Friction Torque Limiter

[TheMan419]

I bought a new tiller. Tarter 5 foot. The manual that came with the PTO shaft is at best useless. A copy can be found https://static1.squarespace.com/sta...5e231ae03b502ad/1488981138666/PTO-Booklet.pdf

According to this manual I have a "Friction Torque Limiter". Is that the same as a slip clutch? If so I would certainly like to properly maintain it and adjust it before I use the tiller.

The manual helpfully explains that I should check for proper operation and the torque can be changed by turning the 8 nuts that hold the thing together. It should be turned 1/4 turn and then check for proper operation.

However nowhere in this helpful manual does it tell me what proper (or improper) operation looks like.

I am a hobby farmer so I work a day job. I can call Tarter, but not while I am sitting in front of the PTO shaft. So I am looking for sage advice from this group.

Is this a slip clutch and how do I check for proper operation?

Thanks as always to this brain trust

 

[RedNeckRacin]

yup its a slip clutch. Proper operation is that it doesn't slip under normal loads. Improper operation would be when it starts smoking due to excess slippage when you are trying to run the tiller in "normal" ground.

 

[JRobyn]

Yes, that's a regular slip clutch. The only way to confirm proper operation (that I am aware of), is if it slips. Gross slippage can be determined either by sound (squealing) or by smell (smoking friction plates) or both. Small slippage can be detected by marking a line on the drive pressure plate and the driven pressure plate. Manufacturers usually purchase and install them pre-set for a torque value that is 10-20% under the design torque limit of the implement. The manufacturers (at least Bush Hog) could care less about the torque limitation of your PTO.

 

[bigtiller]

The slip clutch is set from the factory so that it will slip when using the maximum hp the gearbox was designed for. You need to adjust it to slip for the hp of your SCUT. Start off by loosening the tension bolts enough that the clutch plates slip. Do this because sometimes they rust together. Then tighten them evenly until they slip well before the engine dies when tilling into a big rock/root/etc.

 

[IslandTractor]

As you make have figured out by now, friction clutches are more art than science. Loosen all 8 bolts until it slips easily when PTO power applied. Then tighten all 8 a bit and try again. If it still slips tighten more. Then try it with actual cutting. It will probably slip in heavy areas. Tighten just enough more so it doesn't slip during routine cutting. You might monitor slipping by noise or smell or smoke or even by using a laser thermometer to document higher temps. Yes, it is a PITA. And, you're not done yet. Every Spring and every time you don't use the mower for more than a month or two (especially if it is exposed to rain), you will need to check that the clutch isn't frozen. How do you do that??? By backing off the 8 bolts until it slips and running through the whole drill again.

IMO slip clutches are only for very frequently used equipment. All others, especially weekend warriors, are better off with sacrificial shear bolts. Those only need maintenance when they break and it only takes five or ten minutes to replace in the field once you've done it a few times

 

[TheMan419]

As you make have figured out by now, friction clutches are more art than science. Loosen all 8 bolts until it slips easily when PTO power applied. Then tighten all 8 a bit and try again. If it still slips tighten more. Then try it with actual cutting. It will probably slip in heavy areas. Tighten just enough more so it doesn't slip during routine cutting. You might monitor slipping by noise or smell or smoke or even by using a laser thermometer to document higher temps. Yes, it is a PITA. And, you're not done yet. Every Spring and every time you don't use the mower for more than a month or two (especially if it is exposed to rain), you will need to check that the clutch isn't frozen. How do you do that??? By backing off the 8 bolts until it slips and running through the whole drill again.

IMO slip clutches are only for very frequently used equipment. All others, especially weekend warriors, are better off with sacrificial shear bolts. Those only need maintenance when they break and it only takes five or ten minutes to replace in the field once you've done it a few times

Yeah that sounds like a real pain..... however the tiller only came with a slip clutch. The rotary mower I have has a shear bolt. Easy enough to understand. Bolt breaks, put in new one. Done and done.

Guess I have a bit of a project for the weekend then.

It will not get exposed to rain as it will remain in the barn until used.

Thanks for detailing the process. Since it was stored outside before I bought it I will have to suspect it needs this process done immediately rather than waiting for next spring. I am going to use it to till up a field of weeds and plant pasture grass for the horses. Already started spraying the round up.

 

[RickB]

Don't commit the error of assuming a slip clutch will not seize up simply because it is stored indoors. Check it properly before each seasonal use. Things just haven't been the same since they took the asbestos out of the friction discs......

 

[TheMan419]

Don't commit the error of assuming a slip clutch will not seize up simply because it is stored indoors. Check it properly before each seasonal use. Things just haven't been the same since they took the asbestos out of the friction discs......

Thanks for tip.

 

[boomer1025]

I remove the PTO drive line in the fall and loosen all the bolts on the slip clutch. In the spring I make sure the disc's in the clutch unit are free, then finger tight all the nuts. Then tighten all the nuts about 1 3/4 turns.

 

[SPYDERLK]

As you make have figured out by now, friction clutches are more art than science. Loosen all 8 bolts until it slips easily when PTO power applied. Then tighten all 8 a bit and try again. If it still slips tighten more. Then try it with actual cutting. It will probably slip in heavy areas. Tighten just enough more so it doesn't slip during routine cutting. You might monitor slipping by noise or smell or smoke or even by using a laser thermometer to document higher temps. Yes, it is a PITA. And, you're not done yet. Every Spring and every time you don't use the mower for more than a month or two (especially if it is exposed to rain), you will need to check that the clutch isn't frozen. How do you do that??? By backing off the 8 bolts until it slips and running through the whole drill again.

IMO slip clutches are only for very frequently used equipment. All others, especially weekend warriors, are better off with sacrificial shear bolts. Those only need maintenance when they break and it only takes five or ten minutes to replace in the field once you've done it a few times

Yeah that sounds like a real pain..... however the tiller only came with a slip clutch. The rotary mower I have has a shear bolt. Easy enough to understand. Bolt breaks, put in new one. Done and done.

Guess I have a bit of a project for the weekend then.

It will not get exposed to rain as it will remain in the barn until used.

Thanks for detailing the process. Since it was stored outside before I bought it I will have to suspect it needs this process done immediately rather than waiting for next spring. I am going to use it to till up a field of weeds and plant pasture grass for the horses. Already started spraying the round up.

Don't commit the error of assuming a slip clutch will not seize up simply because it is stored indoors. Check it properly before each seasonal use. Things just haven't been the same since they took the asbestos out of the friction discs......

Maybe thats why Iv been able to run mine for 50+ yrs with no such maintenance. Outside storage rain shielded.​

When mine starts slipping noticeably I just tighten it. 3 or 4 adjustments over 50yrs. But we definitely do stuff that cause micro slipping so the clutches get a modicum of automatic scrubbing.