HYDRAULIC MOTORS - Frequently Asked Questions (FAQ''s) Notes | EduRev

: HYDRAULIC MOTORS - Frequently Asked Questions (FAQ''s) Notes | EduRev

 Page 1


LECTURE 10 AND 11 
 
HYDRAULIC MOTORS 
FREQUENTLY ASKED QUESTIONS 
1. Differentiate between hydraulic pump and hydraulic motor 
Pump converts mechanical energy provided by prime mover to fluid energy.  Hydraulic motor 
uses fluid energy and converts it to mechanical movement of the actuators, either rotary or linear. 
2. List the advantages of hydraulic motor over electric motor 
o Hydraulic motors are indeed smaller at identical power and especially torque. Their speed 
and position can be regulated very well, though not as precisely as for electric motors. 
Price also was a bit lower because of the inverter. 
o When machine stalls due to some snag, direction of the hydraulic motor can be reverered 
easily and safe using pressure relief valve. Electric motor would trip or burn out 
o Where electric motors, which can deliver only rotational power and must be sized to suit 
the load application, hydraulic motors are much smaller in size even when the application 
involves heavy loads. 
o  In a heavy electromechanical system a big electric motor needs to be directly located on 
the motion axis which may not be always feasible. It would also require a continuous 
supply of electricity usually from an external source. 
3. List four important application of hydraulic motor 
o Electric motor coil winding  
o Oil pipeline inspection equipment  
o Undersea camera manipulation  
o Jumbo jet maintenance jacks  
o Milling and sawing applications  
o Dynamite blast hole pump drive  
o Automatic clamping  
o Textile washing agitators  
o Orange peeling machines  
o Fan drives  
o Diamond wheel dresser  
o Drill and tap machine tool  
o Chicken processing machinery  
o Conveyor drives  
o Due to the high torque at low speeds, loaders and other construction equipment use heavy 
hydraulic motors to drive the wheels for moving the machines around 
Page 2


LECTURE 10 AND 11 
 
HYDRAULIC MOTORS 
FREQUENTLY ASKED QUESTIONS 
1. Differentiate between hydraulic pump and hydraulic motor 
Pump converts mechanical energy provided by prime mover to fluid energy.  Hydraulic motor 
uses fluid energy and converts it to mechanical movement of the actuators, either rotary or linear. 
2. List the advantages of hydraulic motor over electric motor 
o Hydraulic motors are indeed smaller at identical power and especially torque. Their speed 
and position can be regulated very well, though not as precisely as for electric motors. 
Price also was a bit lower because of the inverter. 
o When machine stalls due to some snag, direction of the hydraulic motor can be reverered 
easily and safe using pressure relief valve. Electric motor would trip or burn out 
o Where electric motors, which can deliver only rotational power and must be sized to suit 
the load application, hydraulic motors are much smaller in size even when the application 
involves heavy loads. 
o  In a heavy electromechanical system a big electric motor needs to be directly located on 
the motion axis which may not be always feasible. It would also require a continuous 
supply of electricity usually from an external source. 
3. List four important application of hydraulic motor 
o Electric motor coil winding  
o Oil pipeline inspection equipment  
o Undersea camera manipulation  
o Jumbo jet maintenance jacks  
o Milling and sawing applications  
o Dynamite blast hole pump drive  
o Automatic clamping  
o Textile washing agitators  
o Orange peeling machines  
o Fan drives  
o Diamond wheel dresser  
o Drill and tap machine tool  
o Chicken processing machinery  
o Conveyor drives  
o Due to the high torque at low speeds, loaders and other construction equipment use heavy 
hydraulic motors to drive the wheels for moving the machines around 
o Cooling fans of equipment that already have hydraulic systems. For example a front end 
loader or excavator.  
o  
4. Explain with neat sketch the working of Gear motor 
 
 
 
5. Write the classification of Piston motor 
Piston motors are classified into following types 
According to the piston of the cylinder block and the drive shaft the piston motors are     
classified as   
o a) Axial piston motors 
o b) Radial piston motors 
According to the basis of displacement piston motors are classified as 
o Fixed displacement piston motors 
o Variable displacement piston motors 
 
Page 3


LECTURE 10 AND 11 
 
HYDRAULIC MOTORS 
FREQUENTLY ASKED QUESTIONS 
1. Differentiate between hydraulic pump and hydraulic motor 
Pump converts mechanical energy provided by prime mover to fluid energy.  Hydraulic motor 
uses fluid energy and converts it to mechanical movement of the actuators, either rotary or linear. 
2. List the advantages of hydraulic motor over electric motor 
o Hydraulic motors are indeed smaller at identical power and especially torque. Their speed 
and position can be regulated very well, though not as precisely as for electric motors. 
Price also was a bit lower because of the inverter. 
o When machine stalls due to some snag, direction of the hydraulic motor can be reverered 
easily and safe using pressure relief valve. Electric motor would trip or burn out 
o Where electric motors, which can deliver only rotational power and must be sized to suit 
the load application, hydraulic motors are much smaller in size even when the application 
involves heavy loads. 
o  In a heavy electromechanical system a big electric motor needs to be directly located on 
the motion axis which may not be always feasible. It would also require a continuous 
supply of electricity usually from an external source. 
3. List four important application of hydraulic motor 
o Electric motor coil winding  
o Oil pipeline inspection equipment  
o Undersea camera manipulation  
o Jumbo jet maintenance jacks  
o Milling and sawing applications  
o Dynamite blast hole pump drive  
o Automatic clamping  
o Textile washing agitators  
o Orange peeling machines  
o Fan drives  
o Diamond wheel dresser  
o Drill and tap machine tool  
o Chicken processing machinery  
o Conveyor drives  
o Due to the high torque at low speeds, loaders and other construction equipment use heavy 
hydraulic motors to drive the wheels for moving the machines around 
o Cooling fans of equipment that already have hydraulic systems. For example a front end 
loader or excavator.  
o  
4. Explain with neat sketch the working of Gear motor 
 
 
 
5. Write the classification of Piston motor 
Piston motors are classified into following types 
According to the piston of the cylinder block and the drive shaft the piston motors are     
classified as   
o a) Axial piston motors 
o b) Radial piston motors 
According to the basis of displacement piston motors are classified as 
o Fixed displacement piston motors 
o Variable displacement piston motors 
 
 
 
6. Define volumetric efficiency, mechanical efficiency and overall efficiency of hydraulic motor 
 
 
 
                                                    
                                  
 
 
 
 
 
 
 
 
 
                                    
                                         
 
 
 
 
 
 
 
 
 
                                             
                                             
 
 
7. Why is the actual flow rate required by the hydraulic motor is higher than the theoretical flow 
rate 
Actual flow rate required by the hydraulic motor  is more than theoretical flow rate because of 
the fluid frictional losses, losses in pipes, losses in fittings, leakage loss etc. 
 
8.  Why is the actual torque output delivered by the hydraulic motor is less than the calculated 
theoretical torque 
Actual output delivered by the hydraulic motor  is less than theoretical torque because of the mechanical 
frictional losses like bearing losses etc. 
9. List the few applications of semi –rotary actuator 
o Semi actuators are used for lifting, tilting in jigs and fixtures 
o Partial Opening and closing of door in machine tools 
o Indexing, swinging and bending in sheet metal applications 
 
10. Where are external gear motor used 
Page 4


LECTURE 10 AND 11 
 
HYDRAULIC MOTORS 
FREQUENTLY ASKED QUESTIONS 
1. Differentiate between hydraulic pump and hydraulic motor 
Pump converts mechanical energy provided by prime mover to fluid energy.  Hydraulic motor 
uses fluid energy and converts it to mechanical movement of the actuators, either rotary or linear. 
2. List the advantages of hydraulic motor over electric motor 
o Hydraulic motors are indeed smaller at identical power and especially torque. Their speed 
and position can be regulated very well, though not as precisely as for electric motors. 
Price also was a bit lower because of the inverter. 
o When machine stalls due to some snag, direction of the hydraulic motor can be reverered 
easily and safe using pressure relief valve. Electric motor would trip or burn out 
o Where electric motors, which can deliver only rotational power and must be sized to suit 
the load application, hydraulic motors are much smaller in size even when the application 
involves heavy loads. 
o  In a heavy electromechanical system a big electric motor needs to be directly located on 
the motion axis which may not be always feasible. It would also require a continuous 
supply of electricity usually from an external source. 
3. List four important application of hydraulic motor 
o Electric motor coil winding  
o Oil pipeline inspection equipment  
o Undersea camera manipulation  
o Jumbo jet maintenance jacks  
o Milling and sawing applications  
o Dynamite blast hole pump drive  
o Automatic clamping  
o Textile washing agitators  
o Orange peeling machines  
o Fan drives  
o Diamond wheel dresser  
o Drill and tap machine tool  
o Chicken processing machinery  
o Conveyor drives  
o Due to the high torque at low speeds, loaders and other construction equipment use heavy 
hydraulic motors to drive the wheels for moving the machines around 
o Cooling fans of equipment that already have hydraulic systems. For example a front end 
loader or excavator.  
o  
4. Explain with neat sketch the working of Gear motor 
 
 
 
5. Write the classification of Piston motor 
Piston motors are classified into following types 
According to the piston of the cylinder block and the drive shaft the piston motors are     
classified as   
o a) Axial piston motors 
o b) Radial piston motors 
According to the basis of displacement piston motors are classified as 
o Fixed displacement piston motors 
o Variable displacement piston motors 
 
 
 
6. Define volumetric efficiency, mechanical efficiency and overall efficiency of hydraulic motor 
 
 
 
                                                    
                                  
 
 
 
 
 
 
 
 
 
                                    
                                         
 
 
 
 
 
 
 
 
 
                                             
                                             
 
 
7. Why is the actual flow rate required by the hydraulic motor is higher than the theoretical flow 
rate 
Actual flow rate required by the hydraulic motor  is more than theoretical flow rate because of 
the fluid frictional losses, losses in pipes, losses in fittings, leakage loss etc. 
 
8.  Why is the actual torque output delivered by the hydraulic motor is less than the calculated 
theoretical torque 
Actual output delivered by the hydraulic motor  is less than theoretical torque because of the mechanical 
frictional losses like bearing losses etc. 
9. List the few applications of semi –rotary actuator 
o Semi actuators are used for lifting, tilting in jigs and fixtures 
o Partial Opening and closing of door in machine tools 
o Indexing, swinging and bending in sheet metal applications 
 
10. Where are external gear motor used 
External gear motors are used for high speed (4000 RPM) and low torque application.  Usually their 
capacity is limited to 5-10 kW 
o Used in Damper Actuators, 
o hydraulic fan drive systems for mobile vehicles 
o Material Handling 
o Earthmoving machines 
o Truck and Bus 
 
11. List the advantages of external gear motor 
o High drive speeds 
o Compact dimensions and low weight  in relation to the power rating 
o Cost--effective 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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