Das Lefèbvre Vélocipède
Research on a Pedal-Driven Velocipede Created by Alexandre Lefèbvre Possibly in 1842.
Abridged Version From Articles Presented in Wheelmen Magazine Issue # 58 and the 12th ICHC Conference Proceedings, San Remo, Italy
Physical Features of the Lefèbvre Velocipede
The Lefèbvre velocipede is constructed in a manner similar to the modern bicycle. Two nearly equally sized wheels, arranged in tandem, are attached by a connecting frame that supports the rider at its mid point. The rear wheel is suspended in a paired, fixed iron triangular frame with stays, one on each side, as with modern bicycles. Nearly all the elements of the modern "diamond frame" are incorporated in the Lefèbvre design. A pivoting handlebar/column of iron and steering system and fork is mounted at the front end of the frame, passing through at a pivot just as in modern bicycles. A power transmission system using paired pedals, levers and power linkage to the rear wheel hub enables continual propulsion of the velocipede forward. The rods and levers automatically cycle the pedals back for use in a succeeding power stroke, without the rider having to raise his legs to re-set the levers. The center frame members, wheel hubs, spokes and felloes, and the handlebar cross member are all constructed of wood. The wood appears to be oak or another similar open grain hardwood. All of the other components are made of hand-forged steel or iron.
The Lefèbvre Velocipede is 74 inches in total length (front of front wheel, to back of rear wheel). The wheelbase is 41 ½ inches long at the hub centers. The bicycle stands approximately 48 inches tall from the ground to the top of the handlebar. The wooden handlebar is 18 ¼ inches wide at the grip ends. The set width ("Q factor") of the pedals and levers is approximately 10 inches on centerline, narrowing from 12 ½ inches where the lever pivot yoke supports the levers below the rider.
The rear wheel is 36 inches in diameter. The front wheel is 30 inches outer diameter. The felloes are constructed from a single piece of steam bent wood, which are warped into a closed circle. The ends are joined with a doubled "V" joint. Each joint is reinforced with a small elliptical metal plate attached at the inside face of the felloe. There are sixteen wooden spokes in the rear wheel and fourteen wooden spokes in the front wheel. The hubs are turned with a modified hourglass shape. The spokes connect at the wider shoulders of the hubs, angled to converge at the felloe. The "spoke dish", the angle from hub centerline, is TWICE that of other velocipedes. The front axle is fixed, with the hub rotating freely about it. The ends of the hubs are faced flat to facilitate insertion and alignment with the front fork ends and the rear drive mechanism.
The rear hub is constructed identically to the front hub, and the spokes are mated to the hub same as the front wheel. The rear axle passes through the hub and is attached to the rear hub by two four-point metal splines that are screwed to the adjoining spokes at either side of the hub. This ingenious system allows for power to be transferred from the cranks and axle through to the rear wheel while distributing the pedaling torque evenly over the delicate wooden wheel components.
Wood Frame and Iron Triangles
The frame, or perch, is composed of wooden and iron components. Wood comprises the main portion that supports the saddle suspension and rider, the wheel-supporting front fork and steering mechanism, rear wheel triangles and drive lever undercarriage. The main part of the perch is fabricated from two pieces of wood. The upper part runs from the decorative snake head back to form the upper perch beam, under the saddle. The upper beam supports the upper ends of the metal frame triangle at its rearmost end. It also supports the spring suspension holding the saddle. A second heavy wood beam is joined to the upper beam just behind the iron steering supports. This beam deflects downward from the line of the upper member. The second beam continues from the midpoint of the upper beam. The lower ends of the iron rear wheel triangles are supported at the back end of this beam. A pair of hand-forged iron triangles attached to the wood frame holds the rear wheel in position, one on each side of the rear wheel. Each triangle is attached to either side of the bottom frame beam by a flattened bracket surface. The left and right sides are welded as one piece by a box-type arrangement that allows the pieces to wrap under the upper wood frame beam. The drive train is anchored at the low part of the triangles As on modern bicycles, the rear frame stays are set widest apart at the rear hub and come closer together at the frame under the seat. The lower stays remain moderately wide to accommodate the pedal levers and the necessary 'Q' factor for the rider's hip width. The narrowing also accommodates clearance for the tie rods and crank arms at the rear hub.
Drive levers and Pedals
The drive levers and pedals are constructed with hand-forged iron to form a stylized 'E' shape. The levers are designed so as to form a 90o angle allowing the downward leg force of the rider to be converted into a horizontal pulling force when applied to the tie rods connected at the rear wheel crank-arms. A pivot point is located approximately 1/3 the length of the lever from the rear connection points. A stirrup supports each pedal platform. The stirrups and lower lever arms form a horizontal plane when the lever is in its lowest position. The arm clears the rider's heel in this position. At the high point of the lever's stroke arc, the lever is positioned vertically under the rider's foot. Two tie rods attach the pedal levers at the vertical connecting point to a pair of opposed crank-arms attached to the extended axle of the rear wheel.
The Mechanics of the Lefèbvre Drive System
The Lefèbvre driving mechanism allows the rider to exert a vertical force, far more efficient than the horizontal or downward kicking forces of the McMillan and Dalzell velocipedes. Next, three different lever arms come into play. The force of the rider pushes down on the distal portion of the pedal arm forcing it down and the upper portion of that arm to move forward about a fixed point. Here a vertical "pushing" force is converted to a horizontal pulling force. In addition, this vertical pivot lever is set with a fulcrum, so that the lever arm length of the lower arm is exactly TWICE the length of the upper segment giving the rider twice the force at the upper pivoting (pulling) point. This vertical-to horizontal force is then further translated by the connecting rods and converted to a rotary motion via these connecting rods, to the third lever arms fixed at the rear wheel axle. This second lever arm is 50 percent longer than the crank arms' third lever with a ratio from pedal to axle, approximately 2:1, 1.5:1. THREE levers per pedal amplify the rider's force to the rear wheel versus two for the McMillan etc, velocipedes. This is in effect "gearing". With this lever system, 1 ft/lb of force at the pedal generates 3 ft/lb of torque at the hub.