Hydraulic motors use high pressure fluid to turn a shaft. There are several types including gear motors, vane motors, and piston motors. Gear motors use rotating gears where fluid pressure creates force. Piston motors are often the most efficient and used in aerospace due to their high power to weight ratio. Performance is determined by efficiency factors like internal leakage and friction. Calculations can determine required pressure, flow rate, power output, and efficiency.

1. Hydraulic Motors
Brought to you by:
Demetri Preonas
Greg Unverferth

2. Overview of Lesson
• How they work
• Types of Motors
• Performance
• Applications

3. How a hydraulic motor works
• High pressure fluid is
used to turn a shaft.
• This is done in many
different ways.
• Much like a cylinder
the power comes from
the pressure acting
over a large area and
creating a large force.

4. Types of Hydraulic Motors
• Gear Motors
• Vane Motors
• Piston Motors
• Limited Rotation Actuator

5. Gear Motors
• External Gear Motor
Model 21300 “B1 Series” Gear Motor
– 2 rotating gears, the Eaton® Heavy Duty Series 1 Variable Motor
area of the gear teeth is
where the pressure acts
to create force
– Both gears turn
simultaneously
– One gear is connected
to the output shaft and
the other is an idler.

7. Gear Motors
• Internal Gear Motors
• Two categories
– Direct drive gerotor,
works much like a
rotary engine.
– Two gears, an inner
and an outer.
– The pressure pushes
them around a center
point, turning a shaft

10. Vane Motors
• Spring loaded vanes
are connected to a
rotor
• The rotor turns inside
a cam ring (elliptical
hole)
• The vanes slide in and
out of the slots in the
rotor to make contact
with the cam wall.

12. Piston Motors
• Many different types of piston motors
• All of them use the same basic principles
• Much like a cylinder, only turns a shaft like
the cylinders in your car engine.
• Generally the most efficient
• High power, high speed, high pressure

13. Piston Motors
• Most efficient
• Often used in
aerospace applications
due to high power to
weight ratio

14. In-line Piston Motors
• Simple construction
• Low cost
• Used in low torque
high speed
applications, such as
machine tools

16. Radial Piston Motors
• High Torque
• Low speed
• Possible application
could be a roller.

18. Bent Axis Piston Motor
• Is one example of variable
displacement motor.
• The angle is altered to
change the displacement.

20. Limited Rotation Actuator
• Also sometimes called
a oscillator.
• Has limited movement
• High torque

22. Performance
• Efficiency • Effv= (rpmact/rpmtheo) * 100
• Effv= volumetric efficiency
• Two factors
• Internal leakage • Effm= (Tact/Ttheo) * 100
– Volumetric efficiency • Effm= Mechanical efficiency
and speed decrease due
to leakage. • Effoa=(Effv/100)*(Effm/100)*100
• Effoa= Over All Efficiency
• Internal friction
– Mechanical efficiency
loss due to torque loss

25. Performance
• The mechanical torque • The rpm desired must
desired must be be specified in order to
specified in order to find required flow
find required working rate.
pressure.
• Q= (rpm * Disp.)/231
• Pin= (T*2π)/Disp.

27. Power
• Hpout= (Tlb-ft * rpm)/5252
• Effoa= (Hpout * 100)/ Hpin

29. You just learned:
• How a hydraulic motor works
• The basics of the different types of motors
• Some possible applications for hydraulic
motors
• How to calculate power
• How to find efficiency