Problems for Practice

PROBLEMS FOR PRACTICE

On Single Plate Clutch

1. A single plate clutch, with both sides effective, has outer and inner diameters 300 mm and 200 mm respectively. The maximum intensity of pressure at any point in the contact surface is not to exceed 0.1 N/mm2. If the coefficient of friction is 0.3, determine the power transmitted by a clutch at a speed 2500 rpm. 

[Ans. 61.69 kW]

2. A single plate clutch, both sides effective, and of 300 mm outside diameter and 100 mm inside diameter transmits power such that the maximum pressure on the plate is not to exceed 100 × 104 N/m2. Assuming uniform wear and coefficient of friction of 0.35, determine the maximum power that can be transmitted at 1500 rpm. Also determine the minimum intensity of pressure and its location.

 [Ans. 343.83 kW; 333 × 104 N/m2; 300 mm]

3. A single plate clutch, effective on both sides, is required to transmit 25 kW at 3000 rpm. Determine the outer and inner radii of frictional surface if the coefficient of friction is 0.255, the ratio of radii is 1.25 and the maximum pressure is not to exceed 0.1 N/mm2. Also determine the axial thrust to be provided by springs. Assume the theory of uniform wear.

 [Ans. 120 mm; 96 mm; 1447 N]

4. A single plate clutch with both sides effective, transmission is 10 kW. The maximum torque developed is 120 N.m. Axial pressure is not to exceed 100 kN/m2. Outer diameter of friction plate is 1.3 times the inner diameter. Determine the dimension of the plate and axial force exerted by the springs. Assume uniform wear and μ = 0.25.

[ Ans. 268.98 mm; 206.9 mm; 2.017 kW]

On Multiple Disc Clutch

5. A multiple disc clutch has five plates having four pairs of active friction surfaces. If the intensity of pressure is not to exceed 0.127 N/mm2, find the power transmitted at 500 rpm. The outer and inner radii of friction surfaces are 125 mm and 75 mm respectively. Assume uniform wear and μ = 0.3. μ 

[Ans. 18.8 kW] 

6. A multiplate clutch has six plates each of outer and inner diameters of 150 mm and 100 mm respectively. Assuming μ = 0.3 and uniform intensity of pressure of 30 × 104 N/m2. Determine the power transmitted at 1200 rpm. 

[Ans. 46.88 kW]

7. A multiple disc clutch has 5 plates having four active frictional surfaces. Determine the axial intensity of pressure between the disc transmitting 37.3 kW at 500 rpm. The inner and outer radii of friction surface are 75 mm and 125 mm respectively. Assume uniform wear and μ = 0.3. 

[Ans. 25.3 × 104 N/m2]

8. A multiplate friction clutch is required to transmit 89.52 kW at 3000 rpm. The plates are alternately of steel and phosphor bronze and they run in oil. The coefficient of friction is 0.08. The internal radius of the friction surface is 0.8 times the radius of the external surface. The axial pressure is limited to 20 × 104 N/m2. If the maximum diameter of the frictional surfaces is not to exceed 250 mm, determine the number of plates required.

[Ans. 10]

On Cone Clutch

9. Determine the axial force required to engage a cone clutch transmitting 25 kW of power at 750 rpm. Average friction diameter of the cone is 400 mm, semi-cone angle 10° and coefficient of friction is 0.25. 

[Ans. 103.27 mm; 94.73 mm]

10. A conical friction clutch is used to transmit 90 kW at 1500 rpm. The semi-cone angle is 20° and the coefficient of friction is 0.2. If the mean diameter of the bearing surface is 375 mm and the intensity of pressure is not to exceed is 0.25 N/mm2, find the dimensions of the conical bearing surface and the axial load required.

[Ans. 196.5 mm; 178.5 mm; 5045 N]

11. A leather faced conical clutch has a cone angle of 30°. If the intensity of pressure between the contact surfaces is limited to 6 × 104 N/m2 and the breadth of the conical surface is not to exceed one-third of the mean radius, find the dimensions of the contact surfaces to transmit 37 kW at 2000 rpm. Assume uniform rate of wear and take coefficient of friction as 0.2. 

[Ans. 202.6 mm; 185.78 mm; 64.73 mm]

12. Power is transmitted by a cone clutch of mean diameter 200 mm, face width 70 mm, and clutch angle of 15° (semi-cone angle). The coefficient of friction = 0.25. The normal pressure on the cone is not to exceed 20 × 104 N/m2. Calculate the maximum power transmitted at 750 rpm. Also determine the axial force required to hold the clutch. Assume uniform pressure. 

[Ans. 17.15 kW; 2.78 kN]

13. A cone clutch with cone angle 20° is to transmit 7.5 kW at 750 rpm. The normal intensity of pressure between the contact faces is not to exceed 0.12 N/mm2. The coefficient of friction is 0.2. If face width is 1/5th of mean diameter, find (i) the main dimensions of the clutch, and (ii) axial force required while running.

[Ans. b = 46.8 mm; r1 = 125 mm; r2 = 109 mm; 1395 N]

14. A cone clutch is used for transmitting a torque of 3 × 105 N.mm. The mean diameter is 200 mm and the semi-cone angle is 12°3'. The coefficient of friction is 0.25 and the normal pressure at the mean radius must not exceed 1.4 × 105 N/m2. Calculate the necessary width of the contact surface. Also find the actual force needed to hold the clutch surface together. 

[Ans. 136 mm; 5478 N]

15. The semicone angle of a cone clutch is 12.5° and the contact surfaces have a mean diameter of 80 mm. Coefficient of friction is 0.32. What is the minimum torque required to produce slipping of the clutch for an axial force of 200 N?

If the clutch is used to connect an electric motor with a stationary flywheel, what is the time needed to attain the full speed and the energy lost during slipping? Motor speed is 900 rpm and the moment of inertia of the flywheel is 0.4 kg.m2.

[Ans. 11.83 N.m; 31.19 s; 1777 N.m]