RPM's and BH

fredhargis · Nov 15, 2010

I've been digging up my garden, both to practice with the BH as well as to loosen up the soil for winter. Got to wondering about where the engine should be while I'm digging (B2920 with BH65). I was running it pretty slow, maybe 1600-1800 RPM and noticed slow movement with the hydraulics; it was almost impossible to move the dipper and the boom at the same time...I expected that. I guess higher RPM would solve the slow movement (?). Does higher RPM give you more force from the cylinders as well?

CHDinCT · Nov 15, 2010

fredhargis said:
I've been digging up my garden, both to practice with the BH as well as to loosen up the soil for winter. Got to wondering about where the engine should be while I'm digging (B2920 with BH65). I was running it pretty slow, maybe 1600-1800 RPM and noticed slow movement with the hydraulics; it was almost impossible to move the dipper and the boom at the same time...I expected that. I guess higher RPM would solve the slow movement (?). Does higher RPM give you more force from the cylinders as well?

RPM has more impact on flow/speed than pressure. Your pressure shouldn't vary too much with RPM's. Maybe a couple hundred psi. So' more RPM's will get you more speed. Enough to move both cylinders at the same time? Don't know.

Transit · Nov 15, 2010

It works this way.
The maximum force that can be generated is dependent on the rated pressure of the pump, typically 2,200-2,400 psi.
If there is a pressure relief valve in the hydraulic system and it is set to a lower value, [1,900psi] that is what you get.
As for RPM, it controls how fast oil is pumped and so the speed that things move. Too much rpms make it difficult to control the hoe because it moves too fast.

Find the rpms that give you the movement you are comfortable with.

MikeInEburg · Nov 15, 2010

fredhargis said:
...it was almost impossible to move the dipper and the boom at the same time..

Remember that your control valves are likely in series so that if you're operating the "upstream" valve, you'll have no flow for the "downstream" valve. Thus your inability to move both dipper and boom at same time may be a plumbing issue, not an RPM issue. Practicing in the garden is a great way to become acquainted with your backhoe!
Mike