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Old 12-24-2012, 02:57 PM   #91
windmill
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Originally Posted by Biebs View Post
Is that a centrifical clutch as speed picks up it engages?? Gravely slip cluth or did you mean Gravity??
"Gravely" is a commerical mower manufacturer that made 2 wheel tractors, and all their power attachments had a slip clutch to protect the gear driven pto.





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Old 12-24-2012, 08:26 PM   #92
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Apparently the Gravely slip clutch is rated for 30-35 lbs slip pressure.

http://www.ytmag.com/cgi-bin/viewit....lk&th=74365%3E

http://www.mytractorforum.com/showthread.php?t=32659

A Yahoo Search for PTO Slip Clutch shows there's all kinds of these things out there, might have some real possibilities. Many are electric. A guy could set one up to run 1WD 99% of the time, then if the going gets rough flip a switch and have electric slip clutch engage 2WD.

The low horsepower part might not be a problem at all if the second drive wheel is just used as a helper to keep things rolling in soft stuff. They're probably used for many horsepower rating. I'm going to look into this a lot deeper, may be a very good solution!
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Old 12-24-2012, 10:55 PM   #93
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I was starting to get excited about the electromagnetic slip clutches but then reality kicked in. They present the same old problems I wanted to avoid: expensive, complicated, heavy, mfr. only specialty parts, can't repair out in the world if at all.

On the non-electric slip clutch models I saw most had very low input power ratings, like for small garden tractor engines/drives. When sizing one would have to consider engine's torque rating plus the multiplication factor of transmission and final drive ratios.
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Old 12-26-2012, 11:08 AM   #94
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Originally Posted by windmill View Post
Here's a Gravely slip clutch, dont have one loose to weigh, but I would guess it is under 4 lbs.
..............................
Weeelll now....


Looking at the "teeth" on the Gravely, it looks like it only works in one direction. I imagine the matching part also has the saw tooth cut.... err, I guess when enough torque is applied the teeth ride up on each other and force the clutch to open, tightening the bolts increased spring pressure to resist opening the clutch...

So if the wheel driven by this unit (hack wheel) has traction and the tug wheel doesn't, this might actually work against you if the spring pressure is set too low. (Cutting power to the high traction side.)

And since there is no way to disconnect power to the tug wheel alone, sharp right hand turns are still going to pit your turning efforts against a locked differential, while left turns should allow the Gravely to work. (This is where I start wondering about consistency, I don't see it performing the same in mud as it does on hardpack... it's too dependant on the spring pressure, although maybe there's a happy medium??)


Uhg... I need to go look at one again. It's been years since I've been near a tractor.

But... I do have something similar out in my shed. Instead of having the saw tooth shaped teeth they are triangular, so will slip in either direction. Not sure what it came from, but it's only about 2" in diameter with a 3/4" shaft.
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Old 12-26-2012, 12:16 PM   #95
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Quote:
Originally Posted by FlySniper View Post
Weeelll now....


Looking at the "teeth" on the Gravely, it looks like it only works in one direction. I imagine the matching part also has the saw tooth cut.... err, I guess when enough torque is applied the teeth ride up on each other and force the clutch to open, tightening the bolts increased spring pressure to resist opening the clutch...

So if the wheel driven by this unit (hack wheel) has traction and the tug wheel doesn't, this might actually work against you if the spring pressure is set too low. (Cutting power to the high traction side.)

And since there is no way to disconnect power to the tug wheel alone, sharp right hand turns are still going to pit your turning efforts against a locked differential, while left turns should allow the Gravely to work. (This is where I start wondering about consistency, I don't see it performing the same in mud as it does on hardpack... it's too dependant on the spring pressure, although maybe there's a happy medium??)


Uhg... I need to go look at one again. It's been years since I've been near a tractor.

But... I do have something similar out in my shed. Instead of having the saw tooth shaped teeth they are triangular, so will slip in either direction. Not sure what it came from, but it's only about 2" in diameter with a 3/4" shaft.
The "teeth" have nothing to do with the function of the clutch, they serve to aline the drive cog on the pto. For the OP's application, it would probably work best to remove them and weld a universal yoke in their place.
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Old 12-26-2012, 02:55 PM   #96
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Originally Posted by windmill View Post
The "teeth" have nothing to do with the function of the clutch, they serve to aline the drive cog on the pto. For the OP's application, it would probably work best to remove them and weld a universal yoke in their place.

I found an exploded view... Not as fancy as I was thinking...
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Old 12-28-2012, 03:34 AM   #97
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Talking .

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Cheers.
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