Setting up New PTO Slip Clutch, and why

[BonnySlope]

Talking about topic, IMO since refreshing my Howard tiller and completing my soil test plot. I fill it's time to go back and loosen clutch springs and set up for my BX. The process seams straight forward, by loosening spring bolts all the way and slip disc however it's accomplished, I've seen some put a large beam (simulating a root) instead of putting it to dirt to cause slippage which I believe is ok for the first initial factory fresh disk plate settings. Then going back to new starting point (DP) of springs just touching washer and bolt and doesn't turn freely. At this point depending on manufacture, tighten one full rotation, others have one and half turns then Run slippage test on site and at this point advance by a quarter turn, that's what my manufacture suggest, IC advances by 1/2 turns until you reach the desired site slippage.
Some may wonder why not just size and run at factory torque setting. Here's an example Series 4 PTO shaft is meant to operate between 25-35 PTO HP, we all know there some variance in what manufactures say required HP, come on we've all pushed those numbers. That's where it puts higher need to adjust Slip clutch for your equipment. If your in between or below PTO series specs. There meant to adjust. Oh, don't think about it, most implements call out and need a series size.

 

[imnukensc]

What?

 

[BonnySlope]

What?

just talking about need to set PTO slip clutch and for those who may want to take short cuts.

 

[Old Machinist]

Best take the clutch completely apart to inspect and clean. I bought a tiller from RK that came with the clutch tightened all the way down and had condensation inside. The disc was rusted onto the metal faces. After removing all the bolts I had to beat it apart with a hammer. After cleaning it all up I found the bolts were too short for proper adjustment. I had to buy new bolts and lock nuts a quarter inch longer. If stored in a dry environment you can get by with loosening and slipping every year for a maintenance check but it it won't turn it's time to take it all apart again to clean the rust out.

 

[Tx Jim]

I fail to understand what HP of tractor has to do with slip clutch adjustment setting. If hard ground is encountered while tilling slip clutch should hold the same regardless of HP. I know slip clutch on my JD 467 baler & Krone AM283S disc cutter has one operating setting regardless of tractor HP pulling it.

 

[Henro]

Probably depends on what the slip clutch is there to protect.

If it’s there to protect the implement, then it could be set to slip at the same point regardless of tractor size.

If it’s there to protect the tractor, then it might be set to slip sooner on a low HP tractor than a high HP tractor.

Just an assumption on my part…

 

[woodman55]

Best take the clutch completely apart to inspect and clean. I bought a tiller from RK that came with the clutch tightened all the way down and had condensation inside. The disc was rusted onto the metal faces. After removing all the bolts I had to beat it apart with a hammer. After cleaning it all up I found the bolts were too short for proper adjustment. I had to buy new bolts and lock nuts a quarter inch longer. If stored in a dry environment you can get by with loosening and slipping every year for a maintenance check but it it won't turn it's time to take it all apart again to clean the rust out.

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Been down that road. My bush hog sat for two years once, one of the fiber disks stuck to the rear plate. Took it completely apart. Lots of rust, plus one fiber was cracked. Put in two new disks, cleaned, buffed the mating surfaces and put a thin film of grease on the pivot/bushing.

I now take all my slip clutches apart ever few years, just to make sure all is well. I also made a gauge for the spring length, so I am not fooling with a caliper, trying to measure springs.

 

[SDT]

I fail to understand what HP of tractor has to do with slip clutch adjustment setting. If hard ground is encountered while tilling slip clutch should hold the same regardless of HP. I know slip clutch on my JD 467 baler & Krone AM283S disc cutter has one operating setting regardless of tractor HP pulling it.

PTO slip clutches are sold for use with tractors of various HP and must be adjusted for use with a specific tractor/mower combination. Failure to do so usually results in a clutch that is adjusted too tightly for use with your tractor. In such conditions the slip clutch MAY be adjusted properly for the mower with which it was sold (one certainly cannot rely upon this), but it will almost certainly not be adjusted properly to protect the PTO mechanism within the tractor. In such situations, which are very common, blade obstruction with an immovable object (or catastrophic mower gearbox failure) may result in catastrophic damage to the tractor PTO mechanism.

Of course, almost no one makes such adjustments and both tractor and mower damages do occur as a result.

Additionally, PTO slip clutches should be loosened and slipped annually to prevent corrosion lock, which results in no protection. Again, very few folks do this. To avoid this issue, I have gone back to shear bolt protection on most mowers after decades of experience.

 

[SDT]

Been down that road. My bush hog sat for two years once, one of the fiber disks stuck to the rear plate. Took it completely apart. Lots of rust, plus one fiber was cracked. Put in two new disks, cleaned, buffed the mating surfaces and put a thin film of grease on the pivot/bushing.

I now take all my slip clutches apart ever few years, just to make sure all is well. I also made a gauge for the spring length, so I am not fooling with a caliper, trying to measure springs.

Bingo.

Good practice.

 

[Elliott in GA]

The Slip Clutch provides the same protection as a shear bolt; it should be adjusted to this shear bolt value regardless of tractor HP or anything else. The manufacturers set the PTO clutch to this value at the factory. The owner is only required to return to this approximate value (has a significant bias towards protection/controlled slip) after the yearly PTO clutch slippage (to ensure corrosion and etc. has not bonded the internal plates together).

You do not use different shear bolts based on tractor HP or anything else. Adjusting your slip clutch to greater or lesser resistance based on some non-manufacturer based protocol is a recipe for problems (too little resistance leading to frequent slippage causing the premature wear of the slip clutch plates or too much resistance causing a reduction or elimination of protect to the drivetrain of the tractor and implement).

See Land Pride slip clutch adjustment video (the same content as in my LP RCR manual):

I slip my PTO clutch every spring (I use the mower throughout the year) on cool, clear day of my choosing. I prefer this routine to the potential of having to replace a shear bolt on a boiling hot summer day, freezing cold winter day or any day when I am trying to get work done. How many times has my slip clutch slipped while I was working over the last 3+ years? I do not know, but I presumed it has slipped a little occasionally. Of course, I never would know (unless you completely stop the mower with some obstruction as opposed to a temporary resistive pulse - I have hit/shattered a few rocks hidden in overgrowth), but I do know that I have not had to stop working to replace a shear bolt for 3+ years (a significant amount of using the RCR to reclaim 10+ acres of chest high weeds, privet hedge and multiflora rose taller than me, the multiflora rose was so thick that I had to claw it down first with my grapple as I could not back over it).

 

[Tx Jim]

PTO slip clutches are sold for use with tractors of various HP and must be adjusted for use with a specific tractor/mower combination. Failure to do so usually results in a clutch that is adjusted too tightly for use with your tractor. In such conditions the slip clutch MAY be adjusted properly for the mower with which it was sold (one certainly cannot rely upon this), but it will almost certainly not be adjusted properly to protect the PTO mechanism within the tractor.

I was referring to equipment slip clutches that come with each implement not aftermarket slip clutches added to pto shaft. I still think type of implement & HP required to operate dictates slip clutch setting not individual tractor HP. If you watch video Elliott posted the slip clutch springs were measured to be 1'' , then all nuts were loosened, clutch plates slipped then all nuts tightened to 1'' with no mention of tractor horsepower.

 

[SDT]

I was referring to equipment slip clutches that come with each implement not aftermarket slip clutches added to pto shaft. I still think type of implement & HP required to operate dictates slip clutch setting not tractor HP

Understood.

The slip clutch sold with a new mower may be adjusted properly for the mower in question but I certainly would not rely upon such assumption. Moreover, mowers have different gearboxes depending upon cutting capacity. Any quality mower sold with a factory adjusted slip clutch will almost certainly be adjusted to the HP rating of the gearbox. Tractor HP plays no part in any factory adjustment process.

The 6' Woods BB720X mower that I recently sold was equipped with a 160 HP gearbox. The L6060 tractor that I operated it with produced 53 PTO HP, more than enough for a 6' cutter in most conditions. Without readjusting the slip clutch from any assumed factory setting, what do you think would have been the weak link in the drive system?

Similar scenarios existed in all of the many other tractor/mower combinations that I have owned over the decades.

Unless one is using a light duty mower with a gearbox rated lower than the PTO power produced by the tractor upon which it is to be used, the slip clutch should be adjusted to the tractor PTO power or slightly more. Without doing so, the slip clutch may well not protect the PTO mechanism within the tractor.

BTDT.

 

[Elliott in GA]

RhinoAg - manufacturer video on slip clutch (spoiler alert: same universal set up without regard to the tractor)

The good thing about springs is that they only weaken over time. If you start experiencing excessive slippage using the factory slip clutch settings, it is time to replace the spring(s) (due to fatigue) and/or the friction plates (due to wear).

Also, Woods Implements slip clutch adjustment from their manual: (same universal setting)

SLIP CLUTCH ADJUSTMENT The slip clutch is designed to slip so that the gearbox and driveline are protected if the cutter strikes an obstruction. A new slip clutch or one that has been in storage over the winter may seize. Before operating the cutter, make sure it will slip by performing the following operation: 1. Turn off tractor engine and remove key. 2. Remove driveline from tractor PTO. 3. Loosen six 12 mm cap screws (7) to remove all tension from the compression springs (5). 4. Hold clutch hub (3) solid and turn shaft to make sure clutch slips. 5. If clutch does not slip freely, disassemble and clean the flange yoke (1), clutch hub (3), drive plates (4 & 5), and thrust plate faces (6). 6. Reassemble clutch. 7. Compress each of the six compression springs (8) by tightening the six cap screws (7) and lock nuts (10). The compression springs should be compressed to a height of 1-7/16", not including washer (9). The minimum spring height is 1.36". See Figure 12. 8. If a clutch continues to slip when the springs are compressed to 1.36", check friction discs (2) for excessive wear. Discs are 1/8" when new. Replace discs after 1/16" wear.