190301d

Question 1

What do hydraulic motors convert hydraulic energy into?

Answer 1

rotary mechanical energy

Question 2

Over time, internal clearances in a motor increase due to wear. What else does this increase?

Answer 2

leakage and oil flow through the drain line

Question 3

Name three categories of hydraulic motors.

Answer 3

1. Gear motors, including external gear motors and gerotor and geroller motors
2. Vane motors
3. Piston motors.

Question 4

True or false: The construction between hydraulic pumps and hydraulic motors is significantly different.

Answer 4

False; In most cases, the construction of hydraulic motors is very similar to the construction of hydraulic pumps.

Question 5

What does reversing oil flow through a hydraulic motor do?

Answer 5

Reversing the oil flow through the motor reverses output shaft rotation

Question 6

Why are gear type motors not commonly used?

Answer 6

Their design makes them poor torque generators

Question 7

Pressurized oil is allowed to flow past the ________ to the rod side of a ram type
cylinder

Answer 7

piston

Question 8

What advantage do telescoping cylinders offer?

Answer 8

additional stroke length is gained from a relatively compact retracted package

Question 9

Why are double-acting cylinders are often referred to as differential cylinders?

Answer 9

There is a difference in the speed and forces generated by extension versus retraction

Question 10

What is the difference between a differential and non-differential cylinders?

Answer 10

nondifferential cylinders have equal piston area and equal volume on both sides of the cylinder.

Question 11

What three things does a leaking piston seal in a differential cylinder result in?

Answer 11

1. increased cylinder cycle times.
2. cylinder drifting in the extension direction.
3. pressure intensification when in the hold position.

Question 12

What is the function of a cylinder rod wiper?

Answer 12

prevent contamination from entering the cylinder.

Question 13

What is the purpose of a piston relief valve?

Answer 13

allow pump oil flow to bypass the piston when the piston reaches the end of its stroke, reducing heat generation

Question 14

In reference to hydraulic cylinder operation, what does the term regeneration refers to?

Answer 14

supplementing pump oil flow to the base end of a double-acting cylinder with oil flow from the rod end which increases cylinder extension speed

Question 15

The quick drop valve used on dozer cylinders provides regeneration when the operator selects ___________

Answer 15

the full lower position

Question 16

The speed of a motor driveshaft depends upon which two factors?

Answer 16

1. Inlet flow rate
2. Motor displacement (capacity)

Question 17

One factor that does not influence motor torque generation is: __________________

Answer 17

inlet flow rate

Question 18

Most motors are equipped with a drain line. What does that line do?

Answer 18

carries leakage oil from the motor to the reservoir

Question 19

Why are external gear motors such poor torque generators?

Answer 19

Due to counteracting forces, torque is generated by inlet pressure acting on the surface area of just one tooth

Question 20

True or False: Gerotor motors are considered to be high-speed low torque motors.

Answer 20

False

Question 21

What is the function of a spool valve in a gerotor motors?

Answer 21

direct the flow of oil to and from the valleys in the gerotor element.

Question 22

Why are balanced vane motors good torque generators?

Answer 22

they can operate at higher pressures than other types of vane motors.

Question 23

Why must some vane motors be equipped with spring-loaded vanes?

Answer 23

Spring-loaded vanes are used to ensure good vane-to-cam ring contact at start-up.

Question 24

What is the main difference between variable and fixed displacement motors?

Answer 24

The speed and torque characteristics of a variable displacement motor will change as their displacement changes

Question 25

Pressure compensated, variable displacement motors vary their displacement in response to changes in motor load.

As the load on the motor output shaft increases,
the motor displacement ______________

Answer 25

increases

Question 26

Why are variable displacement motors prevented from reaching the zero displacement position?

Answer 26

The motor will hydrostatically lock and stall (freewheel) in the zero displacement position

Question 27

In a piston motor the cylinder barrel and pistons are often referred to as?

Answer 27

Rotating group

Question 28

Three types of piston motors?

Answer 28

1. Axial
2. Bent
3. Radial

Question 29

In a piston motor how is leakage oil returned to tank?

Answer 29

A drain port/line

Question 30

What are the 2 most common set angles that can be set as swash plate displacement?

Answer 30

6.5 and 19

Question 31

If a motors swash plate goes into a perpendicular position, what could happen?

Answer 31

The circuit would go into a hydrostatically locked situation allowing motor to freewheel (stall).

Question 32

Pressure compensation allows for the motor to have what?

Answer 32

It allows the motor to have a swash plate that is automatically adjusted according to load on the motors output shaft.

Question 33

How is maximum torque achieved in a piston pump?

Answer 33

With the swash plate at minimum flow angle.
Least speed. Maximum torque

Question 34

True or False: A bent axis piston motor cannot be made to bend at 6.5 or 19 degrees?

Answer 34

False: A bent axis piston motor will use the rotating group as the swash plate.

Question 35

How does a bent axis piston motor become a fixed displacement motor?

Answer 35

The motor housing holds the rotating group in a bent shape.

Question 36

How does the bent axis piston motor become a variable displacement motor?

Answer 36

This is achieved by using the rotating block as a swash plate.