Sprockets Mounting sprocket to hub of unusual diameter.

Discussion in 'Transmission / Drivetrain' started by jim_himself, Jan 10, 2011.

  1. jim_himself

    jim_himself Member

    I recently purchased the BMP combo drive kit (James as usual was great to deal with and gave my a fair price) to switch my gp460 friction drive to a chain drive (the roller slippage with such a powerful engine was starting to annoy me) and I am now trying to find the best way to mount a sprocket to my wheel hub. I originally planned to use the Maniac Mechanic clamshell adapter, but Pirate Cycles doesn't offer one that fits my hub (diameter of 1.061in). I was wondering if anyone has experience with any of the alternatives. I REALLY don't want to buy a new wheel as I am very happy with the one I have. (and yes I have searched around the forum:D)

    Thank you in advance for any help

  2. professor

    professor Active Member

    The only alternative I can think of is the rag joint.
  3. jim_himself

    jim_himself Member

    I can think of two others, the pineapple drive that Spookytooth sells and the LiveFastmotors clamshell, I was wondering if anybody had experience with these mounts. I want something that won't destroy my spokes and rim, so the rag joint is out of the question.
  4. loquin

    loquin Active Member

    Here's a thought.

    The MM Modus sprocket adapter is sized for 1.182 - 1.187 inch diameter hub. Yours is 1.061 inches.

    You could shim using 1/16" (0.0625) thick material.

    1.061 + (2 x 0.0625) = 1.186

    If you wanted, you could also use a thick inner tube (with rubber somewhat thicker than 1/16") as the rubber will compress some...
  5. jim_himself

    jim_himself Member

    I had thought about that but didnt think that it would work, know that you mention it im gonna give it a go, which size sprocket should i get, i know bigger gives more low smaller more high, but dont quite know how it work with gear reduction
  6. loquin

    loquin Active Member

    Jim, a larger rear sprocket gives you better acceleration (and better hill climbing ability,) but, at the expense of a lower top speed.

    Take a look at two calculators available at the site.

    The first is the gear ratio calculator utility. You enter the various gear ratios in your drive train, the wheel size, and engine RPM, and the utility calculates the potential top speed. It doesn't consider the engine power, drive train efficiencies, or aerodynamic limits, though.

    The second utility is the power calculator. It's useful to tell you approximately how much power you have at the engine, to have to push the bike along at a given speed.

    It allows you to enter the slope and /or wind speed, and to adjust the default temperature and drive efficiency.
    Last edited: Jan 17, 2011
  7. loquin

    loquin Active Member

    Now, the GP460 is rated at 4.2 HP at 11000 rpm...

    That's enough power to run at 55 mph, on the flat...

    But, (disregarding how unsafe that would be on a bicycle,) what about hills? Personally, I would gear the motor to have a top end of about 35 mph, and, with max torque at 8000 RPM, your best hill-climbing speed would be at the 25-26 mph range.

    That motor should be able to take you (assuming 250 pounds of rider, 50 pounds of bike & engine) up a 15 percent slope at 26 MPH.

    To get that, you would use the 1.75 inch drive pulley and 5 inch driven pulley (with the BMP belt drive jackshaft) and an 8 tooth drive sprocket with a 65 tooth driven sprocket at the axle, for a total reduction of 23.81:1

    (With BMPs sprocket jackshaft, too get about the same total ratio, your sprockets would be

    8 to 27 , engine to jackshaft, and 8-55, jackshaft to axle, with a total ratio of 23.2:1)
    Last edited: Jan 17, 2011