Check out the recently unveiled split-derailleur Supre Drive, a unique drivetrain that Canadian company Lal Bikes claim is as reliable an internal gearbox, but comes in a lighter weight package…
Named after Pierre Lallement, inventor of the pedal-crank, Lal Bikes was founded by Cedric Eveleigh, a mechanical engineer and inventor of the Supre Drive. Lal plans to manufacture the parts used in the patented Supre Drive system—the derailleur, chain tensioner, and idler pulley—and sell them to bike companies. In short, the Supre Drive is a completely new drivetrain that was developed by separating the two functions of a traditional derailleur—chain tensioning and shifting. It does so by moving the tensioning system to the middle of the bike, which only adds 100-200 grams to the overall system, according to Lal. It also increases the reliability of a derailleur based system by eliminating the pulley arm. Watch the video below and scroll down to read Lal’s own description of how it works…
How it Works
from Lal Bikes
“The following image shows how the Supre Drive works. The blue line represents the chain in the lowest gear, and the red line represents the chain in the highest gear. When shifting from a high gear to a low gear, the chain tensioner arm pivots counter-clockwise around the bottom bracket axis.
The derailleur has a gear shifting mechanism like that of conventional derailleurs, but there is only one pulley and no tensioner arm. The task of tensioning the chain is moved to the middle of the bike while the derailleur is focused solely on shifting. This enables the drivetrain to have more ground clearance, as shown in the following comparison with a conventional derailleur.
There’s no derailleur hanger and no B-limit, making the derailleur easier to adjust.
The tensioner arm is connected by a cable to a cartridge that contains a spring and a damper. The cartridge is inside the down tube. Whereas conventional derailleurs produce increasing chain tension in the low gears, the tensioner system of the Supre Drive produces approximately constant chain tension across all gears. This is achieved by decreasing the leverage of the cable on the tensioner arm as the tensioner arm rotates back during shifts to lower gears. This decrease in leverage compensates for the increase in force from the spring. The approximately constant chain tension improves the efficiency of the Supre Drive. Additionally, the large size of the pulleys also improves the efficiency of the Supre Drive.
The damper is hydraulic and works far better than current derailleur clutches. It’s speed-sensitive, meaning that there’s a lot of force when the tensioner arm rotates fast (which occurs while riding over rough stuff) and there’s less force when the tensioner arm rotates slowly (which occurs while shifting).
The Supre Drive is compatible with off-the-shelf hubs, bottom brackets, cranks, chains, shifters, and cassettes. Two specific requirements are a 52mm chainline and a T47 bottom bracket. The latest version of the Supre Drive works with a Shimano 10-51t cassette (although the prototype bike shown here has a 10-45t cassette). Shifting performance is the same as a full Shimano drivetrain.”
Find more details about the Supre Drive over at LalBikes.com.
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