Here's a bit of Hydraulic info.

**frijoli** · 01-03-2010, 03:48 PM

Rule of thumb.

1 GPM x 1500PSI = 1 HP

The actual formula is HP = PSI x GPM ÷ 1714
Since this is theoretical, and efficiency of a hydraulic system is typically 75 to 90 percent the rule of thumb is very close.

Clay

**Hamstn** · 01-03-2010, 09:09 PM

Not sure if I quite follow you. Am I reading the following correct?

1gpm x 1500psi = 1500hp so a motor powered by 1500psi at 1gpm will produce 1500hp or it takes 1500hp to produce. but using the other formula I get .875hp which sounds more reasonable.

Since you the hydraulic expert here I have a question. I am building a power unit to use in my shop to run a press and then maybe other things such as a cherry picker. I do not know the GPM of the pump or its rated PSI, but I will look in parts book to see if it is listed. I went to get my gauge to set it up to test and it is broke so till I get another I will not know what kind of PSI I can produce. I don't even know if the motor will have enough gump to run it.

Any way what is the formula to determine how many tons I will have with a given cylinder?

**frijoli** · 01-03-2010, 09:12 PM

Hamstn said
"Not sure if I quite follow you. Am I reading the following correct?

1gpm x 1500psi = 1500hp so a motor powered by 1500psi at 1gpm will produce 1500hp or it takes 1500hp to produce. but using the other formula I get .875hp which sounds more reasonable.

Since you the hydraulic expert here I have a question. I am building a power unit to use in my shop to run a press and then maybe other things such as a cherry picker. I do not know the GPM of the pump or its rated PSI, but I will look in parts book to see if it is listed. I went to get my gauge to set it up to test and it is broke so till I get another I will not know what kind of PSI I can produce. I don't even know if the motor will have enough gump to run it.

Any way what is the formula to determine how many tons I will have with a given cylinder?"

I accidently dropped a one! I also fixed it.

Yes there is. easy to.

**Hamstn** · 01-03-2010, 09:24 PM

Ok my pump is: PUMP ASSY, header lift, cessna, 12 gpm. PSI I guess would be a factor on how fast I turn it. Cylinder I think is 3" bore.

Hoping to get it to test stage tomorrow or Tues. Problem I think I am going to have is my 1.5hp motor has a bearing out and the other I have is probably .75hp or I can go to a big one that is over kill that I think is 5-7hp. Shooting for 35ton minimum and hope for closer to 50ton. I do have bigger cylinder but it is a bit longer then I want.

**frijoli** · 01-03-2010, 09:29 PM

Originally Posted by Hamstn

I do not know the GPM of the pump or its rated PSI, but I will look in parts book to see if it is listed. I went to get my gauge to set it up to test and it is broke so till I get another I will not know what kind of PSI I can produce. I don't even know if the motor will have enough gump to run it.

Any way what is the formula to determine how many tons I will have with a given cylinder?

Area of piston x PSI = pounds of force.

Area = 3.14 x radius x radius (radius is half the bore diameter)

so a 4" cylinder has a radius of 2. 3.14 x 2 x 2 = 12.56sq" area

Most pumps are capable of 1500psi. 1500psi x 12.56sq" = 18,840 pounds of force, or 9+ tons.

Notice the relationship between pound per square inch, and the area of square inches?? 1 PSI x 1 square inch = 1 pound of force

Clay

---------- Post added at 10:29 PM ---------- Previous post was at 10:25 PM ----------

Originally Posted by Hamstn

Ok my pump is: PUMP ASSY, header lift, cessna, 12 gpm. PSI I guess would be a factor on how fast I turn it. Cylinder I think is 3" bore.

No the it isn't related to PSI.

12gpm is a function of how fast you spin it. PSI is what determines what HP you need, and what the pump can produce.
Most Cessna gear pumps are easily capable of 1500psi, and some will go much higher.

so 12gpm x 1500psi = ? Go back to the rule of thumb!

I'll follow up in the AM. I think you're headed down the wrong path.
Clay

PS. I keep getting ripped on post count!!!!

**Gadget** · 01-03-2010, 09:34 PM

Try a post without quoting and see if the count goes up.

**frijoli** · 01-03-2010, 09:36 PM

okay. It's just confusing if you don't do this without specifics.

Thanks Gadget

**Hamstn** · 01-03-2010, 09:39 PM

So I would be looking at needing a 10hp motor just to get 9tons with a 4" cylinder.

"I think you're headed down the wrong path"
I am just shooing in the dark on my own here so this is why I am sking these questions. Maybe you can get in the right direction with what I have to work with. I am sourcing parts from an old combine.

Yes my count didn't go up either and I had a quote then removed it...not difference

**Gadget** · 01-03-2010, 09:40 PM

I didn't know that quoting would not add to the count. I never noticed it until you brought it up and I looked at the posts. I will mention this to Simon and see if the developers can change this behavior. I will also see if he can give a little leeway on the posts knowing this.