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The Warsaw Voice » Other » September 30, 2009
Technology
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Hitting high gear
September 30, 2009   
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As every cyclist knows, derailleur gears need to be maintained from time to time so that the chain properly shifts from one set of sprocket wheels to another. With time, "free play" sets in though and even the best mechanisms of this kind fail to work precisely. This shortcoming can be eliminated thanks to an invention by a Polish engineer who has filed a international patent application under the Patent Cooperation Treaty (PCT).

What causes problems with classic gears? The ratchet or gear blocking mechanism which serves to shift the position of the chain is located in the gearshift or gear lever at the handlebars. On the way to the chain, there are parts that stand in the way of smooth transmission. This inspired engineer Władysław Hura from the southern city of Bielsko-Biała to come up with an idea to move the gear blocking mechanism from the gear lever, mounted at the handlebar, to the derailleur, or gears proper.

Hura, who runs a bicycle, motorbike and motorcycle service business, has gained popularity in the Podbeskidzie region as a designer of machines and appliances. He has a number of patents to his name.

"My idea differs from those applied in classic gears," says Hura. "Classic gears are open-type designs unprotected from mud and dust. My innovative derailleur is controlled by a loop-shaped endless cable. The gear blocking function has been moved to the derailleur, which is enclosed in a casing with a rubber "concertina" that protects the mechanism from dirt."

Hura says his invention is "based on the use of a two-way derailleur control mechanism using an endless cable and a simple and reliable transmission ratio mechanism in a closed casing. The relocation of the gear blocking mechanism from the handlebar to the derailleur mechanism means that the derailleur operates reliably, the transmission ratio is selected accurately and maintained stable, and that the derailleur will not be put out of adjustment but will be resistant to extreme operating conditions and mechanical damage."

Prototype research has revealed that the new mechanism is reliable and easy to assemble, Hura says. It can be assembled on any bicycle. The inventor has designed the gears especially with trekking and roadster bicycles in mind. The new gears work well under load and are fit for mountain bikes. Design work is in progress to modify the new gears so as to increase shifting speed and adapt it to racing requirements.

"The new derailleur is mostly for those looking for riding comfort and reliability," says Hura. "My derailleur fully meets these requirements. Most people use simple gears because they cannot afford high-class mechanisms. Thanks to my idea, it will be possible to produce these kinds of luxury gears while keeping the price down."

The prototype's seven-speed freewheel transmission takes only 0.4 seconds to change gears. Importantly, the derailleur has an encoded gear selection. Thanks to its modular design, the mechanism is easy to repair. Unlike in the case of classic derailleurs, it is enough to replace a single part rather than the whole mechanism. For the time being, Hura's derailleur is at the prototype stage. The designer is looking for an investor to launch production.

Ewa Dereń


Factfile
Derailleur gears are a variable-ratio transmission system commonly used on bicycles, consisting of a chain, multiple sprockets and a mechanism to move the chain from one sprocket to another.

Modern front and rear derailleurs typically consist of a moveable chain-guide that is operated remotely by a cable attached to a shift lever mounted on the down tube, handlebar stem, or handlebar. When a rider operates the lever while pedaling, the change in cable tension moves the chain-guide from side to side, "derailing" the chain onto different sprockets.
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