Another Gear shifting idea

Discussion in 'General Questions' started by Jeco, Sep 8, 2010.

  1. Jeco

    Jeco Member

    Hi,

    I found this idea on another site. I was thinking about this kind too a couple of days ago, also read something brief about it in this site (searched first). Will this idea work? Maybe with a heavy duty mechanism to change gears?

    Thanks!
     

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  2. GearNut

    GearNut Active Member

    I had a Harley TX125 that had a similar set up. The smaller sprocket was aligned with the engine sprocket. The larger sprocket was dished to allow it to fit over the small sprocket in order to keep proper chain alignment when the larger sprocket was used.
    This is due to the fact that most chains require perfect or near perfect sprocket alignment or else they will jump off the sprockets. Chains for shifting bicycles are designed to tolerate sprocket mis-alignment. Your idea may work but finding an engine drive chain that will tolerate that sort of sprocket alignment may pose a challenge.

    FWIW, the Harley was manually shifted. You also had to add or remove a small section of chain to accommodate the varying chain length depending on which sprocket was used. It took about 10 minutes to "shift".

    I do recall Suzuki, (or was it Yamaha?) enduros back in the 1970's that had 2 engine sprockets. You shifted them by a lever and had to walk the bike until the chain completed it's change over.
     
  3. 5-7HEAVEN

    5-7HEAVEN Guest

    How About This Shifter?

    Suppose you fabbed a long lever that was spring-loaded and pivoted off the chain stay. When pulled inward, the lever contacting the chain would "persuade" the chain to jump onto the other sprocket.

    Would that work?
     
  4. Huff&Puff

    Huff&Puff New Member

    Gotta take up the slack....

    Wouldn't work without a device to take up the chain slack when you shifted to the smaller sprocket - you'd need something like the rear derailleur on a 10-speed bike. It moves the chain over, and it also moves a pulley forward or back to work like a chain tensioner. Maybe all you need is a heavily modified long-cage touring derailleur (and a machinist to do the mods!):evilgrin:
     
  5. Jeco

    Jeco Member

    Probably That would work. Changing gears at high speed I think will be dangerous though. I hope someone can fabricate something like this and be proved reliable and safe.
     
  6. 5-7HEAVEN

    5-7HEAVEN Guest

    It IS dangerous at high speed if the chain locks up between sprockets.

    If the derailleur is out of adjustment, chain may lock up between gears, wheel locks up, rear wheel skids, loss of control, bike hits curb, rider hits road.:ack2:

    Ask me how I know this.:jester:

    Ohhhh, but when everything is adjusted well, the sound and feel of powershifting at high speed is a thrill you'll never enjoy with a single-speed MB.
     
  7. Jeco

    Jeco Member

    I think you did the first working protoype ha (almost working)..and found out the cons the hard way (pavement) ;)
     
  8. 5-7HEAVEN

    5-7HEAVEN Guest

    Naaaah, mine is aftermarket Scooterguy in-frame kit with shift kit.

    My engine goes "YEAH(1st gear), YEAh(2nd),YEah(3rd), Yeah(4th), yeah(5th), YES(6th), YEs(7th), Yes(8th)!!!
     
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