More torque for my Power trac?

[SnowRidge]

Well, I am going to give you guys a hint of how mine works. I have a Eaton VSP pump. Close to the bypass valve, are two relief valves. I believe they are set at 2750 psi. When you turn the bypass screw/nut or whatever, you open both the relief valves so the fluid can travel fwd or reverse, depending on which direction you are pushing /pulling. I am sorry that you guys don't have a relief valve. However, in the back of my mind, I am thinking there has to be a relief valve somewhere in the system.

There isn't any. That's why the engine stalls if the machine is pushing or pulling the immovable object and has good traction.

 

[J_J]

Please read my update in my previous post..

 

[SnowRidge]

Please read my update in my previous post..

Did you ask him about a high pressure relief valve? The relief valve in the Sauer Danfoss pump is for the charge pump.

If there was a relief valve for the wheel circuit, the engine wouldn't stall under an excessive load.

 

[J_J]

If the relief is not set correctly, the HP suppled to the pump will deplete at max rpm, and the engine will stall. If the engine had enough HP, it would force the pump to relieve, or explode. That is written in stone.

 

[J_J]

If I remember right, some of the 425 owners said that the engine stayed running, and it just grunted in a tough situation. To me that sounds like that some relief valves are working on the 425.

 

[SnowRidge]

There are a lot of posts regarding the PT-425 bogging the engine when the tram circuit is overloaded. Here's just one of Moss's.

If you search the forum on bog or bogs you will find a lot more.

 

[woodlandfarms]

There has to be a relieve valve. Reasoning is...

If the pump is built tight enough to create 2500 PSI, and is direct drive, then when the pump hits an imoveable object (ie oil with no place to go) the engine and pump stop dead. The oil has no place to go and that sudden shock will cause an explosion, not a bog.

If I am running my tractor and flip on the PTO with nothing attached, the engine will bog, and bog bad, maybe stall depending on variables. But still, there is a relief valve.

The only way I could see that the pump does not have a relieve valve is that the pressure relief is in the tram configuration. That the oil goes through the forward and reverse circuits when pressure is needed to be relieved.

But what do I know... I can get an actor to show up, and have the camera pointed the right way. End of high paid skill set.

 

[J_J]

Snowridge,

Do you have the Danfoss series 15 VSP pump?

 

[J_J]

Carl,

There is a good reason for the situation with the PTO pump. With the engine running and using tram pump and steering pump, there is some HP left to run the PTO pump under normal condition. But like you said you fail to plug the QD up. You are now asking that diesel to cough up some some extra HP to overcome the new imposed load, deadhead. If the PTO relief don't go off, the pump will blow, or the engine will die.

There is one small chance that I can think of that the system would have no relief valve. That is when there is not enough HP to power the pump to get it up to the test pressure, and what happens then, is the engine bogs down because it is trying to make pressure and but just don't have the guts to do it. If other things were stopped like steering, or lift, PTO, some more HP would be available to unbog the engine. Several of the owners have mentioned about cutting off the PTO just to get up the hill.

There are some Danfoss pumps that do not have relief valves, because the end receiver will install their own. They are an option, and in my opinion, necessary. There is also some logic to the fact that if you have a habit at bogging the motor out a lot, The life cycle of the pump and engine will diminish.

 

[MossRoad]

My PTO circuit has reliefs. I know that as I can see them and, if you have the PTO hoses disconnected and accidentally hit the PTO switch, you hear the engine growl and the relief open and you shut everything down quick.

My drive circuit, I have no idea if there are reliefs or not. As I've stated in other posts, I've never heard a relief open in the drive circuit. A few times I have slammed into immovable objects such as hidden tree stumps under a sand pile and it will instantly kill the engine.

If I push up against an immovable object on purpose and step on the go pedal the tires will break lose and spin most of the time as I have turf tires. If, however, I have incredible traction, the engine will bog down to the point that it will kill it. If there are reliefs in the drive circuit, they are set higher than the point that the engine can provide enough power to push the fluid past the reliefs.

BTW, this is a 2001 model PT425 with the Kohler Command 25HP engine.

 

[SnowRidge]

Snowridge,

Do you have the Danfoss series 15 VSP pump?

It's a Danfoss Series 15VP.

 

[SnowRidge]

From some Danfoss sales literature concerning hydrostatic drive products of all sizes:

The closed circuit piston pump is normally factory
equipped with a charge pump, charge pressure
relief valve, and a control. It may also be equipped
with high pressure protection devices such as relief
valves or pressure limiters. A loop flushing
shuttle valve can be integral to the pump or motor, or
may be installed externally. Other components such
as the reservoir, heat exchanger, and filter are added

Emphasis added.

 

[SnowRidge]

There has to be a relieve valve. Reasoning is...

If the pump is built tight enough to create 2500 PSI, and is direct drive, then when the pump hits an imoveable object (ie oil with no place to go) the engine and pump stop dead. The oil has no place to go and that sudden shock will cause an explosion, not a bog.

It isn't direct drive, in that there are six hydraulic hoses involved, which have some shock absorbing qualities. Be that as it may, Sauer Danfoss also builds an integrated version of the same hydrostatic pump. It has the pump and drive motor in the same case. The engine input shaft is on one end, and the drive output shaft is on the other. There are no hydraulic hoses at all in the high pressure circuit.

It doesn't have a high pressure relief valve, either.

These are low horsepower systems. It looks like the design is simply rugged enough to absorb the occasional shock of excessive loading.

Relief valves are essential on the other systems. Without them, the machine would be unusable. Imagine having your engine stall each time your steering reached lock, or when you ran the tilt to its limits, or if an implement suddenly froze up, which actually happened to me. Unlike the tram circuit, reliefs on those circuits are required. They simply have to be there.

Even if it would be nice to have high pressure reliefs in the tram circuit, PT would never spend the money to put them on. Power Trac doesn't do nice.

 

[ponytug]

Stray,

Not to get your goat, but this might help you;

M561 Gamma goat, 6 wheel hydraulic drive...103HP, floats...

All the best,

Peter

 

[J_J]

SnowRidge.

Since you have one of these pumps, how about you calling Terry and ask him if PT ordered the pumps with relief valves. He has already told me yes, but please go ahead and ask for yourself, and maybe we will know the truth. I can see where they install on the pump, but it is an option.

Stray, do you have this same pump?

 

[SnowRidge]

SnowRidge.

Since you have one of these pumps, how about you calling Terry and ask him if PT ordered the pumps with relief valves. He has already told me yes, but please go ahead and ask for yourself, and maybe we will know the truth. I can see where they install on the pump, but it is an option.

Stray, do you have this same pump?

Did you specifically ask, and did he specifically tell you they have high pressure relief valves, as opposed to the charge pump relief valve, which is standard?

Where do you see them installing on the pump? The only place for additional relief valves is in the implement circuit. The implement circuit is an extension of the charge pump, and it is not used in the PTs. Those are roughly 800 PSI reliefs, BTW, not suitable for the tram circuit.

 

[J_J]

Did you specifically ask, and did he specifically tell you they have high pressure relief valves, as opposed to the charge pump relief valve, which is standard?

Where do you see them installing on the pump? The only place for additional relief valves is in the implement circuit. The implement circuit is an extension of the charge pump, and it is not used in the PTs. Those are roughly 800 PSI reliefs, BTW, not suitable for the tram circuit.

http://www.sauer-danfoss.com/stellent/groups/publications/documents/product_literature/bln-10006.pdf

Page 26 of 32 From what I can figured out, that is where they go, if installed. Maybe you can check your pump to see if anything is under that cap. If you see a nut or screw adjust, then I suspect they are there. If blank, then they are not installed.

 

[SnowRidge]

http://www.sauer-danfoss.com/stellent/groups/publications/documents/product_literature/bln-10006.pdf

Page 26 of 32 From what I can figured out, that is where they go, if installed. Maybe you can check your pump to see if anything is under that cap. If you see a nut or screw adjust, then I suspect they are there. If blank, then they are not installed.

I think those ports are just capped. If I get a chance, I will pull whatever is there tomorrow.

I think I figured out why the Service Manual doesn't mention those ports or the high pressure reliefs. It is dated 1990. The Technical Information document is dated 2000. The Service Manual is completely out of date. It doesn't mention the SAE "A" Auxiliary Flange either. I believe that is used on the newer PT-425s that have all the pumps on one end. It is not present on my pump.

 

[stray]

Guys i sent this note to Power-Trac. I sent it yesterday and didn't get a reply today so i sent again today. As soon as and if i get an answer i will share it with you all.

I have been doing some engineering on my 2003 422 22 horse power robin engine Power trac. Several of us are involved in the aspect of being able to change the gearing to a slower more powerful speed by running all 4 wheel motors in a parallel mode rather than the right left pair of 2 motor serious. I have designed and install a quick disconnect system that allows me to switch back and forth from the 2 serious to the 4 motor parallel mode. I am sure you are aware of the Tractorbynet site for the Power-tracs. We would appreciate it very much if you can set us straight on relief valves.

Questions
First: does my wheel motors on the 2003 422 have relief valves in them. If so what were they set on from your factory?

Second: Does the charge system have relief valves or valve in it? What was it set on?

Third: does the tram system have relief valves in it and if it does what was it set on.

You have a lot of Lowell PT owners on the tractor-by-net site and this seems to be a hot topic. Any help you can give us on this will be shared and appreciated by several Pt Owners. Sevel people with the 425痴 are interested in this too.

Here is a link to the tread on this. Please help us with as much detail info on the relief valve as you can.

Craig A Cooter


http://www.tractorbynet.com/forums/power-trac/137695-more-torque-my-power-trac.html

 

[J_J]

Do you guys not have parts manuals for VSP pumps. If you do, it will indicate whether you have relief valves.