More torque for my Power trac?

[SnowRidge]

Those pictures aren't displaying for me...

Anyone else having problems viewing them?

None. They worked fine earlier and are working now. Maybe TBN had a glitch when you were on.

BTW, my cache is emptied each time I close my browser, so I'm not looking at cached images.

 

[KentT]

None. They worked fine earlier and are working now. Maybe TBN had a glitch when you were on.

BTW, my cache is emptied each time I close my browser, so I'm not looking at cached images.

Thanks! They work for me now... not sure what was going on earlier...

 

[MossRoad]

Those pictures aren't displaying for me...

Anyone else having problems viewing them?

I noticed they are loading slowly, displaying line-by-line. They take much longer to load than most, but do come in eventually.

 

[SnowRidge]

I noticed they are loading slowly, displaying line-by-line. They take much longer to load than most, but do come in eventually.

I was on at the same time, Moss. I am still not having any issues. Must be a network thing somewhere.

 

[MossRoad]

Yeah, I just loaded one that I didn't have in my cache and it took 12 seconds.

 

[MossRoad]

I just looked at the size of the file and it was just a tad over 1 meg in size, so that may explain it.

 

[stray]

Sorry guys I will reduce the size next time

 

[J_J]

Stray,

Have you had one wheel off the ground to see what happens to each of the wheel motors. It would seem like, if one wheel is off the ground, all the pump fluid would go through that motor, and with little resistance, and very little pressure. Have you noticed /heard the relief valves activating in the parallel mode. Have you done some of the impossible things that you could not do before. I still don't understand how you can put 3000 psi on 4 wheel motors rated for 1500 psi. Perhaps you have not exceeded the 1500 psi yet. I am thinking that when you said you noticed some improvement, you may have been running those motors at their peak psi rating, whereby they normally would run at 1500.

I ment to ask you about the different type tires on your machine. Is the overall diameter of the lug tires and the lawn tires the same?

 

[stray]

JJ the tires are close the same but not the same. I believe when we talk theory and forget about the reality of say wheel efficiency, wheel motor leak through, flow dynamics and even tire-ground contact creep we tend think things that should happened do not and things that should not happened do. For instance one wheel off the ground and no torque to the other three. While in theory the other wheels would have no power but in reality while it does decrease power to the other three there is enough resistance in the motor and lines at free spin (especially at full throttle) to leave some power to the other three. . And if a little pressure is put to the free spinning wheel (some contact to the ground) then much more power is put to the other three. I don稚 know what the traverse pumps psi is set on but I would be willing to bet it is closer to 2000psi than to 3000. Also when feeding 4 individual wheels there is a lot of volume to fill to reach the pumps maximum psi output. Even with that said I have at several times in full throttle pushed up against a pile of dirt, pushed as hard as the pt could with all wheels on the ground and none spinning. The pt would just grunt and bog down if I pushed it past its power limit. The PT does seem to push much harder in the 4 parallel mode than the factor mode.
Thanks JJ and others as well for keeping this discussion alive. It is bringing out a lot of points and facts about the aspects of this project that I could never cover by myself. I will keep posting my findings and experiences right down to the last blown wheel motor. If it happens that is. But I truly do not think it will. Knock on wood. LOL

 

[BobRip]

Stray, if you push hard while picking up something heavy that should take some load off the rear wheels. I would think that you would get wheel spin and not be able to push as hard. Or even lift the rear wheels off the ground. Try that and give us a report.

 

[SnowRidge]

Even with that said I have at several times in full throttle pushed up against a pile of dirt, pushed as hard as the pt could with all wheels on the ground and none spinning. The pt would just grunt and bog down if I pushed it past its power limit.

Even though I have a different tram pump, I get the same thing. If I overload the machine trying to pull a heavy trailer up an incline that is too steep for load I am towing, the engine just bogs. I have never heard a relief open in that situation.

 

[stray]

Bob that is exactly right and is one of the things I was referring to when I said that some techniques had to be different. Although I can push harder when getting a load of dirt it must be a different push-lift combo to fill the bucket with unloosened dirt. But it is different not necessarily harder to fill the bucket. Also with a full bucket teetering on the edge of overweight in the 4 wheeled parallel mode while turning sharply backing up the back wheels can lift off the ground and the PT will not move. A that point you need to straighten up a little till the wheels catch to move on back. It is a little more of a positive backup turn in the factory mode but I will say it is not a hard thing to deal with in the 4 wheel mode.

There are some disadvantages as to the wheel spin problem but so far it has not been near as bad as I thought it would have been. I really couldn稚 say for sure which set up would be best to fill the bucket. In lifting and moving very heavy objects probably the factory mode would be better. But both you seem to be able to get it done. I will say that when using the bucket or box blade (to level dirt fill) it seems to be better to be in the factory speed mode. With it I can push down and move more positively and quicker. With that said I can still level dirt in the 4 wheel parallel mode just not as efficiently.

All and all unless you have a place like up a hill that you cannot go or work with just keep the factor mode. If you do have places or jobs the Pt will not climb or go with or without a load then this may be a good thing to do. I for sure would use the quick disconnects to be able to relatively easy switch back and forth. I have not been the solenoid valve route yet so I will leave that to your imagination.

 

[stray]

Snowridge, pulling a trailer up hill with a heavy load of dirt and staling out is what made me go back to investigating the parallel mode. I assume what happens is while slowly increasing the flow from the tram pump there is a pressure point where the relief valve is opening. Then when you ask for more flow by pushing on down on the peddle the pressure decreases, the relief valve closes, but the pump can not provide the pressure to open the relief while trying to produce the increased flow. Does that make sense? The tram pump can only pump the required psi to open the relief valve up to a certain amount of flow after that point pressure goes down as you ask for more flow.

Maybe saying it like this is a simpler way to understand what is happining -------- The more FLOW you ASK you PowerTrac tram system to produce or try to produce the less PRESSURE it will be able to produce.

 

[SnowRidge]

I'm not sure what happens with the PT-422. The PT-425 doesn't appear to have any relief valves in the tram circuit.

According to the factory service manual, the Sauer Danfoss tram pump in my machine has no internal relief valve(s) in the high pressure side, except for an optional relief valve that can be installed in the implement circuit. The implement circuit isn't used in the PT application. There is a relief valve for the charge pump.

 

[J_J]

I'm not sure what happens with the PT-422. The PT-425 doesn't appear to have any relief valves in the tram circuit.

According to the factory service manual, the Sauer Danfoss tram pump in my machine has no internal relief valve(s) in the high pressure side, except for an optional relief valve that can be installed in the implement circuit. The implement circuit isn't used in the PT application. There is a relief valve for the charge pump.

In a hydraulic system, you have to have a relief valve, or bad things will happen. It is either in the pump itself, or an external relief valve. If external, there should be two relief valves, one on the fwd, and one on the rev circuit. If you have a parts manual for your pump, look through the parts for one or two relief valves..

 

[SnowRidge]

In a hydraulic system, you have to have a relief valve, or bad things will happen. It is either in the pump itself, or an external relief valve. If external, there should be two relief valves, one on the fwd, and one on the rev circuit. If you have a parts manual for your pump, look through the parts for one or two relief valves..

There is no relief valve in the pump on those circuits according to the manual, which is what I said in the post you quoted.

 

[J_J]

Well, do you have external relief valves?

Do you have a hose going from the tram pump directly to a wheel motor.

 

[J_J]

Stray,

I believe you can solve a lot of the mystery about the pressure from the tram pump by putting a hydraulic gage in the Fwd pressure line from the pump. I sure would like to know what all the readings are in different situations. Slow speed, stalling, one wheel off the ground, etc. I don't know if I mentioned this or not, but in using Quick Connects in the pressure line from the pump, you run the risk of damaging your pump if you accidentally forgot to plug in a QD, otherwise dead heading a pump.

UPDATE


I just got off the phone talking to Terry. He verified what I was thinking. He said the relief valve is on the pump. He did say that it is located in different places for the early 425, and the later 425.

If you guys have a parts list for that pump, I am sure you will find a relief valve or two.

I have never come across a VSP pump that did not have a relief valve. Rules are rules.

 

[SnowRidge]

Well, do you have external relief valves?

Do you have a hose going from the tram pump directly to a wheel motor.

There are no external relief valves. The four hoses go directly from the T fittings on the pump to the wheel motors.

 

[J_J]

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.