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Rh forward the driver obtained a view of the road ahead through the opening between the two parts. This was a valuable feature for driving in rain, when the screen was often covered by dew which interfered with vision through it. It was known as the rain-vision effect. In Germany it became customary to provide a compartment in the body into which the hood disappeared when folded. Elsewhere a boot or cover of some rainproof material was drawn over the hood when it was folded. In the early two-part wind-screens both glasses were completely surrounded by the frames, and the frame members at the middle of the, screen interfered to a certain extent with the view ahead. This objectionable feature was eliminated by confining the frame to three sides of the glass. Windscreens of this type were known as clear- vision. Extra wind-screens ahead of the rear seat were sometimes fitted.

The wheel equipment of the earlier cars was almost entirely of the wood-spoked type. Woods suitable for rims and felloes became rare, however, especially in Europe, and a strong tendency toward the use of metal wheels then set in. In fact, with one or two exceptions, all British manufacturers of passenger cars fitted metal wheels as regular equipment on their 1920 models. There were three types of metal wheels for passenger cars viz. wheels similar in shape to wood-spoked wheels, made of two steel pressings welded together

11.—Section of Rudge-Whitworth demountable wire with Pugh triple lacing.

(chiefly used in England), wire-spoked wheels and disk wheels (figs. 11, 12, and 13). An improvement in wire-wheel design, which was a great factor in rendering these wheels practical for heavy, powerful vehicles, was the triple lacing due to John V. Pugh of England. Disk wheels came into extensive use during the war; they may be divided into single and double disk types. To secure the necessary lateral stiffness with a single disk it was customary to cone the disk, and, moreover, the disk was usually

12.—Michelin disk wheel, outside view and section.

reduced in thickness from the hub toward the rim, either by turning in the lathe or by rolling. All motor vehicle wheels are provided with steel rims designed to take the pneumatic or solid rubber tires. The original type of motor vehicle rim for the double-tube pneumatic tire was the clincher rim, the edges of which are formed into clinchers to hold the beaded edges of the tire cover. This type of rim remained the standard in Europe, but American manufacturers early adopted the detachable rim, which permits of the use of a steel cable core in the edges of the tire cover to make it inextensible. In the earlier detachable rims one flange of the rim was removable, and the tire could be stripped off sideways after the flange had been detached. Some of these detachable flange rims could be used with both clincher and straight-sided tires, and were therefore known as universal rims. Later, when the clincher tire was given up by American manufacturers for all except the smallest sizes, a different type of detachable rim was introduced, in which there is a joint in the circumference of the rim. After opening; the locking mechanism of this joint the rim can be contracted sufficiently to pass through the tire. In order that detachable rims may always be free-working the rims must be thoroughly rust-proofed, and care must be taken in handling the rim not to distort it.

In the early years of the motor-car, when a tire was punctured or otherwise defective, the operator was obliged to make a repair on the spot, or at least remove the tire cover, insert a new tube, replace the cover and inflate the tire anew. This was always an unpleasant interruption of a pleasure drive and a most aggravating occurrence in the case of an urgent business trip. The difficulty was overcome by the adoption of the demountable wheel in Europe and the demountable rim in America. American motorists thereafter carried one or two spare rims fitted with fully inflated tires, and in case of a puncture merely removed the rim with the defective tire and replaced it with a spare rim and inflated tire, an operation usually requiring from 10 to 15 minutes, leaving the repair of the damaged tire to be done at home or at a tire service station. European motorists carry spare wheels with inflated tires in the same way. The advantage of the demountable rim over the demountable wheel is that the spares weigh less; the advantage of the demountable wheel is that it weighs less than a wheel with a demountable rim, and especially that with it there is less weight near the circumference of the wheel, where it has a strong flywheel action. Moreover, with the detachable wheel the detaching mechanism is at the hub, farther removed from rust-promoting influences.

13.—Sankey pressed steel wheel, and section.

The structure of demountable rims may be briefly described as follows: forced over the felloe of the wood wheel is a steel felloe band with a wedge surface on its outside, and an inward flange on one edge through which and the wood felloe pass the felloe band bolts. Over this felloe band is passed the rim carrying the tire, which is formed with a wedge surface on its inside, adapted to engage the wedge surface on the felloe band. Rim lugs with wedge-shaped projections are threaded over the ends of the felloe band bolts, and the nuts on the bolts are then screwed up, forcing the wedges into the space between the felloe band and the rim. In this way the rim is subjected to both radial and lateral pressure and is centred and firmly held on the felloe band. Both clincher and detachable rims can be used in connexion with demountable rims.

Solid rubber tires are vulcanized on to the steel base bands, and wood wheels to be fitted with such tires have a steel felloe band shrunk over them. The tires are then mounted on the wheels in a demountable way by means of wedge rings, side flanges and bolts. Cast-steel wheels generally have one wedge ring cast integral and do not need a side flange on that side.

There is one notable difference in the commercial practices of American and European motor-car manufacturers. In the United States it is customary to sell cars complete with bodies and all necessary equipment, so that upon being filled with fuel and water they can immediately take the road. The equipment usually includes such items as wind-screen, lamps, speedometer, jack, tire pump and tools. European manufacturers, on the other hand, previous to the World War, often made it a practice to sell only the bare chassis and