Hydraulic Motors

Brought to you by:

Demetri Preonas

Greg Unverferth

Overview of Lesson

• How they work

• Types of Motors

• Performance

• Applications

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.

Types of Hydraulic Motors

• Gear Motors

• Vane Motors

• Piston Motors

• Limited Rotation Actuator

Gear Motors

• External Gear Motor– 2 rotating gears, the

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.

Model 21300 “B1 Series” Gear MotorEaton® Heavy Duty Series 1 Variable Motor

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

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.

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

Piston Motors

• Most efficient • Often used in

aerospace applications due to high power to weight ratio

In-line Piston Motors

• Simple construction• Low cost• Used in low torque

high speed applications, such as machine tools

Radial Piston Motors

• High Torque• Low speed• Possible application

could be a roller.

Bent Axis Piston Motor

• Is one example of variable displacement motor.

• The angle is altered to change the displacement.

Limited Rotation Actuator

• Also sometimes called a oscillator.

• Has limited movement • High torque

Performance

• Efficiency• Two factors• Internal leakage

– Volumetric efficiency and speed decrease due to leakage.

• Internal friction– Mechanical efficiency

loss due to torque loss

• Effv= (rpmact/rpmtheo) * 100

• Effv= volumetric efficiency

• Effm= (Tact/Ttheo) * 100

• Effm= Mechanical efficiency

• Effoa=(Effv/100)*(Effm/100)*100

• Effoa= Over All Efficiency

Performance

• The mechanical torque desired must be specified in order to find required working pressure.

• Pin= (T*2)/Disp.

• The rpm desired must be specified in order to find required flow rate.

• Q= (rpm * Disp.)/231

Power

• Hpout= (Tlb-ft * rpm)/5252

• Effoa= (Hpout * 100)/ Hpin

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