Two Speed Automatic Transmission

msrfan

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Sep 17, 2010
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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.
 

motorhedfred

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Jul 31, 2009
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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.
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.
 

motorhedfred

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Jul 31, 2009
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Th
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.

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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Tony01

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Nov 28, 2012
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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?
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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motorhedfred

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Think there would be until you slow down enough for the second speed clutch to disengage then would be none.............Curt

How they work.
https://www.parduebrothers.com/minibike/twospeedthreechainminibiketransmission.pdf
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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Tony01

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Nov 28, 2012
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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?
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.
 

motorhedfred

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Jul 31, 2009
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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.
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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zean

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Dec 5, 2010
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I think Sick Bike Parts has the White Industries flanged super extra heavy duty free wheel, sprockets and 5/8 inch freewheel to shaft adapter.
 

msrfan

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Sep 17, 2010
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I was wondering if you remember where you got those oneway sprockets? and how did they hold up?
I was wondering if you remember where you got those oneway sprockets? and how did they hold up?
Hey greggor. I found all the one way needle bearings on ebay and the sprockets at Mc Master Carr. I bought machinable sprockets and bored them to press fit the bearings into. I had a lathe where I worked at the time and was able to do the machine work. Check out Staton. They have a huge variety of sprockets, shafts, bearings, freewheels and adapters.
 

greggor51505

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Jan 14, 2021
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Hey greggor. I found all the one way needle bearings on ebay and the sprockets at Mc Master Carr. I bought machinable sprockets and bored them to press fit the bearings into. I had a lathe where I worked at the time and was able to do the machine work. Check out Staton. They have a huge variety of sprockets, shafts, bearings, freewheels and adapters.
Awesome Thank you