Hydraulic question.

[Bison]

I have a hydrostatic driven pivot tonque Hay bine(NH 114) i have some trouble with.(posted a little lower down on the page)
The drive is a tractor PTO driven pump that drives an orbit motor wich in turn drives the entire bine.( there is no slip clutch anywere in the drive line and all the componets are either chain driven and/or keyed to their respective mates,none of the keys are sheared)
There is a 3500 psi relief valve between the pump and the motor and is the only safe guard it seems.
The bine RPM's seems to slow down as soon as i start to cut hay and wont cut clean unless i crawl.
I thought maybe the orbit motor was getting weak so i tested that by blocking it from turning and engaged the PTO slowly to see what pressure(5000 psi gauge) the system would attain before the relief valve would trip.
Turns out the relief valve trips at 3500 psi ( the right setting per OEM manual)
So it seems the pump is OK,...but what about the Orbit motor?
Could it still be shot even though it lets the relief valve build pressure to OEM specs before relieving pressure.?

 

[J_J]

The motor is going to slow down as the pressure builds.

What should be the cutter rpm?

The resistance to work, as in cutting, will slow the motor and cause the pressure to build until you stall the motor and the relief goes off.

The motor is blocking the fluid at stall and the pump is still trying to pump, so the flud has to go somewhere, and if it can not be relieved good enough, something will burst be it a hose motor, pump, fitting, etc.

Say a hyd pump is pumping 10 GPM with a capacity to go to 3500 psi. This will take about 24 HP.

So now take a hyd motor 3 cu in, and using the 10 GPM, the rpm should be about 770.

As you get close to stall speed, the psi goes up, and GPM goes down. Motor slows down.

The motor at full potential should develop about 20.4 HP

Torque on that motor is about 1672 in lbs at 3500 psi.

AT 2500psi, the torque would be about 1194 in lbs.

If you put a flow meter and pressure gage in the system, you can see what is happening. Most people would not have the flow meter, but the pressure gage is readily available.

Perhaps something is binding or the cutters are dull.

When the PTO is running, the pump is running at whatever rpm the PTO is driven, and the hyd motor takes the GPM provided and does work.

If you install a pressure gage in the circuit, you can see what is happening to the pressure.

 

[dfkrug]

The bine RPM's seems to slow down as soon as i start to cut hay and wont
cut clean unless i crawl.

Since you blocked the mechanism and tested the system with a guage and
got full relief pressure, that indicates that the internals of your hyd motor
are probably OK. And the pump is probably OK.

What I suspect is that a bearing somewhere has seized or material (hay?) has
wound its way around a shaft, causing excessive friction. This added
resistance requires more power to go the speeds you used to go.

I agree that, ideally, a flow meter would be nice to have to do a dynamic
test (with pressure guage, too). I sure don't have one.

 

[Bison]

I think i found the problem.
I found a busted 0 ring in the relief valve housing between pressure and relief side on the relief valve cartridge resulting in loss of pressure and flow straight back to the tank.