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auxillary pump for power steering


iweld

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I plan to mount a small hyd pump on the back side of my Onan on a 9020. I would like to plumb in to the hydro cooler line for the pump inlet so it won't have to have its own resivoir. Can anyone tell me if this is going to pose a problem? I'm currently using the charge pump for the p.s., but I want to end this practice. Thanks for any comments.
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I believe you can use the same reservoir as long as you use separate feed lines and return line on the aux. pump. If you tee the aux. pump pickup into the return line from the oil cooler it could cause a cavitation problem. If you tee the aux pump pickup into the feed line to the cooler the oil wouldn't go though the cooler. I would run a separate pickup line from the reservoir to the aux pump then tee the return line in to the feed side of the oil cooler. you can tee into the existing pick up line if it is of sufficient size to handle both pumps. Hope this is understandable.
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First of all I want to end the use of the charge pump because my hydro. rebuilder recommended it. He said it will shorten the life of the charge pump because of the amount of use. (you steer much more than run implements) As for UCD's helpful answer. Won't I risk cavitation anyway by trying to drag up all that oil to the pump from the reservoir with it's own dedicated inlet? What kind of running pressure/volume is there through the oil cooler? Thanks.
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thedaddycat
Unless I have a gross misunderstanding of hydro systems, the charge pump supplies fluid at a low pressure(about 125 psi) to your main hydro pump(maybe 1200 psi or so?), which is any time the clutch is out. That being said, I have a hydraulic lift pump and valve assembly from another brand of tractor that I'd be willing to sell. It is made by Cessna, makers of some of the early hydro lifts for our brands if I'm not mistaken. You'd have to modify it to suit your needs, and it's set up for pulley drive like the hydro lifts on the early Simplicity and AC tractors. I believe these pumps are set to 1250 psi buy the internal relief valve.
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Thanks for the pump offer daddycat, but I have a small pump and relief valve already. As for the charge pump operation. "An implement relief valve is added to the transmission circuit which allows intermittent operation of the Charge Pump at higher pressure (up to 800 PSI). The implement Circuit must be of the "open Center" type so that when not in operation the excess Charge Pump flow spills across the Charge Pump housing. When the Implement Circuit is being operated the charge pressure can build up to the higher setting of the Implement Relief Valve." The steering valve that I'm using is of the open center type, so I'm not asking the 800 PSI of the charge pump all the time. Just when I steer (which is quite often);)This is probably why my mechanic advises not using it for steering. I don't claim to be an expert on hydrostats by any means. This is quoted right out of the Simplicity repair manual.
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