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How does this clutch work?

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Brian Rupnow:
After building the dog clutch for the drag saw, I asked for any friction clutch plans that people could find. Mike sent me this link. It looks like something I could use/build, but I can't tell how it works. It seems that the arm, part #A227 moves the slider, #A225 ahead and forces the comma shaped pieces #A223 apart. I assume that once the part #A225 is captured by these arms #A223, it will stay in place. Somehow the pressure of the spring #A238 must be involved here, to make the arms #A223 spring loaded to hold the expander cone part #A225 in place. There is a very faint dashed outline that shows these comma shaped parts #A223 in the position they would have if the slider cone A225 was not engaged. The only way I can figure a clutching action here is if there were gear teeth in the comma shaped part and a rack style series of annular grooves in the shaft it slides on, forcing everything to the right to put pressure on the friction disc #A189.  Maybe I'm overthinking this. Any other explanation of how this works will be gladly listened to.---Brian

Looks to be the same clutch as on old garden tractors. Pull the handle in and it pushes the clutch faces together and spins the outer shaft.

Brian Rupnow:
I've been studying on this thing, and I think I have it figured out. I'll have to make a model to confirm what I think. It seems that the secret to this mechanism is all in the spring and the comma shaped pieces. When those comma shaped pieces are forced outward by the expander cone, they not only trap the expander cone but a tit on the bottom of the comma shaped piece makes the whole stack up of parts become marginally longer--enough to put pressure on the friction disc. Of course the magic in this isn't in engaging the clutch--it's in also capturing the handle so it can't slip out of engagement.

Brian Rupnow:
Okay--Burned a few brain cells on this one. The clutch which I posted a link to in post #1 is not an "over center" clutch. It does however, not only engage and disengage the clutch thru pressure on the friction material, but also traps the handle so it won't jump out of engagement. This is a very clever design, and I had to study it a lot to see what was really happening. I have modelled it in both engaged and disengaged positions. EDIT EDIT--I have updated these drawings based on information from Velocette.

Beautiful drawings, Brian. And a lingering question answered!



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