*note: if this problem proves too difficult, don't worry, thanks for your time anyway... :P*

Hi,

I'm currently attending a subject in college which is to do with the basic princlples of hydraulics. We were recently given a learning outcome/test to do in our own time. The thing is, my lecturer isn't very keen on helping me with the first question, even though he did go over the formulae etc... I am rather poor at maths, and I am wondering if someone would be able to help me with question 1 on my learning outcome.

Here is the actual question. It should be very simple if you know the formula to go with it. That's all I'm looking for, the FORMULAE, not the actual answers... Here is the question:

A pump discharge pressure is given as 20 bar and the flow rate is 65 litres/minute, the cylinder diameter us 125 mm, the stroke 750 mm and the piston rod diameter is 38 mm. Assuming no losses in the system, calculate the following -

a) the max force on the cylinder piston extending
b) the max force on the cylinder whilst retracting
c)the length of time taken for the cylinder piston to extend
d) the length of time taken for the cylinder piston to retract
e) the power developed in the system
f) the hydraulic pump speed given that the pump displacement is 0.2 litre per rev.
g) the power output of the eletrical motor assuming an 8.5 % allowance is made above the circuit generated
h) what should the minimum flow rate be

Thanks for reading.

A In a hydraulic system, the pressure is equal at all points. The force would be the pressure on the piston times the area.

B I think it would be the suction pressure you don't have times the area.

C&D The flow per minute divided by the displacement should equal the cycles per minute. Assuming the pump is driven at a constant rate, each stroke will be half the minutes per cycle.

E (A+B) times cycles per minute times the length of the stroke gives the work per minute. Convert that to the proper power unit.

F?? If it is driven by a crankshaft, the RPM should equal the cycles per minute, an intermediate result of C&D.

G 1.085 times E

H Again?? Wasn't the flow rate a given?

Maybe somebody else will understand F and H better.