Friction generator

Discussion in 'Electrical' started by birddog1148, Apr 3, 2010.

  1. birddog1148

    birddog1148 Member

  2. birddog1148

    birddog1148 Member

  3. GearNut

    GearNut Active Member

    I don't know much about troubleshooting links, but I bought a generator powered light kit on closeout from Target. I plan on installing it as intended some day. No light when stopped does not bother me much.
  4. Esteban

    Esteban Active Member

    These were not designed for excess speed, so beware.
  5. birddog1148

    birddog1148 Member

    Thats why I thought if it was driven off the chain to feed a battery pack it may work better. Using a small sprocket instead of the roller should turn it slower right?
  6. chefdouglas

    chefdouglas Member

    I tried one with a sprocket that I attached(12 teeth), my dad had one on his bike when I was a kid. Any way it worked really well for a mile then died. I spent a few hrs trying to get it to work again no luck. I didn't have it going to a battery if you have better luck I'd like to know.Mine was going to a 12 v MC head light and a cheap plastic red light. Both lights still work on a battery now.
  7. SimpleSimon

    SimpleSimon Active Member

    Your links do not work because of forum settings designed to frustrate spammers. You are required to have a specific number of posts before your links will be functional. No, I do not know what that number is.

    As for the friction generators, they really do not like speeds in excess of 12-15 mph, as their output voltage is entirely rpm dependent. I tried the small sprocket running on the chain once - the generator burnt out very quickly. If you did the math to figure the effective gear ratio of one running as intended against a tire sidewall, then put a sprocket on the generator to produce the required rpm range, it will work.

    Heck, set it up to be the chain tension idler.
    Last edited: Apr 4, 2010
  8. chefdouglas

    chefdouglas Member

    Simon what size sprocket do you recommend? I'd give it another try if I thought I wasn't going to throw away money.
  9. birddog1148

    birddog1148 Member

    The chain tensioner idea was what i was thinking.:cool2:
  10. SimpleSimon

    SimpleSimon Active Member

    Measure the radius to the contact area on the sidewall from the axle, then multiply that by the classic formula: R * 6.2832 (2 pi) = C(ircumference)

    That gives you the linear inches the generator wheel will run over. Calculate the generator wheel circumference, divide it into the wheel circumference, that gives you the rpm of the generator per revolution of the wheel. Calculate the revolutions of the bike wheel per mile, multiply that by 12, then multiply that number by the rpm of the generator.

    Once you know the operating rpm of the generator, treat the sprocket on it as the driven sprocket in a gear ratio calculator with your engine output sprocket as the drive. That will tell you the size sprocket you'll need.

    Do, please, run that output through a battery. Oh, and make your generator sprocket freewheel capable.
  11. loquin

    loquin Active Member

    Keep this in mind:
    • as others have said, bottle generators output is dependent on speed, and you'll burn out bulbs when you go too fast with them.
    • The bottle generators don't last too long, as the 'bearings' can't take much in the way of side thrust. This means that, if you are adding a sprocket to one, you really can't use it as a chain tensioner - it would soon lock up...
    • they're terribly inefficient. You can feel a noticeable drag when they press against the tire, even if you're not using the light.
    There are some European designs that seem to work pretty well though - that are well built and reliable. You might look into them, instead. There are also hub dynamos - shimano and Sturmey-Archer come to mind. Not only do they avoid the road gunk issue, but, they are efficient, low-drag approaches that have less issues with overvoltage than the bottle generators. Plus, the Sturmey-Archer version comes with a drum brake...
  12. motorpsycho

    motorpsycho Active Member

    i too thought the tire generator would work...but, they will burn out FAST.
    so here's what i did..
    I used the headlight and the tail light that came with the generator/ light kit. (bought the kit off e-bay for like $15.00 or something)
    I took the bulb out of the headlight, and got a small flashlight with 3 super bright L.E.D. bulbs in it for like $5.00 at wal mart. I put the 3 L.E.D. bulbs in the center of the chrome headlight reflector in a triangle pattern in place of the single 3 watt bulb. I got a battery holder for 4 AA batteries, and wired it up to an on/off switch from an r/c truck. the headlight works extremly well, and it's plenty bright to see at night. using the headlight lens that has diffusing lines in it, the light is spread out in front and to the sides pretty good. It isn't just a single beam of light out in front of you like a flashlight.
    I did the same thing with the tail light, but it only has one L.E.D. bulb in it, and it's powered by 3 small watch style batteries and is wired to another r/c truck on/off switch. the L.E.D. and the batteries for the tail light came out of a small pen flashlight that i got at wal mart. (it cost like $3.99, it has 3 batteries in it, and it comes with 3 extra batteries)
    sure, i have AA batteries and small watch style batteries that will go dead after awhile, but i made these lights last year, and i am still on the same batteries...and they are still very bright. L.E.D.'s draw very little voltage.
    Last edited: Apr 9, 2010
  13. Tango911

    Tango911 New Member

    with LEDs now days just seend like a cheap light weight light is the way to go instead of adding a generator to the bike. or how bout solar charges during the day and lights up at night ha ha.
    i do remember the old generators tho, still pretty innovative.
  14. AussieSteve

    AussieSteve Active Member

    The problem with LEDs is that they don't produce enough light.
    Even my current Cateye halogen light is only useful to about 25kph.
    There's nothing like a decent battery, generator and reasonably-sized incandescent bulbs. ie 12V 18/18W dual filament or halogen.
    My generator runs off the shift-kit jackshaft instead of friction drive, but the principle is the same, with lower friction losses.
    The (dual) headlight I'm using has 2 x 12V, 18W/18W bulbs, allowing 18W, 36W, 54W or 72W.
    Can almost burn a hole through anything that gets in the way. LEDs don't compare.
  15. Esteban

    Esteban Active Member

    BUT, I still like the looks of an old Raleigh 3 speed with factory light kit !! A CLASSIC !
  16. AussieSteve

    AussieSteve Active Member

    I don't care what my bike looks like, as long as I can see where I'm going.