Will shift kit help with strong headwinds?

Discussion in 'Motorized Bicycle General Discussion' started by wheelbender6, Jan 2, 2012.

  1. wheelbender6

    wheelbender6 Active Member

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    I was only managing around 12 mph against the headwinds in Houston today on my China girl (I normally cruise at 25 mph). Aero mods could probably get me 2 or 3 mph. Would a shift kit help by allowing to select a gear where I can maintain max torque rpm? I also considered just installing a derailleur/cluster and adding good old human power in the headwinds.
     
  2. 5-7HEAVEN

    5-7HEAVEN Well-Known Member

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    Yes, a shift kit with low gear ratios will definitely help in headwinds and steep hills. Keep in mind that human power doesn't help much, when the engine is driving the same chain.

    You could also buy a generic windshield from a Chinese scooter on ebay. They are relatively cheap and easy to install.
     
  3. killercanuck

    killercanuck New Member

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    Shift kit will definitely keep you in the power band. Unless you've got a single speed rear hub, lol.

    I've got 7 gears to play with, going into wind 3rd or 4th... coming back with the wind 7th, all at same engine rpm :p Same with towing or bastid hills, 1st, 2nd

    A 'shield would be more for comfort than extra speed wouldn't it? Depends on the shape of it I guess, eh?
     
  4. The_Aleman

    The_Aleman New Member

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    Having optimum pedal gear ratios and the willingness to pedal will greatly enhance the riding experience on these!
    Gear cluster and 50+T crank sprocket, keep pedaling at 28 :D

    As for shift kits, setting a shift kit up so that you can contribute your pedal power at the optimum time is the way to go. By default, the shift-kit puts your "pedal" redline way below the HP peak. To counter that you must run a huge (60+) outer crank sprocket to increase the engine gear reduction.
     
  5. 5-7HEAVEN

    5-7HEAVEN Well-Known Member

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    Interesting.....

    HOWEVER, the inside chainring is the pedalling one. Having one with less teeth results in low gear ratio and good pulling power for the engine. Unfortunately, not for pedalling power and engine power simultaneously. I haven't measured it, but I don't think a 50t will fit on the inside chainring position. It will hit the chainstay frame. Also, a large bicycle chainring REALLY screws up the gear ratios for engine application. Compare these figures:

    Use the 24t chainring and 9t jackshaft for stump-pulling low gear (45.43:1, like a 111t rear sprocket) and 15.62:1 in 8th gear (15.62, like a 38t sprocket).

    Use a 30t chainring for 36.35:1 (88t sprocket) and 12.49(30t) in 8th gear.

    Use a 36t for 30.29:1 (74t) and 10.41:1 (25t) in 8th gear.

    Use a 50t for 21.8:1 (53t) and 7.5:1 (18t) in 8th gear.

    In retrospect, this 21.8:1 first gear w/50t sprocket is similar to 6th gear (21.3:1) with a 24t chainring.

    To summarize, if you could get a 50t bicycle chainring to fit a bike w/shift kit, it would not be a good choice for engine power.

    But hey, that's only my calculated opinion. We can all agree to disagree.....until someone actually installs a large sprocket as their bicycle chainring..shft.

    A 60t engine chainring? Lemme do more pencil-scratching, lol.

    Ok, with a 60t engine chainring and 9t jackshaft, that's 31.02:1 in 1st gear w/34t sprocket (like a 76t rear wheel sprocket).

    In 8th gear, that's 10.22:1(like a 25t sprocket).

    You can pedal well in 8th gear, but will that 50t fit in there?
     
    #5 5-7HEAVEN, Jan 3, 2012
    Last edited: Jan 3, 2012
  6. The_Aleman

    The_Aleman New Member

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    DUH, but SBP's stock ratio doesn't favor pedal power. By default, you will arrive at pedal redline long before engine redline. This is why a larger outer crank ring is needed so you can gear down engine. If one wanted to gear up pedal, too, he would need an even larger outer crank sprocket.

    I wasn't talking 50T for your bike. Or any shift kit bike. I was talking large chainring for use with OP's bike to go with the derailleur he was thinking about getting for his single-speed bike.

    Which is what I'd be doing if King's Sales & Service wasn't ignoring people right now. I need a 51/67 crank sprocket set! :D

    I have a 36/48 currently. I'm gearing up pedal and gearing down engine. Looking for 60 pedal RPM @ 4000 engine RPM, 120 @ 8000.

    Emphasis on assist :D
     
  7. 5-7HEAVEN

    5-7HEAVEN Well-Known Member

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    I hear you about King's customer service department.

    The OP mentioned "shift kit", which infers multiple gears.

    OP also mentioned just installing derailleur/cluster and adding good old human pedal power.
     
  8. The_Aleman

    The_Aleman New Member

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    No matter what, pedaling always helps, tho. It doesn't matter if one has a shift-kit or not.

    Humans can pedal more torque than many car engines for short bursts.
     
  9. 5-7HEAVEN

    5-7HEAVEN Well-Known Member

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    Yes, I agree.
     
  10. andrewflores17

    andrewflores17 New Member

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    http://www.youtube.com/watch?v=7h7AmVPpaEY&feature=player_embedded


    could always try a propeller like this guy did

    i think that the shift kit may help you find the best gear ratio for the wind your hitting i live in colorado and wind is my bigest killer for speed try to plan your route if you can to have some sheilding from the wind or to have it only on your side for as long as possible before going head on at it
     
  11. breno

    breno New Member

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    Be sure to post the speed difference it makes in those head winds if you go Ahead with the shift kit.:)
     
  12. moonerdizzle

    moonerdizzle New Member

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    That propeller looks like very bad news.
     
  13. Wally

    Wally New Member

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    I am as happy as a pig in ... I finally got the SBP shift kit together and took it for a spin. I had a 35 Kph head wind and it didn't even feel it. I do recommend it.
     

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