared pedals. Sharing suitably modified pedals affixed to the crank of a single rider bicycle has a number of advantages with respect to the conventional tandem configuration:
1) An existing bicycle can be quickly converted to serve in either a single rider or tandem mode.
2) The cost of the special pedals and seating means are far less than the cost of a dedicated tandem bicycle.
2193~7 3) Since almost all mechanical parts are shared by both riders, the gross vehicle weight is less than that of a dedicated tandem bicycle.
Various attempts to implement such a scheme have been proposed by Liljenberg (2,706,418), Sykes (3,457,803), Kelly (2,337,246), Raba (2,361,708) and Ridgeway(2,715,342). However, none of the prior art has resulted in a viable solution due to one or both of the following drawbacks:
Drawback #1: inadequate road clearance. The means for accommodating the rear rider' s feet on the pedals extends the rotateable pedal assembly outwards from the bicycle such that the pedal can occasionally contact the road. The "side by side" foot placement embodiment proposed in the prior art caused pedal grounding during turns. The "over/under" foot placement embodiment proposed in the prior art also yielded inadequate road clearance to the pedal assemblies (since the rear rider's feet were located beneath the pedal assembly's bearing spindle).
Drawback #2: poor ergonomics. The seating accommodation was such that the two riders experienced ergonomic fatigue while pedaling (due to interference between their legs).
It is therefore the objective of the present invention to provide a tandem bicycle propulsion system which eliminates the aforementioned drawbacks inherent to the prior art. The present invention achieves this objective by providing a kit of three sub-assemblies that are attachable to a conventional, single rider bicycle and which together modify said bicycle such that:
1) Both riders can directly actuate the same footpedal assemblies while continuously maintaining adequate clearance between the road and pedal assemblies.
2) A second rider can sit comfortably upon the modified bicycle at a location behind and below the first rider which contributes to adequate clearance between the riders' legs.
3) The front rider can adjust the location of the front seat both forwards and upwards with respect to its normal location, thereby contributing towards adequate leg clearance between the two riders during all phases of crank rotation.
DESCRIPTION OF THE KIT'S THREE SUB-ASSEMBLIES:
Sub-assembly #1: The Pedals A conventional bicycle pedal is comprised of a slab shaped footpedal member which is rotateable and substantially symmetrical about the pedal's bearing spindle. The present invention accommodates the feet of both the front and rear riders upon the same footpedal assembly by providing the front rider with a non-rotateable upper footpedal member eccentrically affixed to and supported somewhat above the rotateable (lower) footpedal member. This dual tiered configuration leaves the lower, rotateable footpedal member available for use by the rear rider during tandem operation of the vehicle. Placing both rider's feet at or above the level of the pedal assembly's bearing spindle insures that the pedal' s ground clearance remains essentially the same as when the vehicle is operated in single rider mode (when the front rider shifts foot location to occupy the lower footpedal members). The dual-tiered footpedal assemblies receive both the front and rear rider' s feet such that they are as close to each other as anatomically possible.
The upper footpedal member is non-rotateably affixed to the rotateable, lower footpedal member by means of compression members affixed at their upper and lower ends to the 219~97 sides of the upper and lower footpedal members. In one preferred embodiment, both upper and lower footpedal members are slab shaped support members of approximately equal width. The spacing between these upper and lower footpedal members as well as the dihedral angle between the plane of the two footpedal members is adjustable by means of multiple fixation points near each end of the compression members which can be used to adjust the effective length of each compression member. The compression members are disposed along the sides of the upper and lower footpedal members such that the rear tandem rider can insert the ball of each foot onto the lower, rotateable footpedal member and thereby apply propulsive foot pressure to the bicycle's crank and chainwheel assembly.
This embodiment of the pedal assembly positions the front rider' s feet at the same distance from the bicycle frame as the rear rider' s feet are from the bicycle frame. This vertical, "over/under" foot configuration permits only heel pressure to be applied to the upper footpedal member. In this mode of operation, the front rider' s heel is positioned on the upper footpedal directly above, the upper surface of the rear rider' s foot such that the front rider's heel fits as closely as possible into the crotch of the rear riders ankle without actually touching it. In a preferred embodiment of the slab shaped upper pedal member, the upper footpedal surface is flared upwards along its rearmost edge. This same flared lip serves as a tactile aid to help the front rider feel when the heel of each foot is positioned on the upper footpedal in its optimal location (i.e.: as far back as possible without actually contacting the crotch formed by the rear rider's foot and shin bone).
In another preferred embodiment of the pedal assembly, the upper footpedal member is approximately twice as wide as the lower footpedal member. This side extended configuration cantilevers the upper pedal well past the lower pedal thereby permitting the front rider to move out and pedal with the ball of each foot. When the front rider' s feet are in this outboard location, the heel each foot is therefore positioned close to the outside of the rear rider's ankles but do not make any contact during pedaling activity. This side extended configuration affords the front rider two options for foot placement: heel in front of rear rider's ankle and heel beside rear rider's ankle.
In a preferred embodiment of the side extended upper footpedal, each upper pedal is comprised of a spar shaped member rather than the slab shaped member described above.
The upper footpedal spar member is supported directly above the pedal assembly'sbearing spindle by means of compression members on each side of the lower pedal. The supporting compression members are affixed at their upper ends to the spar shaped pedal member at both the inboard end of the spar and at the point along the spar corresponding to the width of the lower pedal member (thereby creating the cantilever required to permit the front rider's heels to extend beside the rear rider's ankles). The same supporting compression members are also affixed at their lower ends to the inboard and outboard sides of the lower (slab shaped) pedal member.
Typically, two compression members are used on the inboard and outboard sides of the pedal assembly thus forming a triangular support configuration. This triangular support configuration is more rigid than the rectangular support structure required to support a slab shaped upper footpedal member. The triangular support structure is comprised of the lower footpedal member (which forms the bottom of each support triangle) as well as the 2i9~7 two compression members which join at the upper footpedal member (thus forming the upper vertex of each support triangle). Since in this embodiment, the front rider's pedaling energy is applied at a considerable distance outboard of the bearing spindle, significant bending moments are introduced into the supporting (compression) members.
Therefore the compression members in this instance will require suitable longitudinal strengthening to withstand the extra load. Typically this reinforcement will take the form of orthogonal webs disposed longitudinally along the compression members (T or Lshaped cross sections).
Optionally, a slab shaped platform element can be adjustably affixed to the spar shaped upper footpedal member to spread the load of supporting the front rider's foot. In an variation of this embodiment, each load spreading platform element is replaced with the cleat taken from a standard "clipless" bicycle pedal. These pedal cleats engage onto the soles of readily available "clipless" bicycling shoes. This alternate platform configuration affords the front rider a more secure footing on the upper footpedal member.
When using the side extensions of the upper footpedals, the front rider's legs are spread further apart than when pedaling in single rider mode. Optimal (straight line) ergonomic positioning of the hip knee and ankle joints with respect to the torso is therefore compromised. To partially compensate for this degraded pedaling posture, the upper footpedal member can be fabricated so as to angle slightly upward from the horizontal thereby permitting the front rider's (slightly splayed) legs to be perpendicularly received on the upper pedals. The compensatory upwards angle of the footpedal should be approximately equal to the angle subtended by the upper pedal's overhang at the length of the rider's leg. This angle can be fixed during construction by making the outboard supports slightly longer than the inboard supports. Alternatively, the angle can be adjusted to the rider's comfort by means of shims placed under the foot support platform affixed to the upper pedal spar member.
This embodiment of the pedal assembly positions the front rider's feet further away from the bicycle frame than the rear rider's feet are from the bicycle frame. This produces an oblique angled, "over/under" foot configuration which permits the front rider's foot pressure to be applied using the ball of each foot while still providing adequate clearance between the riders. In this mode of operation, the ball of the front rider's foot is positioned on the outboard extension of the upper footpedal member such that the front rider's heel is as close as possible to the outside of the rear riders ankle without actually touching it. This mode of operation provides the front rider with an ergonomically correct pressure point (on the ball of the foot).
In a preferred embodiment of the side extended upper footpedal, the overhanging side extensions have readily available "clipless pedal" mechanisms affixed at their outboard extremities. These shoe fixation mechanisms operate in conjunction with cleats embedded in the bottom of "clipless pedal" bicycle shoes thereby enabling the front rider to more solidly affix each foot the pedal assembly.
When using the invention in single rider mode, the lone rider pedals in the conventional manner by applying propulsive force to the lower, rotateable footpedal members.
219.?!~7 However, during tandem mode operation, the lower footpedal members become occupied by the rear rider, and the front rider must shift foot position upwards to pedal using the upper footpedal members. Tandem pedaling action is accomplished by placing the balls or heels of the front rider's feet onto the upper footpedal member of each of the two-level footpedals. The front rider then applies propulsive force by exerting foot pressure onto the assembly. The front rider' s foot pressure is transmitted down the compression members and into the lower footpedal members, thereby augmenting the rear riderspedaling force already being applied to the bicycle's crank and transmission assembly.
Foot pressure exerted by the rear rider onto the lower footpedal members is transferred directly to the pedal assembly's bearing spindle with virtually no eccentric offset or turning moment (i.e.: the ball of the foot applies force symmetrically, both fore and aft of the bearing spindle). However, pressure applied by the front rider onto the upper footpedal member is applied at a point that is substantially eccentric to the assembly's axis of rotation, thereby creating a potentially unstable force geometry. If the force vector of the front rider's applied pressure does not pass exactly through the assembly's axis of rotation, the pedal's eccentricity creates an unstable turning moment about the pedal assembly's bearing spindle. The instability of this force geometry is proportional to the eccentricity of the upper footpedal member (i.e. proportional to the distance between the upper and lower footpedal members). Slight variations in pedaling action exerted by the front rider tend to produce a force vector which often passes either forward or aft of the assembly's axis of rotation, thereby inducing a destabilizing torque. If left uncontrolled, this rotational instability could easily cause the entire footpedal assembly to rapidly spin when a strong pedaling force is exerted by the front rider. Such unstable rotation could quickly dislodge both riders' feet from the pedal assembly, causing loss of power to the vehicle and possible injury to the riders.
To address this problem, the present invention provides two mechanical means which help the riders to achieve a dynamic balance of rotational forces about the pedal assembly's bearing spindle. The first means for counteracting unstable rotational force is simply to provide means which position the two riders' feet on the pedal assembly as close together as physically possible. This close proximity between the two riders' feet minimi7es the lever-arm effect caused by the upper pedal's eccentric location.
Minimi7ing the upper pedal member's lever-arm effect helps to minimizes the unstable rotational force however it cannot completely eliminate the danger caused by rotational instability. Unless great care is exercised by the front rider, the natural variability of foot attitude inherent to natural pedaling motion still causes brief torque surges in the whole footpedal assembly. The present invention must therefore provides a second means for counteracting the unstable torque inherent to the front rider's eccentric point of pressure application. This innovation is based on harnessing an equal and opposite compensatory torque generated by the rear rider' s pedaling force.
The rear rider could theoretically apply the required compensatory torque to the pedal assembly by shifting the location of foot pressure backwards and forwards along the lower footpedal member as required, to stabilize the torque produced by the front rider' s natural pedaling motion. However, given the rapidity with which such compensatory torque must be applied, the rear rider would quickly tire of continually shifting foot position fore and aft on the lower footpedal. The most natural and relaxing muscular 219~f ~3~7 action for applying brief periods of compensatory torque is not moving the foot but rather applying greater heel pressure or toe pressure as required to stabilize the pedal assembly.
Unfortunately, the dimensions of a standard bicycle pedal are adequate for controlling torque instability in this manner. The problem is that the lever arm distance of a standard lower pedal member around its bearing spindle is too short compared to the long lever arm distance of the upper pedal to the same axis of rotation.
The present invention solves the problem of leverage arm inequality by modifying the lower pedal. The rear rider's heel and toe pressure can only have the desired stabilizing effect if the rear rider's foot is disposed so that it is fully supported from heel to toe on the pedal (thereby providing adequate leverage arms about the bearing spindle). The necessary support is provided by two additions to the lower footpedal member:
1 ) A rear extension of the lower footpedal such that the lower footpedal member is asymmetric about the bearing spindle. The rear footpedal extension provides heelsupport for the rear rider, thereby permitting the rider's heel pressure to precisely modulate stabilizing torque into the pedal assembly.
2) A conventional bicycle toe-clip affixed to the front edge of the lower pedal member which extends the forward extent of the pedal to magnify the stabilizing effect of downward toe pressure. The toe clip also serves to bind the forepart of the foot to the pedal thereby preventing the toe from lifting as corrective heel pressure is applied.
Sub-assembly #2: The Rear Seat The second of the three functional sub-assemblies which comprise this invention provides a means for the second rider to sit comfortably on the modified bicycle at a location behind and below the front rider. This function is provided by a second (rear), bicycle seat together with the support members needed to adjustably affix it to the bicycle in the correct ergonomic location.
The rear bicycle seat is adjustably supported and positioned along a substantially horizontal rail member. The support rail member is affixed near its front end to the upper seatstay members of the bicycle's frame using appropriate mounting brackets and/or tube clamps. Rear support for the horizontal rail member is provided by two compression members affixed at their upper ends near the rear end of the rail. These compression members are affixed at their lower ends to each side of the bicycle frame near the location of the rear axle. A clamping mechanism is provided which adjustably affixes the rear rider's seat at the point along the support rail member which provides comfortable leg extension to the rear rider's (lower) footpedals.
For optimal ergonomic interaction with the front rider, the rear seat' s support rail must be kept as low as possible on the bicycle' s structure. The requirement for maximum vertical clearance between the two riders is to provide adequate clearance between the rear rider's knees and the front rider's buttocks when each pedal is at the top of its stroke. The compression members supporting the horizontal rail member therefore have multiple fixation points. This adjustable length permits the support rail to be positioned as low as possible on the bicycle (such that it just clears the rear tire). Additional vertical leg clearance between the riders is created by configuring the internal support structure of the rear seat as well as the clamping device used to adjustably affix it to the support rail 2193~97 member in a manner that positions the rear seat as close as possible to the support rail member.
Many existing bicycles are fitted with cantilever style rear brakes affixed to the seat-stay frame members which protrude far enough outwards from the frame that they would contact the rear rider' s inner thighs during pedaling activity. To eliminate this ergonomic problem, the present invention provides means for re-locating the existing brake assembly behind the rear rider's legs such that no interference with the brake assembly is experienced during pedaling. This clearance is established by providing an additional pair of cantilever brake pivots affixed to the two vertical compression members which support the rear seat assembly. These pivot pins are located on said members such that the existing brake cantilever assemblies can be transferred from the seat-stays to their new locations and maintain correct frictional engagement with the rear wheel-rim. The existing brake actuation cable is replaced with a longer one which can reach from the handlebar brake lever to the new brake location on the rear seat rail supports. To accommodate the brake cable, a standard cable ferule is affixed to the rear of the seat support rail such that the cable's outer sheath is correctly positioned and restrained with respect to the re-positioned rear brake cantilever assemblies.
As an alternate means of providing adequate side clearance between the rear rider's inner legs and the existing rear brake assembly is to elimin~te the rim-friction rear brake altogether and replace it with a disk brake or internal expansion hub brake. In fact, since the bicycle's gross vehicle weight will be approximately doubled by the addition of a second rider, it would be a prudent safety measure to improve the vehicle's braking power in this manner.
In a preferred embodiment, the rear seat support assembly also provides a backrest which compliments the semi-recumbent posture of the rear rider. The backrest provides two functions:
1) It provides a more restful seating position for the rear rider during slow, relaxed cycling activity.
2) It prevents the rear rider from sliding backwards during hard pedaling.
In a preferred embodiment, the support rail assembly also incorporates a pair ofhandholds located behind the rear seat. These handholds can be used by rear rider to maintain a stronger hold on the bicycle during hard maneuvers. They can also be used by the rear rider to occasionally raise off the seat, thereby momentarily relieving pressure on the buttocks or to absorb road shock.
Sub-assembly #3: The Front Seat The third of the three functional sub-assemblies which constitute the present invention provides a means for adjustably re-positioning the front rider's seat forward and upward with respect to its location during single-rider operation. This re-positioning is required to insure adequate vertical clearance between the front and rear riders' legs for all angles of crank rotation. During tandem pedaling, the rear rider' s legs must move in close proximity behind the front rider's legs without any mutual interference. However, the frame geometry and seat location of a typical single rider bicycle, cannot provide enough 21933~
vertical separation between the front and rear seats to support continuous clearance between the top of the rear rider's thigh and the bottom of the front rider's thigh.
To achieve the necessary vertical clearance from the rear rider, the front rider' s seat location must also be moved upwards from its normal, single rider location. Whenconverting from single rider mode of operation to tandem rider mode of operation, the front rider' s feet must be re-positioned from the lower to the upper footpedal members.
In order to maintain the front rider's correct leg extension distance to the upper footpedal member, the front seat must therefore be raised by a distance approximately equal to the distance between the upper and lower foot pedal members. Raising the front seat the required amount could be accomplished by simply extending the existing seatpost's adjustment. Unfortunately the bicycle's existing seatpost is often not long enough to permit the required amount of additional vertical movement. More importantly, simply extending the existing seatpost actually moves the front seat backwards into the abdomen of the rear rider (due to the backwards slope of the bicycle frame's seat tube). Therefore, the present invention must provide a specialized mechanism for increasing both vertical and horizontal separation between the front and rear riders.
To provide this function, the present invention uses an adjustable, cantilevered seatpost mechanism with two degrees of freedom which enables the front rider to both raise and move front seat forward. The front seat adjustment mechanism is essentially a cantilevered member affixed to the top of the seatpost. The cantilevered member acts as a rail along which the front seat can be adjustably affixed. By sliding the front seat back and forth along this rail member, the riders can adjust their horizontal separation for comfort and adequate clearance during pedaling. During this horizontal adjustment procedure, correct leg extension for the front rider as well as adequate vertical clearance between the riders' legs is also obtained by adjusting the seat height (using the bicycle's existing seatpost adjustment mechanism).
Additional Design Elements The present invention is intended primarily for converting existing single rider bicycles to tandem operation however the invention can also be incorporated into the design and fabrication of new single/tandem bicycles. In the case of such newly fabricated bicycles, the frame geometry could be optimized for a more balanced weight distribution bylengthening the chainstay frame members. The front fork geometry could also be modified to provide the greater strength and high speed stability required for tandem operation. Components such as wheels, brakes and frame tubing could also be upgraded to improve durability under the greater loads imposed by dual rider operation.
Lengthening the chainstays would place the rear rider's weight further forward with respect to the rear axle and thus help to control any tendency for the front wheel to leave the ground during hard acceleration or when climbing steep grades. However, in the case of converting an existing single rider bicycle to provide tandem capability, lengthening of the chainstay frame members would be prohibitively expensive. In such cases, thetendency towards front end lightness can be controlled by simply moving the front rider's weight forward onto the front wheel. To facilitate the front rider' s forward weight transfer, "bar-end" handlebar risers can be purchased and added to the kit. These 2193~97 auxiliary handholds can be adjustably positioned to provide alternate handholds that are somewhat above and forward of the handholds used for single rider operation.
Using the alternate handholds provided by the optional "bar-end" handlebar risers displaces the front riders hand location along approximately the same vector as the front rider's seat and pedal positions have been displaced as a result of converting from single rider to tandem mode of operation. The alternative handholds therefore re-establish the front rider's ergonomically correct (single-rider) posture.
Handholds may also be provided for the rear rider (either integral to the seatpost or integral to the backrest/seat support rail). However, in most instances simply holding onto the seatpost can serve to adequately brace the rear rider's body during hard pedaling.
During normal use, the rear rider' s hands and arms are not needed to control the vehicle.
The rear rider is therefore free to hand aid the process of pedaling by alternately pressing down on whichever knee is on the downward, power stroke. This hand assisted mode of operation utilizes the muscle power of the upper body to augment that of the legs, thereby improving the overall efficiency of the vehicle.
In addition to the vehicular application described above, the present invention can also serve as a bicycle stand. To accomplish this mode of operation, the operator simply rotates the crank such that either pedal is immediately aft of its lowest point and leaning the bicycle onto it. Gravitational force naturally rotates the pedal assembly so that the upper pedal member is closest to the ground. This contact point with the ground serves as a bicycle stand by virtue of the fact that the gravitational force of the bicycle onto the pedal imparts a forward motion to the vehicle (through the transmission). This forward force is countered-balanced by the frictional contact that pedal assembly has with the ground. This dynamic balance of forces enables the bicycle to be statically supported by the pedal assembly.
With respect to the prior art:
By eliminating the additional crank and pedal assembly normally required by the rear tandem rider, the present invention provides a significantly lighter vehicle. Weight savings are also achieved by eliminating the additional drive chain normally required to link dual crank assemblies as well as the additional frame members needed to form the elongated frame inherent to previous tandem bicycle designs.
Furthermore, mechanical friction in the vehicle's drive train is significantly reduced by elimin~ting the second pair of footpedal bearings, the second crank bearing and the second drive chain and sprocket assembly required by previous tandem bicycle designs.
Furthermore, due to the rear rider' s seating position being situated more fully within the slipstream created by the front rider, the vehicle's wind resistance is reduced compared to conventional tandem bicycle designs.
Furthermore, by eliminating the need for a second crank and pedal assembly, a second drive chain and chainwheel assembly as well as the additional frame members needed to form an elongated frame, the cost of fabrication of the present invention is significantly reduced compared to previous tandem bicycle designs 219 ~3 9 9 rl~
Furthermore, since the present invention is of similar size and weight as a single rider bicycle, the same vehicle can still be efficiently propelled by a single front rider when no second rider is available to help pedal.
Furthermore, the present invention permits an existing single rider bicycle to be quickly converted into a tandem bicycle and back to a single rider bicycle.
Furthermore, when not in service as a vehicle, the present invention acts as a bicycle stand.
2193~97 DRAFT DRAWINGS AND DETAILED DESCRIPTION:
In drawings illustrating an embodiment of the invention:
FIG. 1 is an elevational view of a conventional single rider bicycle having tandem rider modifications mounted thereon which are constructed in accordance with and embodying the present invention: said bicycle being illustrated as occupied and actuated by a front rider pedaling with the heels of the feet.
FIG. 2 is an elevational view similar to figure 1 except that the front rider is using the side extension embodiment of the upper footpedal members, thereby enabling pedaling with the balls of the feet.
FIG. 3 is an elevational view similar to figure I except that the bicycle is illustrated being unoccupied by riders and the pedal assemblies are rotated to their support stand locations whereby the upper foot support surface contacts the ground when the vehicle is leaned over towards it.
FIG. 4 is an enlarged view of FIG. 1 illustrating details of the pedal assembly with the riders' feet correctly positioned.
FIG. 5 is an enlarged view of FIG. 2 illustrating details of the pedal assembly with the riders' feet correctly positioned.
FIG. 6 is an enlarged view of FIG. 2 illustrating details of the rear seat support assembly.
FIG.7 is an enlarged view of FIG. 1 illustrating details of the front seat support assembly fabricated using large diameter tubing.
MORE DETAILED TEXTUAL DESCRIPTION REFERENCED TO THESE
DRAWINGS WILL FOLLOW IN A FINAL AMMEDMENT TO THIS PATENT
APPLICATION:
The present invention is comprised of three sub-assemblies:
1 ) - The dual level pedals.
2) - The rear seat and its attendant support structure.
3) - The front seat raising and advancement mechanism.
When affixed to a conventional single rider bicycle structure, these three sub-assemblies operate in concert to effect its conversion to tandem operation.
Referring to the working embodiment illustrated in FIG. 1 which illustrates the relationship between the present invention's three main sub-assemblies: the front rider places the rear part of each foot onto the upper pedal surface member ## of each of the dual level pedal assemblies. The front rider's foot is thus displaced vertically upward with respect to its normal, single rider location on the rotateable lower surface member, by a distance equal to the distance between the upper and lower pedal surface members.
To compensate for this change in reach to the pedals, the front seat is also displaced upward the same distance by adjustably re-positioning the seat adjustment members ##.
The seat adjustment members also permit the seat to be adjusted forward of its conventional location so as to provide clearance for the rear rider and transfer weight onto the front wheel. The rear rider sits on the rear seat ## and places the front part of each foot on the rotateable, lower pedal surfaces ## and adjustably positions the rear seat ##
along the support rail ##
Referring to the workable embodiment illustrated in FIG. 3 each of the two upperfootpedal surface members ## is adjustably affixed to and supported substantially above its corresponding rotateable, lower footpedal surface member assembly ## by means of a series of substantially vertical compression members ##.
The upper footpedal surface member ## has a series of drilled tab members ## bent downwards along its sides so as to provide fixation points for the compression members ##. Each lower footpedal surface is comprised of a hub ## which rotates around the pedal' s bearing spindle ## which in turn is affixed to the crank arm ## of the bicycle' s existing transmission mechanism. Two U shaped members comprised of a central section ## and two drilled end tab sections ## bent at 90 degrees to the central member are affixed to the front and rear of each pedal hub ##. The two central sections ## affixed to the pedal hub ## serve as foot support surfaces for the rear rider. The drilled tab members ## provide lower fixation points for the vertical compression members ##supporting the upper footpedal member ##.
The upper end of each compression member ## is rotateably affixed to its respective upper footpedal tab ## using matching holes and a tightening fastener ## which serves to prevent rotation once a comfortable angular adjustment is set. The lower end of each compression member ## is affixed to the lower footpedal surface member using a similar rotateable fixation means as is employed at the upper end, however it has multiple fixation holes ## to permit the length of each compression member to be adjusted to suit both rider's pedaling comfort. Depending on the anatomical configuration of each rider, the upper footpedal member ## is fixed at a greater or lesser angle and separation with respect to the lower footpedal member ##.
Referring to the workable embodiment illustrated in FIG. 4, the main support rail member ## for the rear rider's seat ## is adjustably affixed to the frame of the host bicycle at both of its ends so as to maintain the support rail in a substantially horizontal position, aligned with the axis of the bicycle and immediately above the bicycle's rear tire. The mechanism for affixing the front of the seat support rail to the host bicycle is comprised of a angled bracket ## which is bolted through the front of the support rail member on one end and at the other end through the hole in the bicycle's seat stay brace ## normally provided to mount the rear brake assembly. The mechanism for affixing the rear of the seat support rail to the host bicycle is comprised of two rail support struts ##.
The top of each of the two rail support struts is bolted to the left and right side respectively of the rear seat support rail using a bolt ##. Spacer elements ## may be inserted between the seat support rail and the rail support struts to provide adequate clearance between the rail support struts and the rear tire. The seat support rail may be of any cross sectional shape however a preferred embodiment employs a circular cross-section as this minimi7es fabrication costs and also permits the use of a seat fixation device described below.
The rear bicycle seat ## is adjustably affixed at a point along the seat support rail ## such that it affords the rear rider a comfortable reach to the lower footpedals. The seat fixation device ## is a clamp which is affixed at its upper extremity to the underside of the rear rider' s seat and at its lower extremity to the seat support rail. In a preferred embodiment, the seat fixation device is the standard commercially available seat post clamp ## used to affix a bicycle seat to the substantially vertical seat post of a conventional bicycle. These inexpensive and commercially available seat clamps are comprised of a compressible clamping band ## which secures to the seatpost said band being rotateably coupled to a pair of pincer clamps ## which secure to the standard dual frame members ## which are integral to the bicycle seat. A single bolt ## through the rotation point of the clamping assembly simultaneously secures the pincer clamps to the seat frame and the compressible band clamp to the seatpost. Tightening bolt ## also fixes the angle between the two clamping elements. Typically the clamping assembly permits at least 180 degrees of rotation between said elements, thereby permitting the clamps for the rear rider's seat ## of the present invention to be rotated 90 degrees from its normal configuration with respect to a vertical seatpost such that the seat can be adjustably affixed to the horizontal seat support rail ##.
Referring to the workable embodiment illustrated in FIG 5, the front rider's seat ## is adjustably re-affixed to a position both forward and above it's normal position by means of a seatpost clamp ##, two 1/4 inch rod members ## and a seat fixation clamp ##. The seatpost clamp is the same mechanism described above that is used to secure the rear seat ## to the seat support rail ## however instead of be affixed to the two standard frame rails ## integral to the seat ##, its two upper clamping jaws ## are affixed to the lower ends of two seat extension rods ##. The seat extension rods are of suitable diameter to engage the seat clamp jaws. The seat extension rods ## are manufactured of sufficiently rigid and resilient material to support the cantilevered weight of the front rider. The upper clamping assembly is comprised of two swivel clamp assemblies identical to those used both to secure the rear seat to the support structure. When the clamp assemblies at both ends of the seat extension rods are loosened, seat extension rods are adjustable both angularly and longitudinally with respect to the clamp mechanism thereby permitting the user to re-position the front seat both above and forward of its single rider location.
The materials used for fabricating the bi-level footpedal apparatus, the rear seat support structure and the front seat raising and advancement mechanism are typically aluminum and steel however other metal alloys and even some reinforced plastics can provide the strength, resilience and light weight that are required. Although the invention has been described with reference to a particular illustrative example, it is recognized that various minor mechanical modifications are possible when implementing this inventive concept.
This prior art modifies the conventional single rider configuration by mounting a rear seat over the rear wheel as well as providing specially constructed footpedals which accommodate the feet of both the front and rear riders. In theory, this approach permits the second rider to sit behind the first rider and apply pedaling energy directly to the shared pedals. Sharing suitably modified pedals affixed to the crank of a single rider bicycle has a number of advantages with respect to the conventional tandem configuration:
1) An existing bicycle can be quickly converted to serve in either a single rider or tandem mode.
2) The cost of the special pedals and seating means are far less than the cost of a dedicated tandem bicycle.
2193~7 3) Since almost all mechanical parts are shared by both riders, the gross vehicle weight is less than that of a dedicated tandem bicycle.
Various attempts to implement such a scheme have been proposed by Liljenberg (2,706,418), Sykes (3,457,803), Kelly (2,337,246), Raba (2,361,708) and Ridgeway(2,715,342). However, none of the prior art has resulted in a viable solution due to one or both of the following drawbacks:
Drawback #1: inadequate road clearance. The means for accommodating the rear rider' s feet on the pedals extends the rotateable pedal assembly outwards from the bicycle such that the pedal can occasionally contact the road. The "side by side" foot placement embodiment proposed in the prior art caused pedal grounding during turns. The "over/under" foot placement embodiment proposed in the prior art also yielded inadequate road clearance to the pedal assemblies (since the rear rider's feet were located beneath the pedal assembly's bearing spindle).
Drawback #2: poor ergonomics. The seating accommodation was such that the two riders experienced ergonomic fatigue while pedaling (due to interference between their legs).
It is therefore the objective of the present invention to provide a tandem bicycle propulsion system which eliminates the aforementioned drawbacks inherent to the prior art. The present invention achieves this objective by providing a kit of three sub-assemblies that are attachable to a conventional, single rider bicycle and which together modify said bicycle such that:
1) Both riders can directly actuate the same footpedal assemblies while continuously maintaining adequate clearance between the road and pedal assemblies.
2) A second rider can sit comfortably upon the modified bicycle at a location behind and below the first rider which contributes to adequate clearance between the riders' legs.
3) The front rider can adjust the location of the front seat both forwards and upwards with respect to its normal location, thereby contributing towards adequate leg clearance between the two riders during all phases of crank rotation.
DESCRIPTION OF THE KIT'S THREE SUB-ASSEMBLIES:
Sub-assembly #1: The Pedals A conventional bicycle pedal is comprised of a slab shaped footpedal member which is rotateable and substantially symmetrical about the pedal's bearing spindle. The present invention accommodates the feet of both the front and rear riders upon the same footpedal assembly by providing the front rider with a non-rotateable upper footpedal member eccentrically affixed to and supported somewhat above the rotateable (lower) footpedal member. This dual tiered configuration leaves the lower, rotateable footpedal member available for use by the rear rider during tandem operation of the vehicle. Placing both rider's feet at or above the level of the pedal assembly's bearing spindle insures that the pedal' s ground clearance remains essentially the same as when the vehicle is operated in single rider mode (when the front rider shifts foot location to occupy the lower footpedal members). The dual-tiered footpedal assemblies receive both the front and rear rider' s feet such that they are as close to each other as anatomically possible.
The upper footpedal member is non-rotateably affixed to the rotateable, lower footpedal member by means of compression members affixed at their upper and lower ends to the 219~97 sides of the upper and lower footpedal members. In one preferred embodiment, both upper and lower footpedal members are slab shaped support members of approximately equal width. The spacing between these upper and lower footpedal members as well as the dihedral angle between the plane of the two footpedal members is adjustable by means of multiple fixation points near each end of the compression members which can be used to adjust the effective length of each compression member. The compression members are disposed along the sides of the upper and lower footpedal members such that the rear tandem rider can insert the ball of each foot onto the lower, rotateable footpedal member and thereby apply propulsive foot pressure to the bicycle's crank and chainwheel assembly.
This embodiment of the pedal assembly positions the front rider' s feet at the same distance from the bicycle frame as the rear rider' s feet are from the bicycle frame. This vertical, "over/under" foot configuration permits only heel pressure to be applied to the upper footpedal member. In this mode of operation, the front rider' s heel is positioned on the upper footpedal directly above, the upper surface of the rear rider' s foot such that the front rider's heel fits as closely as possible into the crotch of the rear riders ankle without actually touching it. In a preferred embodiment of the slab shaped upper pedal member, the upper footpedal surface is flared upwards along its rearmost edge. This same flared lip serves as a tactile aid to help the front rider feel when the heel of each foot is positioned on the upper footpedal in its optimal location (i.e.: as far back as possible without actually contacting the crotch formed by the rear rider's foot and shin bone).
In another preferred embodiment of the pedal assembly, the upper footpedal member is approximately twice as wide as the lower footpedal member. This side extended configuration cantilevers the upper pedal well past the lower pedal thereby permitting the front rider to move out and pedal with the ball of each foot. When the front rider' s feet are in this outboard location, the heel each foot is therefore positioned close to the outside of the rear rider's ankles but do not make any contact during pedaling activity. This side extended configuration affords the front rider two options for foot placement: heel in front of rear rider's ankle and heel beside rear rider's ankle.
In a preferred embodiment of the side extended upper footpedal, each upper pedal is comprised of a spar shaped member rather than the slab shaped member described above.
The upper footpedal spar member is supported directly above the pedal assembly'sbearing spindle by means of compression members on each side of the lower pedal. The supporting compression members are affixed at their upper ends to the spar shaped pedal member at both the inboard end of the spar and at the point along the spar corresponding to the width of the lower pedal member (thereby creating the cantilever required to permit the front rider's heels to extend beside the rear rider's ankles). The same supporting compression members are also affixed at their lower ends to the inboard and outboard sides of the lower (slab shaped) pedal member.
Typically, two compression members are used on the inboard and outboard sides of the pedal assembly thus forming a triangular support configuration. This triangular support configuration is more rigid than the rectangular support structure required to support a slab shaped upper footpedal member. The triangular support structure is comprised of the lower footpedal member (which forms the bottom of each support triangle) as well as the 2i9~7 two compression members which join at the upper footpedal member (thus forming the upper vertex of each support triangle). Since in this embodiment, the front rider's pedaling energy is applied at a considerable distance outboard of the bearing spindle, significant bending moments are introduced into the supporting (compression) members.
Therefore the compression members in this instance will require suitable longitudinal strengthening to withstand the extra load. Typically this reinforcement will take the form of orthogonal webs disposed longitudinally along the compression members (T or Lshaped cross sections).
Optionally, a slab shaped platform element can be adjustably affixed to the spar shaped upper footpedal member to spread the load of supporting the front rider's foot. In an variation of this embodiment, each load spreading platform element is replaced with the cleat taken from a standard "clipless" bicycle pedal. These pedal cleats engage onto the soles of readily available "clipless" bicycling shoes. This alternate platform configuration affords the front rider a more secure footing on the upper footpedal member.
When using the side extensions of the upper footpedals, the front rider's legs are spread further apart than when pedaling in single rider mode. Optimal (straight line) ergonomic positioning of the hip knee and ankle joints with respect to the torso is therefore compromised. To partially compensate for this degraded pedaling posture, the upper footpedal member can be fabricated so as to angle slightly upward from the horizontal thereby permitting the front rider's (slightly splayed) legs to be perpendicularly received on the upper pedals. The compensatory upwards angle of the footpedal should be approximately equal to the angle subtended by the upper pedal's overhang at the length of the rider's leg. This angle can be fixed during construction by making the outboard supports slightly longer than the inboard supports. Alternatively, the angle can be adjusted to the rider's comfort by means of shims placed under the foot support platform affixed to the upper pedal spar member.
This embodiment of the pedal assembly positions the front rider's feet further away from the bicycle frame than the rear rider's feet are from the bicycle frame. This produces an oblique angled, "over/under" foot configuration which permits the front rider's foot pressure to be applied using the ball of each foot while still providing adequate clearance between the riders. In this mode of operation, the ball of the front rider's foot is positioned on the outboard extension of the upper footpedal member such that the front rider's heel is as close as possible to the outside of the rear riders ankle without actually touching it. This mode of operation provides the front rider with an ergonomically correct pressure point (on the ball of the foot).
In a preferred embodiment of the side extended upper footpedal, the overhanging side extensions have readily available "clipless pedal" mechanisms affixed at their outboard extremities. These shoe fixation mechanisms operate in conjunction with cleats embedded in the bottom of "clipless pedal" bicycle shoes thereby enabling the front rider to more solidly affix each foot the pedal assembly.
When using the invention in single rider mode, the lone rider pedals in the conventional manner by applying propulsive force to the lower, rotateable footpedal members.
219.?!~7 However, during tandem mode operation, the lower footpedal members become occupied by the rear rider, and the front rider must shift foot position upwards to pedal using the upper footpedal members. Tandem pedaling action is accomplished by placing the balls or heels of the front rider's feet onto the upper footpedal member of each of the two-level footpedals. The front rider then applies propulsive force by exerting foot pressure onto the assembly. The front rider' s foot pressure is transmitted down the compression members and into the lower footpedal members, thereby augmenting the rear riderspedaling force already being applied to the bicycle's crank and transmission assembly.
Foot pressure exerted by the rear rider onto the lower footpedal members is transferred directly to the pedal assembly's bearing spindle with virtually no eccentric offset or turning moment (i.e.: the ball of the foot applies force symmetrically, both fore and aft of the bearing spindle). However, pressure applied by the front rider onto the upper footpedal member is applied at a point that is substantially eccentric to the assembly's axis of rotation, thereby creating a potentially unstable force geometry. If the force vector of the front rider's applied pressure does not pass exactly through the assembly's axis of rotation, the pedal's eccentricity creates an unstable turning moment about the pedal assembly's bearing spindle. The instability of this force geometry is proportional to the eccentricity of the upper footpedal member (i.e. proportional to the distance between the upper and lower footpedal members). Slight variations in pedaling action exerted by the front rider tend to produce a force vector which often passes either forward or aft of the assembly's axis of rotation, thereby inducing a destabilizing torque. If left uncontrolled, this rotational instability could easily cause the entire footpedal assembly to rapidly spin when a strong pedaling force is exerted by the front rider. Such unstable rotation could quickly dislodge both riders' feet from the pedal assembly, causing loss of power to the vehicle and possible injury to the riders.
To address this problem, the present invention provides two mechanical means which help the riders to achieve a dynamic balance of rotational forces about the pedal assembly's bearing spindle. The first means for counteracting unstable rotational force is simply to provide means which position the two riders' feet on the pedal assembly as close together as physically possible. This close proximity between the two riders' feet minimi7es the lever-arm effect caused by the upper pedal's eccentric location.
Minimi7ing the upper pedal member's lever-arm effect helps to minimizes the unstable rotational force however it cannot completely eliminate the danger caused by rotational instability. Unless great care is exercised by the front rider, the natural variability of foot attitude inherent to natural pedaling motion still causes brief torque surges in the whole footpedal assembly. The present invention must therefore provides a second means for counteracting the unstable torque inherent to the front rider's eccentric point of pressure application. This innovation is based on harnessing an equal and opposite compensatory torque generated by the rear rider' s pedaling force.
The rear rider could theoretically apply the required compensatory torque to the pedal assembly by shifting the location of foot pressure backwards and forwards along the lower footpedal member as required, to stabilize the torque produced by the front rider' s natural pedaling motion. However, given the rapidity with which such compensatory torque must be applied, the rear rider would quickly tire of continually shifting foot position fore and aft on the lower footpedal. The most natural and relaxing muscular 219~f ~3~7 action for applying brief periods of compensatory torque is not moving the foot but rather applying greater heel pressure or toe pressure as required to stabilize the pedal assembly.
Unfortunately, the dimensions of a standard bicycle pedal are adequate for controlling torque instability in this manner. The problem is that the lever arm distance of a standard lower pedal member around its bearing spindle is too short compared to the long lever arm distance of the upper pedal to the same axis of rotation.
The present invention solves the problem of leverage arm inequality by modifying the lower pedal. The rear rider's heel and toe pressure can only have the desired stabilizing effect if the rear rider's foot is disposed so that it is fully supported from heel to toe on the pedal (thereby providing adequate leverage arms about the bearing spindle). The necessary support is provided by two additions to the lower footpedal member:
1 ) A rear extension of the lower footpedal such that the lower footpedal member is asymmetric about the bearing spindle. The rear footpedal extension provides heelsupport for the rear rider, thereby permitting the rider's heel pressure to precisely modulate stabilizing torque into the pedal assembly.
2) A conventional bicycle toe-clip affixed to the front edge of the lower pedal member which extends the forward extent of the pedal to magnify the stabilizing effect of downward toe pressure. The toe clip also serves to bind the forepart of the foot to the pedal thereby preventing the toe from lifting as corrective heel pressure is applied.
Sub-assembly #2: The Rear Seat The second of the three functional sub-assemblies which comprise this invention provides a means for the second rider to sit comfortably on the modified bicycle at a location behind and below the front rider. This function is provided by a second (rear), bicycle seat together with the support members needed to adjustably affix it to the bicycle in the correct ergonomic location.
The rear bicycle seat is adjustably supported and positioned along a substantially horizontal rail member. The support rail member is affixed near its front end to the upper seatstay members of the bicycle's frame using appropriate mounting brackets and/or tube clamps. Rear support for the horizontal rail member is provided by two compression members affixed at their upper ends near the rear end of the rail. These compression members are affixed at their lower ends to each side of the bicycle frame near the location of the rear axle. A clamping mechanism is provided which adjustably affixes the rear rider's seat at the point along the support rail member which provides comfortable leg extension to the rear rider's (lower) footpedals.
For optimal ergonomic interaction with the front rider, the rear seat' s support rail must be kept as low as possible on the bicycle' s structure. The requirement for maximum vertical clearance between the two riders is to provide adequate clearance between the rear rider's knees and the front rider's buttocks when each pedal is at the top of its stroke. The compression members supporting the horizontal rail member therefore have multiple fixation points. This adjustable length permits the support rail to be positioned as low as possible on the bicycle (such that it just clears the rear tire). Additional vertical leg clearance between the riders is created by configuring the internal support structure of the rear seat as well as the clamping device used to adjustably affix it to the support rail 2193~97 member in a manner that positions the rear seat as close as possible to the support rail member.
Many existing bicycles are fitted with cantilever style rear brakes affixed to the seat-stay frame members which protrude far enough outwards from the frame that they would contact the rear rider' s inner thighs during pedaling activity. To eliminate this ergonomic problem, the present invention provides means for re-locating the existing brake assembly behind the rear rider's legs such that no interference with the brake assembly is experienced during pedaling. This clearance is established by providing an additional pair of cantilever brake pivots affixed to the two vertical compression members which support the rear seat assembly. These pivot pins are located on said members such that the existing brake cantilever assemblies can be transferred from the seat-stays to their new locations and maintain correct frictional engagement with the rear wheel-rim. The existing brake actuation cable is replaced with a longer one which can reach from the handlebar brake lever to the new brake location on the rear seat rail supports. To accommodate the brake cable, a standard cable ferule is affixed to the rear of the seat support rail such that the cable's outer sheath is correctly positioned and restrained with respect to the re-positioned rear brake cantilever assemblies.
As an alternate means of providing adequate side clearance between the rear rider's inner legs and the existing rear brake assembly is to elimin~te the rim-friction rear brake altogether and replace it with a disk brake or internal expansion hub brake. In fact, since the bicycle's gross vehicle weight will be approximately doubled by the addition of a second rider, it would be a prudent safety measure to improve the vehicle's braking power in this manner.
In a preferred embodiment, the rear seat support assembly also provides a backrest which compliments the semi-recumbent posture of the rear rider. The backrest provides two functions:
1) It provides a more restful seating position for the rear rider during slow, relaxed cycling activity.
2) It prevents the rear rider from sliding backwards during hard pedaling.
In a preferred embodiment, the support rail assembly also incorporates a pair ofhandholds located behind the rear seat. These handholds can be used by rear rider to maintain a stronger hold on the bicycle during hard maneuvers. They can also be used by the rear rider to occasionally raise off the seat, thereby momentarily relieving pressure on the buttocks or to absorb road shock.
Sub-assembly #3: The Front Seat The third of the three functional sub-assemblies which constitute the present invention provides a means for adjustably re-positioning the front rider's seat forward and upward with respect to its location during single-rider operation. This re-positioning is required to insure adequate vertical clearance between the front and rear riders' legs for all angles of crank rotation. During tandem pedaling, the rear rider' s legs must move in close proximity behind the front rider's legs without any mutual interference. However, the frame geometry and seat location of a typical single rider bicycle, cannot provide enough 21933~
vertical separation between the front and rear seats to support continuous clearance between the top of the rear rider's thigh and the bottom of the front rider's thigh.
To achieve the necessary vertical clearance from the rear rider, the front rider' s seat location must also be moved upwards from its normal, single rider location. Whenconverting from single rider mode of operation to tandem rider mode of operation, the front rider' s feet must be re-positioned from the lower to the upper footpedal members.
In order to maintain the front rider's correct leg extension distance to the upper footpedal member, the front seat must therefore be raised by a distance approximately equal to the distance between the upper and lower foot pedal members. Raising the front seat the required amount could be accomplished by simply extending the existing seatpost's adjustment. Unfortunately the bicycle's existing seatpost is often not long enough to permit the required amount of additional vertical movement. More importantly, simply extending the existing seatpost actually moves the front seat backwards into the abdomen of the rear rider (due to the backwards slope of the bicycle frame's seat tube). Therefore, the present invention must provide a specialized mechanism for increasing both vertical and horizontal separation between the front and rear riders.
To provide this function, the present invention uses an adjustable, cantilevered seatpost mechanism with two degrees of freedom which enables the front rider to both raise and move front seat forward. The front seat adjustment mechanism is essentially a cantilevered member affixed to the top of the seatpost. The cantilevered member acts as a rail along which the front seat can be adjustably affixed. By sliding the front seat back and forth along this rail member, the riders can adjust their horizontal separation for comfort and adequate clearance during pedaling. During this horizontal adjustment procedure, correct leg extension for the front rider as well as adequate vertical clearance between the riders' legs is also obtained by adjusting the seat height (using the bicycle's existing seatpost adjustment mechanism).
Additional Design Elements The present invention is intended primarily for converting existing single rider bicycles to tandem operation however the invention can also be incorporated into the design and fabrication of new single/tandem bicycles. In the case of such newly fabricated bicycles, the frame geometry could be optimized for a more balanced weight distribution bylengthening the chainstay frame members. The front fork geometry could also be modified to provide the greater strength and high speed stability required for tandem operation. Components such as wheels, brakes and frame tubing could also be upgraded to improve durability under the greater loads imposed by dual rider operation.
Lengthening the chainstays would place the rear rider's weight further forward with respect to the rear axle and thus help to control any tendency for the front wheel to leave the ground during hard acceleration or when climbing steep grades. However, in the case of converting an existing single rider bicycle to provide tandem capability, lengthening of the chainstay frame members would be prohibitively expensive. In such cases, thetendency towards front end lightness can be controlled by simply moving the front rider's weight forward onto the front wheel. To facilitate the front rider' s forward weight transfer, "bar-end" handlebar risers can be purchased and added to the kit. These 2193~97 auxiliary handholds can be adjustably positioned to provide alternate handholds that are somewhat above and forward of the handholds used for single rider operation.
Using the alternate handholds provided by the optional "bar-end" handlebar risers displaces the front riders hand location along approximately the same vector as the front rider's seat and pedal positions have been displaced as a result of converting from single rider to tandem mode of operation. The alternative handholds therefore re-establish the front rider's ergonomically correct (single-rider) posture.
Handholds may also be provided for the rear rider (either integral to the seatpost or integral to the backrest/seat support rail). However, in most instances simply holding onto the seatpost can serve to adequately brace the rear rider's body during hard pedaling.
During normal use, the rear rider' s hands and arms are not needed to control the vehicle.
The rear rider is therefore free to hand aid the process of pedaling by alternately pressing down on whichever knee is on the downward, power stroke. This hand assisted mode of operation utilizes the muscle power of the upper body to augment that of the legs, thereby improving the overall efficiency of the vehicle.
In addition to the vehicular application described above, the present invention can also serve as a bicycle stand. To accomplish this mode of operation, the operator simply rotates the crank such that either pedal is immediately aft of its lowest point and leaning the bicycle onto it. Gravitational force naturally rotates the pedal assembly so that the upper pedal member is closest to the ground. This contact point with the ground serves as a bicycle stand by virtue of the fact that the gravitational force of the bicycle onto the pedal imparts a forward motion to the vehicle (through the transmission). This forward force is countered-balanced by the frictional contact that pedal assembly has with the ground. This dynamic balance of forces enables the bicycle to be statically supported by the pedal assembly.
With respect to the prior art:
By eliminating the additional crank and pedal assembly normally required by the rear tandem rider, the present invention provides a significantly lighter vehicle. Weight savings are also achieved by eliminating the additional drive chain normally required to link dual crank assemblies as well as the additional frame members needed to form the elongated frame inherent to previous tandem bicycle designs.
Furthermore, mechanical friction in the vehicle's drive train is significantly reduced by elimin~ting the second pair of footpedal bearings, the second crank bearing and the second drive chain and sprocket assembly required by previous tandem bicycle designs.
Furthermore, due to the rear rider' s seating position being situated more fully within the slipstream created by the front rider, the vehicle's wind resistance is reduced compared to conventional tandem bicycle designs.
Furthermore, by eliminating the need for a second crank and pedal assembly, a second drive chain and chainwheel assembly as well as the additional frame members needed to form an elongated frame, the cost of fabrication of the present invention is significantly reduced compared to previous tandem bicycle designs 219 ~3 9 9 rl~
Furthermore, since the present invention is of similar size and weight as a single rider bicycle, the same vehicle can still be efficiently propelled by a single front rider when no second rider is available to help pedal.
Furthermore, the present invention permits an existing single rider bicycle to be quickly converted into a tandem bicycle and back to a single rider bicycle.
Furthermore, when not in service as a vehicle, the present invention acts as a bicycle stand.
2193~97 DRAFT DRAWINGS AND DETAILED DESCRIPTION:
In drawings illustrating an embodiment of the invention:
FIG. 1 is an elevational view of a conventional single rider bicycle having tandem rider modifications mounted thereon which are constructed in accordance with and embodying the present invention: said bicycle being illustrated as occupied and actuated by a front rider pedaling with the heels of the feet.
FIG. 2 is an elevational view similar to figure 1 except that the front rider is using the side extension embodiment of the upper footpedal members, thereby enabling pedaling with the balls of the feet.
FIG. 3 is an elevational view similar to figure I except that the bicycle is illustrated being unoccupied by riders and the pedal assemblies are rotated to their support stand locations whereby the upper foot support surface contacts the ground when the vehicle is leaned over towards it.
FIG. 4 is an enlarged view of FIG. 1 illustrating details of the pedal assembly with the riders' feet correctly positioned.
FIG. 5 is an enlarged view of FIG. 2 illustrating details of the pedal assembly with the riders' feet correctly positioned.
FIG. 6 is an enlarged view of FIG. 2 illustrating details of the rear seat support assembly.
FIG.7 is an enlarged view of FIG. 1 illustrating details of the front seat support assembly fabricated using large diameter tubing.
MORE DETAILED TEXTUAL DESCRIPTION REFERENCED TO THESE
DRAWINGS WILL FOLLOW IN A FINAL AMMEDMENT TO THIS PATENT
APPLICATION:
The present invention is comprised of three sub-assemblies:
1 ) - The dual level pedals.
2) - The rear seat and its attendant support structure.
3) - The front seat raising and advancement mechanism.
When affixed to a conventional single rider bicycle structure, these three sub-assemblies operate in concert to effect its conversion to tandem operation.
Referring to the working embodiment illustrated in FIG. 1 which illustrates the relationship between the present invention's three main sub-assemblies: the front rider places the rear part of each foot onto the upper pedal surface member ## of each of the dual level pedal assemblies. The front rider's foot is thus displaced vertically upward with respect to its normal, single rider location on the rotateable lower surface member, by a distance equal to the distance between the upper and lower pedal surface members.
To compensate for this change in reach to the pedals, the front seat is also displaced upward the same distance by adjustably re-positioning the seat adjustment members ##.
The seat adjustment members also permit the seat to be adjusted forward of its conventional location so as to provide clearance for the rear rider and transfer weight onto the front wheel. The rear rider sits on the rear seat ## and places the front part of each foot on the rotateable, lower pedal surfaces ## and adjustably positions the rear seat ##
along the support rail ##
Referring to the workable embodiment illustrated in FIG. 3 each of the two upperfootpedal surface members ## is adjustably affixed to and supported substantially above its corresponding rotateable, lower footpedal surface member assembly ## by means of a series of substantially vertical compression members ##.
The upper footpedal surface member ## has a series of drilled tab members ## bent downwards along its sides so as to provide fixation points for the compression members ##. Each lower footpedal surface is comprised of a hub ## which rotates around the pedal' s bearing spindle ## which in turn is affixed to the crank arm ## of the bicycle' s existing transmission mechanism. Two U shaped members comprised of a central section ## and two drilled end tab sections ## bent at 90 degrees to the central member are affixed to the front and rear of each pedal hub ##. The two central sections ## affixed to the pedal hub ## serve as foot support surfaces for the rear rider. The drilled tab members ## provide lower fixation points for the vertical compression members ##supporting the upper footpedal member ##.
The upper end of each compression member ## is rotateably affixed to its respective upper footpedal tab ## using matching holes and a tightening fastener ## which serves to prevent rotation once a comfortable angular adjustment is set. The lower end of each compression member ## is affixed to the lower footpedal surface member using a similar rotateable fixation means as is employed at the upper end, however it has multiple fixation holes ## to permit the length of each compression member to be adjusted to suit both rider's pedaling comfort. Depending on the anatomical configuration of each rider, the upper footpedal member ## is fixed at a greater or lesser angle and separation with respect to the lower footpedal member ##.
Referring to the workable embodiment illustrated in FIG. 4, the main support rail member ## for the rear rider's seat ## is adjustably affixed to the frame of the host bicycle at both of its ends so as to maintain the support rail in a substantially horizontal position, aligned with the axis of the bicycle and immediately above the bicycle's rear tire. The mechanism for affixing the front of the seat support rail to the host bicycle is comprised of a angled bracket ## which is bolted through the front of the support rail member on one end and at the other end through the hole in the bicycle's seat stay brace ## normally provided to mount the rear brake assembly. The mechanism for affixing the rear of the seat support rail to the host bicycle is comprised of two rail support struts ##.
The top of each of the two rail support struts is bolted to the left and right side respectively of the rear seat support rail using a bolt ##. Spacer elements ## may be inserted between the seat support rail and the rail support struts to provide adequate clearance between the rail support struts and the rear tire. The seat support rail may be of any cross sectional shape however a preferred embodiment employs a circular cross-section as this minimi7es fabrication costs and also permits the use of a seat fixation device described below.
The rear bicycle seat ## is adjustably affixed at a point along the seat support rail ## such that it affords the rear rider a comfortable reach to the lower footpedals. The seat fixation device ## is a clamp which is affixed at its upper extremity to the underside of the rear rider' s seat and at its lower extremity to the seat support rail. In a preferred embodiment, the seat fixation device is the standard commercially available seat post clamp ## used to affix a bicycle seat to the substantially vertical seat post of a conventional bicycle. These inexpensive and commercially available seat clamps are comprised of a compressible clamping band ## which secures to the seatpost said band being rotateably coupled to a pair of pincer clamps ## which secure to the standard dual frame members ## which are integral to the bicycle seat. A single bolt ## through the rotation point of the clamping assembly simultaneously secures the pincer clamps to the seat frame and the compressible band clamp to the seatpost. Tightening bolt ## also fixes the angle between the two clamping elements. Typically the clamping assembly permits at least 180 degrees of rotation between said elements, thereby permitting the clamps for the rear rider's seat ## of the present invention to be rotated 90 degrees from its normal configuration with respect to a vertical seatpost such that the seat can be adjustably affixed to the horizontal seat support rail ##.
Referring to the workable embodiment illustrated in FIG 5, the front rider's seat ## is adjustably re-affixed to a position both forward and above it's normal position by means of a seatpost clamp ##, two 1/4 inch rod members ## and a seat fixation clamp ##. The seatpost clamp is the same mechanism described above that is used to secure the rear seat ## to the seat support rail ## however instead of be affixed to the two standard frame rails ## integral to the seat ##, its two upper clamping jaws ## are affixed to the lower ends of two seat extension rods ##. The seat extension rods are of suitable diameter to engage the seat clamp jaws. The seat extension rods ## are manufactured of sufficiently rigid and resilient material to support the cantilevered weight of the front rider. The upper clamping assembly is comprised of two swivel clamp assemblies identical to those used both to secure the rear seat to the support structure. When the clamp assemblies at both ends of the seat extension rods are loosened, seat extension rods are adjustable both angularly and longitudinally with respect to the clamp mechanism thereby permitting the user to re-position the front seat both above and forward of its single rider location.
The materials used for fabricating the bi-level footpedal apparatus, the rear seat support structure and the front seat raising and advancement mechanism are typically aluminum and steel however other metal alloys and even some reinforced plastics can provide the strength, resilience and light weight that are required. Although the invention has been described with reference to a particular illustrative example, it is recognized that various minor mechanical modifications are possible when implementing this inventive concept.
Claims (19)
1) A tandem bicycle propulsion system utilizing a single pedal crank assembly, said crank being directly actuated by means of rotateable footpedal assemblies shared by both front a rear riders, said footpedal assemblies being comprised of a lower load-bearing surface member substantially symmetric to the pedal's bearing spindle which receives pressure from the rear rider's foot together with an upper load-bearingsurface member which receives pressure from the front rider's foot, said upper member being affixed to and supported substantially above the lower footpedal member such that the force vector of front rider's pedaling effort can be exerted so as to pass downwards through the center of the pedal assembly's bearing spindle.
2) INSERT SEPARATE CLAIM FOR REAR EXENTSION SLAB TO LOWER
PEDAL TO ENABLE REAR RIDER TO COUNTERACT TORQUE INSTABILITY
CAUSED BY ECCENTRICITY OF FRONT RIDER'S POINT OF PRESSURE
APPLICATION.
PEDAL TO ENABLE REAR RIDER TO COUNTERACT TORQUE INSTABILITY
CAUSED BY ECCENTRICITY OF FRONT RIDER'S POINT OF PRESSURE
APPLICATION.
3) INSERT SEPARATE CLAIM TO COVER FRONT EXTENSION TO LOWER
PEDAL WHICH ALSO ACTS AS A TOE-CLIP AND ENABLES REAR RIDER
TO COUNTERACT TORQUE INSTABILITY CAUSED BY ECCENTRICITY OF
FRONT RIDER'S POINT OF PRESSURE APPLICATION.
PEDAL WHICH ALSO ACTS AS A TOE-CLIP AND ENABLES REAR RIDER
TO COUNTERACT TORQUE INSTABILITY CAUSED BY ECCENTRICITY OF
FRONT RIDER'S POINT OF PRESSURE APPLICATION.
4) INSERT SEPARATE CLAIM FOR SIDE EXTENSIONS TO UPPER FOOTPEDAL
MEMBERS WHICH PERMIT THE FRONT RIDER TO APPLY FOOT PRESSURE
USING EITHER THE BALLS OF THE FEET (BY PUSHING ON THE SIDE
EXTENSONS OF THE UPPER PEDALS) OR THE HEELS OF THE FEET (BY
PUSHING ON THE INNER PORTION OF THE UPPER PEDAL).
MEMBERS WHICH PERMIT THE FRONT RIDER TO APPLY FOOT PRESSURE
USING EITHER THE BALLS OF THE FEET (BY PUSHING ON THE SIDE
EXTENSONS OF THE UPPER PEDALS) OR THE HEELS OF THE FEET (BY
PUSHING ON THE INNER PORTION OF THE UPPER PEDAL).
5) INSERT SEPARATE CLAIM FOR SHOE CLEAT AFFIXED TO UPPER
SURFACE OF THE SIDE EXTENSION OF THE UPPER FOOTPEDAL
MEMBERS WHICH PERMITS THE FRONT RIDER TO SECURE EACH FOOT
TO THE UPPER FOOTPEDALS.
SURFACE OF THE SIDE EXTENSION OF THE UPPER FOOTPEDAL
MEMBERS WHICH PERMITS THE FRONT RIDER TO SECURE EACH FOOT
TO THE UPPER FOOTPEDALS.
6) INSERT SEPARATE CLAIM TO COVER ADJUSTMENT OF ANGLE AND
DISTANCE BETWEEN PEDAL'S UPPER AND LOWER MEMBERS
DISTANCE BETWEEN PEDAL'S UPPER AND LOWER MEMBERS
7) INSERT SEPARATE CLAIM TO COVER HEEL STOP ON UPPER PEDAL
MEMBER TO CORRECTLY POSITION FRONT RIDER'S HEEL
MEMBER TO CORRECTLY POSITION FRONT RIDER'S HEEL
8) INSERT SEPARATE CLAIM TO COVER UPWARDLY ANGLED SIDE
EXTENSION TO COMPENSATE FOR SPLAYED LEG RIDING POSITION OF
THE FRONT RIDER
EXTENSION TO COMPENSATE FOR SPLAYED LEG RIDING POSITION OF
THE FRONT RIDER
9) INSERT SEPARATE CLAIM TO COVER TRIANGULAR SUPPORT FOR A
SPAR-LIKE UPPER FOOTPEDAL MEMBER.
SPAR-LIKE UPPER FOOTPEDAL MEMBER.
10) A bicycle configured in accordance with claim 1 to which a rear rider's seat is affixed at a location immediately behind and substantially lower than the front rider's seat such that, when both rider's feet are engaged onto the bi-level footpedal assemblies, their legs do not interfere with each other when applying pedaling force to the pedal crank, for all angles of pedal crank rotation.
11) INSERT SEPARATE CLAIM FOR REAR BRAKE RE-POSITIONING MEANS
12) INSERT SEPARATE CLAIM TO COVER BACKREST ON REAR SEAT
ASSEMBLY
ASSEMBLY
13) INSERT SEPARATE CLAIM TO COVER REAR RIDER HAND HOLDS (BOTH
ON FRONT SEAT RISER AND REAR SEAT SUPPORT)
ON FRONT SEAT RISER AND REAR SEAT SUPPORT)
14) INSERT SEPARATE CLAIM TO COVER HAND AIDING OF REAR LEGS
15) A bicycle configured in accordance with claim 1 and claim 2 to which a front seat position adjustment device is affixed between the seat and seatpost, said adjustment device comprised of a rail member affixed to the top of the seatpost, said rail member being horizontally cantilevered forward from the upper extremity of the seatpost and engaging a sliding fixation device which in turn engages the standard seat support members integral to the lower structure of standard bicycle seats, thereby permitting the front seat to be adjustably re-positioned somewhat forward of its normal location.
16) INSERT ADDITIONAL CLAIM TO COVER STAND FUNCTION OF
INVENTION (CONTACT SURFACE AND POSSIBLE ANTI-ROTATION LOCK)
INVENTION (CONTACT SURFACE AND POSSIBLE ANTI-ROTATION LOCK)
17) INSERT CLAIM TO INTEGRATE THE THREE MAJOR COMPONENTS INTO A
KIT (SUCH THAT IMPROVEMENTS TO ONE OF THE ELEMENTS DOESN'T
CONSTITUTE A NEW INVENTION).
KIT (SUCH THAT IMPROVEMENTS TO ONE OF THE ELEMENTS DOESN'T
CONSTITUTE A NEW INVENTION).
18) INSERT ADDITIONAL CLAIM TO COVER HANDLEBAR EXTENDERS THAT
PERMIT THE FRONT RIDER'S ERGONOMICS TO BE MAINTAINED WHEN
IN THE DUAL RIDER MODE.
PERMIT THE FRONT RIDER'S ERGONOMICS TO BE MAINTAINED WHEN
IN THE DUAL RIDER MODE.
19) INSERT SEPARATE CLAIM TO COVER BOTH CASES: A KIT TO CONVERT
EXISTING BICYCLES AS WELL AS NEWLY CONSTRUCTED BICYCLES
INCORPORATING THE SAME DESIGN PRINCIPALS BUT WITH OPTIMISED
FRAME GEOMETRY AND STRENGTHENED COMPONENTS.
EXISTING BICYCLES AS WELL AS NEWLY CONSTRUCTED BICYCLES
INCORPORATING THE SAME DESIGN PRINCIPALS BUT WITH OPTIMISED
FRAME GEOMETRY AND STRENGTHENED COMPONENTS.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002199997A CA2199997A1 (en) | 1996-12-27 | 1997-03-14 | Tandem bicycle propulsion system utilizing a shared footpedal and crank assembly |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2194029 | 1996-12-27 | ||
| CA002194029A CA2194029A1 (en) | 1996-12-27 | 1996-12-27 | Tandem bicycle propulsion system utilizing a shared footpedal and crank assembly |
| CA002199997A CA2199997A1 (en) | 1996-12-27 | 1997-03-14 | Tandem bicycle propulsion system utilizing a shared footpedal and crank assembly |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2199997A1 true CA2199997A1 (en) | 1998-06-27 |
Family
ID=25678952
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002199997A Abandoned CA2199997A1 (en) | 1996-12-27 | 1997-03-14 | Tandem bicycle propulsion system utilizing a shared footpedal and crank assembly |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2199997A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL1034557C2 (en) * | 2007-10-19 | 2009-04-21 | M A Rietveld Beheer B V | Bicycle e.g. sports bike, has frame attached to two seats for supporting persons, and drive shaft including set of pedals placed between another set of pedals, where one seat is placed lower than another seat |
| CN105905197A (en) * | 2016-05-25 | 2016-08-31 | 江苏帕维电动科技有限公司 | Adjustable electric bicycle back seat |
-
1997
- 1997-03-14 CA CA002199997A patent/CA2199997A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL1034557C2 (en) * | 2007-10-19 | 2009-04-21 | M A Rietveld Beheer B V | Bicycle e.g. sports bike, has frame attached to two seats for supporting persons, and drive shaft including set of pedals placed between another set of pedals, where one seat is placed lower than another seat |
| CN105905197A (en) * | 2016-05-25 | 2016-08-31 | 江苏帕维电动科技有限公司 | Adjustable electric bicycle back seat |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |