potential alternative power?

Discussion in 'Motorized Bicycle General Discussion' started by Cody, Feb 17, 2014.

  1. Cody

    Cody New Member

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    ive thought of a pneumatic drive setup to add to a gas bike, since motors are pretty much air compressors why not take a small 4 stroke, like a leaf blower or something similar, and instead of burning gas have the compressed air from the exhaust go to a pneumatic wrench with a sprocket attached to it driving the chain. I need your opinions and critiques cuz im rather serious about getting this to work.
     
  2. Agreen

    Agreen Member

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    Unfortunately the seals in a pneumatic wrench are plastic, so they wouldn't last very long at all.
     
  3. Cody

    Cody New Member

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    is there a way to sub them out for something stronger or is there a pneumatic driver of any sort that would work?
     
  4. bluegoatwoods

    bluegoatwoods New Member

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    Consider for a moment a $100 air compressor with an impact driver on the end of the hose.
    Imagine you've worked out some kind of adaptor that this impact driver can hold onto on one of your bike's wheel hubs. Now you hit the trigger and the impact driver is spinning your wheel.

    A fairly cheap impact driver is capable of delivering maybe 125 ft/lbs of torque. Really I'm guessing there. It's been a long time since I've actually taken a look at the matter. But let's imagine I've got it right. The real world values are bound to be close.

    Since the tire surface on a 26 inch wheel is fairly close to one foot from the axle, we can round things off and figure that the 'driving force' being applied to the road is 125 lbs. This is respectable, but it's not huge. If you relied on this much torque to get going from a complete stop, it would be a slow speed-up. But I imagine it would be plenty of torque while you're rolling, particularly if you helped with pedaling.

    Of course you'll have to carry an air tank on your bike. And I suspect that one of those $20 air tanks might not give you much range. I could picture a small tank built to nuclear bomb specs that would allow you to compress a whole lot more air than a cheap tank would. But you'd need a better air compressor than the one we've imagined above. The tank itself would be fairly heavy. And if you were really cramming a lot of air into it, then the weight of the air itself might start adding up.

    I don't know how close I am to the real truth in this matter. But I suspect that a pneumatic drive train might well be do-able in theory, but very cumbersome in practice.

    Sorry. I don't want to be discouraging.

    And if you prove me wrong, that'd be pretty cool.
     
  5. Cody

    Cody New Member

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    what if there was no tank in the picture, if you were to take a small 4 stroke and directly attach the pneumatic drive to the exhaust port of a motor that wasn't burning anything and link the motor to the tire or chain and the pneumatic to the wheel or chain do you think that would work? im using a 2stroke motor and im looking for more low-end without technically adding to my current cc (48) as I don't have a class m license
     
  6. Ludwig II

    Ludwig II Well-Known Member

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    Go hydrostatic, put a lawnmower drive in a front wheel.
     
  7. Ludwig II

    Ludwig II Well-Known Member

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  8. livesteamfan

    livesteamfan New Member

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    Assuming I'm understanding you properly, you want to have a second engine that acts as an on-demand air compressor? If so, you're in for more trouble than you might think. It can be done, but it would require modification to the camshaft. What I've seen done is have both intake and exhaust open and close at the same time and then have the air blown out through a check valve in the spark plug hole. If you're looking at using straight exhaust gasses, you'll end up stalling or destroying the engine before it builds up any kind of pressure because it's not intended to run anything off the exhaust gasses. Also, an impact wrench would probably not be the best idea either because they actually kick in both directions and it is not a steady, smooth motion like what you want to propel a bike. Something more like the air motor in a die grinder would be better. Sorry to sound like I'm knocking the idea down, I've seen air powered vehicles before, but for a bike, I don't see it working to well. If you still want to try, have at it and prove me wrong, it'd be nice to see something like that actually work.
     
  9. Ludwig II

    Ludwig II Well-Known Member

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    OK, let's get lateral. Engine drives a multistage axial compressor, blows air through trunking to a multistage turbine and gear reduction unit in a hub. Exhausts behind vehicle, now slipstream/tailgate!
     
  10. Agreen

    Agreen Member

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    What he's saying is that he wants to use the exhaust from the engine as a source of compressed air to drive the pneumatic wrench. Not another engine, but the existing engine that already drives the rear wheel, then use a pneumatic wrench to assist with taking off.

    You might be able to get metal seals made, but once again I wouldn't see it lasting very long based on the heat.

    Another thought is how much pressure are you expecting the engine's exhaust to pump out? Because at a certain amount of back pressure, the engine will just cut off.
     
  11. Cody

    Cody New Member

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    im meaning use a 4stroke as a compressor, it receives no fuel, so no burn and no heat, and the motor is constantly turning with the tire and constantly supplying pressure while moving, but none while at stop, pneumatic drive is rigged to stay on and aid in acceleration, my biggest worry is braking
     
  12. Cody

    Cody New Member

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    and I don't know how much pressure the motor will put out, all I know for sure is that the pressure will increase in proportion to my speed
     
  13. Kioshk

    Kioshk Active Member

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    _NOW_ I get what you're trying to describe! I must say, the Telephone Game this thread has produced is amusing. Oddly enough, I was thinking of something similar recently: use a small wheel-driven piston to compress air on demand into a small container for use on a pneumatic-horn. In fact, I imagined that the "on-demand" could be simply using the brakes: engage the pump only when braking thus assisting braking. In any case, I'm afraid what you're proposing is extremely inefficient. I suspect there are available solutions to a simpler wheel-driven compressor-pump, and I'm interested to know what these solutions are.
     
  14. Cody

    Cody New Member

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    thank you man, someone gets it :) if you find anything that can help us out email me [email protected]
     
  15. Agreen

    Agreen Member

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    Aha! Now it makes sense.

    Use a freewheel so it won't overrun the air tool. You probably would want to use an air ratchet of some sort instead of an impact. Also, you'll want a relief valve to prevent over pressurizing the tank.
     
  16. scotto-

    scotto- Custom 4-Stroke Bike Builder

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    Use a compression release for braking as was done with 2-strokes in the 60's and 70's. Simple and semi effective....
     
  17. Cody

    Cody New Member

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    my main concerns are will the motor hold up, whats a relief valve, and what size sprocket should I attach to the pneumatic drive?
     
  18. Agreen

    Agreen Member

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    Your real concern should not be whether the engine holds up, but rather if the pneumatic wrench holds up.

    A relief valve is usually a poppet style valve that opens at a certain pressure.
     
  19. Cody

    Cody New Member

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    what could happen to it? back to the seals?
     
  20. Ludwig II

    Ludwig II Well-Known Member

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    Sustained high rpm might be bad for the internal gears, as they're designed for intermittent use and low rotational speed.
     

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