oil hydraulics questions

Discussion in 'Propulsion' started by Guest62110524, Jun 16, 2009.

  1. Guest62110524

    Guest62110524 Previous Member

    I am building some new wheels and rolls
    the power is hydraulic
    I have a motor, Vs is 110 cm3, but is not Vs litres a sec?
    cm3 is 110, torque is 1.5 nm bar, speed is 5-750 rpm
    I only need 10 rpm or wheel travel 3.---4 feet min, torque required for 8mm plate is very little, I cant work out how much even though I have done 100,s plates
    question is, how should I size the pump, should I just aim for say 3kw3ph motor and pump to suit, before I used a 1.5 at 1500rpm, and it was idling with 8mm, even on things like bow nose plates
    how best to change flow rate? the other day in De. I saw a frequency converter, 45--90 Hz, tiny thing worked well
    thanks
    and is this motor suitable? rather thaN 4 POLE 1450
    3 phase 5.5 HP x 2850 rpm 2 pole
     
  2. Guest625101138

    Guest625101138 Previous Member

    I expect the 110cm^3 is the volumetric displacement. At 10rpm you will require the pump to deliver 1100cm^3/min. That is 1.1lpm.

    If you assume the motor will give ample torque at 100bar then the power required is:

    Power = Flow x Pressure (kW)

    Where flow is in m^3/s
    Pressure is in kPa

    Power = 1.1/1000/60 x 100 x 100 = 0.183kW

    A rough and ready hydraulic system will give at least 50% efficiency so say 50%. Motor power is therefore 360W or say 0.5HP.

    Your observations on your previous 1.5kW motor support this. You really do not need any bigger.

    Been ages since I have done any hydraulic component selection. For such a small amount of power you will do OK with a constant displacement pump (say little gear pump), relief valve set to limit the motor torque and a control valve to feed the motor.

    The variable speed using variable frequency would be nice. However you may need a wider speed control than 2:1 range. Are you sure the 45 - 90Hz is not the speed limit setting rather than the actual range. You can certainly get full speed control.

    You can also get variable volume pumps but they are expensive.

    I would walk into a Rexroth dealer and ask them for a system that will do the job. Would help if you know the wheel torque required or the likely maximum motor pressure.

    Rick W
     
  3. Guest62110524

    Guest62110524 Previous Member

    thankee sorrr
     

  4. gonzo
    Joined: Aug 2002
    Posts: 15,189
    Likes: 925, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Most hydraulic systems are regulated by a valve. The pump produces more flow than necessary, and the surplus fluid returns to the tank. If you need a lot of precission, there are flow and pressure regulators.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.