I have an idea (The L-Package)


Mr. Big Hot Pastrami
Feb 26, 2003
Bozeman, MT
I was just looking over the G-Boxx thread when an idea hit me. A liquid drive system, the L-Package (I want to have something other than boxx at the end). So here is how I see it happening. Around the bottom bracket area have a sealed compartment(Main Drive Casing(MDC)) that houses the drive liquid (most likely some type of oil due to it being lighter weight than water and having a higher vaporization point than water) and an impeller with variable pitch on the blades to control the speed of the liquid. The MDC will have two hoses attached to it, one for fluid coming in and the other for fluid going out. These two hoses will be attached to the rear hub which has an impeller inside it that has fixed blades. The pitch on the MDC impeller will be controlled by an electronic 'shifter', which would probably be a potentiometer. As for batteries I think it would be easiest to have them attached on the frame in the same sort of style as the water bottle batteries for some light systems.


Aug 6, 2007
Longview, Washington
There was a guy something like 2 years back working on having a hydraulic drivetrain. I don't recall which board it was on, perhaps PinkBike. I believe he had a prototype made, which looked like a big Poly chainguard about and inch wide and big enough to cover a 40t+ sprocket.
Not sure what he had planned for shifting.



Turbo Monkey
Jun 20, 2005
a-town biatches
you know with a little bit of imagination its not that far of a stretch for me to see it working. now the way im thinking is making it work like an automatic transmision for your car. make it shift by changing the preassure inside the cassing and making something like clutch packs to shift and hold it into gear. now as far as allowing us to shift it withough it doing it itself we could just install stops like they do in AT's to where you can acctually shift it threw the gears. i mean its a far stretch but it could work.


Turbo Monkey
Feb 7, 2004
alex. va. usa.
the problem with your idea is that impellers don't work at the low rpm's of the human cadence. the idea has been brought up in many college competitions and a good solution has never been found. all the solutions were at least 10 times less efficient than the cog chain combo we currently use.
Apr 16, 2006
Golden, CO
Yea the main problems are efficiency - Partly the reason why we still use chain and deraillure, it's so damn efficient.

Also To get around efficiency issues, groups at schools like polytec have integrated hydraulic accumulators. Basically a capacitor - it stores up hydraulic fluid in some kinda pressue resevoir (fluid/diaphragm/air pressure perhaps) and you can release it for a "boost" when you need it most a.k.a. hill's.

I think the purely mechanical method will reign supperior until humans stop powering the bikes.

You could do something similar to a steam engine design - with fluid however, and have the piston's actuation rod points vary in distance from the vertex of the primary drive to create a "variable transmition." This would also get around the impeller's high differential speed. but would create a dead spot at 0* and 180* that would need to be addressed biometrically.