"WHEELS IN WAR."
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The Problem of the Heavy-duty Motor Wheel as Resolved by the War.
0 NE OUTCOME OF war's grim and searching test, so far as the heavy motor is concerned, has become manifest. This is the type of wheel best suited to all-round hard Work. True it will be conceded that, in military service, a wheel is subjected to far harder -gruelling than it would ever receive during uneventful commercial operations, but it is up to us to take full advantage of every lesson the war is able to teach us.
Shall the, wheel be of wood, pressed steel, wire spoke, or east steel? Shall the pregaed-steel type follow disc or spoke lines ? A brief analysis of the problem, so far as it has been solved by service, will proVe illuminating. ,
. Taking the wood wheel first, as probably being the most familiar, it must be conceded that it has given Such an indifferent showing under war conditions as to lead certain authorities to aver its complete elimination from the heavy-motor vehicle realm. Already it has disappeared from wheel construction in about 90 per cent. of vehicles of European manufacture. It may be pointed out that the objections to the wood wheel; especially in the fighting zones, are too pronounced to be' ignored. As compared with steel, it lacks strength, has a shorter life, is readily affected by varying climatic and weather conditions, is more expensive, has a disadvantage in weight, and a lower factor of safety. The last-named defect may not be so significant under peace as under war conditions, but even in everyday commercial service it is a feature -which must not be lightly disregarded.
Wood v. Steel. _
The vogue of the wood wheel.is dying hard. A certain recrudescence has attended the entrance of the United States into the war arena. American makers, from the mere fact that second-growth hickory was abundant and constituted an excellent wheel constructional material, have certainly', been able to produce wheels of this class superior to their European competitors. But the, supplies of the essential raw material are shrinking : ' hickory wheels have deteriorated. Moreover; the American experts detailed to European war service to glean points have been so impressed with the results achieved by the metal -wheel as to have communicated their favourable impressions to the home manufacturers. .
But when we come to consider the metal wheel, definite Selection of a universal type is more difficult. So many-factors have to be taken into consideration, while here individual or national predilection eXercises a distinct. influence. So far as heavy loads are concerned; the east-steel 'wheel holds the field for vehicles above 2 tons. 'Practically :110 lorries of 3, 4 and 6 tons capacitSnow built in this country, France or Italy are fitted With wood -Wheels. While British builders are divided betweenthe cast and the disc types; each of Which possesses distinctive recommendations, -.French andItalian makers plump for -the cast steel design. Here, again, decision is divided. There i.S' the type with hollow spokes, which doubtless• are satisfactory, but 'present '2., somewhat difficult foundry: :proposition. The alternative is the wheel having spokes -of transverse .sectitin in the form of a cross. So far as the steel wheel is concerned, shell splinters, which would cripple or damage seriously a wooden wheel, exercise but slight injury ; while, in the ease of a,vehicle catching. fire, of course the steel
B28 wheels remain virtually unaffected, whereas wood most likely would be destroyed.
During the war the steel disc wheel has undergone considerable development., Indeed, it may be said to have provided one of the revelations of the war. So far as France is concerned, the Michelin steel disc has attained a distinct measure of success, large quantities being supplied to French lorry builders. Italy is following suit, the F.I.A.T. Co. for instance, Which decided in favour, of the metal wheel so far back as 1903, fitting it td all their 1 and 11-ton pneumatictyred lorries.
What of the Wire. Wheel.
This wheel comprises the usual rim and a steel disc of uniform thickness stamped to the correct shape. The disc is forced into the rim and then electrically welded and cold riveted to the latter. Finally, two steel discs are riveted to the central portion of the wheel, and these three thicknesses of metal are drilled to receive the five, six or ten studs, by which the wheel is held in position. This type of wheel 'certainly has many favourable characteristics. It is strong, moderately light, immune from the deteriorating influences of climate conditions, is readily detachable, comparatively .easy to make, and, finally, is easy to clean. Consequently, it .will be seen to possess all the essential virtues of the ideal wheel.
Is it surprising that, under these circumstances, the wheel is highly popular ? Practically the entire Italian aviation service and a considerable proportion of the French aviation a.nd ambulance services are equipped therewith. The Michelin Co. is striving to popularize the wheel in every possible direction. The fast lorries are being so fitted, while heavy touring cars requiring dual tyros on the rear wheels are likewise being equipped. But in this direction weight is a sonie-What adverse factor, the singles in front and duals at rear being heavier than a set of wood wheels with detachable rims. The fact that a spare complete wheel is carried contributes to this adverse feature. No mention of the steel wheel would be complete without mention of the Sankey detachable wheel of the pressed-steel type, but of the spoke variety, stamped in two halves and welded together. While having the appearance of the wood wheel, it has none of itt defects, arid so has scored a distinct success.
So far as the war carries us, the wire wheel does not appear to have made distinct progress. It is very rarely used by the French army, while in the Italian army it is likewise sparingly employed. The French authorities have standardized the Michelin steel disc for the staff cars, while in the Italian army the tendency is to use the Sankey steel wheel in this field. The British army makes a greater use of the wire wheels than any of our Allies. But when the wire wheel is fitted with a steel disc, the greatest objection to this type is overcome. With the return of peace it is certain that the steel wheel will receive greater attention from 'both manufacturers and users. Its manifold advantages' ate so obvious and emphatic. There will doubtless be a diversity of types and modifications of those which at present are rendering such excellent service. But variety of design is inevitable: it is inherent to the train of thought. Much technical data are being gathered, and when these details are sorted mit by fertile brains, a big crop of varieties in details of design must eventuate. But one thing is certain: the days of the wood wheel have virtually passed.