# Shared Flashcard Set

## Details

Hydraulic Motors Chapter 10
Chapter 10
39
Mechanical Engineering
03/16/2010

Term
 Define Hydraulic Motors
Definition
 Hydraulic Motors Convert the movement (kinetic energy) and pressure (potential energy) of a stream of hydraulic fluid into continuous moving energy of a rotating shaft.
Term
 What determines the torque or force output of a Hydraulic Motor.
Definition
 The pressure of the fluid admitted to the motor.
Term
 What is the general construction of hydraulic motors similar to?
Definition
 The general construction of hydraulic motors is similar to that of hydraulic pumps. However, some changes are made so that the mechanisms can operate as motors and be more efficient.
Term
 Why is efficiency important in a hydraulic motor?
Definition
 Efficiency is important because energy losses that occur in the system and in the hydraulic pump affect motor operation.
Term
 True or False - To make sure that the pump delivers as much fluid to the motor as possible, the volumetric efficiency of the pump is usually lower than its mechanical efficiency.
Definition
 False.The volumetric efficiency of the pump is usually higher than its mechanical efficiency.
Term
 How do hydraulic motors differ from hydraulic pumps in their operation?
Definition
 Motors need a starting or breakaway torque large enough to start rotation while fully loaded. This means overcoming the total starting friction within the motor and the connected load. Motors only have to contend with their own breakaway torques and starting friction.
Term
 How are hydraulic motors classified?
Definition
 Hydraulic motors are classified by the:1. Driving Elements2. Principle of operation.
Term
 Are Hydraulic Motors Positive Displacement or Nonpositive Displacement type.
Definition
 Hydraulic motors are all of the positive-displacement type.
Term
 True or False - Hydraulic motors deliver smooth rotary movement.
Definition
 FalseBecause of their construction, they have an intermittent or pulsating shaft output motion.However, the pulsations are so small that the practical effect is one of relatively smooty motion and constant torque.
Term
 Name two types of positive displacement motors.
Definition
 Fixed-displacementVariable-displacement
Term
 How can the shaft output speed of a fixed-displacement motor be changed?
Definition
 Change the pressure ad flow rate of the hydraulic fluid that turns the motor.
Term
 How can the shaft output speed of a variable-displacement motor be changed?
Definition
 Change or alter the physical arrangement of the motor's mechanism.
Term
 Why are most hydraulic motors of the fixed-displacement type?
Definition
 Because Variable-displacement motors are more complex and less efficient than fixed-displacement motors.
Term
 What factors affect the rating and selection of a motor for an application?
Definition
 1. Overall Performance2. Operational problems3. Speed4. Installation Cost5. Operating and Maintenance Cost6. Mechanical and Volumetric Efficiency7. Pressure range8. Speed range9. Starting Torque10. Estimated Service Life11. Size and Weight12. Mounting Requirements13. Noise
Term
 Define operating pressure of a motor
Definition
 The operating pressure of a motor is the pump pressure of the hydraulic system minus the line losses.
Term
 What determins the selection of a hydraulic motor operating speed?
Definition
 The application.
Term
 What governs a hydraulic motor's speed?
Definition
 The fluid flow rate.
Term
 Define Motor Torque.
Definition
 The torque of a motor is the twisting effect that causes a piece of equipment to rotate.
Term
 What is the equation for calculating the torque of a motor?
Definition
 Torque = 0.16* displacement(in^3)*psi*efficiency factor.
Term
 Name the three types of motor torque.
Definition
 1. Starting torque.2. Running torque3. Stalling torque
Term
 What is starting torque?
Definition
 The starting torque is the turning force the motor exerts from a dead stop.
Term
 What What is running torque?
Definition
 Running torque is exerted when the motor is running and changes whenever there is a change in fluid pressure.
Term
 What is stalling torque?
Definition
 Stalling Torque is the force necessary to stop the motor.
Term
 What is an Ideal Motor?
Definition
 An Ideal Motor is defined as having no power losses due to friction and leakage and is 100% efficient.
Term
 What is the formula to calculate the mechanical horsepower output of a hydraulic motor?
Definition
 HP=torque(lb-in)*shaft speed(rpm)/63,025
Term
 What is the formula for calculating input horsepower?
Definition
 hp = (gpm *psi)/1714
Term
 What is the formula for calculating overall efficiency?
Definition
 overall efficiency = output hp/input hp
Term
 What is the formula for calculating flow?
Definition
 flow(gpm) = (displacement(in^3)*shaft speed(rpm))/231 in^3/gal
Term
 When selecting a replacement motor for an existing system what fluid characteristics must be considered.
Definition
 1. Viscosity2. Viscosity Index3. Volatility4. Resistance to foaming5. Oxidation and corossion resistance6. Fluid effects on seals.
Term
 What is the typical service life for hydraulic motors?
Definition
 Similar to that of pumps1000 hrs to 15000 hrs depending.
Term
 What are the different types of hydraulic motor construction?
Definition
 1. Gear2. Vane3. Axial-piston4. Rotary-piston
Term
 What are the three types of hydraulic gear motors?
Definition
 1. External2. Internal3. Nonseperated
Term
 How is the displacement adjusted in a variable-displacement axial-piston motor?
Definition
 By manually or automatically changing the angle of the swash plate.
Term
 Internal gear motors--inner & outer gear set with an output shaft. The inner geear has 1 less tooth than the outer gear.
Definition
 Internal gear motor
Term
 2 matching gears in an enclosed housing. One output shaft & 1 idler shaft.
Definition
 External gear motor
Term
 Matched gears; similar to an internal gear motor.
Definition
 Gerotor motor
Term
 Balanced--shaft is balanced to prevent shaft & bearing wear. Designed to have 2 inlets & 2 outlets internally.
Definition
 Balanced Vane Motor
Term
 Unbalanced--load can stress the shaft & bearings
Definition
 Unbalanced Vane Motor
Term
 This motor can be fixed or variable displacement, several styles;in-line axialBent axis axialRadial
Definition
 Piston Motors
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