A new Hungarian developed chain-less bike debuts today in Padova, Italy. The bike has been developed by a team of designers at the Schwinn Csepel Zrt..
Here is the technical description of the chain-less bike called Stringbike.
The bicycle has a new driving system using steel wires instead of chains, which has the following main units:
Pedal. This is basically identical with those of conventional bikes. Respective pedals are arranged at either side of the frame, and the cyclist rotates the two pedals around a central pivoted axis.
Eccentric discs. The pedal axis rotates these discs at both sides of the frame. The discs has a specific, kidney like shape which determines the driving characteristic i.e. the angular displacement of the rear wheel of the bicycle as a function of the angular position of the pedal shaft. The chosen shape provides for a conventional driving characteristic i.e. the same as if a chain-driven bike with circular gears were used. In a more expensive model the discs can be changed with other ones having different shapes, whereby the driving characteristic can be changed in a tour or in a contest, to load different muscle groups.
The swinging unit, comprising a pair of oppositely swinging arms arranged for swinging movement around a pivoted auxiliary axis. The rotation of the eccentric discs results in the swinging movement of the arms in forward and backward direction.
Transmission (speed) changer. This unit is a controlled slide. It changes the longitudinal position (height) of respective pulleys guided along the swinging arms. The height of the two pulleys is always the same. When the pulley is in the outermost position, the transmission ratio is at maximum, while in the innermost position this ratio is at minimum.
Rear shaft unit comprises respective freewheels at each side. The outer surface of the free wheels defines respective cable drums.
Wires interconnecting the respective cable drums with the pulleys. One end of each wire is attached to the cable drum and the other one to the frame.
Cable biasing means, which is a double cable reel arranged at the upper portion of the rear fork, just oppositely relative to the rear brake. The two reels are spring biased to each other, and they hold thin biasing wires wound around the respective cable drums. The role of this means is to keep the pulling wires always under tension.
Properties of the new bicycle
1. Possibility of changing the driving characteristics by changing the discs. Since the possibility of using different driving characteristics freely has been provided by this new chainless bicycle, it will be the question of further tests and experiments to determine which kinds of characteristic are ideal for different driving and terrain conditions. With our model that uses a normal driving characteristic, the driving under different fields is just as in case of usual bicycles.
2. Changing the transmission ratio at any time. At almost every moment one of the two wires does not transmit large forces, it is exposed only to the biasing force. This enables the continuous or quasi-continuous change of the transmission ratio under high load and also in stationary position when the pedals are not turned. By this property a skilled rider can overcome curly streets with a higher speed as if he had a conventional bicycle, since he has a fast and free control of the transmission ratio, and the manipulation itself cannot take his attention away from his driving task.
3. The steel wires do not slip, the driver cannot feel that there is any delay or slip between the movement of the pedal and of the bike.
4. Due to the new design there are no gear wheels and chain, there are no contaminating parts in the driving system, such as the usual soiling of clothing with oil.
5. The rear wheel can be disassembled from the frame without any difficulty, the removal of the rear wheel does not affect the wiring and the driving system. Disassembling takes only a few seconds.
6. The previous properties enable transportation of the bicycle in a minimised space i.e. with removed front and rear wheels. The bicycle is so clean that it can well be placed either in the trunk or in the rear compartment of most cars, since the frame is not too large without the two wheels. While this was impossible with conventional bicycles, since the chain was dirty and the removal of the rear wheel required the disassembly of the chain which was a time-consuming operation.
7. A further advantage is that the attachment position of the strings on each side need not be identical. This allows asymmetric loading of the legs. Since no one has identical joints and muscles on both legs, if one has a weaker leg, a lighter load can be applied. Alternatively, if one wished to load a leg more during training, this may also be done easily. This is not possible with conventional bicycles.
8. From the point of view of marketing, the funny form and mode of operation of the bicycle can offer a huge marketing potential. The almost unchanged form of bicycles might have bored people in the last several decades. This new form may well become into the focus of attention and become fashionable. In this aspect the interesting dynamic of the movement is very attractive.
9. The lifetime of components, especially that of the wires can be longer than in case of chains and wheels, which are exposed to wear and abrasion.
10. The number of components can be less than in case of a conventional bicycle with several front and rear gears. Following an initial training period, the manufacturing costs can go below to those of conventional bicycles if the production can be organised in a sufficiently large scale.
Inventors: Gábor RÁCZ, Róbert KOHLHEB, Olivér Vonhauser
International Application Number: PCT/HU95/00006
International Patent Classification: B62M 1/02
Danunbia Attorney: Michael LANTOS