3pt Clutches - Slip & Overrun

[3Ts]

I have a new to me Woodland Mills chipper and started wondering about a PTO slip clutch. I use a slip clutch on my bush hog and my rototiller, I'm wondering if I need one on the chipper? It has a large rotating mass but not much room for a slip clutch. How do you determine which implements get a slip clutch or an overrunning clutch?

 

[RickB]

If your chipper has belt drive I wouldn't be concerned about a slip clutch. Few belt driven implements have them.
If your tractor DOES NOT have an internal PTO brake I would not be concerned with an ORC.

 

[joecdeere]

Two totally different things, a slip clutch is to protect your tractor and implement from a sudden PTO stoppage, as in hitting something with your bushhog that it can’t deal with, or getting something caught in your tiller that keeps it from turning while the tractor is still putting power to it. As Rick stated, the belts on the chipper work as a slip point if it jambs. An ORC (overriding coupler) which is really just a huge ratchet is designed as a way to keep an implement that still has inertia from spinning weight (again bush hogs were famous for it) from powering the tractor forward even when the operator had the clutch down, the mower powered the transmission from the rear through the PTO. With the invention of double clutches and independent PTO systems this happening is much less. Older tractors such as the N series of Ford, early Massey’s, and lots of the early imports should have a ORC as standard equipment. Some later tractors had the ORC built into the PTO.
There is no telling how many tractors have been driven into houses, barns, cars, and one of my uncles put his 9N into a lake because he couldn’t stop. The best modern need that a OCR is great for as Rick pointed out is that things like a mower, chipper, etc that have to wind down to a stop after you turn off the PTO is killing the PTO brake on tractors that have independent PTO’s. Hopefully all my babbling makes some sense.

 

[5030]

2 words, slip clutch

 

[LouNY]

4 words,
nope, over running clutch

OR a combination unit
Bare Co USA - P.T.O: Over-run (freewheel) Couplings
bottom of the page has links to standard duty and heavy duty

 

[RickB]

The three current models of Woodland Mills chippers all have shear bolt protection on the PTO shaft. 2 are direct drive and one is belt driven. If the OP's chipper has shear bolt protection a ship clutch is unnecessary.

 

[5030]

Had a pto chipper and it's a helluva lot easier to set a slip clutch than replace 5 matched Vee belts because you smoked them by stuffing in a knot the chipper decided not to eat. Don't really need an over running clutch so long as you idle the unit down, but a slip clutch is a necessity unless you want to replace belts. I didn't.

 

[5030]

The issue with most pto chippers is the close proximity of the input to the pto. A Weasler slipper fits nicely in that space and still allows a short pto shaft.

 

[RickB]

Adding a slip clutch to a driveline that has a shear bolt is unnecessary.

 

[Thunder chicken]

As stated, the WM chippers have shear bolts on the pto shaft. My snowblower has several shear bolts, no slip clutch. I’d think if anything, the snowblower ought to have a slip clutch. I change 1/2 a dozen or so shear bolts a season. But maybe it’s best having it ‘work’ till it don’t….. I unknowingly smoked the clutch on the bush hog this summer, chunk of log jammed it up somehow and I didn’t notice till smoke was pouring off the clutch! Was quite a sight…. New disks needed now, a lot more $$ than a cheapo bolt. I suppose the shock the mower gets would break bolts very frequently….