unit – 1 rolling contact bearing...unit – ii design of shafts, keys & coupling q.3 a) theory...

UNIT – 2 DESIGN OF SHAFT,KEYS &

COUPLING

FUNCTION OF KEYs: i) The primary function of the key is to transmit the torque from the shaft to the hub of the mating element and vice versa. (ii) The second function of the key is to prevent relative rotational motion between the shaft & the joined machine element like gear or pulley.

Introduction of Keys

• Keys A key can be defined as a machine element which is used to connect the transmission shaft to rotating machine elements like pulleys, gears, sprockets or flywheels.

Classification of keys

1. Sunk key

2. Saddle keys

3. Tangent key

4. Kennedy keys

5. Round key & taper pins

6. Splines

• Sunk keys: This key provided in the half in the keyway of the shaft & half in the keyway of the hub or boss of the rotating elements.

Types of sunk key

1. Rectangular key

2. Square key

3. Parallel key

4. Gib headed key

5. feather key

6. woodruff key

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1.Rectangular sunk key

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2. Square key

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The only difference between a rectangular sunk key and a square sunk key is that its width and thickness are equal, i.e.

3. Gib-head Key

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4. Feather key: it prevents relative rotary motion, but permit the relative motion between the shaft & hub.

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5. Woodruff key: Woodruff key used in machine tools & automobiles.

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4. Tangent Key

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Kennedy key: This key has two tapered square keys placed 900 apart it is used in heavy duty application.

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5. Round Key

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6. Splines / Axial key

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Advantages : 1 Uniform transfer of torque 2 Lower loading on elements 3 No relative motion between “key” and shaft 4 Axial motion can be accommodated (can cause fretting and corrosion) 5 Mating element can be indexed with a spline

Design of Rectangular sunk key

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1

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2

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COUPLING

Function of coupling

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1. Couplings are used to connect two shafts for torque transmission in different applications. It may be to connect two units such as a motor and a generator.

2. To reduce the transmission of vibrations & shocks between to connected shafts.

Types of coupling

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1. Muff or sleeve or box coupling 2. Protected Type Flange coupling 3. Unprotected Type Flange coupling 4. Bush Pin Type Flexible coupling

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Oldham's Coupling

Universal Coupling

Deference between Rigid coupling &

Flexible coupling

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Sr. No.

Rigid coupling

Flexible coupling

1. It is used only when there is perfect alignment between axes of 2 shaft.

It is also used when misalignment between axes of 2 shaft.

2. It is also used when motion is free from vibration & shocks.

If vibration & shocks is present this coupling is used.

3. No use of flexible elements. Flexible elements like rubber bush is used.

4. It cannot tolerate such misalignment. It can tolerate 0.5mm of lateral or axial misalignment & 1.5 degree of angular misalignment.

5. Cost is less. Cost is more.

6. E.g. Muff coupling, Protected & unprotected type rigid flange coupling.

E.g. Universal coupling, oldham coupling, & Flexible bush-pin type coupling.

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F L A N G E

C O U P L I N G

P R O T E C T ED

TYP E

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F L E X I B L E

C O U P L I N G

BUSH

PIN

TYP E

In-Sem Exam Structure

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UNIT – I : Design of Simple Machine Elements

Q.1 a) Theory 04 Mark

b) Theory or Numerical 06 Mark

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Q.2 Numerical or sometime derivation 10 Mark

UNIT – II Design of Shafts, Keys & Coupling



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UNIT – III Design for Fluctuating Load



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TOTAL

30 Mark

unit – 1 rolling contact bearing...unit – ii design of shafts, keys & coupling q.3 a) theory...

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