periphery by means of a heavy spring connected in such a way that it is restrained from end movement by a suitable means of fastening to the crankshaft. As long as the spring keeps the clutch cone in contact with the flywheel and the spring is permitted to exert its full pressure, the clutch cone and flywheel are firmly locked together to form practically a rigid coupling. When it is desired to release the clutch a shifting yoke carrying clutch release rolls is

Fig. 144.-Cone Clutch Used on Pope-Hartford Motor Cars.

adapted to bear against an upstanding flange attached to the clutch cone and to pull the cone out of engagement with the motor flywheel by compressing the clutch spring.

The form of cone clutch shown at Fig. 145 is known as the inverted type because the clutch cone is held in contact by a spring pushing the cone away from the flywheel and having an inverted taper so that the more the cone is pushed away from the flywheel

the greater will be its degree of frictional adhesion with the applied ring that serves as a female clutch member. To release a clutch of this type it is necessary to push the cone toward the flywheel, while in the forms shown at Fig. 144 it is necessary to pull the clutch cone away from the flywheel.

Q. What is the female member, and how is it made?

A. The female member of a cone clutch is usually the driving portion and is made of cast iron, either in the form of an applied ring machined with an internal taper, as shown at Fig. 145, or it may be integral with the motor flywheel as is common practice. When the inverted type of clutch is used, it is necessary to bolt the female member in place to the flywheel, as shown at Fig. 145.

Q. What is the cone made of? A. The clutch cone is usually a light aluminum casting or a sheet steel stamping.

Q. What is the angle of the Fig. 145.-Simple Inverted Cone cone taper and why? Clutch of Foreign Design.

A. The usual angle employed for clutch cone is twelve and onehalf degrees and this is used because it is the least that can be utilized and have a clutch that will release promptly and yet not require excessive spring pressure to keep the parts in contact when transmitting power. More gradual tapers are apt to produce wedging and make it difficult to release the clutch promptly, while more abrupt tapers will cause the clutch to slip, unless the parts are held together by considerable spring pressure.

Q. Why is it desirable to make the cone as light as possible? A. The clutch cone is usually made light so that it will not spin

or rotate appreciably after it has been released from the driving member. The heavier the clutch cone, the greater will be its inertia or tendency to revolve, due to the power stored in its rim.

Q. What materials are used to face the clutch cone with? A. The clutch cone is usually faced with a good grade of oak tanned sole leather though in some cases asbestos fabrics have been used with success. In some constructions the cone is of metal, studded with cork inserts, though as a rule the cone is faced with leather even if cork inserts are used. Materials are used for facings that are not likely to be affected by oil or heat and that have a high coefficient of friction with cast iron of which the female member is invariably composed.

Q. What does "coefficient of friction" mean?

A. The "coefficient of friction" is a term used to indicate the amount of frictional adhesion various materials have for each other under similar conditions of pressure.

Q. Name the "coefficient of friction" of various surfaces in

contact.

A. A table of triction coefficient of various materials compiled from tests made by the Cork Insert Co. follows:

The coefficient will vary with condition of the contacting surface. Smooth and hard surfaces offer less resistance than rough and yielding ones. In metal to metal clutches different materials are usually employed for the opposing surfaces such as bronze and steel

in multiple disc clutches or cast iron or bronze and steel in three plate types. A coefficient of friction of 0.10 means that the adhesion between the surfaces will be 10% of the total pressure producing frictional contact. Therefore, a combination leather and cork friction facing acting against dry cast iron, as in a cone clutch, and having a coefficient of 0.35 will adhere to the member against which it contacts with a force equal to about of that keeping the surfaces in contact.

Q. How is clutch cone kept in contact with female member? A. The clutch cone in practically all cases is held in engagement with the female member by the pressure of one or more coil springs. In some constructions the clutch cone is brought into engagement by means of levers actuated by some member that can be locked in place to hold the parts in contact until released.

Q. What is the function of the ball thrust bearing?

A. As will be observed by referring to Figs. 143 to 145 in no case is the spring pressure applied directly to the clutch cone and a ball thrust bearing is always interposed to take the spring thrust against the cone. This is used in order to permit the parts to operate independently of each other when the clutch cone is moved so the spring is compressed. The ball thrust bearing has so little friction that the full spring pressure may be exerted against it without causing rotation of the cone when that member is out of engagement with the flywheel rim. If no ball thrust bearing was used when the clutch cone was pushed away from the female member, the spring in contact with the driving member would tend to impart its rotary motion to the clutch cone and keep it turning when it is desirable to have it stop when released.

Q. What are the advantages of the cone clutch?

A. The cone clutch is a very simple form that is easy to operate and understand. When properly designed it will transmit the entire power of the motor to which it is applied without slipping and it can be made to release promptly and to engage gradually if desired.

Q. What is the main disadvantage of a cone clutch?

A. Owing to the mass of the clutch cone and its leather facing

there is a tendency for the cone to continue to rotate when released from driving engagement with the flywheel. The rim of even the lightest cone and its leather facing have appreciable weight, and while this is not much it is carried at a sufficiently large radius. from the center so the cone has considerable momentum and acts, to some extent, as a flywheel. This continued rotation is called "spinning" and is objectionable, because it makes gear shifting difficult.

Fig. 146.-Showing Construction of Clutch Cone Brake Used on Pope-Hartford Cars.

Q. How is "spinning" prevented?

A.

Continued rotation of the clutch cone is easily prevented by applying some form of braking member which will come in contact with the revolving cone after it has been pulled clear of the flywheel. A simple clutch brake is shown at Fig. 146. The friction pad A is carried by the clutch shifter yoke B in such a way that it comes in contact with the clutch cone only when this has been withdrawn a certain distance by the yoke F and the rolls G, as previously described. Suitable adjustments are provided at C, D, and E, so