More torque for my Power trac?

[SnowRidge]

FWIW, My 425 has a B&P pump. I've never heard reliefs operating on it. The engine seems to run out of torque first.

That's the pump with the omega sign, right? What year is your 425?

 

[Gravy]

JJ,

I don't have a manual. I haven't even figured out the model number of my pump. The ID plate was evidently left off or removed by PT.

Snow Ridge,

Yes. The Omega was the only way I identified it. I think my 425 is a 2005. It has the Robin engine and the higher torque White wheel motors.

 

[SnowRidge]

JJ,

I don't have a manual. I haven't even figured out the model number of my pump. The ID plate was evidently left off or removed by PT.

Snow Ridge,

Yes. The Omega was the only way I identified it. I think my 425 is a 2005. It has the Robin engine and the higher torque White wheel motors.

Removed by PT, most likely. Did they switch to Bondioli & Pavesi when they dumped the Kohlers for the Robins, or was it at some other time?

 

[Gravy]

I don't really know, but I would guess that they switched engines, pumps, and motors all at once as part of a redesign.

 

[SnowRidge]

Well now, who wants to be the first to look and see if there are relief valves installed. According to the diagram, they are on the rear of the pump, about a third from the top. If you look on the the pages in the PDF , pages 26 of 32, you will see. The question is do all 422's and/or 425's have this pump?

Here is a Steiner manual for a product that also uses a Series 15 pump. In this case, the valves shown behind those caps are check valves, not relief valves. Those part numbers appear to be Steiner numbers, not Sauer-Danfoss or Sundstrand numbers.

The check valves are used to admit hydraulic fluid from the charge pump into the closed loop. From what I can divine about this pump design, it looks like at some point the engineers designed a two way valve to optionally replace the check valves. The two way valves appear to function as a check valve in one direction and a relief valve in the other.

The relief function certainly isn't working on my machine, so I am assuming mine has the check valves like the Steiner.

 

[3238dpw]

Stray,
Well I was thinking about this the other day. I was wondering how this has been working for you now that have had this setup for a while.

 

[stray]

The truth is that I ran the lower speed set up for a while, found out what it would do and haven稚 changed it back since. (I use quick disconnects to change speeds. It would be great to engineer this with electronic switches) I have relative flat land and the need has not come up for the lower gear. AS I stated before the lower speed set up does increase the pulling and pushing power without harming the pump or wheel motors. You have to operate the PT different than when it is in normal speed mode. It is hard to explain but you can still do the same thing with more push pull power. You just have to do it differently. As far as worrying about the higher pressure, that is only in theory. Actually if anything there is less risk of pressure damage than in regular speed mode. It has to do with wheel slippage and even pressure on all four wheels when best traction is taking place. If I ever have a project that puts the lower gear to good use I値l be sure to post it. Thanks for asking and I will try to answer any question about this as best I can.

 

[J_J]

Things we know.

12.5 cu in hyd motors, 1500 psi, 16 GPM, 300 rpm. Torque 3000 in lbs

A 25 HP engine can run a 1500 psi pump with a 25 GPM output. Some of that HP will go to the other pumps. So figure about 20 HP for the tram pump, at 1.3 cu in. at 1500 psi, pumping 16 GPM.

A single hyd wheel motor at 16 GPM, at 1500 psi, will turn at 300 rpm, and have 3000 in lbs of torque. 4 hyd motors will have 12,000 in lbs or 1,000 ft lbs of torque.

If two motors are in series, the psi is divided across both motors. If the first hyd motor stalls, what happens to the fluid? Does that give more GPM to the other series circuit.

When you exceed the torque limitation, you force a great resistance to the flow of fluid, and the engine can not handle the blockage, and some fluid will be relieved, and the engine will struggle to compensate, and if you don't let off the treadle, for a smaller flow rate, the engine will die. Keep in mind, you are changing pump displacement, with the treadle.

If the VSP pump was a 3000 psi pump, and you now are sending 3000 psi across two motors is series, and then those two circuits were in parallel, that would change things.

If you put 3000 psi across a 1500 hyd motor, it will probably fail. However, it will run at it's designed pressure for a long time as long as you don't put a large load on it to cause the pressure to increase up to 3000 psi. A relief valve would work, but that is a waste in energy.

If that VSP pump is a .8 cu in 3000 psi pump, a 12 GPM pump, will take a 25 HP engine and that is to supply all 4 wheel motors.

Just something to think about.