Two Speed Automatic Transmission

Discussion in 'Hubs, Gearboxes, Sprockets and Chains' started by msrfan, Apr 14, 2013.

  1. msrfan

    msrfan Well-Known Member

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    Can't freewheel in opposite directions. It's been a while since I've ridden the bike (it's in storage) but if I remember correctly you're right about compression braking as long as a clutch is locked up.
     
  2. motorhedfred

    motorhedfred Member

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    I guess I should have clarified. Knowing that freewheel sprockets will only transfer power in one direction, and also knowing that a lot of freewheel sprockets have a threaded attachment (obviously also only one way rotation lest you loosen the attachment threads by turning it in the wrong direction) I specified keyway style freewheeling one way sprockets as the keys at allows them to be installed in either direction.

    If I correctly understand the way these freewheel sprockets work, when the drive sprocket is spinning faster than the driven sprocket, it engages. Looking at the bicycle from the left, the sprockets and jackshaft must turn counter clockwise to roll the bike forward with the engine's output shaft spinning faster than the rest. When the centrifugal clutch engages, the bike begins accelerating forward.

    Looking at the drivetrain from the rear wheel to the engine, when you let off the throttle the rear wheel is now spinning faster than the sprockets, jackshaft....ect due to the ratios. As long as there's a speed differential a second set sprockets (maybe only one?) that engage in the opposite direction of rotation, engine braking SHOULD occur until the shaft speeds equalize. When you re-apply power, the second freewheel sprocket/s SHOULD disengage and be overrun by the drive sprockets.

    I'm still not 100% sure of all this and maybe it's a moot point if the clutches stay engaged all the way down to the bicycle speed where the primary clutch engages.
     
  3. Tony01

    Tony01 Well-Known Member

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    Depends on how 2-speed is setup; with this one the power runs through a clutch in top gear. Top gear is just like a single speed. Freewheel is for all gears lower than top gear.

     
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  4. motorhedfred

    motorhedfred Member

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    and that's where the freewheel sprockets setup for deceleration come in.
     
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  5. Tony01

    Tony01 Well-Known Member

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    That’s not how this works. But if you can draw it, be interesting to see what you’re thinking.
     
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  6. motorhedfred

    motorhedfred Member

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    Th
    Thanks for posting the video. You seem to be quickly easing up on the throttle when you anticipate the second clutch engagement. Is that for a cleaner engagement?
     
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  7. Tony01

    Tony01 Well-Known Member

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    Yes. It has already begun the shift. Depending on load shifting up, or engine braking slowing down, the shift speed can vary. It is a very natural riding setup that can easily be ridden with one hand.
     
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  8. motorhedfred

    motorhedfred Member

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    Thank you! That's both interesting and encouraging.
     
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  9. curtisfox

    curtisfox Well-Known Member

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  10. motorhedfred

    motorhedfred Member

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    Thank you for taking the time to share this information Curt. I've been all over the web searching for information on the centrifugal clutch where the bell spins with the shaft instead of freewheeling. I can't find a thing. Do you know what it's properly called so I can do a web search or where a person could buy one?
     
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  11. msrfan

    msrfan Well-Known Member

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    I got all my info researching Rupp mini bike TT500 2 speed clutch.
     
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  12. motorhedfred

    motorhedfred Member

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    That helped, thank you. Some of the most interesting information was here on motorbicycling.com including some of WayneZ's 2-speed v-belt drive ideas.
     
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  13. Tony01

    Tony01 Well-Known Member

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    The comet 2-speed possibly had that. The 2nd gear shift was based on engine speed not jackshaft (rear wheel) speed. Doesn’t really make sense to me but that’s how they did it. If you are looking for this to have your clutch on the jackshaft in a single speed setup, you can set it up with a regular clutch by driving the JS from the engine and bell output to rear wheel.
     
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  14. motorhedfred

    motorhedfred Member

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    Here's my thoughts. If there's a ratio reduction from the clutch bell sprocket to the jackshaft (I'm referring to a ball bearing mounted shaft between the engine centrigul clutch and the rear wheel) and the second centrifugal clutch's mechanism, the second clutch needs more engine rpm to spin the jackshaft up to it's engagement rpm. Given that the driven sprocket will be freewheeling, when the jackshaft gets up to speed the second clutch takes over with it's ratio.
     
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