Hydraulic Circuits Technical Discussion

[PowerTracManiac]

Found some hydraulic diagrams of an 1850. TU woodlandfarms.
There are 2 pumps on the 1850 and on my 1460. 1)Variable volume pump and 2) pto pump.

Looking at the first pdf diagram below (hydro 5) it seems the wheel circuit fluid is drawn from the tank, through the main filter to the variable volume pump and then to all the wheels? Where is the front/back hydraulic treadle in this diagram? It seems to draw fluid from the main tank through the main filter but fluid does not return to the tank in this diagram? Seems this fluid would get extremely hot if not cooled and returned to main tank somehow?

The second diagram (hydro7) below shows both the PTO pump and the Variable Volume Pump. The PTO pump circuit is not filtered or cooled in line? This PTO fluid is pulled from the tank and returned to the tank directly.
The Variable Volume Pump in the second diagram (hydro 7) shows a line going off it (@fitting 21) to the oil cooler and then to the return in the tank. Is this the line that returns the fluid from the wheel circuit? If yes, then the wheel circuit is cooled and then returned to the tank where any metal shavings would be cleaned by the main filter before the oil is served to the Variable Volume Pump in diagram (hydro 5 ) for the wheel circuit.
It's actually the PTO circuit that is not filtered and any metal shavings from a failed wheel would eventually go into the tank and then directly to the pto pump without being filtered.
Or maybe I am reading this all wrong?

 

[ponytug]

Found some hydraulic diagrams of an 1850. TU woodlandfarms.
There are 2 pumps on the 1850 and on my 1460. 1)Variable volume pump and 2) pto pump.

Sorry, I cut your post into a few pieces are there are several different questions.

There are three pumps, the third is the auxiliary and runs the cylinders, lift steering, etc.

Looking at the first pdf diagram below (hydro 5) it seems the wheel circuit fluid is drawn from the tank, through the main filter to the variable volume pump and then to all the wheels? Where is the front/back hydraulic treadle in this diagram? It seems to draw fluid from the main tank through the main filter but fluid does not return to the tank in this diagram? Seems this fluid would get extremely hot if not cooled and returned to main tank somehow?

Yes, and no. The hydraulic treadle comes off the variable volume pump and goes back to it. Some variable volume pumps are hydraulically controlled, but some are cable controlled.

The wheel drive circuit loses a little oil through motor seals (aka case drains) that goes back to the tank (that's where @kjm3232's filings got back to the main tank, I believe). To make up for that lost oil, the charge pump in the variable volume pump suctions oil out of the tank through the filter and into the charge pump that pressurizes the variable volume pump, providing cooling and make up oil. Most of the motor drive oil recirculates pump to motor to pump, so no cooling (yes it gets warm), and the fresh oil helps keep the oil from degrading too quickly. I check the temperature of my motor cases on hot days, and stop for a pause if they are "really hot" (yes, totally subjective). Case drains help wash dirt and debris out of the motor, as they are generally pulling oil from a cavity adjacent to the axle seal, which is where dirt would normally get in, and also where bearing debris gets washed to. Having a case drain helps wash that away and keep it out of the system.

The second diagram (hydro7) below shows both the PTO pump and the Variable Volume Pump. The PTO pump circuit is not filtered or cooled in line? This PTO fluid is pulled from the tank and returned to the tank directly.
The Variable Volume Pump in the second diagram (hydro 7) shows a line going off it (@fitting 21) to the oil cooler and then to the return in the tank. Is this the line that returns the fluid from the wheel circuit? If yes, then the wheel circuit is cooled and then returned to the tank where any metal shavings would be cleaned by the main filter before the oil is served to the Variable Volume Pump in diagram (hydro 5 ) for the wheel circuit.
It's actually the PTO circuit that is not filtered and any metal shavings from a failed wheel would eventually go into the tank and then directly to the pto pump without being filtered.
Or maybe I am reading this all wrong?

Diagram 7 is for the PTO pump. Variable volume circuits are not illustrated.The PTO circuit is neither filtered out of the tank nor on the return line. Sigh.

It is only the PTO circuit that goes through the oil cooler, and then only when the PTO is operating, otherwise the oil is returned to the tank.

On hydraulic systems designed for a long life, generally there is a tank filter feeding all the pumps, and many also have a return line filter from hydraulics that can be disconnected, and where dirt will get in. (I highly recommend cleaning with brake cleaner before connecting any the quick connect fittings.) Without naming names, I was told that PT doesn't include the other filters because the are a horsepower drain, and a source of heat. I believe some PT machines came with a high pressure filter before the steering / loader valve circuit. (E.g. @woodlandfarms? who might be able to comment in more detail.)

Does that help?

Generally low pressure oil filters are cheap,
suction filters slightly more expensive (extra structure to help keep cold oil from collapsing the filter),
return line filters much more expensive (due to the potential shock loading of 2-3,000psi across the filter), and
high pressure high flow filters are very pricey, as in hundreds of dollars pricey.

All the best,

Peter

 

[PowerTracManiac]

Appreciate you, Peter.

 

[m5040]

It is only the PTO circuit that goes through the oil cooler, and then only when the PTO is operating, otherwise the oil is returned to the tank.

I think PT changed the routing of newer machines. My 1460's oil cooler fan will actuate after about 5 min even if I don't use the PTO hyd circuit.

The wheel motor circuit is definitely not cooled on my 1430 as when brush cutting, I have to take a break after about 3-4 hours, they get weak.

 

[PowerTracManiac]

Good technical info in link below;

REPLACING PTO PUMP

I have to replace the PTO pump in my PT-1445. I suspected it was going bad after trying to use the stump grinder/trencher, and several other umplements. They would run, but woule slow down to dead stop. I don't have much room to unbolt the pump and slide it off the back of the tram pump so I...

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