Locked up and nowhere to go

[J_J]

What does RPS mean? I don't have one on my machine. Someone said something about a charge pump valve.

 

[ponytug]

J.J. It is the aluminum block with the PTO solenoid in it, along with a pressure relief a pressure regulator, and the all important shuttle valve.
Relief, Pto, Shuttle valve= RPS?
Photos at PT-1845 Shuttle Ball Repair

On my 1445 the RPS is located adjacent to the hydraulic oil tank, and below the diesel tank on the left side, ahead of the left rear motor.

The charging valve is a steel block with a large spring coming out of it, and has the accumulator attached to it. On my 1445, it is behind the left rear motor, bolted to the outside wall of the tub, with the spring hindmost. It is just below the dipstick on my engine. It seems to have many of the brake tender features, but is not connected to a manual pump.

I hope that this helps.

All the best,

Peter

What does RPS mean? I don't have one on my machine. Someone said something about a charge pump valve.

 

[J_J]

Actually, I was looking for the breakdown of the letters RPS. I have seen it mentioned somewhere else, but can't remember, you know, that CRS thing.


I did some web surfing and found out the letter designation for RPS. It means Return Pressure Sensing.

Read this and see if it makes any sense in reguards to the PT.

HYDRAULIC SELECTOR VALVES
In the F-15, the hydraulic selector valves have a design feature called return pressure sensing (RPS) which was incorporated to improve hydraulic system reliability. Selector valves with RPS will not operate if there is a leak in the selected lines or in the return line to the first check valve. This prevents the pilot from switching into a failed hydraulic circuit where the oil would be directed overboard, thus losing the entire system, or half a system if the failure was in one of the RLS branches.
Return pressure sensing blocks the pressure to the solenoid pilot-operated section of the selector valve. The block is achieved by sensing the loss of return line pressure in the subsystem lines which have failed. Subsystems which must be operated after failure have emergency back-up provisions.
In selector valves, care was also taken to design out "man traps" such as doors or surfaces that are hydraulic-ally positioned open or closed upon removal of electrical power. An example is the F-15 speed brake valve which remains in a full trail position (both selected lines become common to return if electric power is removed from the aircraft).

 

[Bob999]

What I wonder is whether it worth installing a 10 micron filter on the upstream side. It would filter all of the oil eventually...

With my 1845 the fluid supply to the accumulator and the Brake Tender/Brake system comes from the variable displacement pump. There is a pressure reducing valve on the RPS block that limits pressure in the brake tender system to 2000 PSI (this statement is based on observation of the maximum pressure observed on the pressure gage located on the manual Brake Tender pump).

Problems of the sort you and Woodland farms are reporting have not been reported by 1845 owners. So--perhaps the fact that the make up fluid supply for the variable displacement pump (from the charge pump) is filtered by a 10 micron filter is important. Based on the discussions and postings here it is my understanding that the fluid supply to the non-PTO portion of the RPS block and the black steel block on your 1445 and on Woodland farms 1850 comes from the Auxiliary pump--and the supply for this pump is taken directly from the hydraulic tank without filtration. Woodlandfarms has also reported a filter --apparently located between the black steel block and the accumulator but is still having the problem. So it seems to me that if the problem is unfiltered fluid that it is causing the problem either in the black steel block or the RPS block.

Because the shuttle ball/valve is part of the drive circuit and fluid is supplied from the variable displacement pump it doesn't seem to me that this valve is causing the problem you and Woodlandfarms is reporting--your problems are in a circuit supplied with fluid supplied by the auxiliary pump. Further your problem is in a circuit that has no filter.

So--given the general concensus that the problem is probably dirt/contamination I would thank that adding a filter could prevent future problems--once the existing problem is resolved.

 

[woodlandfarms]

Hey bob, My filter is upstream. Between the RPS and the black steel block.

Now, I could have messed up when changing a filter and got dirt into the system.

Also, I think that Ksimolo found out that the filter we share (he has an 1850) is a 25 micron and not a 10 (I have never looked).

The only system on my PT that is filtered prior to the pumps is the wheel motors. But as it is a somewhat closed loop system, how much is being filtered is in question. Although, the supply pipe is big (1" to the filter - 3/4" coming out).

Carl

 

[Bob999]

Hey bob, My filter is upstream. Between the RPS and the black steel block.

Now, I could have messed up when changing a filter and got dirt into the system.

Also, I think that Ksimolo found out that the filter we share (he has an 1850) is a 25 micron and not a 10 (I have never looked).

The only system on my PT that is filtered prior to the pumps is the wheel motors. But as it is a somewhat closed loop system, how much is being filtered is in question. Although, the supply pipe is big (1" to the filter - 3/4" coming out).

Carl

Carl,

Thanks for the clarification. Can you describe the fluid path--My understanding is that it flows from the auxiliary pump to the RPS block to the inline filter between the RPS block and the black steel block and then from the black steel block it flows --??

 

[woodlandfarms]

Hmmm You are a difficult b#*&%%d.

This is from memory

One goes to the brakes, one goes to steering and one goes to lift and tilt. And I think one goes to the Draft control. The brakes line then somehow feeds back from the brake to the hydraulic treddle.

I have a hose on the top that goes to overflow.

Peters should be the same... Ksimolo's is identical to mine, so he may know better... I am just not near the PT anytime soon...

 

[Bob999]

This is from memory

One goes to the brakes, one goes to steering and one goes to lift and tilt. And I think one goes to the Draft control. The brakes line then somehow feeds back from the brake to the hydraulic treddle.

I have a hose on the top that goes to overflow.

Peters should be the same... Ksimolo's is identical to mine, so he may know better... I am just not near the PT anytime soon...

You have the hydraulic treadle! My machine doesn't. So--it seems that the differences in the hydraulic system are related to the hydraulic treadle.

Another question--does your machine have the Brake tender system and if so are the brakes external disk brakes that are spring applied and hydraulically released?

PS--I purchased my machine new from PT in May of 2003 and it does not have the hydraulic treadle. That strongly suggests that your machine was built after May 2003.

 

[woodlandfarms]

OK, now things are going to get weird.

First, I have no identification on my tractor as to serial or date. Those were removed. I need to dbl check with Ken, but who he (we) purchased from said it was a 2002 model. But, the guy was high as a kite so who knows.

Second, I do not have a visible brake system like the that 1850 that had been rolled in the lake. I just have wheel motors.

What has me really confused is that my wheel motors have 3 hoses runing to them (as I remember). Two large and one small. I always thought the small was the brake system, but it has to be the overflow/purge/whatever the name is I cannot remember.

So, I have NO clue how my systems brakes work. Here is a pix of the front drivers wheel and the hoses I see going to it (taken some time ago).

Maybe there is a 4th line (Case Drain, now I remember) that is hidden from this photo... Ken, Peter?

 

[ponytug]

My 1445 has spring applied brakes internal to the hydraulic motors. They were the #1 reason that I bought a 1445, the #2 reason being that I didn't think I needed the 45 degree slope rating on the 1850. Whenever I spin out on a steep slope, I revisit that decision, but I have no plans on selling my machine!

All the best,

Peter

You have the hydraulic treadle! My machine doesn't. So--it seems that the differences in the hydraulic system are related to the hydraulic treadle.

Another question--does your machine have the Brake tender system and if so are the brakes external disk brakes that are spring applied and hydraulically released?

PS--I purchased my machine new from PT in May of 2003 and it does not have the hydraulic treadle. That strongly suggests that your machine was built after May 2003.