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LESSON TWENTY-FOUR

WHEELS, RIMS AND TIRES

Q. What types of wheels are used for automobiles?

A. Automobile wheels may be divided into two main classifications, those made of wood and the forms composed entirely of metal. Wooden wheels are generally of the artillery type, while metal wheels may be any one of four different forms. The most common metal wheel construction is the wire spoked form similar in appearance to those used on bicycles and motorcycles. Other forms are composed of two metal discs riveted to the hub at the center portion and together at the rim. There is another method of metal wheel construction patterned after the artillery wooden wheel excepting that it is made up of tubing and channel sections brazed together to form the complete assembly. A form of metal wheel that is receiving some application in heavy vehicle service is composed of a large steel casting, having fewer spokes than the usual artillery wheels. These spokes are cast with flanges or ribs which act as a reinforcement and the wheel is a very substantial member. Q. Describe construction of artillery wheel.

A. The wooden portions of an efficient form of artillery wheel used for pleasure cars are clearly shown at Fig. 209. The spokes, which are made of hickory, are joined together at the central part of the wheel by a series of interlocking mortise and tenon joints which form a very strong assembly and they are inserted into holes in a wooden felloe at their outer ends. The complete artillery wheel with metal hub and rim in place is shown at Fig. 210, while the two forms outlined at Fig. 211 show clearly the method of holding the lower end of the spoke securely between the main hub casting and the metal flange which acts as a clamping member. The main casting serves as a housing for the bearings on which the wheel revolves.

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Fig. 209.-Wooden Parts of Typi- Fig. 210.-Heavy Artillery Wheel cal Artillery Wheel for Motor Trucks.

The wheel shown at A, Fig. 211, is a lighter form than that outlined at B and is intended for application on the front axle of a motor truck. The heavier and stronger wheel with sprocket and brake drum attached is one of the traction members that revolve on the rear axle. The rubber tires with which these wheels are provided are not shown in this view but the appearance of a complete wheel with sectional block tires and retaining flanges in place is clearly depicted at Fig. 210.

Q. Describe a typical cast-steel wheel for motor trucks.

A. Heavy cast-steel wheels intended for use on a large motor truck of German design are shown at Fig. 210-a. That at A is a front wheel and is fitted with a single tire. That at B is a rear wheel with rim of sufficient width to take two solid rubber tires side by side. The wheel construction consists of a steel casting having cored spokes and rim to give it lightness, provided with a plain bearing hub. The construction of the front and rear wheels is similar except that the hollow rim and spokes of the latter are of larger size and the spokes are provided with bosses through which the

bolts holding the driving sprocket and brake drum in place are secured. The use of plain bearings is not general on American motor trucks on account of the friction present when the wheels are heavily loaded. Plain bearings are suitable only where truck speeds are very low and the motor has a margin of power over the actual requirements.

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Fig. 210A.-Motor Truck Wheels of German Design Made by Steel Casting Process.

Q. Outline construction of wire spoke wheels and state their advantages.

A. A tangent spoke wire wheel adapted for automobile use complete with tire is shown at Fig. 212, while the various methods of wire wheel construction in vogue are outlined at Figs. 213, 214, and 215. Wire wheels may be of either the double or triple spoke construction as indicated at A, Fig. 213. The double spoke type follows lines that have been established as standard in bicycle and motorcycle construction and differs but slightly from the wheels used on the lighter vehicles except in the matter of structural strength of the components. The triple spoke construction has been devel

oped especially with the requirements of the heavier forms of selfpropelled vehicles in mind and is stronger than the form having a lesser number of spokes.

The spokes are similar in construction to those used in bicycle wheels but are much stronger and made of higher grade material

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Fig. 211.-Part Sectional View of Heavy Artillery Wheels Used on Packard Trucks.

on account of the severe duties they perform. The spoke is provided at the lower end with a button head to keep it from pulling through the hole in the hub when it is tightened by the threaded nipple at the upper end passing through and having a head which bears against the rim. After the spokes of a wire wheel are in place all the nipples are screwed up so that the tension on practically all

the spokes is as nearly the same as it is possible to obtain and have the wheel run true. The method by which the upper end of the spoke is attached to the rim is clearly outlined at Fig. 213-B.

The construction depicted at Fig. 214 is the Rudge-Whitworth wire wheel fitted with the Houk quick detachable rim. The wheel is of English design and is widely used abroad. It is of the triple spoke pattern and is made so it can be removed easily from the inner hub casting in which the bearings are carried. The hub shell to which the spokes are fastened is held in place by means of a substantial locking nut F which keeps the serrations in the hub members firmly together to insure that the two parts B and E will turn as a

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unit when the lock nut F is tight

Wheel.

Wire Spoke

ened. The wheels shown at Fig. Fig. 212.-Typical 215 are an American pattern known as the McCue, that at A being a front wheel while the form outlined at B is used on a live axle and serves as a traction member.

It is claimed that with wire wheels considerably more elasticity is present than in wooden members and that this type of wheel is much easier on tires. Experiments conducted during the past two or three years have served to establish the belief in some quarters that wire wheels double the life of tires as compared to wooden wheels. The main reason advanced is that wire wheels are extremely light at their peripheries and the reduction of weight at this point overcomes the flywheel effect and heavier blows of the wooden wheel rim when it strikes an obstruction in the roadway. The difference between the effect of shock on the tires of a wooden wheel with a heavy demountable rim at its periphery and the wire wheel with its light

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