A question about official motor ratings for presses.

[basher]

I have spent quite a bit of time looking at power packs and their requirements . and in the mean time have purchased a few ebay bargains .
I plummed in a 7.5 hp power pack to my press . it puts out 6gpm (measured from ram speed 4 inch ram at 2 inch per second) and will easily hit 3000 psi without drawing too many amps for the motor rating, the motor does however strain but it is only momentary I think running it at 3000psi full time would be a problem in the long run.
when I look up the tables the requirement for that flow and pressure is 12.3 hp.....
so are the tables incredibly conservative ? or should I be running a bigger motor?

[Blacksmith Johnny]

I belive the tables are based on full load, 100% duty cycle. your individual needs will determine what you can actualy get away with.

[doc]

Basher,
You should really be running a bigger motor unless your need for a full 3000 psi is very intermittent. Since your working out all this hydraulic stuff late;y here's a link that may be of help http://www.surpluscenter.com/Hydraulic.htm

[Jeddly]

Basher, by my calculations, you can drop down to 2500 psi with that 4" ram, and still be over 30K. Also, if you bring the gpm down to 4 @ 2500psi, that 7.5hp motor will be happier. You may lose some speed though, and I've heard you really need the speed with a hydraulic press.

[basher]

I have dropped the psi I have been running the press at to 2000psi. the motor seems happier and I am happier running the whole rig at a lower pressure .
I mainly use the press for punching now (big hammer installed and doing the grunt work) and speed is the key, to prolong tooling life you need to be in and out of the metal as quick as possible.