How much HP can be sent thru the bike chain?

Discussion in 'Performance Mods' started by professor, Oct 11, 2010.

  1. professor

    professor Active Member

    I am thinking of the derailer type chain for a shift kit project.
    I am considering something radical- an in-frame twin engine Techumseh snow blower bike and it needs gears.

  2. Ghost0

    Ghost0 Guest

    Although I could not find any specific data on bicycle chains I did find the following. A standard 41 chain is rated to 2000 pounds. A chain lesser than a bicycle chain was rated at 900 pounds so that should give you some range to go by. My marginally educated guess would say that a multi speed bike chain would be around 1000 pounds and a 410/BMX chain I would say in the 1200 pound range.
  3. 5-7HEAVEN

    5-7HEAVEN Guest

    I'm running 4.2hp/GP460 engine thru 8-speed derailleur-type chain. I have used an expansion pipe before, which helped the engine produce more power.

    JMO, my bike's "Achilles' heel" is its bike chain. I've broken many chains, but the one on the bike has been there the longest.
    Last edited by a moderator: Oct 12, 2010
  4. 5-7HEAVEN

    5-7HEAVEN Guest

    I installed an SBP expansion pipe for the Happy Time engine on my 460 engine, and a new K&N air filter. There is now more power running thru the chain, but it's holding.:bowdown:
  5. professor

    professor Active Member

    Good reports, apparently the dogs in the derailer are holding too. I hadn't thought aboutl them until I read a post about the stregnth of the freewheels.
  6. 5-7HEAVEN

    5-7HEAVEN Guest

    The chain and cassette takes its worst beating at a dead stop. Methinks bike parts would last longer if you pedal first, then apply power. With my shift kit and cassette, it's impractical. First gear for the engine is the exact opposite for pedalling from a standstill, and vice versa. If I pedal off in 7th gear, then I'd have to shift all the way up to 2nd gear, then motor away. With stop and go traffic, it's not a good option. With cassette sprockets, you need to downshift through the gears before coming to a dead stop. If not. you wreak havoc on the cassette, especially when applying engine power.

    However, if I had an 8-speed internal hub or a NuVinci hub, pedalling from a standstill would work. Internal hubs can shift gears at a stop. Cassette gears cannot; the rear wheel has to be in motion to shift gears.
    Last edited by a moderator: Oct 15, 2010
  7. 5-7HEAVEN

    5-7HEAVEN Guest

    Switching to 8mm chain, sprockets and NV hub. The 8mm drive is from pocketbikes, which are made to handle several HP.
  8. 5-7HEAVEN

    5-7HEAVEN Guest

    I believe mine are on its way out, even though the derailleur is new. Sometimes I'll miss a shift and stop the bike.Then the engine's like in neutral. I'm thinking that the chain jumped. I look down at the chain, it's still in place and I drive away from a standstill.

    Go figure.
  9. professor

    professor Active Member

    5-7 here is an idea for you. Can you run the pedal side sprocket to a big chain ring (swapping out the current one- I assume the current one is small) so that you can start out in the same gear as the engine.
    Glad you figured out the problem is the dogs.
  10. 5-7HEAVEN

    5-7HEAVEN Guest

    Professor, if I did that, all my gear ratios would change drastically.

    1st gear changes from 32.55:1 to 19.88:1...

    Only 1st thru 4th gear would be able to be used, but not effectively.

    Fifth, 6th, 7th and 8th gear unusable, too high.
    Last edited by a moderator: Oct 21, 2010
  11. machiasmort

    machiasmort Active Member

    Pro, He's right, the cassette is your weak link in the drive train. Look at modern MB's. That's the reason for gear boxes! They wouldn't have spent all of that money developing them for no reason!

    As for the chain, I used to pedal 20+ miles a day for 10yrs! Never broke one! Had 2 cassettes Karp in that time tho!
  12. 5-7HEAVEN

    5-7HEAVEN Guest

    The main reason my bike chains break is because they jump off and snag between the frame, chainring retaining bolts and the chainring sprocket.:detective:
    Last edited by a moderator: Oct 22, 2010
  13. professor

    professor Active Member

    Well this has been a productive post. I am glad I asked. I think I will pass on a higher powered bike using the derailer. Thanks for the info guys.
  14. 5-7HEAVEN

    5-7HEAVEN Guest

    Did I mention that if the derailleur is out of adjustment, the chain will jam, locking the wheel and throwing you off the bike at 25mph?

    Ask me how I know that.:whistling:
  15. machiasmort

    machiasmort Active Member

    It’s not so much the HP as it is the torque Pro. Would make an interesting project, and I know you if anybody could do it! I would seriously baby it tho and remember not to stress it too much…

    Besides you'd be the only kid on the block w/one!
  16. HeadSmess

    HeadSmess Well-Known Member

    okies, i finally actually snapped my original chain!

    and i mean...snapped! ive never had a chain shear thrugh a plate like that before...and thats with 15 odd years riding motos...

    so i decided to try a heavy duty BMX chain.

    tip.... try and get over 100 links(if available? iunno...)what i got was 98. just one more link!!!!!!

    i had to find a new rear sprocket, all i had was a 36... down from 44 is a huge difference! no bottom end!

    anyway. pack says will take 1300kgf, whatever that means, while typical chain is 850kgf... 250 kgf pin power... so, im still confused. whats a kg...f?

    anyway, it takes it quite well, except...

    certain speeds it gets some nasty side to side vibration happening... mostly when the engine fourstrokes... so it maynt hold up terribly long becuse of the fatigue it just normally wouldnt experience? iunno. shall see. runs a lot smoother than the old 420 moto chain though :)

    maybe an extra idler wheel on the drive side to stop the vibration? maybe...
  17. machiasmort

    machiasmort Active Member

    One of the tractor supply places, makes a chain that the guy's were using. I think the chain is called 410?
  18. philski

    philski New Member

    hi Headsmess the kf is a bit confusing using metric and imperial at the same time, 550 foot per pounds per second = one horse power

    doing a rough calculation the 1300kgf chain is good for 5.2HP
    i use a lot as they have a lots of info on chain dynamics, strengths etc
    the international standard is ISO 9633 /2001 and it will give you the minimum strength for a bicycle chain
    Last edited: Oct 31, 2010
  19. HeadSmess

    HeadSmess Well-Known Member

    aye, that it is....but i dont think it is an imperial/metric thing. the strain is measured as static loading, just tension. theres no time factor, so therefore, no power factor. (power is torque(strain/pressure) * time)

    im thinking the f is more just "force" a strange word to use though. meaning i could lift 1300kg with this chain? maybe i should test this!

    kpa psi bar kg/cm, arrrrgh!
  20. Old Bob

    Old Bob Member

    You should be asking how much torque you can put through bicycle chain. HP is relative to rpm and torque.

    A 200 hundred pound person could stand on a pedal crank that is one foot long and apply 200 lbs ft torque to the chain, as long as its not moving there is 0 (zero hp) but a lot of force on the chain.

    Conversely, at typical two stroke ped engine makes less than 2 lbs ft torque at about 8000 rpm or equal to 2.5 hp.

    Which will break the chain first?