MD 2 - FInal Boss [Flywheel, Brakes, Clutches, Bearings]

Flywheel

reservoir which stores energy when the supply of energy is more than the requirement and releases when the requirement is more than the supply

Flywheel

heavy wheel attached to rotating shaft to smooth the transfer of power from an engine to a machine

1. Smoothing the Power output

2. Energy storage systems

3. Delivery of energy

4. Control the alignment of mechanical system, gyroscope, and reaction wheel.

Use of a Flywheel:

steel, bearings

Flywheels are made of ______ and rotate on convetional ______.

carbon fiber composites

High-energy density flywheels can be made from [ ] and use magnetic bearings, which allow them to rotate at speeds up to 60,000 rpm (1kHz).

balancing, Starting, Reducing the load, Speed, Weight

Functions of a flywheel BSRSW

1. [ ] the engine

2. [ ] an engine

3. [ ] on the drive train

4. [ ] reducing

5. [ ] manipulation

Solid disc, Rimmed, High-velocity, Low-velocity

Types of flywheel

Solid disc flywheel

used in a single flywheel threshing machine that is made of cast iron. Is equipped with flywheel hub and disc.

Rimmed flywheel

explodes at a much slower speed than a full disc wheel of the same weight and diameter.

High-strength steel

For a minimal weight and high energy storage, a rimmed flywheel can be form from [ ] and manufactured as a centrally thich conical disk.

High-velocity flywheel

• speed b/n 30,000 to 80,000 rpm.

• Can be set up to 100,000 rpm

• Have magnetic levitation bearings and light depending on size.

• more expensive than LVF.

Low-velocity flywheel

• has a speed of 10000 rpm.

• heavier, bulkier, and cheaper than HVF

• require maintenance

• installation requires concrete structure

Cast or nodular cast iron, steel, or aluminum

Flywheels in car engines are made of?

High-strength steel, or composite flywheels

have been proposed for use in vehicle energy storage and braking systems

Efficiency

of a flywheel is determined by the max amount of energy it can store per unit of weigth.

speed of rotation or angular speed, energy

As the [ ] of the flywheel is increased, the stored [ ] is increased.

1. wind turbines

2. Advanced technology transit buses

3. automobile engines

4. electric cars

5. satellites to control direction

Applications of flywheel: WAAES

cost, power output, energy storage capacity, energy density, energy-efficient

Advantages of a flywheel: CPEEE

1. Less overall [ ]

2. High

3. High ,

4. High

5. Safe, reliable, [ ], durable

Coefficient of fluctuation of speed

ratio of max fluctuation of speed to the mean speed

Coefficient of steadiness

reciprocal of coefficient of fluctuation of speed

speed

As the flywheel absorbs energy its [ ] increases, and it gives up energy its [ ] decreases

tensile stress due to centrifugal, bending stress due to torque, shrinkage stress due to unequal cooling

Stresses in flywheel arms

High-energy density flywheels

can be made from carbon fiber composites and use magnetic bearings, which allow them to rotate at speeds up to 60,000 rpm (1kHz).

Flywheel, Balanced wheel, flywheel pulley

It equalizes the energy exerted and the work done, thus preventing exessive or sudden changes in speed.

10000

Experience specifies the conventional limit of flywheel operations to be at 6000 ft/min for cast iron and ____ ft/min for cast steel

10 to 13

Cast iron flywheels are commonly design with a factor of safety of?

Flywheel

It absorbs and equalizes energy in case the resistance to motion varies, and is used to equalize the energy exerted and the work done.

10 to 13

In flywheel design, the normal factor of safety is?

brake

a device by means of which artificial frictional resistance is applied to a moving machine member, in order to retard or stop the motion of a machine.

kinetic energy, potential energy

In the process of performing this function, the brake absorbs either [] of the moving member or [] given up by objects being lowered by hoists, elevators etc

heat

The energy absorbed by brakes is dissipated in the form of [ ]. This [ ] is dissipated in the surrounding air (or water which is circulated through the passages in the brake drum) so no excessive heating of the brake lining.

1. unit pressure

2. coefficient of friction

3. peripheral velocity,

4. projected area

5. dissipate heat equivalent to energy absorbed

Design or capacity of a brake depends upon the following factors:

Clutch

keep the driving and driven member moving together.

Brake

stop a moving member or to control its speed.

pure translation
pure rotation
both translation and rotation.

The energy depends on the Type of motion of a body:

brake lining

The energy absorbed by the brake and transformed into heat must be dissipated to the surrounding air in order to avoid excessive temperature rise of the [ ].

coefficient of friction, torque capacity

When the temperature increases, the [ ] decreases which adversely affect the [ ] of the brake.

friction lining

At high temperature, there is a rapid wear of [ ], which reduces the life of lining. Therefore, the temperature rise should be kept within the permissible range.

300-500, 600

Temp range and max of Drum Bulk in F.

1000

Engagement temp in +F.

200-300, 300-400

Temp range and max of Lining Bulk in F.

brake drum mass, braking time, heat dissipation capacity

The temperature rise depends upon the [ ], the [ ] and the [ ] of the brake.
BBH

65 – 70

Brake lining: For leather, fibre and wood facing = °C

90 – 105

Brake lining: For asbestos and metal surfaces that are slightly lubricated = °C

180 – 225

Brake lining: For automobile brakes with asbestos block lining = °C

29.5

The value of C {coeff of heat transfer) may be of the order of [ ] W / m2 /°C for a temperature difference of 40°C

44

The value of C {coeff of heat transfer) increase up to [ ] W/m2/°C for a temperature difference of 200°C

low wear rate

low coefficient of thermal expansion.

high coefficient of friction
high heat resistance.
high heat dissipation capacity

Material characteristics for brake lining

1. Hydraulic brakes

2. Electric brakes

3. Mechanical brakes.

Types of Brakes according to the means used for transforming the energy by the braking element

Hydraulic brakes

pumps or hydrodynamic brake and fluid agitator,

Electric brakes

e.g. generators and eddy current brakes

hydraulic and electric brakes

• cannot bring the member to rest

• used where large amounts of energy are to be transformed while the brake is retarding the load such as in laboratory dynamometers

• used for retarding or controlling the speed of a vehicle for down-hill travel.
  
  
  

Radial brakes, axial brakes

Types of Brakes according to the direction of acting force:

Radial brakes

• the force acting on the brake drum is in radial direction.

• sub-divided into external brakes and internal brakes.

• may be block or shoe brakes and band brakes. (by friction element)
  

band brake

consists of a flexible band of leather, one or more ropes, or a steel lined with friction material, which embraces a part of the circumference of the drum.

Clutch

used to connect a driving shaft to a driven shaft so that the driven shaft may be started or stopped at will, without stopping the driving shaft.

automobiles

The use of a clutch is mostly found in

driven shaft

In order to change gears or to stop the vehicle, it is required that the [ ] should stop, but the engine should continue to run.

driven shaft

should be disengaged from the driving shaft

clutch

The engagement and disengagement of the shafts is obtained by means of a [ ] which is operated by a lever.

Positive, friction

Types of Clutches

Positive clutches

used when a positive drive is required.

jaw or claw clutch

The simplest type of a positive clutch is a

jaw clutch

permits one shaft to drive another through a direct contact of interlocking jaws.

Sunk key, feather key.

Jaw clutch - It consist of two halves, one of which is permanently fastened to the driving shaft by a [ ]

The other half of the clutch is movable and it is free to slide axially on the driven shaft, but it is prevented from turning relatively to its shaft by means of [ ]

Square type, spiral type.

The Jaws of the clutch may be?

square jaw type

engagement and disengagement in motion and under load is not necessary.
will transmit power in either direction of rotation.

spiral jaws

may be left-hand or right-hand, because power transmitted by them is in one direction only.
used where the clutch must be engaged and disengaged while in motion.

jaw clutches

The use of [] are frequently applied to sprocket wheels, gears and pulleys. In such a case, the non-sliding part is made integral with the hub.

Friction clutches

application in the transmission of power of shafts and machines which must be started and stopped frequently. w/s

Friction clutches

in which power is to be delivered to machines partially or fully loaded.
w/s

force of friction

is used to start the driven shaft from rest and gradually brings it up to the proper speed without excessive slipping of the friction surfaces.

friction clutch

In automobiles, [ ] used to connect the engine to the drive shaft. In operating such a clutch, care should be taken so that the friction surfaces engage easily and gradually bring the driven shaft up to proper speed.

proper alignment

The [ ] of the bearing must be maintained and it should be located as close to the clutch as possible.

high and unifom Cf,

not affected by moisture and oil,

withstand high temps due to slippage,

high heat conductivity,

high resistance to wear and scoring.

Materials for Friction Surfaces

1. It should Cf

2. It should not be affected by oil

3. It should have the ability to temps

4. It should conductivity

5. It should wear

contact surfaces,

low weight,

external force,

provision for repairs,

provision for carrying away heat,

guard

Considerations in Designing a Friction Clutch

1. suitable material forming

2. moving parts -

3. not require any [ ] to maintain contact of the friction surfaces.

4. have

5. have [ ]

6. The projecting parts should be covered by [ ].

1. Disc or plate clutches

2. Cone clutches,

3. Centrifugal clutches

Types of Friction Clutches

1. single disc (Plate clutch)

2. multiple disc clutch

Types of Disc or plate Clutches

Disc or plate clutches

Consists of a clutch plate whose both sides are faced with a frictional material (usually of Ferrodo)

Disc or plate clutches

Clutch It is mounted on the hub which is free to move axially along the splines of the driven shaft.

multiple disc clutch

used when a large torque is to be transmitted.

Automobiles, motorcycles, trucks

Applications Disc clutches

Cone clutches

• was extensively used in automobiles, but now-a-days it has been replaced completely by the disc clutch.

• It consists of one pair of friction surface only.
  

sunk key

In a cone clutch, the driver is keyed to the driving shaft by a [ ] and has an inside conical surface or face which exactly fits into the outside conical surface of the driven.

Low-speed/high-torque (marine engines)

Applications Cone clutches

Centrifugal clutches

• usually incorporated into the motor pulleys

• consists of a number of shoes on the inside of a rim of the pulley.

• outer surface of the shoes are covered with a friction material
  
  
  

centrifugal clutches

uses centrifugal force to engage and disengage the clutch automatically. It has shoes or pads connected to the driving shaft, which press against the drum when the rotational speed increases.

scooters, small motorcycles, lawnmowers, go-karts, and chainsaws

Applications Centrifugal clutches

1.     Friction power

2.     Torque

3.     Axial force

4.     Spring deflection

5.     Coefficient of friction

6.     Max Pressure

In designing a plate clutch, you must determine this key factors: FTCASM

bearings

a machine element which support another moving machine element (known as journal).

Bearings

It permits a relative motion between the contact surfaces of the members, while carrying the load.

lubricant

In order to reduce frictional resistance and wear and in some cases to carry away the heat generated, a layer of fluid (known as [ ] ) may be provided

lubricant

used to separate the journal and bearing is usually a mineral oil refined from petroleum, but vegetable oils, silicon oils, greases etc., may be used.

1. direction of load to be supported

a. radial bearings

b. Thrust bearings

2. nature of contact

a. Sliding contact bearings

b. Rolling contact bearings

Classifications of Bearings

1. Depending upon the

2. Depending upon the

radial bearing

the load acts perpendicular to the direction of motion of the moving element.

thrust bearings

the load acts along the axis of rotation.

sliding contact bearings

the sliding takes place along the surfaces of contact between the moving element and the fixed element.

• are also known as plain bearings.
  

rolling contact bearings

steel balls or rollers, are interposed between the moving and fixed elements. The balls offer rolling friction at two points for each ball or roller.

full journal bearing
partial journal bearing.
fitted journal bearing

Types of Sliding Contact Bearings

slipper or guide bearings

The sliding contact bearings in which the sliding action is guided in a straight line and carrying radial loads
usually found in cross-head of steam engines.