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One standard option for the Brompton folding bicycle is to use a 3-speed hub gear (roughly a 30% difference between gear ratios) in combination with a 2-speed derailleur gear (roughly a 15% difference) to give 6 distinct gear ratios; this is an example of half-step gearing. Some Brompton suppliers offer a 2-speed chainring 'Mountain Drive' as ...
They can be used individually, as an external derailleur or an internal hub gear, or in combinations such as the SRAM Dual Drive, which uses a standard 8 or 9-speed cassette mounted on a three-speed internally geared hub, offering a similar gear range as a bicycle with a cassette and triple chainrings. Derailleur gears. Cogset; Crankset; Hub gear
A gearbox bicycle is a bicycle that uses a gearbox [1] [2] to convert torque and rotational speed from the power source, usually the rider's legs, to what is desired at the drive wheel. The gearbox is usually incorporated into the frame near the crank , and it may be used in addition to or instead of derailleur gears or a hub gear . [ 3 ]
The width of early Shimano 6- and 7-speed cassettes was 36 mm, and early 8-speed 40 mm wide. Shimano then changed again and standardised 8-11 speed cassettes on 41.5 mm and second generation 7-speed to 38 mm. The widening of the sprocket carrier on the cassette hubs to 41.5 mm resulted in a decrease in the distance between the hub flanges.
The only application currently commercialized is the internally geared bicycle hub. The NuVinci CVT replaces derailleurs and other internally geared hubs, and provides a gear ratio range of about 350%, similar to that on bicycles with 8- or 9-speed hub gears, or with double chain rings (most racing or fast road bicycles). [12]
The front derailleur, however, switches gears almost 30% faster than Dura-Ace’s mechanical counterpart. [1] On traditional bikes, the front derailleur is problematic because the chain can be under tension and has to make a large vertical jump between chainrings. The electronic system's controlled motion overcomes these problems.
One-way bearing combining sprags and bearing rollers in one race Sprags jam when driven and slide when in reverse. A sprag clutch is a one-way freewheel clutch.It resembles a roller bearing but, instead of cylindrical rollers, non-revolving asymmetric figure-eight shaped sprags, or other elements allowing single direction rotation, are used.
Before epicyclic gears were used in bicycle hubs, they were used on tricycles. Patents for epicyclic hubs date from the mid-1880s. [5] [6] The first patent for a compact epicyclic hub gear was granted in 1895 to the American machinist Seward Thomas Johnson of Noblesville, Indiana, U.S.A. [7] This was a 2-speed but was not commercially successful.