PTO Slip Clutch Installation

[SimS]

After replacing many shear bolts on my 5' Bush Hog I have decided to install a slip clutch. I need to know what grade of bolts I should use to attach the clutch. Some folks say "Just slap on Grade 8 and go for it". I'm thinking that I will probably go with Grade 5 "just in case". Also, what is the preferred way of adjusting the clutch? I read a Bush Hog manual that says that the clutch should be adjusted periodically by loosen the bolts and letting it slip for 2-3 seconds and then adjusting it to the proper spring length. My question is how does the same spring length dimension account for clutch plate wear? I'm assuming that you must adjust to compensate for wear. Any advice or experience is appreciated. Thanks.

SS

 

[rdbrumfield]

Adjusting to spring length keeps the pressure at a predetermined value. If you are going tjo adapt a slipclutch jto the shaft that has the shear bolt, I would bet that you will be shearing bolts for a while until you get the clutch set at the right limits. DO NOT PUT GRADE 8 BOLTS IN. Go with the ones that the manual calls for. In hard pulling you will probably smoke the clutch some to let you know to back off, but better that than a destroyed gear box. Once you have determined that you have the clutch adjusted to the limits of the shear, measure the springs and tuck your findings in your manual for future reference.
I used to have a mower with the shear system, I couldn't haul enough bolts in the tool box. I have since went to a heavier hog with the clutches. Have replaced the clutches a few times, but then I do some extreme mowing.

 

[em14]

The slip clutch is easy to damage if you aren't watchful ... after you install the clutch or after it has sit idle for a long time, you need to adjust it so that it will slip just a little when you start to use it ... this is so the clutch surfaces get the grease, rust and what ever cleaned out ... just let the clutch slip for a few rpm .. not many ... then tighten the adjustment so that in normal cutting it is not sliping ... but (this is the part of the instruction I always disliked because it means trial and error to get it right), not so tight that it will not slip when you hit that immovable object ... I would hope that you got instruction about this with your slip clutch when you bought it ... if the clutch is mounted using the shear pin bolt to secure it to the shaft then one or the other is going to have to be "weaker" of the two and you want that to be the slip clutch ... If you have mutli springs pull them down to the same height all around ... If you have a single "Big Nut" used for the adjustment it's easier to adjust .. my experince with shear pins they seem to shear awful easy and even if they don't shear for a while they take a beating and progressively get weaker then shear anyway .. They don't give those clutch disk away and they aren't cheap ... but I sure got tired of replacing pins ...

 

[BillyP]

I have a slip clutch on my cutter but there's no adjustment.

Billy

 

[em14]

Interesting, how do you account for the wear of the clutch. When the implement hits something and causes the clutch to slip I would think there would be wear of the fiber disk. Or does yours have fiber disk or something else?
Leo

 

[BillyP]

It has the disks. I looked through the whole owner's manual and it says nothing about an adjustment. The clutch is on a JD 616 cutter. The manual does show how to disassemble and inspect it. It says if the disks are glazed (shiny and glossy), replace but mention of an adjustment. So, I don't know.

Billy

 

[rdbrumfield]

the fiber discs do wear and I adjust up as needed. When it starts to slip too easily just take a turn or two on the pressure springs.

 

[Wingnut]

I dunno .... it may be just me ... but everytime I've snapped a shear pin .... and let me tell you, Tractor Supply has sold me a few! ... it has been because I got WAY too aggressive. I've never broken one from any problem with the deck or power ... just from trying to chop down too much brush at one time (say four 2 inch trees instead of one at a time). Same with the auger ... only time I broke a shear pin is when my foot slipped and I moved the tractor while boring.
So I'd have to ask ... are you sure that your deck is big/strong enough and you're not trying to push it too hard? I'd be a shame to go to all the effort of buying and installing a clutch when it didn't solve the problem.

 

[Trev]

Dumb question time:

Does the JD4300 have a slip clutch built in to the PTO system? I've heard of adding them, but I think the ones I've heard of are a different beast altogether.. they, for example, let the finish blade spin down slowly rather than stopping dead when you disengage the PTO. I think we're talking different things here.. things to protect implements and the PTO drive mechanism..

The ones I've heard of are often described as helping to attach implements because they turn freely in one direction. This isn't what you're refering to here, right?

Bob

 

[pcmem]

Bob,

You're not thinking about overrunning clutches are you?
We use them on old gear drives so when you want to stop while brush hogging the momentum from the spinning blades won't back drive the tractor through the PTO geartrain. An added bonus is that they freewheel in the direction of rotation so you can rotate by hand the PTO to connect to the impliment.

FWIW,
Michael

 

[Trev]

<font color=blue>Bob,
You're not thinking about overrunning clutches are you?</font color=blue>

Yep! /w3tcompact/icons/smile.gif That's exactly what I was thinking of! /w3tcompact/icons/blush.gif

Whole different ballgame, eh?

What I'm asking now is, does a JD4300 have the type of clutch that protects the PTO powertrain? I think it must, as when I pick up a rock in my tiller, the tractor engine slowly dies, as opposed to *instantly* dying. I assume a clutch must be included in the drivetrain to allow this?

 

[rdbrumfield]

Chances are that you have a slip clutch on the drive on the tiller. If it does not and the tractor slowly dies, it is slipping the tractor clutch, not a good thing, but better than ripping the gears out of the tractor.

 

[Bird]

I can't imagine it being anything other than what rdbrumfield has said. Of course, we're assuming that when that tiller picks up a rock, it promptly quits turning. So, if you don't have a slip clutch already on the tiller PTO drive shaft, I'd be checking the clutch adjustment on the tractor.

 

[SimS]

I agree that sometimes being too aggressive can snap a shear pin. Most of mine snap when I hit some hidden log or stump beneath the brush. I hoping to slip the clutch and continue on. I will be setting up the clutch this weekend and I will report back. I'm taking all of the great responses found here and trying them out. Thanks for the advice.

SS

 

[DavidH]

I'm going to get a slip clutch for my Rhino SE-6 and I was worried about damage to the PTO. The guy at TSC said to put a Grade 8 bolt where the slip clutch connects to the cutter, but use the standard shear bolt where it connects to the PTO. That way there is no way to damage your tractor.

 

[rdbrumfield]

I would have to challenge the intelligence of the fellow that told you to put grade 8 on the slip end and a grade 5 on the spline side, which will never slip on the tractor d-shaft. Stay with the recommended shear grade on the mower input shaft. If you tighten the clutch too much you will still have a safety valve for the gear box. Those shear pins wear over time and will part, even with the slip clutch, just have some spares and if you are going through them lighten the pressure of the clutch.

 

[JimMc]

I would venture a guess that most cutters with slip clutches really have no driveline protection at all. By this, I mean that at least annually, you should do just as em14 has suggested. Many times the metallic particles and the steel disk in the clutch rust together and your "slip" can't happen. Lots of new cutter parts and drivelines are sold every spring because few people do this maintenance. In fact, many dealers shy away from selling a slip clutch to novices because they have had bad experiences.

Now, am I saying slip clutches are bad? No way, I put slip clutch drivelines on every PTO implement I get, with the exception of belt driven final drives (ie most finish mowers). Changing one tractor PTO output shaft was enough for me. But unless I know the clutch hasn't seized, I take the time to do the maintenance before I ever engage the PTO.

Good advice em14.