Is this safe? (PTO shaft/rotary cutter)

[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

except.. if you rely upon the tractor clutch as the only means of protection.. about the only thing you are protecting is the engine.. the poor trans and pto section of the tractor get abuse they may not get with a simple grade 2 bolt thru a shear plane or a clutch designed to slip 'on demand'.

no way I'm putting my machine thru extra abuse due to bad judgement of not using one of the 2 most widely available and easilyl installed torque limiters out on the market.

again.. good seatbelts and airbags are not a replacement for brakes.. they are backups to those brakes.. just like your tractor clutch is a backup to the driveline protection..

sorry spyder.. I don't think you are gonna get many votes 'for' not using outboard driveline protection....

soundguy

 

[SPYDERLK]

#33 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.

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.
larry

#35 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

except.. if you rely upon the tractor clutch as the only means of protection.. about the only thing you are protecting is the engine.. the poor trans and pto section of the tractor get abuse they may not get with a simple grade 2 bolt thru a shear plane or a clutch designed to slip 'on demand'.

no way I'm putting my machine thru extra abuse due to bad judgement of not using one of the 2 most widely available and easilyl installed torque limiters out on the market.

again.. good seatbelts and airbags are not a replacement for brakes.. they are backups to those brakes.. just like your tractor clutch is a backup to the driveline protection..

sorry spyder.. I don't think you are gonna get many votes 'for' not using outboard driveline protection....

soundguy

Not looking for any votes. Didnt recommend or describe not using secondary protection.

again.. good seatbelts and airbags are not a replacement for brakes nor are they even remotely related. They are not backups, like use of the emergency brake or downshifting, or shifting an auto into reverse would be. Thats not good either, but the best I can do with the inappropriate analogy.
We are talking about a component designed into a system that offers automatic protection to the system to prevent damage to itself under extreme conditions of use. All clutches having friction plates are slip clutches. The difference is just the setting of the slip point.
larry

 

[greg_g]

We are talking about a component designed into a system that offers automatic protection to the system to prevent damage to itself under extreme conditions of use. All clutches having friction plates are slip clutches. The difference is just the setting of the slip point.

Sorry, I can't agree either - with your representing the onboard tractor clutch as a form of protection against misuse of PTO driven implements that is. It is a drive clutch - not a driven clutch. The whole idea behind a drive clutch - is to set it to drive. The typical implement PTO shaft slip clutch is a driven clutch. The whole idea behind it is to set it to slip. I don't think your perception has legs Larry

//greg//

 

[SPYDERLK]

Sorry, I can't agree either - with your representing the onboard tractor clutch as a form of protection against misuse of PTO driven implements that is. It is a drive clutch - not a driven clutch. The whole idea behind a drive clutch - is to set it to drive. The typical implement PTO shaft slip clutch is a driven clutch. The whole idea behind it is to set it to slip. I don't think your perception has legs Larry

//greg//

Theres no difference between the 2. All clutches are driven on 1 side and drive something on the other. If its a friction plate type like were talking here it is made to accommodate some slip, whether on engagement or overload. Slipping wears them. Thats the main reason you dont want the interior clutch to slip under full engine power. During implement startup it must slip some as it is engaged so that there is a graceful startup. After engagement it has to be designed such that it can take full engine torque - and then some - so that it will never slip under normal drive circumstances. To do this it must sustain enuf torque to stall the tractor engine. Under a slow stall or bog down situation it shouldnt slip at all. If it did we would see them replaced frequently on tractors that run rotary cutters. Shearing a 3/8" shear bolt takes about 100HP worth of torque at 540 RPM. Since 30 - 40 HP tractors have little problem shearing these it shows that the internal clutch slips at or above the 100 HP torque rather than anywhere near the 35 HP torque. You would really like to set an external slip clutch somewhere pretty high in the range but below where the shear bolt gives. Since a slip clutch sustains a [relatively] steady torque when slipping it would bog or stall the engine fairly promptly if set at an 80 HP torque. The internal clutch would not come anywhere near as close to slipping as it did breaking the shear bolt. If friction is set down anywhere near engine stall torque tho you definitely have potential slip clutch problems and will have to frequently adjust it for wear and be very alert to prevent burning it up if you use the equipment to capacity.

My point in all of this is that the tractor pto is pretty strong and has a clutch sized for it that has an overload slip point well above the tractor torque [so it doesnt burn up], but low enuf to slip within the strength of pto components. Still, you dont ever want it to slip except as you engage it and you always would want to use external means to keep it from seeing overloads sufficient to slip it. This would wear the clutch out and stress parts repeatedly to near their full strength. There is however, a large safe range above the tractor steady state torque and below the pto clutch slip torque. Shear bolts make use of the top of this range on ~35HP tractors. They break in an instant, and since the tractor may hardly slow you arent aware of the huge transient load on the pto system. Theres just no reason to be conservative for the tractor sake when adjusting a slip clutch. High in the range is still below where those shearbolts are breaking.
larry

 

[dieselsmoke1]

Not having a PTO shaft clutch is not be the best setup, however it's certainly not an automatic death sentence to tractor driveline components. This is the OEM driveline on my 47 yr old Bush Hog Stumpjumper, joints and all. My Dad had no respect for machinery and would grind anything a MF35 would push over. It may break something tomorrow, however it's got a pretty good record going so far.

 

[JRobyn]

OK, now getting back to the OP's issues.....

Bill, I have the "other" kind of slip clutch with coil spings on my cutter, but every year, before it's first use, I do the recommended clutch maintenance, which is to intentionally slip the clutch some to insure that the plates are not rusted and stuck together. To do this, I loosen all of the springs a LOT and then "energetically engage" the PTO. Generally this will instantly cause the loosened clutch to slip totally (i.e. cutter blades barely turn). This is generally accompanied by a small cloud of rust/disk dust right around the clutch. One time I had to drop the cutter on some very heavy/high grass to get it to break loose. This might be necessary in your case. Either way, loosen it up a lot and make sure it slips freely. This also helps one to see exactly how the parts of the clutch work (i.e. what turns, what remains stationary, etc.). I let the slipping clutch spin for at least a few seconds to insure that the plates are burnished and free of rust/corrosion. If the clutch is LOOSE, spinning it like this will build up some heat, but not enough to damage the plates. Don't let it spin for more than about 15-20 seconds. Then retighten the springs per manufacturer's guidance if available OR tighten in small increments as needed to prevent most slippage as others here have described.

- Jay

 

[bill333]

Jay,
thanks very much, this helps me a lot.

I tried to do the first step, loosening the nut (which holds my springs) but I need to buy another pipe wrench -- that nut looks to be about 3 1/2 to 4 inches, and I don't have a wrench that big.

I hope that I can fit a wrench between the nut and the gearbox, it looks a little tight.

 

[rambler]

Jay,
thanks very much, this helps me a lot.

I tried to do the first step, loosening the nut (which holds my springs) but I need to buy another pipe wrench -- that nut looks to be about 3 1/2 to 4 inches, and I don't have a wrench that big.

I hope that I can fit a wrench between the nut and the gearbox, it looks a little tight.

Bill, I didn't read all the replies on here. I recall you discussing this in a different thread, and I thought - how odd.

So, you have a slip clutch, and your driveline is just fine as it is built, and the crosses in the joints can be taken aprt with the C clips on the _inside_ of the cup.

You got instructions on how to adjust the slip clutch - basically take it apart, put it back together making sure the plates move - so all should be good.

Now, your whole problem is that the driveline is 4 inches too short. Correct?

Is this a pretty short driveline, or is it fairly long? Does it compress pretty close together when in use at certain times? Or does it have a lot of 'spare room' as you raise & lower the cutter?

What I'm getting at is that, in certain cercomstances, you can just replace the front 1/2 of the pto with one that is 4 inches longer, and leave the back 1/2 as is.

But you have to make _sure_ there is room for an off-centered setup, so that when the pto collapses as short as needed, that it idoesn't bottom out!

That would save you 1/2 the cost of this.

--->Paul

 

[Soundguy]

might also add a pto stub extender for that short distance..

soundguy

 

[bill333]

Bill, I didn't read all the replies on here. I recall you discussing this in a different thread, and I thought - how odd.

So, you have a slip clutch, and your driveline is just fine as it is built, and the crosses in the joints can be taken aprt with the C clips on the _inside_ of the cup.

You got instructions on how to adjust the slip clutch - basically take it apart, put it back together making sure the plates move - so all should be good.

Now, your whole problem is that the driveline is 4 inches too short. Correct?

Is this a pretty short driveline, or is it fairly long? Does it compress pretty close together when in use at certain times? Or does it have a lot of 'spare room' as you raise & lower the cutter?

What I'm getting at is that, in certain cercomstances, you can just replace the front 1/2 of the pto with one that is 4 inches longer, and leave the back 1/2 as is.

But you have to make _sure_ there is room for an off-centered setup, so that when the pto collapses as short as needed, that it idoesn't bottom out!

That would save you 1/2 the cost of this.

--->Paul

Yes, sorry about that. I started along the lines of thinking I absolutely had to get the PTO shaft off the attachment, but I've received so many good ideas here -- including yours above -- that I decided to start another thread on just dealing with the PTO shaft length issue.

I did not know I could buy 'half a shaft.' This would definitely work if I can find one.

Right now I'm only using one PTO attachment, the rotary mower. Without the quick links, there is about a 6 inch overlap on the current PTO shaft. With the quick links, it drops to just 2 inches, hence the problem.

Another suggestion someone made is to get a quick link system that mounts on top of the lift arms instead of 'behind' them and does not extend the arms out. I'm looking in to this. There is a system for about $100, and even though I already have a system, this might be the easiest approach.