Pump pressure

Hi Digger104

What RPM do you actually require for the cinder spreader? What is the gear ratio when driven by PTO?

The skid-steer presumably requires most of the available oil output just to operate 'as is' so, you will need to re-use the oil. This will be a matter of compromise as the skid-steer performance will be reduced to accommodate the required oil for the cinder spreader.

You will need, probably, a 'pressure compensated flow control' to give you what you will require for the cinder spreader but, this will depend on the type of pump on the skid-steer. If this pump is fixed displacement, you would use the PCFC to 'bleed oil' off the existing system. If the pump is variable displacement then a simple throttle may suffice however, this only takes care of the RPM of the cinder spreader. You would need a three port 'pressure reducing valve' (with perhaps a fourth port to tank) to give you a sub-circuit operating at a lower pressure than the main system.

If the current skid-steer hydraulic system is hydrostatic (most likely) operating in closed loop, leave that system alone. There will also be a charge pump (fixed displacement and usually quite small) operating off the back of the hydrostatic pump. Leave this alone as well. Look for a small to medium sized independent pump working in open circuit that would operate external cylinders. Look to divide the flow from this pump as indicated above with a PRV and/or PCFC. Also give a thought to cooling. If there is pressure drop (across a motor), there is heat generated!

Also the motor that you have may not have sufficient bearing capacity in the nose but I'm unsure how you intend to configure the cinder spreader!

Any extra information you can provide will give you a more definitive answer.

Good luck with it!

Do you have a fixed pump or variable displacement pump? What is the year and manufacture of the machine with the pump?

HI and thanks for the response. I have two skid steers which I will use. the one is a 2004 277B Cat rubber track and the other is a 2006 Bobcat S220, I'm not sure what pump they have, but I was just going to use the aux hydraulics used to run other equipment. I do think I have this figured out, I'm planing on using a adjustable flow control valve with a built in relief value. Thanks.

You have it under control that way. Also you can mount the flow control valve on the spreader then it will work on ether machine with out change the machine settings.

Hi Digger104

If you intend to use the lower pressure rated motor, DONT use your valve with a pressure relief built in to achieve the lower pressure. It would either lower the pressure so that existing cylinders wouldn't work (or lift enough) or cook the oil.

You will need a pressure REDUCING valve which operates differently to a pressure relief valve.

I would recommend that you 'Tee' into the existing system with the PRV to give you a system leg that you can run the motor from.

You will also need a control valve that is open centre when closed to allow the motor to run down progressively when switched off otherwise you may suck the seals out of the motor!

Watch that you don't throttle the aux pump. It will be a fixed displacement and MUST displace the oil/rev. You would need to 'bleed off' oil to the motor to progressively slow it down.

Good luck!

If you have a Bobcat skid steer, aux. hydraulics is just that. It is extra hydraulics, a seperate pump than your mobile hydraulics. you will need a 4 way valve with open center and pressurre relief. A flow control will also give you speed control, PTO is about 500 rpm