Clutch Construction

CONSTRUCTION

The main parts of the clutch are the driving members, the driven members, and the operating members.

The driving members are attached to the engine crankshaft and turn with it. They usually consist of two cast-iron plates or flat surfaces machined and ground to a smooth finish. Cast iron is used because it contains enough graphite to provide some lubrication when the driving member is slipping during clutch engagement. One of these surfaces is usually the rear face of the engine flywheel. The other is a heavy, flat ring, one side of which has a machined surface. This part is known as the pressure plate, which is fitted into a steel cover and contains some of the operating members. It is bolted to the flywheel. We will discuss the operating members contained in this assembly later in the lesson.

The driven member is attached to and turns with the transmission input or clutch shaft, also called the main drive pinion. It is a disk with a splined hub and is free to slide on the splines of the shaft, but it drives the shaft through these same splines. The driven member may be called a clutch plate or a clutch disk. We will call it a clutch disk to keep from confusing it with the pressure plate.

The clutch disk is usually made of spring steel in the shape of a single flat disk or a number of flat segments. Facings are attached to each side of the disk by means of copper rivets. These facings must be able to withstand the heat produced by friction when the clutch is slipping. The most commonly used facings are made of cotton and asbestos fibers woven or molded together and impregnated with a binding agent. Very often, copper wires are woven or pressed into the material to give it more strength.

To make clutch engagement as smooth as possible and eliminate chatter, several methods have been used to give a little flexibility to the driven disk. One type of disk is "dished" so that the inner and outer edges of the facing make contact with the driving members first, and the rest of the facing makes contact gradually as the pressure on the disk increases and the disk flattens out. In another type, the steel segments attached to the splined hub are slightly twisted, which also causes the facings to make gradual contact as the disk flattens out.

The driven member of the clutch usually has a flexible center to absorb the vibrations caused by the crankshaft, which would be sent through the drive assembly unless they were eliminated. The flexible center is usually made up of steel springs placed between the hub and the steel disk. The springs permit the disk to momentarily turn faster or slower than its hub. At times, the springs may be fully compressed; the disk then returns to its original position when the spring decompresses. This slight backward and forward movement, permitted by the spring, allows the clutch shaft to turn at a more steady rate than the crankshaft. This reduces some of the vibration and results in a smoother power flow.
The operating members consist of the components required to apply and release the pressure which holds the driving and driven members in contact with each other; they include such things as springs, linkage, levers, bearings, and so forth, depending on the type of clutch.

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Article Pages
1. Drive Train Intro
2. Principles Of Torque
3. Fundamentals Of Gears
4. Types Of Gears
5. Gear Principles
6. Principle Of Gear Ratios
7. Principle Of Torque Ratios
8. Operation Of A Gear Train
9. The Construction And Operation Of A Planetary Gearset
10. Operating Principles Of A Planetary Gearset
11. Why Clutches Are Needed
12. Clutch Construction
13. Types Of Clutches
14. Clutch Operation
15. Clutch Maintenance
16. Introduction To Manual Transmissions
17. Types Of Manual Transmissions
18. Manual Transmission Construction
19. Manual Transmission Operation
20. The Powerflow In Manual Transmissions
21. Manual Transmission Lubrication
22. Manual Transmission Ventilation
23. Constant Mesh Transmissions
24. Synchromesh Transmissions
25. Power Take-Offs
26. Power Take-Offs Construction And Operation
27. Input Gear, Output Shaft and Shifter Fork
28. Inspecting The Transmission
29. Leaking Lubricants In A Manual Transmission
30. Leaking Seals In A Manual Transmission
31. Testing Transmissions For Malfunctions
32. Power Take-Off Inspecting And Testing
33. Automatic Transmission Introduction
34. Automatic Transmission Fundamentals
35. Drive Train Mechanisms
36. Drive Train Operation
37. The Drive Train Arrangements Of The Automatic Transmission
38. Simpson Drive Train
39. Hydraulic System Of The Automatic Transmission
40. Hydraulic Supply System
41. Torque Converter Feed Circuit
42. Range Control System
43. Vehicle Speed Versus Engine Loading
44. Transfer Case
45. Transfer Operation
46. The Construction And Operation Of Sprag Units

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