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OPINIONS FROM OTHERS.
Page 108
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The Editor invites correspondence on all subjects connected with the use of commercial motors. Letters .should be on one side of the paper only and typewritten by preference, The right of abbreviation is reserved, and no responsibitity for views
expressed is accepted.
The Springing of Six-wheelers.
The Editor, THE COMMERCIAL MOTOR.
[2606] ir,-Mr. William Cochrane's letter in the issue of The Commercial Motor for June 7th does not convince me that the claim of the rigid six-wheeler are overrated or that the publicity given to this design is "window dressing and whitewash."
I have "stooped to examine the remarkable Ford chassis," and to me it is obvious that the frame is in no way rigid, especially when the brakes are applied. Transverse springing on the Ford chassis was probably originally adopted as the best type of springing available at the cheapest cost, the Ford being designed to sell at as low a figure as possible.
The Ford frame could be made more rigid than it is at present if four coil springs were fixed at each corner of the frame members directly over the axle ends, assuming the "rate" of the springs to be the same as the transverse leaf springs now fitted. These coil springs would have the effect of doing away with the bending stresses imparted to the frame by the leaf springs which are attached to the middle of the rear cross-member by their centres.
The War Office type six-wheelers cannot be classed as innovations as many of them have now been in daily service for nearly two years in Africa, India, Australia and elsewhere and have given complete satisfaction where other vehicles with a single driving axle would have failed at the start. If Mr. Cochrane really believes these vehicles will not stand the test of time, how does he account for the recent extension of the W.D. subsidy grant to rigid six-wheelers of £120 over three years?
A test run between two Fords and a six-wheeler between Minehead and Lynton and back would show the Ford at its best and the six-wheeler at its worst from a performance point of view, as the latter has not been primarily designed for transport over roads but over broken country where soft tracks are met with. Skidding on sharp bends is not the big drawback that Mr. Cochrane imagines, as the rear axles are kept as near together as possible, while the tread of the tyre " gives " to a certain extent without detriment to its life. Only in cases where the second back axle is some distance from the first back axle is it necessary to steer the back wheels.
Several pages of The Coirpmereial Motor would be required to go over all Mr. Cochrane's arguments, which involve highly technical points in design, but it must suffice here to say that, undoubtedly, the rigid-frame six-wheeler is a proved job as against a type which, however good scientifically, is not available for commercial tests, but only as a model which has vet to be proved under the worst road conditions.—Yours faith fully, Gi BADEN SMALL. Kensington, W.14.
The Editor-, THE COMMERCIAL MOTOR.
[2607] Sir,—In reply to the letter of Mr. Ronald Whitehead, published in the issue of The Commercial Motor for May 17th, I am sorry I cannot publish details of the design of my transversely sprung vehicle, because it is not yet fully covered by patents. If Mr. Whitehead will assist me to recover my models from the War Office I shall be pleased to show them to him or any other expert on suspensions privately, and demonstrate that they possess (1) absolutely rigid chassis, (2) unlimited wheel movement, (3) freedom from bounce and rolling on curves, and (4) ability to transverse uneven ground at speed.
Whilst fully appreciating the performance of the W.D. six-wheeler, I am quite convinced that a better D54 performance would be put up by a transversely sprung vehicle carrying three tons Without axles and fitted with a four-wheel drive—practically speaking an " improved Ford "—at a third of the cost of the W.D. sixwheeler with its many gadgets, not necessary in a transversely sprung vehicle.—Yours faithfully, London, N.W.6. WILLIAM COCHRANE.
Attention to Giant Pneumatics.
• The Editor, TEE COMMERCIAL MOTOR.
[2608] Sir,—We do not often find it necessary to differ from' you in the matter you publish regarding tyres, but we are afraid that we must comment upon the remarks made on page 546 of the issue dated June 14th, under the heading "Is the Solid Tyre . Doomed? " You mention as one -of the merits of a pneumatic tyre the following :—" Inflation is but seldom required; in fact, we know of cases where tyres have run for many thousands of miles without this being necessary."
Thiscreates an entirely wrong impression. For the successful and economical use of pneumatic tyres for heavy vehicles, attention to the inflation pressure at regular intervals, whether the tyres appear to require itor not, is absolutely vital. The user may neglect most other things about pneumatic tyres with a less chance of loss than if he neglected the inflation pressure.
It is the experience of engineers in charge of the largest fleets that regular attention to the maintenance of the correct inflation pressure is the most important point in connection with the success of their transport. They know it very well and in most eases have made adequate arrangements for its attention as part of the ordinary routine maintenance work.
They are not likely to be influenced by your remarks, but the smaller user who may be hesitating between solid tyres and pneumatic tyres is likely to be misled, and when he gets unsatisfactory service he might easily point to your remarks as his authority for assuming that inflation pressure matters .comparatively little.
Although we have had vast experience and have an immense fund of information regarding the use of giant pneumatic tyres, we do not know of any authenticated cases where they have run for many thousands of miles without attention to the inflation pressure being necessary.
We have come across cases where the users have been judging the necessity by the mere appearance of the tyres, and have come to the conclusion that the necessity did not exist, but the actual application of a pressure gauge showed that the facts were entirely contrary to the impression.
In any event, it is not safe to take it for granted. It is not a difficult job to ascertain, say, weekly whether the correct pressure is in the Wes and to restore any that has been lost. As a matter of fact, this is about 95 per cent, of the secrets of the successful use of pneumatic tyres on motor vehicles.—Yours faithfully, W. BOND, Technical Director's Office. (For The Dunlop Rubber Co., Ltd.) [We agree with Mr. Walter4Bond that attention should be given weekly, or even daily, as a matter of routine, to the condition of pneumatic tyres, but it is by no means an uncommon,px-perience after a certain period of running to find, by the pressure indication on the gauge, that no further air supply is necessary, and thus inflation is not called for. The reason for this is well known and need not be dealt.with here. Mr. Bond is right when he urges the point that success with giant pneumatic tyres can only be gained by scrupulous attention to their inflation pressure.—ED. CIL]