Posted: 25 - May - 2010 at 07:45 | IP Logged

I'm starting to agree with bobodu, maybe the pump is too big for the engine or I am not able to maintain proper tension and once I get under load the pump starts slowly creeping inward until the belt slips.  The pump is rated for max 25 gpm and when i disconnect the return line and run things, fluid circulates just fine.  Even when I actuate the valves, fluid still circulates through just fine.

Curiuosly, when i jack one side of the machine up and actuate the valve on that side, the wheels spin just fine, but when I lower the machine to the ground and do it, the wheels will not spin and that is obviously when I have had the slippage problem.

This is a fairly simple hydraulic setup, so I know I'm overlooking something obvious, but I just want to move slowly through the process so I don't destroy anything. 

Basically the line comes from the tank to the pump, pump to one valve, valve to the wheel motor, back to the tank.  I'm not even worried about the second wheel motor on the other side at this point.  I want to figure out why the one won't work. 

I do have a smaller pump on my cadtrac so if all else fails, I may take that pump off and try it on this machine to see if pump size is the issue.  I just hate like heck to mess with the machine that currently works!!  Too bad everything hydraulic costs so much because it would be so much easier to experiment with different pumps and configurations to find the one I like best.

Posted: 30 - July - 2010 at 23:51 | IP Logged

Rule of thumb (and my calculator program under the file area will help figure what rpm you need to run) is about 1 hp per gpm and that depends on the psi you are running at.  If you have the relief valve set correctly the engine should not die.  If you don't have a relief valve then go back to the house (unless you have the puter in shop you are in the house) and order one.  For hydraulic motors you should have one of those two-way doobie snatchers that protect the motor in both directions.  You will need one for each motor.  Some are even made to mount on those motors with manifold type connections (of course thats not the type you have).  Crossover is the type of relief valve you want.

https://www.surpluscenter.com/item.asp?item=9-5373&catna me=hydraulic

This one looks good and has the correct type of fittings.

https://www.surpluscenter.com/item.asp?item=9-7674&catna me=hydraulic