Chains and sprockets, info and index

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.
BalorNG   1 kW

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Re: Chains and sprockets, info and index

Post by BalorNG » Oct 29 2021 6:23am

I think I might have something to contribute to this tread.
I've tried both belts, 25 pitch chains and even got a plastic chain.

Belts a great when it comes to zero maintenance, but considerably lossy when it comes to small pulleys and need pretention, and very careful alignment - or you'll get even more losses and skipping.

Chains, *waxed* chains that I use, are pretty much as durable as belts, also need extremely little maintenance (once very 1000 miles or so), are much more tolerant of misalignment and need no pretention, BUT are *NOISY*.

Plastic chains are actually no less noisy (plastic rattles quite a bit), but supposed to need no lubrication... low load rating, but that is not a problem for me, I do not need insane power.

And than I've had an idea - how about cogs *overmolded* with rigid, but still damping enough TPU?
I've already 3d printed me a 12T cog for my 'crank drive'/pedal generator (bicycle singlespeed chain) and it actually last for quite a while (about 1000km) before one of the teeth gets sheared - and I can output 500+ watts in my training sessions.

By using a composite cog with a steel 'core and 3d printed in 'vase mode' layer of TPU gluded to it, it might actually be the best of both worlds.
I've already 3d printed a cog entirely of TPU and it even kind of works at lower powers, but than skips not unlike a belt (cog remains intact). It does do a fine job of damping chain noise, so the idea has merit I guess.

Image
Image

I'll try with a 3d printed 'core' for now, I fear it will get sheared pretty fast, but might just work...

Hummina Shadeeba   10 MW

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Re: Chains and sprockets, info and index

Post by Hummina Shadeeba » Oct 29 2021 12:53pm

Wonder how a small sprocket would do printed on this:
https://markforged.com/materials/contin ... rbon-fiber


I see a lot of larger composite sprockets for sale. Smaller sprockets of course are subjected to more strain but doubt they’re made using the best materials and methods possible.

The larger sprockets don’t seem to make much noise.. if only could make a quieter small sprocket.

Theoretically I think a composite could be stronger and more durable than even steel. I imagine a good ratio of long strand carbon to resin and maybe a Kevlar running surface would do it.

BalorNG   1 kW

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Re: Chains and sprockets, info and index

Post by BalorNG » Oct 30 2021 4:20am

Yea, that's my whole point.
By the way, I think 'tpu-coated' *deraileur pulleys* is already a pretty good idea, they are made from plastic anyways and do not see high loads.

Anyways, I've tried that at about 200w load, seems to work:
Image

Obviously it wll not work at very high powers, but for a 'close to legal' assists watts and using something like TF8 chain with a steel core pulley will likely work well for up to 1kw or so I Presume.

Will certainly not be cheap unless you do it yourself, the process is pretty fiddly.

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