Stock hydraulic couplers

[J_J]

My 1445 uses a lever to operate a valve to the PTO. The quick connects for the implements are on the front of this valve. I can vary the speed on the PTO. The lever is down by the right foot on the center panel. The PTO pump runs all the time, but unless you are using a hydraulic motorized implement, the fluid is bypassed to tank and is only filtered when the tram pump filters the oil. I am thinking of putting an input filter similar to the tram filter on the input of the PTO pump with a filter gage. In this situation, it will filter 100 % of the time. I might even put an electric kill switch on the filter. so the pump is not destroyed when the filter is clogged.

Has any one considered the fact that if the wheels are not turning, very little of the oil in the system is filtered. The only oil in this situation that might be filtered is the charge pump oil, and this pump is making up for any oil lost in the case drain of the tram pump. I believe this data is correct. If you find it wrong, please correct.

 

[duane]

JJ,

The charge pump output is based upon engine RPM. At full RPM on a PT422/425, the charge pump is putting out just over 5 gpm. The charge pump flow makes up for any fluid lost in the tram circuit, and the rest flows out a charge circuit relief valve to the hydraulic cooler and back to the reservoir. So at standstill at full rpm, the entire contents of the reservoir should be filtered and through the hydraulic cooler every couple of minutes

Duane

 

[J_J]

My understanding is a little different. I don't mind being corrected. I thought that the charge pump is designed to always keep fluid on the squash plate. and to replace any fluid that was lost in the pump/motor circuit. If the wheels are not moving, there would min lost. At max wheel movement, max speed, the system is rated for the loss of fluid that slips through, and goes to case drain and through the cooler and back to tank. You say 5 gpm on the 422/425, I don't know, is it that bad, or is this a normal figure? Any idea of the gpm that run through the hydraulic motors?

 

[J_J]

Some manufactures make some quick disconnects that are designed to disconnect under pressure. This could be an answer for your problem . They are more expensive.

 

[MossRoad]

I thought the tram pump always pulled fluid no matter the angle of the swash plate... that the fluid just bypassed the drive motor circuit until the operator stepped on the pedal, which changed the angle of the plate, which directed fluid forwards or backwards through the drive motor circuit as needed. ?? Now I have to find some on-line hydraulic course and start reading! /forums/images/graemlins/smile.gif

 

[J_J]

I believe that hydrostatic pumps are a demand type pump in that very little fluid is flowing unless the fwd/back levers call for action. I have been wrong before, but always willing to learn.

 

[MossRoad]

<font color="blue">I have been wrong before, but always willing to learn. </font>

Not me... I make people beat me silly about the head until I understand it fully... then I ask if they are sure? /forums/images/graemlins/tongue.gif

 

[J_J]

If I ever break out my wallet, you know you are wrong. /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

 

[J_J]

David, The only way we could prove or disprove our thoughts is to remove the return hose from the cooler, and measure.

The charge pump is a fixed-displacement pump used to ensure the main pump remains full of fluid. It must be a very small pump inside the main pump. Some circuits show it as a pump, piggy backed to the variable displacement pump. The charge pump circuit is comprised of the charge pump, a relief valve and two check valves. Once the pump is charged to the pressure of the relief valve, about 250 to 350 psi, the rest of it is expelled into the case drain and then to the cooler. One of the hydraulic experts said that the charge pump, pumps about 20% of the variable displacement volume. At rest, no wheel movement, I do not think that it pumps full tram flow.

 

[MossRoad]

That makes sense to me.

When we bleed the pump after changing the hydraulic filter, is that the charge pump we are dumping back to the tank?