Indubitably
100 W
- Joined
- Jan 9, 2010
- Messages
- 126
I've been farting around with the idea of using a high speed rc motor for my next build, simply because the little buggers are cheap as frak, crazy efficient, and weigh a fraction of what a comprably rated hub would weigh. The only problem is that no matter how I slice it, I keep coming back to the fact that I need to run them through a heavy, expensive, and inefficient transmission. In the best of situations it seems I can hope to run a simple jackshaft setup that manages to get my motor somewhere near its happy place without breaking the bank, but the moment I drop even a nexus 3 into the mix my efficiency / dollar suddenly goes to shit. Everything else seemed to invariably lead me down an endless rabbit hole of prohibitively time consuming and expensive customization, that would yield at best a marginal improvement in efficiency.
So I started looking around for pretty much any means of power transmission whatsoever, that came in a modular format versital enough that I could put something custom together withoutout having to reinvent the wheel, yet was common enough that I could actually get my hands on it at a reasonable price, and I just kept coming back to pnuematics. Now, I know that compressed air isn't really a viable energy storage medium for a bike because of its poor power density, but why not use it as a means of power transmission? I'm thinking the way to go would be a closed loop with a series of check valves, a pressure reservoir, and a vacuum reservoir. The system would be thermally isolated, so that the heat created by compression in the pressure reservoir (and lack there of created by decompression in the vacuum reservoir) would only serve to further drive the pressure differential, and what ever thermal bleed over might occur, would at least be kept within the system so that thermal power loss would be minimized.
Presumably, with large enough volume, a small amount of energy could be stored by simply allowing the wheel to drive air into the vacuum reservoir, which would act like a kind of regenerative breaking capacitor, or you could just let the system turn the electric motor to charge the batteries, or some combination of both.
The basic idea is to get the natural torque conversion of a pneumatic system, but with the power density of batteries, while allowing the electric motor to do its thing at a happy rpm where it will never be in danger of over heating, and to do it with generic parts widely available at a fairly reasonable price so it can be easily assembled as a single module that can be conveniently fitted to the bike and or removed for maintainance (with standard replacement parts).
What do you guys think? Is this doable? Would I be better off with hydraulics? Am I going to wind up spending just as much as I would on a gear head and a nexus 3 anyway, or perhaps just missing some fundamental drawback that makes it more of a pain in the ass than its worth? Comments and corrections are greatly appreciated, but I haven't even drawn this thing out on paper yet, so please bare with any obvious mistakes.
So I started looking around for pretty much any means of power transmission whatsoever, that came in a modular format versital enough that I could put something custom together withoutout having to reinvent the wheel, yet was common enough that I could actually get my hands on it at a reasonable price, and I just kept coming back to pnuematics. Now, I know that compressed air isn't really a viable energy storage medium for a bike because of its poor power density, but why not use it as a means of power transmission? I'm thinking the way to go would be a closed loop with a series of check valves, a pressure reservoir, and a vacuum reservoir. The system would be thermally isolated, so that the heat created by compression in the pressure reservoir (and lack there of created by decompression in the vacuum reservoir) would only serve to further drive the pressure differential, and what ever thermal bleed over might occur, would at least be kept within the system so that thermal power loss would be minimized.
Presumably, with large enough volume, a small amount of energy could be stored by simply allowing the wheel to drive air into the vacuum reservoir, which would act like a kind of regenerative breaking capacitor, or you could just let the system turn the electric motor to charge the batteries, or some combination of both.
The basic idea is to get the natural torque conversion of a pneumatic system, but with the power density of batteries, while allowing the electric motor to do its thing at a happy rpm where it will never be in danger of over heating, and to do it with generic parts widely available at a fairly reasonable price so it can be easily assembled as a single module that can be conveniently fitted to the bike and or removed for maintainance (with standard replacement parts).
What do you guys think? Is this doable? Would I be better off with hydraulics? Am I going to wind up spending just as much as I would on a gear head and a nexus 3 anyway, or perhaps just missing some fundamental drawback that makes it more of a pain in the ass than its worth? Comments and corrections are greatly appreciated, but I haven't even drawn this thing out on paper yet, so please bare with any obvious mistakes.