DISK CLUTCH

Classification: GENERAL
 DISK CLUTCH
A clutch is a machine member 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. The use of a clutch is mostly found
in automobiles. A little consideration will show that in order to change gears or to stop the vehicle, it is
required that the driven shaft should stop, but the engine should continue to run. It is, therefore,
necessary that the driven shaft should be disengaged from the driving shaft. The engagement and
disengagement of the shafts is obtained by means of a clutch which is operated by a lever.
Types of Clutches
Following are the two main types of clutches commonly used in engineering practice

1. Positive clutches, and 2. Friction clutches.

Positive Clutches
The positive clutches are used when a positive drive is required. The simplest type of a positive clutch is a jaw or
claw clutch. The jaw clutch permits one shaft to drive another through a direct contact of interlocking jaws. It consists
of two halves, one of which is permanently fastened to the driving shaft by a sunk key. 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 feather key. The jaws of the clutch may be of square type or of spiral type

Classification: GENERAL
 DISK CLUTCH

Friction Clutches
A friction clutch has its principal application in the transmission of power of shafts and machines which must be started and
stopped frequently. Its application is also found in cases in which power is to be delivered to machines partially or fully loaded.
The 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. In automobiles, friction clutch is 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. The
proper alignment of the bearing must be maintained and it should be located as close to the clutch as possible. It may be noted that
:
1. The contact surfaces should develop a frictional force that may pick up and hold the load with reasonably low pressure between
the contact surfaces.
2. The heat of friction should be rapidly *dissipated and tendency to grab should be at a minimum.
3. The surfaces should be backed by a material stiff enough to ensure a reasonably uniform distribution of pressure.
 DISK CLUTCH
Material for Friction Surfaces
The material used for lining of friction surfaces of a clutch should have the following
characteristics :
Did you know?

During operation of a clutch, most of the work done against frictional forces opposing the motion is liberated as heat at the
interface. It has been found that at the actual point of contact, the temperature as high as 1000°C is reached for a very short
duration (i.e. for 0.0001 second). Due to this, the temperature of the contact surfaces will increase and may destroy the clutch.

1. It should have a high and uniform coefficient of friction.

2. It should not be affected by moisture and oil.
3. It should have the ability to withstand high temperatures caused by slippage.
4. It should have high heat conductivity.
5. It should have high resistance to wear and scoring
Properties of materials commonly used for lining of friction surfaces.
Types of Friction Clutches
Though there are many types of friction clutches, yet the following are important from the
subject point of view :
1. Disc or plate clutches (single disc or multiple disc clutch),
2. Cone clutches, and
3. Centrifugal clutches.
Note : The disc and cone clutches are known as axial friction clutches, while the centrifugal clutch is called radial friction clutch
 DISK CLUTCH
Design of a Disc or Plate Clutch

1. Considering uniform pressure. When the pressure

is uniformly distributed over the entire area of the
friction face
𝐹 𝑊
𝑃= ↔ 𝑃=
𝐴 𝜋 (𝑟 − 𝑟 )
Single disc or plate clutch
Number of pairs of contact surfaces,
For a single disc or plate clutch, normally both sides of the disc are effective. 𝑇 = 𝜇𝑥𝐹𝑥𝑟 𝑥𝑛
Therefore a single disc clutch has two pairs of surfaces in contact (i.e. n = 2) n = n1 + n2 – 1
 DISC CLUTCH
UNIFORM PRESSURE (NEW) UNIFORM WEAR (OLD)
𝑇 = 𝜇𝑥𝐹𝑥𝑟 𝑥𝑛
2 𝑟 −𝑟 1
𝑟 = 𝑟 = (𝑟 + 𝑟 )
3 𝑟 −𝑟 2
Mean Friction Radius 1 𝑑 −𝑑
𝑟 = 1
3 𝑑 −𝑑 𝑟 = (𝑑 + 𝑑 )
4
𝐹 𝐹 = P ∗ π ∗ (𝑟 −𝑟 ) 𝐹 = C ∗ 2π ∗ (𝑟 − 𝑟 )
𝑇 = μ ∗ 𝐹 ∗ 𝑟 ∗ (n) 𝑇 = πμ ∗ 𝐶 ∗ (𝑟 − 𝑟 )

TORQUE 2π π 𝑪 = 𝑷𝒎𝒂𝒙 ∗ 𝒓𝟐
𝑇 = μ ∗ 𝐹 ∗ (𝑟 − 𝑟 ) ∗ (n) 𝑇 = ∗ μ ∗ 𝐶 ∗ (𝑑 − 𝑑 ) (use)
3 4
𝐶= 𝑃 ∗𝑟
𝑃 = 2π ∗ 𝑇 ∗ N 𝑃 = 2π ∗ 𝑇 ∗ N
𝐶 = 𝑃 ∗𝑟
POWER 4π 𝑃 = 2π ∗ C ∗ μ ∗ (𝑟 − 𝑟 ) ∗ N ∗ n
𝑃= ∗ μ ∗ (𝑟 − 𝑟 ) ∗ N ∗ n
3
π
π 𝑃= ∗ C ∗ μ ∗ (𝑑 − 𝑑 ) ∗ N ∗ n
2
𝑃= ∗ μ ∗ (𝑑 − 𝑑 ) ∗ N ∗ n
6
CONE CLUTCH
CONE CLUTCH
 CONE CLUTCH
UNIFORM PRESSURE (NEW) UNIFORM WEAR (OLD)
𝑇 = 𝜇𝑥𝐹𝑥𝑟 𝑥𝑛
2 𝑟 −𝑟 1
𝑟 = 𝑟 = (𝑟 + 𝑟 )
3 𝑟 −𝑟 2
Mean Friction Radius 1 𝑑 −𝑑
𝑟 = 1
3 𝑑 −𝑑 𝑟 = (𝑑 + 𝑑 )
4
𝐹 𝐹 = P ∗ π ∗ (𝑟 −𝑟 ) 𝐹 = C ∗ 2π ∗ (𝑟 − 𝑟 )
𝑇 = μ ∗ 𝐹 ∗ 𝑟 ∗ (n) 𝑇 = πμ ∗ 𝐶 ∗ (𝑟 − 𝑟 )
𝑪 = 𝑷𝒎𝒂𝒙 ∗ 𝒓𝟐
TORQUE 2π π (use)
μ 𝑇 = ∗ μ ∗ 𝐶 ∗ (𝑑 − 𝑑 )
𝑇 = 3 ∗ (𝑟 − 𝑟 ) ∗ (n) 4Sin θ 𝐶= 𝑃 ∗𝑟
Sin θ
𝐶 = 𝑃 ∗𝑟
𝑃 = 2π ∗ 𝑇 ∗ N 𝑃 = 2π ∗ 𝑇 ∗ N

4π 𝑃 = 2π ∗ C ∗ μ ∗ (𝑟 − 𝑟 ) ∗ N ∗ n
𝑃= ∗ μ ∗ (𝑟 − 𝑟 ) ∗ N ∗ n
3Sin θ
POWER π
𝑃= ∗ C ∗ μ ∗ (𝑑 − 𝑑 ) ∗ N ∗ n
π 2Sin θ
𝑃= ∗ μ ∗ (𝑑 − 𝑑 ) ∗ N ∗ n
6Sin θ
 PROBLEM IN CLUTCH
1. Determine the maximum, minimum and average pressure in a plate clutch when the axial force is 5 kN. The
inside radius of the contact surface is 60 mm and the outside radius is 120 mm. Assume uniform wear

2. A plate clutch having a single driving plate with contact surfaces on each side is required to transmit 120 kW
at 1300 rpm. The outer diameter of the contact surfaces is to be 300 mm. The coefficient of friction is 0.4.

(a) Assuming a uniform pressure of 0.20 N/mm2; determine the inner diameter of the friction surfaces.

(b) Assuming the same dimensions and the same total axial thrust, determine the maximum torque that can be
transmitted and the maximum intensity of pressure when uniform wear conditions have been reached

3. A tesla diesel engine develops 170 PS at 1800 rpm with a single plate with three pairs of friction surfaces
transmitting the power and outside diameter of 300mm and face width of 30mm. Determine the inside diameter,
axial force, coefficient of friction if the uniform pressure is 0.16 N/mm2

4. A cone clutch is integrated inside the flywheel of an engine that produces 50 horsepower at 1200 rpm. The
cone has a face angle of 12° and a maximum diameter of 15 inches. The coefficient of friction is 0.3. The typical
pressure on the clutch face should not exceed 13 psi. Determine the face width necessary and the axial spring
force necessary to engage the clutch.