How do hydraulic cylinders compare to hydraulic motors in terms of motion and oil consumption?

How do hydraulic cylinders compare to hydraulic motors in terms of motion and oil consumption?

• A. Cylinders produce linear motion and consume oil only while moving; motors produce rotary motion and consume oil continuously.
• B. Cylinders produce rotary motion and consume oil continuously; motors produce linear motion and consume oil only while moving.
• C. Cylinders and motors both consume oil continuously while operating.
• D. Cylinders consume oil only when idle; motors consume oil only during startup.

Answer: (A)

The key idea is how each actuator converts fluid power into motion and how that affects fluid flow. A hydraulic cylinder is a linear actuator: pressurized oil pushes a piston to extend or retract, producing straight-line motion. Once the movement stops—either at the end of travel or when the load locks the cylinder in place—the flow largely stops, so oil is consumed mainly during actual movement.

A hydraulic motor, by contrast, is a rotary actuator: pressurized oil drives rotation. To keep turning, the motor needs a continuous flow of oil, so the system must keep circulating fluid even if the speed is constant. That’s why oil is considered to be consumed continuously when the motor is powered.

So cylinders give linear motion with oil flow mainly during movement, while motors give rotary motion with continuous oil flow to sustain that motion.