PROS AND CONS OF THE RIGID SIX-WHEELER.
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Some Notes from the Interesting Discussion Following the Paper on Mechanical Vehicles for the Army, Read by Capt. C. H. Kuhne, D.S.O., 0.B.E., R.A.S.C., Before the Institution of Mechanical Engineers.
LaA FTER the conclusion of a remarkably interesting
Paper on the development of mechanical vehicles for general load-carrying duty in the Army, with special reference to the W.D.-type rigid-frame sixwheeled lorry, read by Capt. C. H. Kuhne, .A.M.I.Mech.E., before the Institution of Mechanical Engineers a few days ago, and already circulated in interested circles, the discussion was opened by MajorGeneral G. F. Davies, C.B., C.M.G., C.B.E., Director of Supplies and Transport, who referred to the work of the M.T. Vehicle Advisory Board, which not only concerned itself with mechanical transport on Army lines but had kept abreast with commercial vehicle developments.
The Board consists of Sir Henry Fowler, K.B.E.; Professor W. E. Dalby ; Lt.-Col. A. E. Davidson, D.S.O. ; and Mr. L. A. Legros, O.B.E.
The author of the paper had referred to a liaison between the Army, the manufacturers, the technical Press and the users. He could not say what that liaison might have meant in relation to the Army, but certainly the manufacturers had begun to trust the Army more than they had formerly.
Professor W. E. Dolby made reference to the first six-wheeler tested at Aldershot (the Renault) and to the work of Col. Nitolett in the long-continued application of various details to eliminate mechanical defects. He stated that torque rods must be used, or some equivalent means devised, to prevent any variation of load as the torque came on the wheels. Each axle in a semi-bogie of the Army type had four degrees of freedom in relation to the ends of the springs, as the springs were attached to a kind of axle box, each connected by a spherical joint to an axle sleeve.
Co-ordinating Army and Civilian Vehicle Requirements.
Col. Fuller said that an enormous amount of experimental work had been done by the War Office since the war to develop the mechanical side. The half-track was tried, but it was not until the six-wheeled or multiwheeled machine was developed that a commercial or civil basis was reached—a matter of vital importance. As a result three classes of machine had been produced —the whole-track, the half-track and the six-wheeler. For an actual fighting machine attention would have t.) be concentrated on the whole-track type, for if an enemy chose to occupy abominable ground it would be necessary to rout him out. Between the " Capital " fighting machine and the civil machine existed certain auxiliary fighting types, such as armoured cars, bridging machines, signalling vehicles, pontoon carriers, etc. Careful consideration was needed before putting these on full tracks, seeing how efficient was the six-wheeled system to-day. The difficulty was not whether the Army should be mechanized, but how.
Mr. E. S. Shrapnell-Smith, C.B.E., pointed out that the key of Empire development was transport by road, rail or sea, and that, in this, politicians and industrialists were agreed. Members had been reminded that railways could take care of themselves, and as presi(lent of the Commercial Motor Users Association he was concerned with the likely exploitation of the fundamental design of the six-wheeler and the discussion of variations of it for ordinary commercial use in the transport of goods and passengers. He congratulated the War Department upon its technical and executive officers whose efforts had produced such wonderful
results. A new era of locomotion had been entered upon, fn the rigid six-wheeler there was a combination of merits which would give it a widespread commercial application. As a director of certain companies, he had had experience with the work of these machines in ordinary commercial practice, and, certainly, the promises made at the time of purchase had been fully borne out. He was glad to learn that it was the intention of the War Department to adopt some method of subsidizing. Six-wheelers would have great application in agriculture owing to the facilities they afforded for getting to crops, fruit, etc. They go Over ground common in our meadows and fields. They were also excellent in snow, of which there was an average of eight days per year, which increased above a certain northern point.
A Hint to Manufacturers.
Mr. L. A. Legros, 0.B.E., emphasized the importance of manufacturers building these machines, and said that it was of equal importance for them to increase their business by supplying clients with vehicles of a type which would enable the crossing of very bad country which often separated places of production from the railheads. He felt it would be very useful t) have taken a close-up film of a tyre on the road when it was just slipping, because it was the shear of the cake of dirt that was the important thing and one which would decide whether the machine was going to slip altogether—always supposing that the engine was sufficiently powerful. A point not sufficiently appreciated by British makers was the clearing away of small down-hanging parts, such as brake levers, parts of steering gear, etc. These were often in what may be termed the danger zone. It was of vital importance to send engineers as well ascommercial men to foreign countries to study existing conditions.
Col.-Commandant Evan Gibii, C.M.G., C.B.E., D.S.O., A.D. of S. and T., in referring to the suggestion that mechanization of the Army might result in a decline in the military spirit, pointed out that the operation of six-wheeler transport at Aldershot had done more than anything else to contradict this. Certain eminent officers and civilians had mrtainly undergone a dissipation of the military spirit when descending, for the first time in six-wheelers some of the steepest slopes. One distinguished gentleman, after descending a 1 in 6 hill, remarked that he was certain it was at least 1 in 4; by lunch time it had reached the figure of 1 in 1.8. It was interesting to note that the reports of the cavalry officers, which might be expected to be somewhat prejudiced against mechanization, were both optimistic and eulogistic.
Actual Experience with Six-wheeled Buses.
Mr. C. Owen Silvers, A.M.I.E.E., M.Inst.T., general manager and engineer to the Wolverhampton Corporation Tramways, stated that he had been using sixwheelers for nine months. He had found that if with twin tyres one punctured, the other was not of much service, being overloaded, whilst, in addition, the faulty tyre tended to become screwed up into the good one and both were soon put out of action.
He would much rather have the driver behind the engine, as this gave better accessibility. One of the six-wheelers had run over, 20,000 miles, whilst the figure of the whole five vehicles was over 50,000. No
• trouble whatever had been experienced with the double, B29 back-axle mechanism or the coupling gear. The original tyres were still on every vehicle, and those which had done 20,000 looked like doubling this .11gure. During the recent period of snow, the six-wheelers kept to scheduled times, but the four-wheelers, particularly those running on solids, were behind time.
Mr. Silvers has adopted an interesting _factor of 100 seat-miles upon which to base petrol consumption, etc. With the four-wheeled vehicles, the petrol consumption was .635 gallon per 100 seat-miles. The rigid frame six-wheelers gave a figure of .369 gallon, a saving of 42 per cent. So far as weight was concerned, the four-wheeler on solids weighed 369 lb. per seat, and the six-wheeler on pneumatics 230 lb. per seat, a saving of 38 per cent. Incidentally, the six-wheelers had bigger engines and gave better acceleration and speed. Electric trolley-buses were also employed. Those on four wheels consumed 3.137 electrical units per 100 seat-miles and the six-wheelers used only 2.264 units, a saving of 28 per cent. The weights in this ease were 305 lb. per seat for the four-wheelers and 211 lb. per seat for the six-wheelers.
The results were so satisfactory that the fleet of sixwheeled vehicles is being enlarged, and some of the tramcars are being scrapped and replaced by sixwheelers each seating 65 passengers.
Inducing Crown Colonies to Use Six-wheelers.
Major-General S. S. Long asked if the country could maintain the number of vehicles required, and could the six-wheeler be brought successfully into commercial use? Further, in the case of a sudden mobilization, where were the necessary machines to come from? He Would not advise spending much money in subsidizing 1,000 or 2,000 vehicles. Such money put out in proper advertising would popularize the vehicles much more rapidly than a payment of £40 for three years. He suggested making a certain number of vehicles and inducing the Crown Colonies to employ them, offering free advice and assistance, and actually providing the service of highly technical and welltrained Army mechanical transport officers. The Crown Colonies were invariably hard up. Although, individually, they might afford a few thousand pounds for vehicles, they would urge that the cost of working without trained drivers and with no one to keep records would be too great. If officers were sent it would he invaluable experience for them. Mr. S. S. Guy pointed Out that there were tremendous possibilities for the use of the six-wheeler on hard roads, and that it would be better to have the vehicles B30 in this country than be forced to go to the Colonies for them. In any event, the Colonies would probably be forced to buy such vehicles.
There was a reduction in six-wheeler operation of 75 per cent, of shock. This made them excellent for fragile goods and passenger work. Probably 60 per cent, of the advantages was due to the elimination, or practically so, of wheelspin. It was only when two wheels diagonally opposed were in the air that wheelspin was possible. He stated that a smaller engipe would be used for the same loads, with reduced petrol consumption and less tyre wear, whilst rear-wheel skids were obviated. In two lorries possessing engines of the same size, one a four-wheeled subsidy type and the other a medium six-wheeler, the subsidy model would carry 30 cwt. and the six-wheeler 3 tons, whilst the drawbar pull of the six-wheeler would be 100 per cent. higher. There would be practically no difference in average speed over long distances, whilst tests have shown that, with the vehicles in question, the petrol consumption of the four-wheeler was one gallon per 19.97 miles, and of the six-wheeler one gallon per 24.9 miles. The steepness of the gradients climbable is increased by 100 per cent. as compared with a fourwheeler. As an example of economy, he mentioned that a six-wheeler capable of carrying 4-ton loads-, which has run over 85 miles per day and a total of over 8,000 miles, showed an average petrol consumption (loaded and empty, and running much of the time in town) of one gallon per 9.76 miles.
A Suggestion Regarding Front-wheel Drive.
Lieut.-Col. T. M. Hutchinson, D.S.O., 0.13,E., mentioned that the riding comfort of the six-wheeler would help it greatly as a means for passenger transport. He referred to the possibility of front wheels stubbing when crossing small ditches, and said that a line of possible development was front-wheel drive. The complication caused by this addition would not be great if the fact is taken into consideration when designing the vehicle. It meant only the provision of a special flange on the gearbox and the means for coupling, so that, for military or extraordinary reasons, it would be possible to fit a front-driven axle, although for ordinary purposes a standard axle could be used.
Undoubtedly, the six-wheeler was less inclined to skid, but the great difficulty lay in the obtaining of efficient brakes and hand controls to work on all wheels. He looked towards forward control to give more loading space, this question being of great importance as
owing to the articulation of the axles, a well-type body was essential for military purposes. Very favourable reports on six-wheelers had been received from India, where the work of the vehicles included passing over rocky ground covered with outcrops and boulders. An auxiliary radiator or steam condenser was necessary in the tropics, and air filters for dusty districts. The most likely way to increase the popularity of the sixwheeler was for the taxation authorities to give them more favourable consideration.
Major. E. G. E. Beaumont said that there would always remain pronounced differences between the commercial civil vehicle and that required for military services
Wing-Commander S. G: Dalton thought that the Air • Force would have more use than the Army, for sixwheeled vehicles in peace time, although in war time their requirements would be equal. Aerodromes are usually a long way from the -road and vehicles must be able to travel across country, also they must be able to proceed to the rescue in cases of crashes. He was quite sure that, before long, every air station would possess six-wheeled vehicles.
General Mance referred to the mud in Iraq and to the fact that a vehicle may have to travel 600 miles between fuel replenishments. Therefore, the weight of chains was important.
Captain C. H. Kultne, in replying, said that, by subsidizing, the War Office would get 1,000 vehicles on the road and of a suitable type, whilst the War Office would have some little say in design, which was really of more value than the actual vehicles, for the manufacturers would know how to make them in a number of works and, as, on mobilization, all sorts of powers could be granted, the type could be put into mass production.
He assured Major Beaumont that the point about which a bogie pivots had no effect on undercutting if the point were somewhere near the level of the centres of the two axles. He was quite prepared to invite Major Beaumont to see a vehicle on a weighbridge and to give an optical demonstration of the fact that, with the vehicle anchored from the rear by a rope and with oir,a, axle on the bridge, when called upon to exert its maximum tractive effort, the weight on that axle would be the same as when the other axle was weighed under the same conditions.
The weight of the track chains was.-4 cwt. At first, they injured the walls of the tyres, but, since then, chains had been designed to offer a fiat surface to guide them on, instead of rounded webs, and the tyre manufacturers now agreed that 'abrasion was so slight as to be negligible. Vehicles' with these chains could easily be run at 15 m.p.h. The War Department was at work On a girder track, but this was not sufficiently advanced to permit results being given. It was bound to be heavier. He hoped to obtain overall chains for single tyres, but Was not Yet ready to talk about this development.