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Join Date: Oct 2008
Re: working pressure, pump speed, and temperature
Thanks for your input.
I have a system pressure gauge on the control panel.
It was a hassle to install, but it's been worth the trouble, it tells me a lot.
So when the system gets hot, the max pressure is dependent on rpm with the other things too, like FEL arms.
I don't know how hot the oil gets; I can put a finger on a steel fitting and it feels around 50 to 60C [120 / 140 F]. I'm surprised that such a small temperature rise has so much effect.
Of course, there could be an internal leak in a valve somewhere.
The electric valve block on the hedge cutter is very old, taken from a street sweeping machine.
Most of the ports are normally open, and there's an extra NC solenoid that blocks the return port when work is being done. So plenty of possibilities for problems.
The cutter motor has a few hundred hours on it, and the pump has unknown thousands of hours.
Anyway, I've found a replacement pump for around $150 that's 50% higher capacity.
It took hours and hours; I had a factory part number, the one on the old pump got me nowhere, I found some from size specs but it's hard to work that way. One error and I get a lot of trouble.
Finally, I found a Bosch number that gets results, and found a replacement. It has an Italian name but at that price, is most likely Chinese.
If I used the tractor 20 hours a week for financial gain, I'd go with the Bosch at $300+. For my use, the cheap one.
Even if the problem is elsewhere, the extra volume means I can use a lower engine speed while cutting, and that's worth the money.
There could be issues with the extra oil volume at higher speeds when using the hedge cutter, as the electric valves aren't rated for it. The motor will be ok but I might need to go to larger hoses.
I'm also changing the pulleys + belt between the cutter motor and the crank that drives the teeth, lowering the ratio from 2:1 to 1.5:1 to get more torque.
The extra pump volume will make up for the lost speed and the new belt is rated for the load [the old one wasn't and I broke a few].
I'm working on new, better cutting blades too, but it's a long road with difficult to find material.