The very fact that the clutch is a more or less flexible - or rather, variable - connection between engine and road wheels makes it necessary that it be kept in the best of shape. It is rather surprising to the novice, with his first clutch trouble, to have his motor racing at the highest possible speed, and to find his car barely moving, but to the experienced driver it is humiliating.
Slipping is the most common of clutch troubles. This is brought about in a cone clutch by oil, grease, or other slippery matter on the surface of the clutch, and can often be cured temporarily by throwing sand, dirt, or other matter on the clutch surface, although this is not recommended. Many times, the clutch leather or facing becomes so glazed that it slips without any oil or grease on it. In that case it is desirable to roughen the surface by taking the clutch out, cleaning the surface with kerosene and gasoline, and then roughing up the surface with a file or other similar tool.
In case it is not desired to take the clutch out, or when it is very inaccessible, the clutch surface may be roughened by fastening the clutch pedal in its extreme out position with some kind of a stick, cord, or wire, and then roughing the surface, as far in as it can be reached, with the end of a small saw, preferably of the keyhole type, about as shown in Fig. 66. Before starting this repair, it is well to soak the leather with neatsfoot oil, pouring this in the night before and allowing the leather to soak up as much of it as it will. This softens the leather and makes the roughening task lighter.
Many drivers make the mistake of driving with the foot constantly on the clutch pedal. This wears the leather surface and helps it to glaze quickly. The constant rubbing, due to slipping it frequently, also makes the leather hard and dry.
When a metal to metal, oiled clutch slips, the trouble usually is in the clutch spring which is too weak to hold the plates together. To remedy slipping with this type then, it is necessary to tighten up on the clutch spring adjustment.
Clutch troubles are not always so obvious. In one instance, the clutch slipped on a new car. In the shop, the clutch spider seemed perfect, also the spring, and properly adjusted, but to make sure, a new clutch was put in. Still the clutch slipped. To test it out still further, the linkage was disconnected right at the clutch and then it held perfectly, showing that the trouble was in the linkage. On examination one bushing was found to be such a tight fit that it would not allow the pedal to move freely enough to release fully. When this was relieved a little, the clutch acted all right.
Clutch springs, like valve springs, mentioned previously, are mean to handle and compress, the best way being to compress and hold them that way until needed. For this purpose, a rig similar to that described for valve springs should be made but of stiffer, stronger stock. A very good one can be made from two round plates, one small, and the other of larger diameter with a pair of L-shaped bolts through it. The spring is placed between the two with the ends of the L's looped over the smaller plate, and then, by tightening the nuts on the bolts, the spring is gradually compressed.
Fig. 66. Method of Roughing-Up Clutch Leather with Saw.
A "fierce" clutch is one that does not take hold gradually, but grabs the moment the clutch pedal is released. In a metal disk clutch, this is caused by roughened plate surfaces and insufficient lubricant, so that instead of the plates twisting gradually across one another as the lubricant is squeezed out from between them, they catch at once and the car starts with a jerk. On a cone clutch, this fierceness is produced by too strong a spring, too large a clutching surface in combination with a very strong spring, or a hard or burned clutch surface, or both.
There are now so many Fords in use that the average repair man feels justified in making special apparatus or tools to save time or work in Ford repairs. For one thing, the clutch disk drum frequently needs removal and this is a difficult job. By means of a simple rigging, however, consisting of a plate and a few bolts, it can be taken off in a few moments and with little trouble. It will be noted from Fig. 67 that the rigging is but a modified form of wheel puller. It consists of a ¼-inch plate of steel with three holes drilled in it for three bolts. The two outside ones have T-head ends and have to be specially made, and made carefully, as this T-head must slip through either one of the oval holes in the web of the drum. When this is done, it is straightened up so as to stand at right angles to the drum and is thus in a position to press firmly against the drum from the inside. There are nuts on the center bolt on both sides of the. plate, the drawing showing only that on the outer end. When the T-bolts are in place, the center bolt, which is slightly pointed and preferably hardened on the end, is screwed down so as to come into contact with the end of the clutch shaft. After tightening this, the T-head bolts are tightened until they pull the drum off the shaft.
Fig. 67. Simple Rigging for Removing Ford Clutch Disk.
A trouble which is bothersome but not dangerous is clutch spinning. This is the name applied to the action of the male clutch member when it continues to rotate or spin after the clutch spring pressure has been released. With the male member connected up to the principal transmission shaft and gear, as is often the case, these members continue to rotate with it. This gives trouble mainly in gear shifting, for the member which is out of engagement is considered to be at rest or rapidly approaching that condition. When at rest, it is an easy matter to mesh another gear with this one; but when this one is rotating or spinning, it is not so easy, particularly for the novice.
Clutch spinning may be caused (1) by a defect in the design, in which case little can be done with it; (2) by a defect in construction - as in balancing, for instance, which can be corrected; or (3) it may be due to external causes, as for instance a bearing which has seized, due to a lack of lubricant, etc.
In any case, the best and quickest remedy is a form of clutch spinning brake. This may consist simply of a small pad of leather, or metal covered with leather, so located on the frame members that the male drum touches against it when fully released. Or it may be something more elaborate as to size or construction, or both. On many modern cars, in fact on practically all good cars, some form of clutch spinning brake is fitted. Thus in Figs. 50 and 60, metal cones of small diameter are provided; in Fig. 51 is found something similar with two V-grooves; while Figs. 56 and 59 show flat concentric disks.