hydraulic forging press questions

andrewh2011

andrewh2011

Joined
Jan 6, 2014
Messages
161
I've been doing some reading and i came across a pre-built press by "coaliron" (didnt want to post the link in case it would be breaking the rules) who build a 16 ton hydraulic press with a 2 hp motor hooked up to an 11 gpm 2 stage pump.

How is that possible? All the pumps i can find in that range say they require a minimum 5 hp motor any less and it will stall out when it goes to switch to the 2nd stage (hi pressure)
sorry if this is a dumb question im having trouble finding much information on the subject.
 
You can put a lawn mower engine in your truck ... it just won't do the job a V-8 will. It might move the truck, but itb will be very slow and have no power. The same for an under powered press. The pump will run, but the output will be lowered because the motor can't supply the power.

The numbers you have seen are what I would suggest. One thing that skews the subject a bit is a gas motor needs to be about twice the size of an electric motor on a press.

I don't have my reference books here, but IIRC most 11 GPH pumps can run on a 3HP electric motor for average work loads.

Check Batson's book out. It has the charts and equations to figure out the motor size needed.
 
The minimum 5hp rating is for gasoline engines given the delay in governor control and torque curves, where electric motors have a level torque curve. This is in regard to the typical 11 gpm 2 stage log splitter pumps like I believe CoalIron uses.
 
Stacy E. Apelt - Bladesmith said:
You can put a lawn mower engine in your truck ... it just won't do the job a V-8 will. It might move the truck, but itb will be very slow and have no power. The same for an under powered press. The pump will run, but the output will be lowered because the motor can't supply the power.

The numbers you have seen are what I would suggest. One thing that skews the subject a bit is a gas motor needs to be about twice the size of an electric motor on a press.

I don't have my reference books here, but IIRC most 11 GPH pumps can run on a 3HP electric motor for average work loads.

Check Batson's book out. It has the charts and equations to figure out the motor size needed.
Click to expand...


kuraki said:
The minimum 5hp rating is for gasoline engines given the delay in governor control and torque curves, where electric motors have a level torque curve. This is in regard to the typical 11 gpm 2 stage log splitter pumps like I believe CoalIron uses.
Click to expand...

ahhh i see thanks guys it makes more sense now. i had wondered why they specified gas engines. Batsons book is the first thing on my list to buy when i actually get serious about building a press. Im just doing some passtime reading for now.
your answers give me more questions though lol
so if it were a smaller pump like 8 gpm would a 2 hp motor be able to drive that at full power? according to the calculator i found a 4 inch cylinder at 8 gpm would run the ram at 2.5 in per second which seems adequate.

my other question is if a pump is rated for "3000 PSI max" would you run it in the high two thousands? i guess the more in depth question here is if you dont run an automatic system (to stop overload) do you just stop pushing the lever when your gauge approaches 3000?
 
The system has the pressure relief built in it. Most folks set it at 2500psi. Going to a lower volume pump will decrease the speed significantly. An 8GPM single stage pump will work for forging, but most folks want closer to 1 IPS ram speed in the high stage. 16/8GPM in a 4" to 5" ram is a very good setup. However, a lot of folks have skipped the two stage pumps and just gone with a single stage. The IPS is half as fast, but the ram is only raised a fraction of an inch on each press step, so it really doesn't matter. In that case, your 8GPM pump and 2HP motor would be just barely enough. You may end up wanting a 3HP, but you can always change the motor later if needed.
 
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