Is this safe? (PTO shaft/rotary cutter)

[greg_g]

Bill 333
See if these pdf attachments help cause a picture is worth athousand words. Look in the Hardee manual on pages 3 and 4 it has a clutch adjustment procedure. the other pdf is a good example of the type of clutch that you have.

Good find, the ones I pointed too didn't include the "older models" section. It also tilts the scale towards Belleville (vs compression) style. Hopefully this will save Bill that next fact-finding road trip.

//greg//

 

[dex3361]

I'd like to add that running any driveline without the protection of a slip clutch or shear pin / bolt is just asking for pto or transmission problems. these units that suposedly don't have a clutch or shear pin..if their if your gearbox has a smooth shaft .. I'd use a grade 2 bolt in it.. notheing harder.. if it's a splined connection on both sides.. then clutch for sure..

soundguy

DITTO

 

[SPYDERLK]

There is a clutch on the pto driveline in the tractor. My experience with serious heavy duty use of a bushog over a 40 year period on 2 different tractors is that this internal clutch ptotects the tractor side effectively. At a guess id estimate this clutch is designed to slip at about 3 times the steady state torque that the tractor engine can apply and that this slippage point is within the safe region for all internal drive line components. I adjust my 5' bushog slip clutch by dropping the bushog onto a pile of loose dirt at full rated rpm. With a 35 to 45HP tractor it should bog the tractor very quickly. You have to act quickly to keep from stalling. Next, I disengage the PTO drive and drop the BH in the dirt to stop it - then quickly feel the slip clutch for heat. If there is none it hasnt slipped - loosen and repeat. If it is hot it has slipped a lot [and you may have noticed that the tractor didnt bog]. In this case the clutch is too loose and must be tightened or it will burn up quickly in heavy steady state cutting like thick grass. This is why sneaking up on a correct setting can be counterproductive. The mating of a 5' or 6' bushog to a tractor in the 40 HP range forms a robust system that does not require coddling. However, if the bh is light duty or this size is being run by a 70 hp tractor then one end of the system is comparatively weak. You could not set the slip clutch as I do because, even with the compliance of soft dirt a quick bog or stall may transmit a transient amt of torque associated with ~3x70 HP. Heavy Duty 5 and 6 foot bushog gearboxes rate at around 100HP. If the slip clutch is frozen you will probably twist the telescoping pto shaft or else damage the bh gearbox. This is not necessarily too much tractor, but the situation demands a tighter balance to keep from burning up the clutch or damaging the implement when you encounter a situation that requires its full capability.
larry

 

[Soundguy]

slipping the pto side of a 2 stage clutch in my tractor is not my idea of a good time.

slipping the main clutch on a non live, single stage clutch machine is not my idea of a good time.

power slipping the wet clutchpack of my independent pto machine is not my idea of a good time.

I'd much rather replace a 50 cent shear pin.. or a 100$ slide on external slip clutch than SPLIT my tractor to replace the main or pto clutch. BTDT.. on independent pto clutchpack on a couple jd before... it's a no-fun job and a tad spendy.

the pto clutch internal to the tractor is there to get the driveline moving.. it shouldn't be the front line of protection especially when there are provisions for that externally.

kinda like saying your car doesn't need brakes as long as it has good seatbelts and airbags.

a quite ridiculous notion really

soundguy

 

[SPYDERLK]

slipping the pto side of a 2 stage clutch in my tractor is not my idea of a good time.

the pto clutch internal to the tractor is there to get the driveline moving.. it shouldn't be the front line of protection especially when there are provisions for that externally.

kinda like saying your car doesn't need brakes as long as it has good seatbelts and airbags.

a quite ridiculous notion really

soundguy

Yes. Agreed for the inaccurate comparison and exaggerative notion of your post. I didnt call it a good time, nor did I recommend it. The fact that the clutch is there and is sized for the tractor makes it able to protect the tractor by slipping on a catastrophic overload. That this clutch is exercised regularly and is housed is a stable internal environment favor its stability of action. This in no way means you should not use an external protective device to prevent it seeing such overload - just that malfunction of the external device is not a death knell to a well designed pto system.
larry

 

[bill333]

Bill 333
See if these pdf attachments help cause a picture is worth athousand words. Look in the Hardee manual on pages 3 and 4 it has a clutch adjustment procedure. the other pdf is a good example of the type of clutch that you have.

I think you found it! Mine looks like the 2 plate model.
From the directions it looks like I just loosen the large nut (8) I think?

I didn't know if I had to loosen the 4 bolts that hold the yoke attachment to the drive plate. (I'm hoping not, as these are rusted and bent)

 

[bill333]

I'd like to add that running any driveline without the protection of a slip clutch or shear pin / bolt is just asking for pto or transmission problems. these units that suposedly don't have a clutch or shear pin..if their if your gearbox has a smooth shaft .. I'd use a grade 2 bolt in it.. notheing harder.. if it's a splined connection on both sides.. then clutch for sure..

soundguy

I understand -- this is why I stopped using the cutter as soon as I came across the information in this forum. (I had used it before I knew better). So right now I'm trying to understand all this (thanks to all for their patient explanations) before I attack by foot high pasture grass.

 

[bill333]

In general a slip clutch is used to protect the tractor if the mower were to hit an immovable object. As the name implies the clutch is suppose to slip so the tractor does not have to absorb the sudden impact. Slip clutches have a cluster of metal disks that are spring loaded. The springs are tightened to a point where there is enough friction between the disks to allow for normal operation. When you exceed the amount of friction for normal operation, like hitting that immovable object, the disks will slip against each other to protect the tractor from the impact.

MarkV

MarkV: This description really helped me understand how it works. Kind of like if a car was driven by a connection between the brakes and the transmission, and the disks where left "on" (slightly rubbing). Weird analogy but it helps me.

I took another look at mine up close, if the amount of rust around the edges is any indication, I'm sure it is seized up. I'm a little confused about the springs, they seem awfully narrow (i.e. there doesn't seem much room for much of a spring) but I guess that is how it looks when fully compressed.

I'll try to attack that nut tomorrow and see if I can loosen it up.

 

[greg_g]

I'm a little confused about the springs, they seem awfully narrow (i.e. there doesn't seem much room for much of a spring) but I guess that is how it looks when fully compressed.

Well, they're still technically compression springs, just not in coil form. Imagine them as very large washers made of spring steel, washers that bend when you push on them - then spring back when you let go. In the case of your slip clutch, they maintain equal circumferential tension on a round pressure plate - which keeps a round friction disc stationary - until feedback force from the mower becomes greater than the tensioning force of the spring. Then the friction disc slips against the pressure plate, because there's more force working against it - than it's tensioned to maintain.

//greg//

 

[bill333]

By george, I think I got it!
Thanks for the explanation, now I can picture it.