Skidding winch - need bigger tractor?

[EE_Bota]

Just for grins, I checked the parts manual for my BX2200 for the PTO relief valve. I searched the entire pdf for "PTO" and no PTO relief valve is found. I searched the word "relief" and several relief valves were found, but none designated as pertaining to the PTO. Yet, I know mine has one.

Looking at my service manual, it is quite clear on my model that my PTO relief valve is in the filter base housing. So, back to the parts manual....

Ok, found it. It is in the assembly "Transmission Case." And, the only word that has anything to do with PTO is "Spring PTO."

So, it is not surprising at all that you may have trouble determining the existence (or lack) from the parts manual alone. The service manual WILL tell the tale.

 

[dstig1]

I searched that area of the PL in great detail. Several times. If it's in there, I can't find it. It might be part of the HST system internals, which has about 1000 parts and no way to figure out how it works. I need to get a shop manual...

 

[rbargeron]

........ I am getting a consensus that the engine should stall, not the PTO shaft. That tells me something is wrong.........

[Edited info about continuously running shaft - used on gear tractors - not on HST]

In conventional pto arrangements a separate dry clutch is engaged manually or the main clutch also controls the pto. But a truly independent pto gets its power from a shaft rigidly coupled to the engine's flywheel that turns whenever the engine does. It is independent of the tractor's driving wheels clutch.

I don't think it is a requirement that pto clutches be able to stall the engine. Many of them do and older tractor designs are all that way. But it seems that if you are using a hydraulic clutch having it slip at a certain point isn't all bad.

In your first post, the winch dug into the ground and pulled pretty hard before the pto shaft stopped, right? Maybe your pto clutch is performing in a safe way.

I've heard of tractors with pto winches pulling so hard the tractor rears up, nearly going over backward before stalling, then going back down with the engine turning backward - not a great situation.

 

[LD1]

I have never owned a HST or even tore one appart. I understand most all thing mechanical and how a HST works. But my question is...on a HST tractor, IS the pto driven by the engine, or is is driven by a hydraulic motor like the wheels??? What makes me wonder this is you guys that own HST's eluding to a pto relief valve.

If it is driven with hydraulics like the wheels, that would explain a lot. There may be no independent relief valve. Maybe the motor that drives it has an internal relief, or maybe it is relieving pressure at the main pump. Without actully driving the tractor at the same time, it is hard to say. If you were driving the tractor, and the wheels AND toe PTO stopped while motor is still running, I'd say it would be the Main pressure relief for the system.

 

[Dead Horse]

OP, call a knowledgable dealer or if you have to, a Kubota rep. You are getting guesses and some potentially very bad advice here.

Go find out the facts about your specific tractor.

 

[LD1]

OP, call a knowledgable dealer or if you have to, a Kubota rep. You are getting guesses and some potentially very bad advice here.

Go find out the facts about your specific tractor.

What exactally is the bad advice that has been given??

If anything everyone is being overly cautious and there may even be nothing wrong with his tractor. We just may not understand how it operates as compaired to a gear tractor but I don't think anyone here has given him bad advice.

To the OP, just a suggestion, try pouring sand in the hydro oil and see of the extra grit helps the PTO hold better.....................


.................oops, I guess I retract my previous statement about no one giving bad advice:laughing:

 

[EE_Bota]

I have never owned a HST or even tore one appart. I understand most all thing mechanical and how a HST works. But my question is...on a HST tractor, IS the pto driven by the engine, or is is driven by a hydraulic motor like the wheels??? What makes me wonder this is you guys that own HST's eluding to a pto relief valve.

If it is driven with hydraulics like the wheels, that would explain a lot. There may be no independent relief valve. Maybe the motor that drives it has an internal relief, or maybe it is relieving pressure at the main pump. Without actully driving the tractor at the same time, it is hard to say. If you were driving the tractor, and the wheels AND toe PTO stopped while motor is still running, I'd say it would be the Main pressure relief for the system.

Since you understand many mechanical things, this will be easy to explain.
You know how a standard clutch in a car works. There is a STOUT pressure plate that squeezes the clutch against the flywheel. The downside is it takes your LEG to release it. That is a lot of force. Also, imagine having to hold your clutch in all the time because you are not using the PTO right now.

In many tractors, the pressure plate is replaced with a hydraulic piston. This has the advantage that it is effortless for the operator to move the lever to engage the PTO. It doesn't even take any hydraulic work to hold it in either, since the flow is negligible. Also, there is never any need to adjust it either in practice, unless it is found to be faulty in some way, and what is to be hoped for is that the faulty condition is due to low relief pressure setting.

There are many disks and plates, such that the clutch can be very strong in terms of it's ability to transmit torque without slipping, and furthermore, in some tractors, like mine, they use the relief pressure flow from the PTO circuit and use that as the pilot flow, or make-up flow for the actual hydrostat set that propels the tractor.

There is something almost identical to the this style PTO in nearly every automotive automatic transmission. The name of the gear set style escapes me right this moment..oops this just in..planetary. The bands brake the drum, but usually there are other parts that constitute a multi-disk clutch pack and the clutches that are "thrown" by a piston driven by hydraulic pressure. I am not that slick on automatic transmissions, so I hope experts won't beat me up on this.

 

[dstig1]

The "consensus" that something is wrong seems to be informed by conventional pto arrangements where a dry clutch is engaged manually or where the main clutch also controls the pto. But the independent pto with its own wet clutch is a significantly different setup. For one thing the pto gets its power from a shaft rigidly coupled to the engine's flywheel that turns whenever the engine does. It is independent of the tractor's driving wheels clutch, whether HST or gear transmission.

I don't believe that is true, but I am not 100% sure. From what I can tell from the parts diagrams, everything goes through the main output shaft of the main clutch (i.e the clutch pedal).

But it seems an intelligent design would allow it to slip at a certain point to protect against huge loads. Setting the clamping pressure on the clutch stack to limit the output torque would be sensible.

If we go back to your first post, the winch dug into the ground and pulled pretty hard before the pto shaft stopped, right? Maybe, just maybe, your pto clutch is performing perfectly.

You could be right, too, but so far there is nobody saying they have ever seen the PTO stall and not the engine, even on fairly recent model tractors.

I have never owned a HST or even tore one appart. I understand most all thing mechanical and how a HST works. But my question is...on a HST tractor, IS the pto driven by the engine, or is is driven by a hydraulic motor like the wheels???

It drives off a gear connected to the output shaft of the main clutch, as best I can tell. It is definitely not hydraulically driven, the only hydraulics involved are those used to engage the PTO.

OP, call a knowledgable dealer or if you have to, a Kubota rep. You are getting guesses and some potentially very bad advice here.

Go find out the facts about your specific tractor.

I'm going to do that very shortly. It seems like the only thing that will answer the question for sure...

To the OP, just a suggestion, try pouring sand in the hydro oil and see of the extra grit helps the PTO hold better.....................

OK, I tried that... the PTO clutch is making a funny noise now. So is the HST. Should I add more sand? :confused2::laughing:

-Dave

 

[dstig1]

In many tractors, the pressure plate is replaced with a hydraulic piston. This has the advantage that it is effortless for the operator to move the lever to engage the PTO. It doesn't even take any hydraulic work to hold it in either, since the flow is negligible. Also, there is never any need to adjust it either in practice, unless it is found to be faulty in some way, and what is to be hoped for is that the faulty condition is due to low relief pressure setting.

There is something almost identical to the this style PTO in nearly every automotive automatic transmission. The name of the gear set style escapes me right this moment..oops this just in..planetary. The bands brake the drum, but usually there are other parts that constitute a multi-disk clutch pack and the clutches that are "thrown" by a piston driven by hydraulic pressure. I am not that slick on automatic transmissions, so I hope experts won't beat me up on this.

No, it is nothing like a planetary gear. The PTO is a simple wet clutch pack. The clutch is actuated hydraulically by a piston, when you move the lever, which in turn moves a valve directing oil to the clutch pack piston. This connects the input side of the clutch to the output that drive the PTO shaft.

Wherever the relief valve is, it is well hidden. I went out and looked over the tractor and there is nothing to adjust, and no relief valve that I could find. It looked exactly like the parts diagram...

-Dave

 

[EE_Bota]

In the following link, I tried to analyze the power flow through my tractor in a trivial way.

http://www.tractorbynet.com/forums/...-2230-front-end-loader-seems.html#post2002836

But don't go there, unless you just want to. I only mention it because it is where I got this idea.

I accounted for all major power in the tractor.

Look at your OWNER"S manual of the following information, and report it if you are so inclined.

Rated Engine HP.
Rated PTO HP.

Unless the two are dramatically different, those two numbers can tell us rather directly whether your tractor can meet both ratings, and have power enough to continue to run with a stalled PTO.

If in fact the rated engine HP is considerably higher than the PTO HP plus parasitic losses, then we have an example of a tractor that can stall it's PTO and just keep right on running like nothing ever happened. That would be a really COOL feature, but not so trivial that it would not be mentioned in the OWNER'S manual, and not so insignificant that it would not be heavily advertised somewhere as a "breakthrough development negating the need for slip clutches, and can save you thousands of dollars in equipment damage." (Can't you just hear the advertising lingo they would use? )