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  • Some Hydraulic Questions

    I was looking at an add for a 16 Ton hydraulic forging press which resembled a log splitter in the vertical position. The cylinder looked to be 4 inch diameter, The stroke was 8 inch, and the ram speed was advertised at 1.6 inch per second.
    The power requirements for the press was 110V @ 20 amps.

    I found an online calculator that found that a 4 inch cylinder @ 2500psi would produce over 31,000 psi, which would be close to the 16 ton, so what electric motor and pump combination will give the 16 tons @ 1.6 ips. with 110 volt @20 amps.


    Link to press:
    https://www.coaliron.com/forging-pre...-forging-press

  • #2
    I gotta run and will explain my calculations tomorrow if I need to but I come up with 5.2 GPM if it is indeed a 4 inch bore cylinder and the speed is 1.6 ips.
    That should require a hair over 7.5 HP, so either my figures are wrong or they are fudging some of their numbers in order for them to claim a 110v @20amp power requirement.

    Oh heck I've got a minute:

    4" X 1.6" volume = 20.11 cubic inches

    1 US Gal = 231 cu.in.

    A flow of 20.11 cu.in. for 60 sec. = 1206.6 cu. in.

    1206.6 + 231 = 5.2 GPM

    Power required to generate that flow @2,500 psi = 7.585 HP
    Home, down in the valley behind the Red Angus
    Bad Decisions Make Good Stories​

    Location: British Columbia

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    • #3
      No telling if the 16 ton pressure and the 1.6 inch travel are at the same setup...... there is a hint that there is either a dual speed setup, or enough hand control. The approach speed of the ram seems much higher than the speed when in contact and forging the blank in the lower videos on the site.

      So the 1.6" speed may be the unloaded, and the 16 ton at a much lower loaded ram speed, which would make sense. Lower speed is lower gpm at pressure, for lower overall power requirement.
      1601

      Keep eye on ball.
      Hashim Khan

      Comment


      • #4
        Interesting- how many rpm would you lose from a synchronous motor at full load, and what is the optimal rpm when you factor in loading and efficiency with a 7.5 horse electric motor? Can you drag a 3600 rpm motor down to say 3000 rpm and get good power without losing efficiency? There should be a number here that you can use in the equation to arrive at the Inches Per Second at full pressure.
        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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        • #5
          Gotta be a two speed pump. I think they trip over at 400-500 psi. 500 psi @ 5.2 GPM is 1.5hp. Which is about as big of a motor as you're going to run on a 110v 20 amp circuit.

          Comment


          • #6
            Originally posted by Boostinjdm View Post
            Gotta be a two speed pump. I think they trip over at 400-500 psi. 500 psi @ 5.2 GPM is 1.5hp. Which is about as big of a motor as you're going to run on a 110v 20 amp circuit.
            +1 Sounds like a two stage pump. They are very common on log splitters for example. Many of them have a adjustment for the trip point, with higher horsepower available you can set it to trip at a higher pressure.

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            • #7
              Originally posted by J Tiers View Post
              No telling if the 16 ton pressure and the 1.6 inch travel are at the same setup...... there is a hint that there is either a dual speed setup, or enough hand control. The approach speed of the ram seems much higher than the speed when in contact and forging the blank in the lower videos on the site.

              So the 1.6" speed may be the unloaded, and the 16 ton at a much lower loaded ram speed, which would make sense. Lower speed is lower gpm at pressure, for lower overall power requirement.
              Originally posted by Boostinjdm View Post
              Gotta be a two speed pump. I think they trip over at 400-500 psi. 500 psi @ 5.2 GPM is 1.5hp. Which is about as big of a motor as you're going to run on a 110v 20 amp circuit.
              Originally posted by Sparky_NY View Post
              +1 Sounds like a two stage pump. They are very common on log splitters for example. Many of them have a adjustment for the trip point, with higher horsepower available you can set it to trip at a higher pressure.
              Yup, exactly what I was thinking too shortly after my reply.
              I would have gotten back sooner but it was in the wee hours when I got home but I see everyone picked up the ball while I was gone.
              Home, down in the valley behind the Red Angus
              Bad Decisions Make Good Stories​

              Location: British Columbia

              Comment


              • #8
                Thanks for all the helpful replies, this hydraulics stuff is confusing.
                So using the 5.2 GPM, I found a online calculator that says 5 GPM will move a 4 inch cylinder @ 1.5 in/sec. Then checked ebay for a 5GPM pump and found this:

                https://www.ebay.com/itm/NorTrac-Cas...AAAOSwPF9cbzhk
                (NorTrac Cast Iron Two-Stage Pump -5 GPM, 1/2in. Dia. Shaft, Model# CBNA-4.2/1.0A) Looks like the high volume low pressure output is 4.2 and the low volume high pressure is 1 GPM.

                I have a 4 inch bore 10 inch stroke cylinder. I'm thinking of converting my bottle jack press that I built years ago to hydraulic. The manual 20 ton jack I use is awfully slow. I might also have a 1-1/2 or 2 hp motor around here.
                Which brings up another question, 1750 or 3450 Rpm.

                The shed that I have the press in doesn't have 220 volts so the 110 would be convenient, especially if I can get 15 ton with it. Even if it is 0.3 in/sec in the high pressure stage.

                Thank You All very much for the help.
                Nick
                Last edited by Nicholas; 04-10-2019, 11:49 AM. Reason: added 0.3

                Comment


                • #9
                  It is a good practice with building anything to start with the job you want to accomplish and work backwards. The same holds true with hydraulic machines. But in this case you have to sort of start with the electric power you have available which limits you greatly. So you have to start at both ends of the equation. So pick the most powerful electric motor you can run on your electric power available then pick how much force you want to be able to apply at the forge end and then you can pick a pump the right size as well as hoses and valves. The lower hp electric motor you have the smaller hydraulic pump in volume per revolution you will have to use in order to be able to produce the force you want. Remember the pump only produces flow. The work produces the force.
                  Location: The Black Forest in Germany

                  How to become a millionaire: Start out with 10 million and take up machining as a hobby!

                  Comment


                  • #10
                    Originally posted by Nicholas View Post
                    Thanks for all the helpful replies, this hydraulics stuff is confusing.
                    So using the 5.2 GPM, I found a online calculator that says 5 GPM will move a 4 inch cylinder @ 1.5 in/sec. Then checked ebay for a 5GPM pump and found this:

                    https://www.ebay.com/itm/NorTrac-Cas...AAAOSwPF9cbzhk
                    (NorTrac Cast Iron Two-Stage Pump -5 GPM, 1/2in. Dia. Shaft, Model# CBNA-4.2/1.0A) Looks like the high volume low pressure output is 4.2 and the low volume high pressure is 1 GPM.

                    I have a 4 inch bore 10 inch stroke cylinder. I'm thinking of converting my bottle jack press that I built years ago to hydraulic. The manual 20 ton jack I use is awfully slow. I might also have a 1-1/2 or 2 hp motor around here.
                    Which brings up another question, 1750 or 3450 Rpm.

                    The shed that I have the press in doesn't have 220 volts so the 110 would be convenient, especially if I can get 15 ton with it. Even if it is 0.3 in/sec in the high pressure stage.

                    Thank You All very much for the help.
                    Nick
                    1750 or 3450 rpm? Look at the specs of the pump being considered. A large portion of the two stage pumps out there are intended for use with small gasoline engines which typically run at 3600 rpm. The rpm of the pump determines the amount of fluid flowing, in gals per min which relates to the speed of the cylinder, the pressure of the pump determines the ultimate force generated by the cylinder.

                    Comment


                    • #11
                      Originally posted by Sparky_NY View Post
                      the pressure of the pump determines the ultimate force generated by the cylinder.
                      The pump does not create pressure, the mass of whatever the cylinder is trying to move creates the pressure. The pump only withstands the pressure. A hydraulic pump has a rated pressure that it can withstand only. It is a basic concept that is often misunderstood even by people that should know better. The pressure is a result of there being enough hp available from whatever is turning the pump that creates the flow to overcome the mass that applies the force to the cylinder.
                      Location: The Black Forest in Germany

                      How to become a millionaire: Start out with 10 million and take up machining as a hobby!

                      Comment


                      • #12
                        Originally posted by Black Forest View Post
                        The pump does not create pressure, the mass of whatever the cylinder is trying to move creates the pressure. The pump only withstands the pressure. A hydraulic pump has a rated pressure that it can withstand only. It is a basic concept that is often misunderstood even by people that should know better. The pressure is a result of there being enough hp available from whatever is turning the pump that creates the flow to overcome the mass that applies the force to the cylinder.
                        That is actually correct. Of course, as you say, the pump has to be able to produce flow AT that pressure.

                        But both ways of looking at it may get to the same result as far as understanding the system enough to know what you are buying.
                        1601

                        Keep eye on ball.
                        Hashim Khan

                        Comment


                        • #13
                          Originally posted by Black Forest View Post
                          The pump does not create pressure, the mass of whatever the cylinder is trying to move creates the pressure. The pump only withstands the pressure. A hydraulic pump has a rated pressure that it can withstand only. It is a basic concept that is often misunderstood even by people that should know better. The pressure is a result of there being enough hp available from whatever is turning the pump that creates the flow to overcome the mass that applies the force to the cylinder.
                          I agree with the description in general but still question if the pump does not create the pressure to move or hold that mass. The amount of pressure developed determined by the mass.

                          What about a case where the pump output is dead ended, there is ZERO mass and the pressure will rise until the motor stalls or the pump explodes, it would seem the pump is creating that pressure, there is no mass in such a case.

                          Still, I think we are in agreement overall.

                          Comment


                          • #14
                            Originally posted by Sparky_NY View Post
                            I agree with the description in general but still question if the pump does not create the pressure to move or hold that mass. The amount of pressure developed determined by the mass.

                            What about a case where the pump output is dead ended, there is ZERO mass and the pressure will rise until the motor stalls or the pump explodes, it would seem the pump is creating that pressure, there is no mass in such a case.

                            Still, I think we are in agreement overall.
                            The end of the pipe is creating the pressure the same as a mass would on a cylinder. It should really be referred to as "the work" creates the pressure then it is more clear.

                            But you are right as to being in agreement with the final outcome in this instance.
                            Location: The Black Forest in Germany

                            How to become a millionaire: Start out with 10 million and take up machining as a hobby!

                            Comment


                            • #15
                              Originally posted by Black Forest View Post
                              The end of the pipe is creating the pressure the same as a mass would on a cylinder. It should really be referred to as "the work" creates the pressure then it is more clear.

                              But you are right as to being in agreement with the final outcome in this instance.
                              Yep, we totally agree.

                              On a log splitter I made, electric 5hp motor/w 2 stage pump, 4in cylinder.... I had a pressure gauge, most wood spit around 1500psi, IF it went over 2000psi you had BETTER be paying attention !! At higher pressures (up to 3000) that wood can let go with explosive force. Without the gauge, you had no idea of how hard it was working, everything worked and sounded the same, speed was the same.
                              Last edited by Sparky_NY; 04-11-2019, 08:17 AM.

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