slip clutch

[Deerlope]

I had the same issue. I bought a Woods 60 inch BrushBull Extreme, and it was shear pinned. Six bolts one day made me start to look around. The dealer wanted $235 for a woods shaft replacement including a slip clutch. Instead I bought the slip clutch add-on from Agri supply. It bolts (with grade eight) to the gearbox input shaft, and accepts the Woods stock pto shaft input, with another gd 8 bolt. No more shearing and I use it very hard at times, in the dirt. It slips and then comes right back up to speed.

Here's the one I bought, and it fit perfectly...
SLIP CLUTCH W/1 3/8SMF M X1 3/8SMOOTH FE - Agri Supply

They have other configurations of it, in case you dont have a 1 3/8 smooth input shaft on your gearbox.

It is my understanding that a SC is rate for the HP of the tractor that is to be used. Do you know what HP this clutch is rated for?

 

[greg_g]

It is my understanding that a SC is rate for the HP of the tractor that is to be used. Do you know what HP this clutch is rated for?

Most I've encountered are adjustable to some degree, typically by varying spring tension. AgriSupply sells mostly the Eurocardan brand, and I know they're adjustable. Their slip clutches should come with a little chart telling how to adjust spring tension to match PTO horsepower.

//greg//

 

[MikeD74T]

It is my understanding that a SC is rate for the HP of the tractor that is to be used. Do you know what HP this clutch is rated for?

You might want to look at this from the other end. The clutch needs to be rated for the input of the implement. i.e. if implement needs 15 HP the clutch must be able to limit transmitted hp to 15 hp, regardless of whether the tractor provides 28 or 200 hp. The clutch prevents transmission of excess hp to the implement.
At the extreme of this is a clutch rated for 200 hp (output) is not likely to be sensitive enough to protect an implement that needs 10 hp. By the same logic if the clutch will only rated to transmit 10 hp it will be constantly slipping & eventually self destruct if the implement demand is 15hp. MikeD74T

 

[greg_g]

You might want to look at this from the other end. The clutch needs to be rated for the input of the implement.

No. Slip clutches protect the tractor first, the implement second. I'd much rather spend $250 replacing an implement transmission than I would $1500 or more repairing a tractor transmission. The (properly maintained and adjusted) slip clutch is designed to avoid both expenses.

It's for that reason you set the slipclutch to release when the input torque exceeds that of your tractors PTO output rating. In other words, the clutch will slip before your tractor's PTO drivetrain starts tearing itself apart trying to keep the implement turning.

//greg//

 

[MikeD74T]

No. Slip clutches protect the tractor first, the implement second. I'd much rather spend $250 replacing an implement transmission than I would $1500 or more repairing a tractor transmission. The (properly maintained and adjusted) slip clutch is designed to avoid both expenses.

It's for that reason you set the slipclutch to release when the input torque exceeds that of your tractors PTO output rating. In other words, the clutch will slip before your tractor's PTO drivetrain starts tearing itself apart trying to keep the implement turning.

//greg//

First, we might be saying the same thing because implement input starts at the outlet of the slip clutch regardless of it's location in the driveline.

I see your point but disagree if you're saying that the slip clutch needs to be able to transmit all the tractor's hp to every implement. I agree that both the tractor & implement need to be protected and are protected by a properly adjusted slip clutch, which may not be the case with a shear pin.
You wouldn't try to run a 20' batwing mower with a 28HP tractor. If you did, any clutch adjusted to protect the tractor probably wouldn't run the mower. Either the tractor would stall or the clutch would overheat & destruct. You probably couldn't even break the batwing shear pin with 28hp. So the 28 hp tractor doesn't need to be protected from a 20' batwing mower. However, you might run a 6' bush hog ( or a hay tedder) with 100 hp tractor. The 100 hp tractor will easily twist the drive shaft off a 6' bush hog without damaging the tractor transmission. The bush *** or tedder does need to be protected from the 100 hp tractor.
As long as the tractor is big enough to run the implement, the implement's slip clutch will also protect the tractor. If it were otherwise each implement manufacturer would have to specify & limit which tractors are suitable to drive their implement.

Actually a simple over running clutch will always protect the tractor from the implement & they're much cheaper. Unfortunately they don't offer any protection to the implement. If the tractor & implement are that closely matched the best protection would be both a slip & over running clutch but with neither tractor or implement needing much protection from each other. MikeD74T

 

[Soundguy]

Now that's a funny thought.. a batwing with a shear pin.. .. IE.. probably 30K$ of tractor and implement.. and no 100$ torque limiter.. :0

soundguy

 

[ROUSTABOUT]

The slip clutch is there to protect against shock loads. Falling off a building doesn't hurt, but the sudden stop does. That is why a bush hog has a slip clutch and a hay rake doesn't. Bush hogs may experience a shock load during normal, intended use. Hay rakes shouldn't have a shock load during their intended use. Never broke a pto or a shaft, but have cut places so rough that the front wheels were off the ground for a quarter mile at a time, steering with the brakes. Riding trees down five inches in diameter. If the front end will knock it over, the back end ought to be able to chop it up. Usually thick, wet grass will make the clutch slip a bit. But, if things are dry it only slips when it hits something solid, just enough slippage to keep from snapping a u-joint or twisting the pto shaft up like a screw. Probably where the phrase "all screwed up" came from.

 

[MikeD74T]

Now that's a funny thought.. a batwing with a shear pin.. .. IE.. probably 30K$ of tractor and implement.. and no 100$ torque limiter.. :0 soundguy

Soundguy, Don't know if you're laughing with or at me. Either is OK! I was just trying to make an extreme example. Admittedly unfamiliar with batwing mowers. MikeD74T

 

[greg_g]

First, we might be saying the same thing because implement input starts at the outlet of the slip clutch regardless of it's location in the driveline.

No, we're not saying the same thing. The input to which I referred was the input to the slip clutch. On any given tractor - at recommended engine RPMs - there is a known quantity of power available at the PTO output shaft. This is typically quantified as PTO horsepower. Horsepower is just another expression of force - or torque. I'll get back to this in a moment.

If you don't own one yourself, a basic slip clutch is typically comprised of at least one friction disc between two pressure plates - one input, one output. Some are are two between three, but the principle is the same. Most commonly, the pressure plates are tensioned with compression springs. The more you tighten the springs, the more pressure is exerted on friction disc(s). When force transferred back to the output side exceeds force delivered to the input side - it "slips".

Back to torque now. Look at the chart here: http://www.tractorbynet.com/forums/...8-slip-clutch-torque-slip-clutch-settings.jpg . These are Eurocardan instructions, note the torque column. By matching spring length to PTO horsepower anticipated at the input, it is designed to slip when countered by xxxx pounds of torque fed back to the output side.

//greg//

 

[MikeD74T]

greg g, I do own & regularly use a slip clutch. I do know how it works & how / when to adjust it. Explain to me how having a slip clutch rated at 30 hp on a 6' bush hog can damage the transmission of a 100 hp tractor but a slip clutch rated at 100 hp won't ??

I believe your chart indicates the settings to limit delivery to the desired HP through the clutch rather than making reference to the HP the tractor can deliver. Any other text associated with the chart? MikeD74T