Bicycle derailure on chain drive

Just thinking out loud. Anyone ever considered putting a derailure on a chain drive eskate? Maybe a cassette with only 2 gears on the drive wheel. Best of both worlds, torque for the start, and speed after you’re moving… derailure will deal with chain tension for 2 different sized sprockets…

I’ve thought of this before but get hung up on needing to have the derailleur remotely/electrically controlled.

I can’t see myself bending down to hit a gear pedal or shifting my footing to step on one. I think this will happen eventually though.

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What about a servo operated derailure? Have a button on your remote that operates the servo.

not wanting to be picky, but it’s called a derailleur.

And also, most of that technology is widespread for bike chains, whose size isn’t ideal for small wheels applications like skateboards / mountainboards. You’d need first to develop a derailleur for smaller chains like the 25H (04) or 06B

I’m using pneumatic tires, I’ve found 35t rear sprockets in the 420 size. As well as 10t front sprockets. Why can’t I just use regular 420 bicycle chain and derailleur? Seems like that would be much easier than reinventing a smaller derailleur… also high torque servos are super cheap, I figure linkage from servo arm to derailleur cable will be super easy. I need to find a super small ppm tx and rx that I could use to run the servos

A 35T would be about 150mm wide, plus some ground clearance. But I guess that could still work on pneumatics if you’re happy with that gearing ratio.

Yea, I clearly need smaller sprockets than 35. The 30t is 126mm that should give plenty of ground clearance with 153mm wheels. Maybe it’s a pipe dream, but I like to think outside the box. I’ve found derailleurs that will run from 10t to 39t sprockets. I am really surprised at the size difference between a 35t #25 chain and a 35t #420 chain. It’s insane, I now see why you recommend the #25 chain over the 420. I’ll keep digging

Interested in seeing if the bike chain would work.

I remember a youtube where someone was using it for a gokart and kept snapping. never figured out if it was alignment, wear, or speed/torque.

Most modern bike chains don’t have a discrete bushing, but rather formed inner plate bushings that give it the flex to cross chain. my current theory is that the torque wedges the bushings and splits the plates.

worn bike chain via sheldon brown

and roller chain via wikipedia

regardless, interested to see if a geared setup is possible.

Other consideration is that the lack of a freewheel (unless you’re adding mechanical brakes) means that you’ll have to deal with the driveline shock of ratio changes without getting bucked.