1. EMD223 Machine Component Design Dr. Mohamad Yusof Idroas Email: meyusof@eng.usm.mymeyusof@eng.usm.my Room: 3.10 (SoME) EMD223 Machine Component Design Dr. Mohamad Yusof Idroas Email: meyusof@eng.usm.mymeyusof@eng.usm.my Room: 3.10 (SoME)

2. EMD223 Lecture Notes You can copy from PCs of MEK1 & MEK2

5. Clutches, Brakes & Flywheels

6. Introduction Clutches, brakes, couplings & flywheels have SIMILAR function: To store and/or transfer rotating energy. Unlike bearings, cams or gears, clutches & brakes depend on friction in order to function. (a) (b) Figure 1: (a) Industrial clutch/brake (b) Cross-section of permanent magnet clutch/brake Source: http://www.precisiontork.com/permmagnet/gallery/permanentmagnet.htmlhttp://www.precisiontork.com/permmagnet/gallery/permanentmagnet.html

7. Introduction Various types of flywheel available with various applications. (a) (b) (c) Figure 2: (a) Spoke flywheel for steam engine (b) Spoke flywheel for Stirling engine (c) Webbed disk flywheel for Stirling engine Sources: http://www.good-win-racing.com/Mazda-Performance-Part/61-1027.html http://www.sioloon.com/f96p400-chasis-and-engine

8. Introduction Various types of flywheel available with various applications. (a) (b) Figure 3: (a) Webbed disk flywheel for F1 race car (b) Webbed disk flywheel for Perodua Kancil

9. Work Mechanism How a clutch/brake works? Clutches are employed in devices which have TWO rotating shafts. One shaft is typically attached to a motor or other power unit (driving shaft) while the other shaft provides output power for work to be done (driven shaft). Brakes act similarly except that one of the member/shaft is fixed. In a drill for instance, one shaft is driven by a motor and the other drives a drill chuck. The clutch connects the two shafts so that they may be locked together and spin at the same speed (engaged), locked together but spinning at different speeds (slipping), or unlocked and spinning at different speeds (disengaged).drill

10. Figure 4 shows a simple disk clutch with one driving & one driven shaft. Driving friction between the two develops when they are forced together. Figure 4: Basic disk clutch Work Mechanism

11. Real applications of clutch work principle in automotive. Figure 5: Automotive-type disk clutch, operating dry. (Courtesy Borg-Warner Corporation) Work Mechanism Two sides of the clutch plate are DRIVEN SURFACES Two DRIVING SURFACES from flywheel & pressure plate

12. Most multiple-disk clutches are operating wet (in oil). The oil serves an effective coolant during clutch engagement and the use of multiple disks compensate for the reduced coefficient of friction. Figure 6: Multiple-disk clutch, operating wet Work Mechanism

13. Figure 7 shows a hydraulically actuated caliper disk brake with a ventilated disk (air circulation through interior passages) for additional cooling. Figure 7: Caliper disk brake, hydraulically operated. (Courtesy Auto Specialities Manufacturing Company) Work Mechanism

14. Dynamic representation of a friction clutch or brake: Figure 8: Dynamic representation of a clutch or brake Two inertias, I 1 and I 2 traveling at respective angular speeds, w 1 and w 2. The driven shaft is to be brought to the same speed by the driving shaft. Analysis of clutch/brake performance will consider: - Actuating force - Torque transmitted - Energy loss - Temperature rise etc. Work Mechanism

15. Mathematical representation of a flywheel: Figure 9: Mathematical representation of a flywheel An input torque T i, corresponding to coordinate i, will cause the flywheel speed increase. A load or output torque T o, with coordinate o, will absorb energy from the flywheel and cause the speed to slow down. Flywheels are designed as such to obtain a specific amount of speed regulation. Work Mechanism

16. Design Analysis Design equations relating critical parameters such as clutch size ( r i, r o ), friction coefficient ( f ), torque capacity ( T ), axial clamping force ( F ), interface pressure ( p ) and no. of friction interfaces ( N ): Refer to R.C. Juvinall book for the derivation of the above design eqns. The derivation is based on critical assumptions such as uniform distribution of interface pressure (for unworn or new clutch) and/or uniform rate of wear at interface (for worn clutch).

17. Design Analysis A parameter in the design of clutches is the ratio of inside to outside radius. Refer to R.C. Juvinall book for the derivation of the above design eqn. The derivation is based on critical assumptions such as uniform distribution of interface pressure (for unworn or new clutch) and/or uniform rate of wear at interface (for worn clutch).

18. Design Analysis Table 1: Representative Properties of Friction Materials, Operating Dry

19. Design Analysis Table 2: Representative Values of Friction Coefficient for Friction Materials Operating in Oil

20. Group Exercise A multiple-disk wet clutch is to be designed for transmitting a torque of 85 N.m. Space restriction limit the outside disk diameter to 100 mm. Design values for the molded friction material and steel disks to be used are f = 0.06 (wet) and p max = 1400 kPa. Determine: (i)The disk inside diameter ( d i ) (ii)The total number of friction interfaces ( N ) (iii)The clamping force ( F )

21. Group Exercise Hint: The total number of friction interface ( N ) must be designed in an EVEN integer. Thus, N which is determined from the following equation must be reset to the nearest EVEN integer.

22. Group Exercise Hint: Possible alternatives: accept the overdesign factor resizing r i and r o Maintain radii ( r i and r o ) but varying p max and F by the factor of overdesign

23. Thank You