Note: Descriptions are shown in the official language in which they were submitted.
,~ 21 94~29
BACKGROUND AND PRIOR~ ART:
This invention relates to bicycles and more particularly to a means for modifying a
~vllv~-"iu-lal bicycle configuration so as to d,CUlllll~Od.li~, 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.
I) 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 Lldl~fulllled into a tandem rider
apparatus. However, the cost of ,uch a vehicle is at least double that of a single rider
bicycle and the safety of such a vehicle on public roads is ~u~ Jlull is~d by both its width
and its handling ~,h-.a~
2) The prior art also reveals a second and more prevalent category of tandem bicycle
which d~ ~ulllluuddLt:s its riders, one in front of the other, upon an elongated frame while
each rider actuates separate pedal and crank assemblies, said assemblies being rotatively
coupled through an auxiliary drive chain. This tandem configuration affords a
considerable gain in mechanical e~fficiency 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 ~ U1II~UIIL~
brakes, some frame l;Ulll~/On~ and some transmission ~UIIII)UII.,.IL~. However, the
elongated tandem configuration still n~cP s the duplication of certain heavy andexpensive UUIII~JUII~,.lt~. two separate pairs of pedals, crank arms and main bearing
assemblies together with the auxiliary chain required to couple the front and rear drive
UUlll,UUll~,llt:~. Furthermore, the elongated frame structure nPrPi~;tA~PC additional frame
members to extend and support the two main triangles which make up a ~;ullv~llLiulldl
bicycle frame. These additional fi ame members also add si~nificantly to the cost and
weight of the vehicle. Furthermole, if no second rider is available to contribute pedaling
energy, the elongated tandem con~ïguration is too heavy and unwieldy for efficient
propulsion by a single rider, thereby limiting the vehicle's versatility as a means of
Lldlls~UI LdLiUII.
3) A third category of prior art exists which is the most relevant to the present invention.
This prior art modifies the conveniional single rider configuration by adding a second
seat assembly as well as footpedals that are modified to A~cornnno/' the feet of the rear
rider upon the same footpedal assemblies as those used by the first rider. 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 conventional tandem
bicycles:
I) An existing bicycle can be easily be converted to serve in either a single rider or
tandem mode.
2 1 94~29
2) The cost of the special pedals and seating means are far less than the cost of a
dedicated tandem bicycle.
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 sLlch 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: The means for accommodating the rear rider' s feet on the pedals extended
the normal dimensions of the rotateable pedal assembly such that the pedal can
occasionally hit the road during u se, thereby causing loss of power to the vehicle and
possible injury to the riders. The "side by side" foot placement configuration proposed
within this prior art caused pedal grounding during tums. . The "over/under" foot
placement configuration proposed within this prior art did not provide adequate road
clearance for the rear rider's feet (the rear rider's feet being located under the pedal
assembly's bearing spindle).
Drawback #2: The seating a~vll~u~vdaiillg for the rear rider was such that the two riders
experience ergonomic fatigue while pedaling due to illlrl rr.,e. c between their legs.
It is therefore the objective of the present invention to provide a tandem bicycle
propulsion system which eliminates the ~rv.rlll~lltivllrd 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:
I) Both riders can direc~dy actuate the same footpedal assemblies while continuously
mrin~Aining adequate clearance between the road and pedal assemblies.
2) A second rider can sit comfortably upon the modified bicycle at an optimal location
behind and below the first rider.
3) The front rider can adjust the location of the front seat both forwards and upwards with
respect to its normal location, thereby providing adequate leg clearance between the two
riders during all phases of crank rotation.
DESCRIPTION OF THE KIT'S THREE SUB-ASSEMBLIES:
Sub-assembly #1:
Both conventional single rider bicycles and conventional tandem bicycles, employ a
footpedal design comprised essentially of a rotateable, footpedal member substantially
symmetric about the crank arm's pedal bearing spindle. The present invention
rrcr,mmr ' 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 . ccrntrirAlly
affixed to and supported somewhat above the concentrically rotateable footpedal member.
The lower (concentric) footpedal member is used by the rear rider during tandem
operation of the vehicle. By placing both rider's feet above the pedal assembly's bearing
spindle, the present invention insures that adequate ground clearance is maintained at
essentially the same distance as when the vehicle is operated in the single rider mode
(when the front rider occupies the rotateable footpedal members). Each of the dual-tiered
footpedal assemblies receives botlh the front and rear rider's feet, one above the other,
such that they are as close to each other as rnArrmir~lly possible. It does so by
21 94029
supporting the front rider's heel in front of, and immediately 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.
To enable correct relative positio:ning of the two riders' feet, the upper footpedal member
is non-rotateably affixed to the rotateable, lower footpedal member by means of
substantially vertical compression members affixed at their upper and lower ends to the
sides of the upper and lower fooq~edal members. In a preferred clllbudilllclll, the spacing
between the upper and lower footpedal members as well as the dihedral angle between
the plane of the two footpedal members is adjustable by means of a multiplicity of
fixation points near each end of the compression members w hich can be used to adjust
the effective length of each l,Ulll~)lCi~ iUII 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 forepart of each foot onto the lower, concentric footpedal
member and thereby apply propu]lsive foot pressure to the bicycle's crank and chainwheel
assembly.
In a preferred clllbudilllcllL, the upper fooqpedal surface is flared upwards along its
rearmost edge to form a more ~~ mic ~lly correct receptacle for receiving the rear
rider's foot. This same flared lip also 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).
When using the present invention in single nder mode, the lone rider pedals in the
conventional manner by applying propulsive force to the lower, rotateable footpedal
members. However, during tandem mode operation, the lower footpedal members
become occupied by the rear rider, therefore the front rider must pedal using the upper
footpedal members. Tandem pedaling action is a, culll~l;shcd by first placing the rear
portion of each of the front rider's feet onto the upper footpedal member of each of the bi-
level footpedals. The front rider then applies propulsive force by exerting heel pressure
onto the assembly. The front rider's heel pressure is transmitted down the ~,UllllJlC~iUII
members and into the lower footp,edal members, thereby augmenting the rear riders
pedaling 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. If the force vector of the front rider's applied pressure does not pass
exactly through the assembly's axis of rotation, the pedal member's eccentricity creates
an unstable turning moment about the assembly's bearing spindle. The instability of this
force geometry is proportional to the ec~_cllLli_i~y of the upper footpedal member (i.e.
proportional to the distance between the planes of the two footpedal members). Since the
present invention forces the front r ider to apply only heel pressure to the footpedal
assembly, slight variations in natu:ral foot movement during pedaling tend to produce a
force vector which often passes somewhat forward of the assembly's axis of rotation,
2~ 9~29
thereby inducing a ~.sfAhilizing ~Forward torque. If left uncontrolled, this rotational
instability could easily cause the entire footpedal assembly lo rapidly spin forwa}d when
a strong pedaling force is exerted by the front rider. Such highly unstable forward
rotation would 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 to achieve
a dynamic balance of rotational forces about the pedal assembly's axis. The first means
for uuullLcld~,Lillg the unstable rotational force is simply to position the two riders' feet on
the pedal assembly as close together as physically possible. This close proximity
between the two riders' feet minimizes the lever-arm effect caused by upper pedal
member's e.~,..LIi~iLy. 1~ .h~g the upper pedal member's lever-arm effect help5 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
forward torque surges in the whole footpedal assembly.
The present invention therefore provides a second means of ~ uuLcld~L;Ilg the unstable
forward torque produced by the front rider's eccentric application of force onto the pedal
assembly. This innovation is based on harnessing an equal and opposite "~ oly
torque generated by the rear rider's pedaling force. The rear rider naturally can apply the
required uulll~cll~dtu~y torque to the pedal assembly by shifting the location of foot
pressure application towards the r ear of the lower footpedal member, thereby inducing the
Culll~cll~dLuly torque required to prevent forward rotation of the pedal assembly. This
rearward ,1;~l,l,1. c",. .,1 of the force vector on the lower footpedal member could
conceivably be accomplished by moving the rear rider's feet backwards and forwards as
required to counteract the variable forward torque produced by i,l~."l.~i~l. .I('ir~ in the
front rider's pedaling motion. However, given the rapidity with which the ~ l y
torque must be applied, the rear rider would quickly tire of continually shifting foot
placement fore and aft on the lower footpedal.
The most natural and relaxing muscular action that applies brief periods of ~ulu~cul~dLuly
torque occurs when the rear rider simply applies downward heel pressure. This heel
pressure creates instant counter-rotative force to counteract the front rider's eccentric
force vector. However, heel pressure can only have effect if the rear rider's entire foot
and pedal member are disposed so that the foot is fully supported from heel to toe. The
present invention therefore provides a modified lower footpedal member which is
constructed a~yllllllcLIi~a]]y so as to provide the necessary foot support. This support is
provided by a rear projection of the lower footpedal such that the lower footpedal
member is asymmetric about the bearing spindle. The rear footpedal extension provides
heel support for the rear rider, thereby permitting the rider' s heel pressure to modulate the
required counter-rotative torque into the pedal assembly.
To avoid fabricating a large and heavy pedal assembly, the rear extension of each lower
footpedal member may be truncated shorter than required to fully support the rear rider's
heel. If this is the case, any overhang of the rider's heel past the end of the rearward pedal
extension creates a bending force which will tend to lift the r ider's toe off the pedal
member (thereby defeating the desired uulll~ dLuly torque modulation). Therefore, the
2~ 94029
.
present invention optionally hluul~ul~Lcs a conventional bicycle toe-clip on the front edge
of the lower pedal member which insures that all of the heel pressure induced corrective
torque is actually transferred into the rotateable pedal assembly.
S~b-assembly ~2:
The second of the three functional sub-assemblies which constitute 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 seconduul~vc;uLiu~al, bicycle seat together with the appropriate support members that affix it to
the bicycle in the correct ergonormic location. The rear seat is adjustably supported and
positioned along a substantially horizontal rail member, affixed at its front end to the
upper seatstay members of the cullvellLiullal bicycle frame. Rear support for said
horizontal rail member is provided by two UUIII~ iiiUII members affixed at their upper
ends to said rail and at their lower ends to each side of the bicycle frame near the location
of the rear axle. The rear rider's bicycle seat is adjustably positioned on said support rail,
to a location behind the front rider's seat.
For optimal ergonomic interaction with the front rider, the rear seat support rail must be
kept as low as possible on the bicycle's structure. The compression members supporting
said rail therefore have multiple fixation points which permit the rail to be vertically
positioned on the bicycle such that it just clears the rear tire. A clamping device is also
provided to adjustably affix the rear rider's seat at a point along the horizontal support
rail member at the location which provides comfortable leg extension to the rear rider' s
(lower) footpedals. Additional vertical leg clearance between the riders is created by
rnmfigllring the internal support structure of the rear seat as well as the clamping device
used to adjustably affix it to the support rail member in a manner that positions the rear
seat as close to its support rail as possible.
Many existing bicycles are fitted with cantilever style brakes affixed to the seat-stay
frame members which protrude outwards from the frame such that they could contact the
rear rider's inner thighs during pedaling activity. To eliminate this ergonomic problem,
the present invention provides me~ans for re-locating the existing brake assembly behind
the rear rider's legs such that no hl~ 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 ~ g~ 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 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 altemate means of providing adequate side clearance between the rear rider's inner
legs and the existing rear brake assembly is to eliminate 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 weighl: will be approximately doubled by the addition of a
2~ 94~2q
.
second rider, it would be a prudent safety measure to improve the vehicle's braking
power in this manner.
The support rail assembly may optionally incorporate a backrest structure which provides
two functions:
The first function of the backrest is to provide a more restful seating position for the rear
rider during slow, relaxed cycling activity.
The second function of the backr,est is to prevent the rear rider from sliding backwards
during hard pedaling.
The support rail assembly may optionally incorporate a pair of handholds 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 to lift the rear rider's body off
the seat, thereby momentarily relieving pressure on the buttocks.
Sub-assembly #3:
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 normal position. This re-positioning is required to insure adequate
vertical clearance between the front and rear riders' legs at all angles of crank rotation.
During tandem pedaling, the rear rider's legs must move in close proximity behind and
beneath the front rider's legs without any mutual interference. Given the geometry and
seat location of the typical single rider bicycle, when both rider's feet are at the top of the
pedaling stroke, the vertical separation between the front and rear seats would not be
great enough to establish sufficient clearance between the top of the rear rider's thigh and
the bottom of the front rider's thi,gh. The present invention already provides means to
seat the rear rider as low as possible with respect to the front rider. Despite these
attempts to optimally position the rear seat to provide maximum clearance between the
riders, the dimensions and geometry of the typical bicycle and the leg size of typical
riders, will still preclude adequate clearance between the riders.
To achieve the necessarv vertical clearance, the front rider's seat location must also be
moved upwards from its normal, single rider location. Since, when converting from the
single rider mode of operation to the tandem rider mode of operation, the front rider
moves from the lower to the upper footpedal members, in order to retain the correct leg
extension distance between the front rider's seat and the upper footpedal member, the
front seat must also be raised by a distance approximately equal to the distance between
the upper and lower foot pedal m~ mbers. The required amount of vertical seat
adjustment could be accomplishe~ simply extending the existing seatpost A~jnctm,nt
ullr~ ~ Aly 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 actnally moves the front seat backwards into the abdomen of the rear
rider. Therefore, the present invention must provide a specialized mechanism forincreasing both vertical and horizontal separation between the front and rear riders.
To provide this function, the present invention uses an adjustable cantilever mPAhArlism
with two degrees of freedom which enables the operator to adjustably raise and move
2 ~ 94029
forward front seat. The front seat adjustment mPch~nicm is a cantilever that's ai'fixed
between the bicycle's existing seatpost and existing (front) seat by means of the existing
seat clamp. In a preferred embocliment, standard bicycle seat clamps are used at each end
of the cantilever to connect it to the seat and seatpost.
A standard bicycle seat clamp pn~vides both angular adjustment and longitudinal
adjustment for the seat by means of two pivoting clamps that affix to the two support rail
members which are integral to the under-structure of standard bicycle seats. In a
preferred embodiment of the present invention, the adjustable cantilever mechanism
consists of two straight seat extension rods, each having the same cross sectional diameter
and spacing as the two horizontal seat support members which are integral to the under-
structure of standard bicycle seatis. The rear end of each seat extension rod can thus be
securely engaged by the bicyclehi existing seat clamp such that each is cantilevered
forward and upward from the top of the seatpost. The two seat extension rods are thus
held parallel to each other at a distance equal to the distance between the seat support
members fabricated into the lowc,r structure of typical bicycle seats. The length of
cantilever in the two seat extension rods can be adjusted to the desired length by sliding
them in the seat clamp prior to tightening the clamp's fixation screw. A second seat
clamp IIIP. h.111;~111 is affixed to the other (upper) end of the two cantilevered members
thereby enabling the seat to be ac justably affixed to the upper end of the cantilevered
members. When the clamp assemblies at both ends of the seat extension rods are
loosened, the seat extension rods are adjustable both angularly and longitudinally thereby
permitting the user to re-position the front seat both above and forward of its single rider
location.
This same seat adjustment mecha,nism also serves to provide a cantilevered suspension
for the front seat by deforming under load to absorb some road shock before it reaches the
rider.
This same seat adjustment mP~hi~ni~im also provides a hand hold which can be used by
the rear rider to stabilize upper body movement on the bicycle.
A.' ' ' ' Design C ' I
The present invention is intended primarily for converting existing single rider bicycles to
tandem operation however the inventive elements can also be i-~,bl~ d~ed into the design
and fabrication of new single/tandem bicycles. In the case of such newly fabricated
bicycles, the frame geometry would be optimized for a more balanced weight distribution
by lPngthPning the bicycle's, horizontal chainstay frame members with respect to their
conventional, single rider proportions. Fork geometry would also be modified to provide
greater strength and high speed stability. Components such as wheels, brakes and frame
tubing would also be upgraded to improve durability under the greater loads imposed by
dual rider operation.
T .~ngihPning 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 ~rcplpr~i nn 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, the
2~ 9432q
tendency towa}ds front end lightness is effectively controlled by simply moving the front
rider's seat somewhat forward of its normal location, thereby re-distributing the front
rider's weight onto the front wheel.
Optionally, "bar-end" handlebar risers can be purchased and added to the kit. These
auxiliary handholds can then be adjusted to displace the front riders hand grips along the
same vector as the front rider's seat and pedal positions have been displaced. The
handlebar adjustment would then3by establish the front rider's posture to a~lulu~illlàL~ly
the same position as before the footpedal position was moved to the upper footpedals and
the front seat was displaced to ~comm. ~P the rear rider.
The rear rider may hand aid the Frocess of pedaling the tandem bicycle by using hand
pressure on his or her knees to more fully utilize the additional muscular force of the
upper body to augment that of the legs.
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 h~ .e.lk.'~,ly aft of its lowest point.
Gravitational force naturally rotates the pedal assembly so as to present the upper pedal
member at lowest 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 (~:hrough the llall~llu~iun). This forward force is
countered-acted by the frictional contact of the pedal assembly has with the ground. The
resulting dynamic balance of forc:es enables the bicycle to be directly 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
eliminating 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.
Ful Lhcillllul~, by eliminating the n:eed 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
2l 9402~
Furthermore, since the present invention is of similar size and weight as a single rider
bicycle, the sarne vehicle can still be efficiently propelled by a single front rider when no
second rider is available to help pedal.
F~l~thcllllulc, 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.
2~ 9402q
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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 two
riders.
FIG. 2 is an elevational view sirrlilar 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.
FIG. 3 is an enlarged view of F]:G. 1 illustrating details of the pedal assembly with the
riders' feet correctly positioned.
FIG. 4 is an enlarged view of F]:G. 1 illustrating details of the rear seat support assembly
and modified rear brake assembly.
FIG. 5 is an enlarged view of F]~G. 1 illustrating details of the front seat support
assembly.
The present invention is compnsed of three sub-assemblies:
I) - The dual level pedals.
2) - The rear seat and its attendant support structure.
3) - The front seat raising and a~b~a~ ..L 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 ~Illbodi~ 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 ~,UIII~)~ ' for this change in reach to the pedals, the front seat is also displaced
upward the same distance by adjostably re-positioning the seat adjustment members ##.
The seat adjustment members also permit the seat to be adjusted forward of its
lliulldl location so as to prc,vide clearance for the rear rider and transfer weight onto
the front wheel. The rear rider sil:s 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 Cullc ~olldillg 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
21 9402~
existing L .~ llliiX~iUII m~ h~nicn I 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 ea.ch 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 CUIIII'UI Idl11C angular adjustment is set. The lower end of each
UUIIIUlU~:~iUn member ## is affixed to the lower footpedal surface member using a similar
rotateable fixation means as is ernployed 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 me mber ##.
Referring to the workable embodiment illustrated in FIG. 4, the main support rail
member ## for the rear rider' s seat ## is adjustably affixed Lo 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 m.~h?ni.cm 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 stluts 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 clllbodilllcllL employs a circular cross-
section as this minimizes fabrical:ion 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 clulJudilllcllL,
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 UUllV~,IlLiUllcl] bicycle. These
inexpensive and cullllllcll,;dlly available seat clamps are comprised of a ~u~ c~ible
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 simnlt?~ollcly 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
21 q4~29
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 affb~ed 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 ra~lulc~d of sufficiently rigid and
resilient material to support the c~antilevered weight of the fiont 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 stlucture. When the clamp assemblies at both
ends of the seat extension rods are loosened, seat extension rods are adjustable both
angularly and loneih~in~lly 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.
Materials for fabricating the bi-le vel footpedal apparatus, the rear seat support structure
and the front seat raising and ad~ ancement 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 ehample, it is recognized that various minor
mechanical modifications are possible when implementing this inventive concept.
