Slip clutch maintainance

[Rch]

On a thread about rotary cutters it was mentioned that slip clutches needed routine maintainance. What exactly do they need?

RCH

 

[Bird]

I don't have a slip clutch on anything (thank goodness!/w3tcompact/icons/smile.gif), but the manual for my tiller says, if you have the slip clutch and the tiller has been "stored for an extended period" to perform an "operational check":
Loosen eight nuts retaining clutch springs exactly one full turn.
With tiller blades firmly on ground and tractor at idle speed, engage tractor PTO drive for 2-3 seconds. Clutch should slip without turning blades. If clutch does not slip, contact your authorized Bush Hog dealer.
Retighten nuts to within 1/64" of original position. Initial spring length is 1-3/32" (27.6mm).

Slip Clutch Adjustment
The slip clutch is factory preset to the correct torque for protecting implement and tractor. Periodic adjustment is recommended; refer to (the operational check I just quoted). Should adjustment be needed, first check to be sure all spring lengths are within 1/64" of being the same. Initial spring length is 1-3/32" (27.6mm). If necessary, loosen nut on any spring that is unequal. Adjust all eight spring retaining nuts 2/3 of a turn (2 flats on a nut) and check clutch slippage. If further adjustment is necessary, do so in 1/3 turn increments or consult your Bush Hog dealer. Adjust only to provide sufficient torque to prevent slippage under normal conditions. When rocks, roots, etc. are present, occasional slippage is normal for drivetrain protection.

Nothing complicated, but doesn't that sound like fun? I'd prefer just staying with the shear pins however I've never sheared a pin and if you're working in rocky ground where pins shear frequently, then I can certainly see an advantage to the slip clutch, and a reason for paying $100 or so extra to get it.


Bird

 

[W5FL]

Unfortunately that procedure will not work on any of the slip clutches that I have had to adjust so far including tiller and mower. Try to measure the length of the springs (best way) or count the number of turns you loosen the nuts, which is several turns. Mine would not slip with all of the nuts loose and the tiller happily ploying the dirt. I had to get it in road base or rocky soil to bust it loose. Then you need to be sure you didn't bust big chunks out of the slip clutch material. Let it slip for 5-10 seconds. Reverse the above process to get the springs back to the correct tension. If you happen to own a torque wrench with a DIAL, you may be able to set the nuts to the same torque that you loosened them by removing only one, clean and oil the threads, then see what the loosening torque is. Mine was 20 ft lbs according to the manual.

Most slip clutches that have not been adjusted after six months of storage (INSIDE OR OUTSIDE) are useless until they have been adjusted and are actually worse than just having a shear bolt - which takes no maintenance.

Since I have lots of rocks to deal with, slip clutches are a necessity, but if I had no rocks, I would not want a slip clutch. /w3tcompact/icons/smile.gif /w3tcompact/icons/smile.gif /w3tcompact/icons/smile.gif

 

[Rch]

Wen, Bird, thanks. I burned up a Landpride 5 ft horizontal cutter slip clutch and 'twist-jammed' it on the implement's shaft.It took the biggest gear puller plus more for the dealer to get it off. The Landpride manuel tells you how to adjust it in a very terse fashion but nothing about routine maintainance. I've got rocks galore courtesy of 17 glaciers! The clutch failed right after I rolled a bowling ball sized rock through the cutter.I think it did protect the tractor PTO drive train.

RCH

 

[W5FL]

Let's see.....

How did you adjust it before you burned it up. A properly adjusted slip clutch with a big rock jammed in the tiller will emit a ball of white smoke that will choke a horse. Nothing will twist up, but it sure acts like it will catch on fire if you don't quickly disengage the pto. That is the advantage of shear pins. They just shear.

Sounds like yours was not properly adjusted and just tore up that part of the clutch which happened to be weaker than the drive train. The biggest problem if they haven't been adjusted is that you can pull the clutch material off of the plates and have to replace the slip clutch material. I guess if you smoke it enough, you may still have to replace it. Mine has only boiled smoke a couple of times.

Tell us more...

 

[Rch]

Wen,I guess I mispoke.It didn't smoke at all- it just quit transmitting power all at once. I then tried to adjust it and it wouldn't adjust so it would run. To put in new clutch plates you have to take the clutch off the implements shaft that enters the gear box. Because it was "twist-jammed" I couldn't get it off.
The cutter is about 8 yrs old and was always stored outside. I never touched the slip clutch til this happened,not realizing it needed periodic adjustment as the plates wore. I think it must have siezed from weather because it sure twisted the square female part of the shaft on the male shaft that goes into the gear box.If I had gone through the adjustment as described above I might of realized the clutch was siezed or ,possibly,broke it loose.
After transport, labor and a new slip clutch, I was out $700.

RCH

 

[W5FL]

Yeah. You are right. The clutch was seized and not slipping at all. When I started to adjust mine, with all bolts visibly loose, the tiller would till just fine in pretty hard dirt. I had to find (not hard) some rocky soil to bump it enough to get it to slip at all. This was with all springs and bolts obviously not holding anything.

The adjustment is because they RUST together and have to be freed up regularly, particularly if setting outside, but also happens if stored indoors.

Guess we all have to learn this lesson the hard way. Cost you $700 to learn it and only cost me $150 to replace the tiller tines that kept breaking. After I fixed(I like that better than adjusted) the slip clutch, you would hear a thump and see about 3 feet where the tiller didn't turn - so there was obviously a big difference. /w3tcompact/icons/smile.gif

 

[tractorman]

Slip clutches require mainternance for several reasons. The main one is that they often tend to rust themselves together, Usually because they are left open to the weather. When they freeze up, you risk damaging the tractor or driveline of the mower. Those people who use their rotary mowers often enough to keep their slip clutches active, do not have to worry as much as the person who uses theirs once or twice a year. Anyone needing more info can feel free to email me. Thanks

 

[jgh]

2000-06-23

Would it make any sense to use silcone spray on any part of the slip clutch? Tell me if I am totally off base.

Keeping things out of the weather also seems to be indicated, esp for those of us that aren't daily users of each of our imps.

Jim

 

[W5FL]

Don't do it!

The slip clutch is set up based on the coefficient of friction for the pad material. Oils would change this. Best course of action is to keep the slip clutch covered or inside and once or twice a year service the slip clutch which only takes about 15 minutes. I bought $120 worth of tiller tines, before I learned this. /w3tcompact/icons/smile.gif Most people would be better off with a shear bolt rather than a slip clutch for mowers and augers, but tillers tend to jam and something is going to give. Kinda like throwing a wrench in the moving machinery to see what happens.