Discussion in 'General Questions' started by nwguy, Aug 9, 2008.

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  1. nwguy

    nwguy Guest

    Anyone here ever dabble with flywheels for energy storage? I'm pondering adding a flywheel to a bike made from an additional 27" bike wheel with added weight at the rim. I could see a v-belt connecting the bike's rear wheel to the flywheel that tightens and loosens via a brake lever. Engage to slow down and spin up the flywheel, disengage while at a stop to let the flywheel spin, reengage to accelerate away from the stop. The flywheel's spokes would need to be shielded with disks for safety and efficiency reasons. Think of it like regenerative braking with hybrid cars. Will post pics when I build a prototype.

  2. HI,

    That is an interesting idea....I wonder if using something smaller than a 27" wheel would be good tho....I mean...would putting 27" wheel on a bike be a little ungainly in terms of size?....Where would it go?....I would be very interested in seeing some sketches...

    I like the idea of assisted starts to avoid having to pedal first before letting off the clutch or having to excessively slip the clutch...

    Good thinking outside the box!

  3. nwguy

    nwguy Guest

    See linked image. I'm thinking over the back wheel and along side, with v-belt pulleys mounted on the hub flange like motorized bike cogs are, so the pulleys are aligned.

    The bigger diameter the wheel the more effective the flywheel action would be. The wheel should be light, except for at the perimeter where the weight would be. Note that the wheel in the linked image is a 26" mountain bike wheel as opposed to a skinny, lightweight wheel.

    Attached Files:

  4. Hmmm....Interesting.....I wonder how many RPM's do you see that additional flywheel wheel turning?...I suppose for additional weight the tire could be filled like a tractor tire (liquid) but I don't know how many RPM's would be safe....Your idea of steel is good too....just make sure it is balanced well....But then again....Hmmm another thought....Would all that weight over on one side of the bike make for awkward handling?

    Maybe a smaller diameter but heavy "dumbell" looking flywheel assembly could be built
    and tucked down low by the bottom bracket / kickstand area....Advantage there would be down low for lower center of gravity / better handling, small diameter means less gyroscope effect (maybe affects handling in a negative way?), and dumbell design means equal weight on both sides of the bike....Just random thoughts late at night ;-)

    I like the idea of a belt drive to spin up the flywheel wheel....Simple yet effective!
  5. Happy Valley

    Happy Valley Active Member

  6. Smerf

    Smerf New Member

    I was just wondering about this a couple of days ago when I was watching an F1 replay.

    What were you thinking of using as a clutch between the flywheel and the normal driveline?
  7. SirJakesus

    SirJakesus Guest

    I'm guessing that this would add stability to a bike too and possibly fight you a little on turns. I had heard about this kind of thing before and I have always wondered why kinetic energy isn't put to better use more often. I can't wait to see what you come up with!
  8. nwguy

    nwguy Guest

    Interesting video. There are actually a few if you search for "pedal flywheel" on YT. The bigger the flywheel the lighter it can be. Seem to be a few trade offs. Have you ever held a bike wheel by the axle and had someone spin it fast, and then tried to wobble it around? Your normal bike wheels have lots of gyroscopic stability, but either they don't have a negative effect on handling, or we're all used to it as part of the package. I think you could only do a horizontal flywheel with a trike, so I'll attempt a vertical arrangement. I thought about mounting a couple of lead scuba weights on opposing sides of a wheel, well balanced and very well secured. Or maybe bending a piece of rebar around the rim. For the engagement mechanism I've got some v belt pulleys and idlers that I plan to use. The idler would push in and out via a cable and tighten and loosen the belt. The weight on one side would be negligible compared to many motor assist arrangements where the whole motor is way off to one side. Certainly not as bad as having one loaded pannier over one side of the rear wheel.
  9. kerf

    kerf Guest

    Aside from starting off, couldn't the same thing be accomplished with a super heavy rear wheel? At speed it would store energy and be much simpler. In any event, the energy in a pedal driven flywheel would cost more effort than it gives.
  10. nwguy

    nwguy Guest

    Well, that's the point isn't it? Starting off.

    The idea is to store the energy that would normally be wasted by braking, and use it for accelerating. You wouldn't want to make your vehicle keep going when you want to slow down.
  11. kerf

    kerf Guest

    Seems like a solution in search of a problem. I've been riding bicycles for 50 years and starting has never been much of an issue, especially with an engine.
  12. Smerf

    Smerf New Member

    Depends a lot on your riding style, getting it up to speed would take extra effort, but just like pedaling a heavy cruiser vs a nice light mtb once you get going you aren't really aware of the extra weight. This isn't just an oddball idea, it's actually being tested on race cars.

    thinking last night, how about mounting it like a friction drive motor. Position it so it hangs back more, of course, so you don't lean into it. Then you could just use the wheel you were talking about and a cable system to drop it onto the tire for take off or spin up, and then raise it when it gets going. If you have it inline with the other two wheels you'll get the least amount of handling problems. It will probably seem a bit slower to turn in though.
  13. kerf

    kerf Guest

    I'm not trying to rain on the parade but the current direction in locomotion seems to be lighter rather than heaver. I increased the weight of my bike with the engine but it produces 16 times more power than I can. The road bikers are spending thousands of dollars on composite frames and wheels to get a 12 lbs bike. Wonder how many would like to add a 50-70 lbs flywheel.
  14. SirJakesus

    SirJakesus Guest

    The beauty of a flywheel is that you could add lots of extra weight by using a heavy duty dual suspension frame, massive tires and rims and still have tons of push with little effort on take offs. The flywheel can be set up to relatively slowly regain its momentum when you're already at cruising speed so it wouldn't be too much of an extra load on the engine or pedals. When you want to take off again and that thing is spinning at possibly thousands of RPM theres a lot of stored kinetic energy there. If done right (or wrong) it could easily flip the bike. Nobodys saying this would be light or simple and in fact all of our bikes are neither. If it could be engineered and implemented in an elegant way you'd be more able to utilize the small amount of power these small engines can produce WITHOUT going beyond the legal HP limitations for a MAB. Not to mention it's a novel idea for a bike if it was worth the extra hassle and didn't turn out looking like a frankenmobile.
    Last edited by a moderator: Aug 10, 2008
  15. nwguy

    nwguy Guest

    I'm shooting for about a ten pound flywheel, so the weight won't be excessive. That much weight at the perimeter of a 26" or larger wheel spinning very fast has a ton of energy. I thought about a friction drive type engagement, but I'd rather have the flywheel be rock steady (not moveable), and engage it with an idler/tensioner. This is a pretty great video about automotive flywheel hybrids (flybrids):
    Last edited by a moderator: Aug 10, 2008