# assigment II

Assignment II (15%)
1. If the applied system pressure is 300MPa and the actuator has a bore of 250mm. Due to
internal leakage, the cylinder has a volumetric efficiency of 90 percent.
a. Find how much extension force can be exerted by a hydraulic cylinder
b. Calculate time the cylinder takes to extend if the pump flow applied to the cylinder was
20 litres per minute and the cylinder had a 500 mm stroke.
2. If the motor displaces 130 cm3 per revolution and the flow to the motor is set at 60L/min.
a) Find the speed of a hydraulic motor
b) calculate flow rate in litres per minute
c) Calculate the required pump input power in kilowatts (kW) for a system that has a pressure
of 80MPa. Assume a volumetric efficiency of 97 per cent.
3. Calculate theoretical delivery flow Qtp and actual delivery flow Qp of a pump which has
stroke displacement qp = 12cm3rev-1. The pump shaft rotation speed is Np =4800rpm and
the pump volumetric efficiency ŋvp= 0:82.
4. A pump which has unit displacement qp = 230 cm3rev-1 operates under pressure p =
300bar. What is the required input torque if pump hydro-mechanical efficiency is ŋhmp =
0:98?
5. Calculate the actual delivery flow rate Qp of a pump if its unit displacement is 𝑉 ∅= 4cm3rad1
and its shaft angular speed is 𝜔p = 400 rad-1. Pump leakage loss is Qvp = 120 cm3s-1.
What is the volumetric efficiency of the pump?
6. Main dimensions of gears in a gear pump are: gear width b = 25mm, number of teeth z =
16, modulus m = 5. Calculate the theoretical delivery flow Qtp when shaft speed is Np =
3000 rpm.