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THE MILITARY MOTOR VEHICLE.

17th November 1925
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Page 9, 17th November 1925 — THE MILITARY MOTOR VEHICLE.
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Which of the following most accurately describes the problem?

A Precis of a Paper Dealing with the Transport Requirements of hie Army, Read before the Institution of Automobile Engineers, by Capt. R. K. Hubbard, O.B.E.

IN ACCORDANCE with a promise made last week, we now deal with the interesting paper recently read by Capt. R. K. Hubbard, 0.11E., before the members of the Institution of Automobile Engineers at Birmingham. It deals only with the general transport vehicle, such as the motorcycle, the light and heavy car, the light and heavy van, the ambulance, the lorry and the wheeled tractor or tractorlorry, and not with the fighting or special machine, such as the Tank. So far as The Commercial Motor is concerned, we deal chiefly with those particular vehicles which come under the heading of commercial vehicles.

The author points out that in peace time the strength of the General Service Mechanical Transport of the Army is far below that required in war and, to all intents and purposes. the Regular Army becomes the Expeditionary Force on the outbreak of war, whilst the Territorial Army becomes the nucleus and the training machine for further expansion. The Territorial Army cannot be afforded anything more than a sprinkling of transport vehicles for training purposes in peace time, its requirements at camp, etc., being met by hiring. Even the Regular Army, relatively immobile in peace time, quartered adjacent to its supplies and well furnished with railway facilities, requires, and is allowed, but a fraction of its transport. Consequently in the short time which would elapse between a declaration of war and the embarkation of the Expeditionary Force, the peace strength of the M.T. would have to be increased approximately 10 times.

Natural evolution produces in a country the domestic transport vehicle most suited to the topographical and economic conditions, but the British Army is probably unique in that it may be called upon to act in practically any part of the world. The theatres of operation may cover practically all conditions of terrain over which it is possible, or impossible, for mechanical transport to function. Other armies are hardly likely to be called upon to operate under such varying conditions. In mountain, bush or desert warfare mechanical transport of any sort may be impracticable, but the ability to use it adds so much to the mobility of the army that every effort must be made to increase the scope

'of the MN. vehicle, so that the utmost use can be made of it.

It is generally conceded that at the conclusion of the war the final rout of the enemy forces on the Western Front was prohibited owing to the immobility inflicted on the victorious armis.

During the Near East crisis in Asia Minor in 1922 the terrain at such places as Chanak was such that heavy lorries could hardly be moved a mile from the place of disembarkation. Light vehicles, up to the 30-cwt. subsidy lorry, could, however, operate comparatively satisfactorily.

In the case of an Expeditionary Force operating overseas the links in the chain of supplies are : (1) Sea transport from home to overseas base.

(2) Rail, river or canal transport to advance bases.

(3) Heavy mechanical transport to "refilling point" by Corps Transport, where loads are broken from bulk and transferred to Divisional Transport.

(4) Light Mechanical transport from "refilling point" to unit transport at "delivery point."

(5) First-line transport from "delivery point" to the troops.

It is only in respect of (3) and (4) that the military suitability of the British motor vehicle need be considered.

It is possible that the first-line transport may, in the future, be mechanicalized, some form of cross-country vehicle being used, but this matter is still at the experimental stage.

The estimated number and types of vehicle required per corps between railhead and "refilling point" are as follow: —3-ton lorries, 676; 30-cwt. lorries, 81; 15-cwt. vans, 93; 8-ewt. vans, 20; ambulances, 142; technical vehicles, such as mobile workshops, store lorries, disinfectors, laboratories, and those for hygiene, bacteriology, searchlights, etc., 78.

As regards the 3-ton lorries, which predominate, the daily "vehicles by miles" of such transport may reach 67,600, which gives an idea of the possible requirements in petrol, oil, tyres and maintenance, and shows the importance of simple, reliable and economical types of vehicle. It is fairly safe to say that the ordinary 3-ton vehicle of the pre-war subsidy type cannot operate except on properly made roads. The approximate number and types of vehicle per division are as follow :-3-ton lorries, 20; 30-cwt. lorries, 247 15cwt. vans, 17; 8-cwt. vans, 11; ambulances, 24; technical vehicles, 19.

On occasion thc daily "vehicles x miles" may approximate 24,700, which again shows the necessity for a reliable and economical vehicle. The cross-Country performance of the 30-cwt. subsidy-type lorry is high compared with the 3-tonner, and it functioned with not too much difficulty over many miles of almost roadless country in Palestine. The need exists for better vehicles than were available during the recent war, particularly because mechanicalization of the fighting arms is increasing their radius of action more rapidly than road conditions are likely to improve.

Military requirements of a vehicle can be defined under two heads (a) Performance, including cross-country ability.

(b) General design and constructional detail.

With regard tb (a), fully loaded it should be capable of the followino, performance : (1) climb 1 in 41 on a hard surface ; (2)'' stop and restart on 1 in 5; ,(3) climb an average gradient of 1 in 10 at 8 m.p.h.; (4) average 30 m.p.h. for one mile on a fist road and 22 m.p.h. for two hours over average roads not exceeding 1 in 15; (5) negotiate soft sand 8 ins. or 10 ins, in depth, unmetalled lanes With soft surface, firm but wet grasslands not exceeding 1 in 10, and short banks, hummocks or undulating natural gravel and water 18 ins. deep; (6) either brake should effectively stop and hold the vehicle on a gradient of 1 in 5 in either direction; and (7) should permit continuous application for a distance of half a mile on an average gradient of 1 in 12 at not less than 8 in.p.h, with the gear lever in neutral.

With regard to (b), the general design must conform to accepted practice so far as concerns the layout and the disposition of the engine. It is important that a high powerweight ratio, a small steering circle and high ground clearance should be provided, this being aomewhat counter to the natural trend of design. Pressure feed to main and big-end bearings is essential the dry sump being necessary to avoid excessive lubrication when negotiating steep banks.

So far, no satisfactory method appears to-have been devised to enable replenishment of engine oil without contamination in desert countries, and here there is room for inventive genius.

Positive drive to the dynamo is essential, and the positions of the carburetter, breather, dynamo and magneto must be high to enable fords to be negotiated. A" recent trial with a vehicle having 101 ins.road clearance showed that it could quite comfortably pass through 4 ft. of water with the simple addition of a waterproof bag over the carburetter and air intake and the upturning of the silencer pipe.

Unit construction has much to recommend it as regards the exclusion of dust and water.

Shutter radiator control is suitable for Arctic climates. in the tropics the temperature rise must not exceed 90 degrees F., as water is a valuable item.

In the gearbox, again, standard practice must be followed, as the sliding gear is overwhelmingly, popular. A wide range of gear 'ratios is desirable; it should be at least 1 in 5. For instance, with direct drive on top and a 1 to 7 axle reduction, the first speed overall should be about 1 to 35. , Both open and enclosed propeller shafts have given satisfactory service. One of the best designs of 30-cwt. lorry to W.D. specification has an enclosed type, and this chassis, as it happens, is the lightest. It is undesirable to specify any particular type of universal joint ; it should !JO ensured, however, that the angle on each joint (when two are used) should be equal and opposite in all positions of the axle relative to the frame, so that uniform .angular velocity of drive may be retained.

The worm-driven axle appears to be the most suitable for military purposes, although it must be admitted that the efficiency of bevel-driven, single and double-reduction axles is materially higher under heavy torque. The outstanding advantage of the worm axle is the abuse which it will withstand. The disadvantages of chain drive are that it wears quickly in sandy country and can easily be put out of action by the dropping of rivets, bolts, etc., into the links of the lower part of the chain. This proved a real difficulty during the disturbances in Ireland.

Only the heavy lorry need remain on solid tyres, and that of 3-ton capacity might very well be shod with pneumatics, which improve cross-country performances, are quieter, easier to replace, reduce the shocks and cause less road damage. On a dark, still night, when Tanks and horse-drawn vehicles could be heard .miles away, a column of 30-cwt. lorries could only be detected, by a person standing 100 yards away, by the slight hiss of the carburetters, although the vehicles were travelling at 12 mph.—a great contrast to the rattle of a column of 3-tonners during the world war.

A turning circle not exceeding 45 ft. diameter is essential. The necessity for a robust front axle will be accentuated if the liegresse and metal half-track systems become generally adopted, the front axle frequently being lifted from the ground and crashed back again.

Three-point suspension of the units is essential, and it is well to employ an extensible pure rubber connection between the top water pipes for the engine and the radiator, otherwise it will certainly be torn off.

As regards braking, transmission brakes are difficult to cool, and rear-wheel or all-wheel brakes can be satisfactory. Even in recent designs of vehicle, loading often upsets brake adjustment to a great extent. One palliative appears to be to provide as much of the leverage required on the axle itself, rather than in the brake pedal or lever and transmission.

It is of considerable importance that all parts subject not only to roadside adjustment, but also to running repair and overhaul should be thoroughly accessible. The author gives some 25 instances.

' Standardization is the antipathy of development, and both are desirable. It is, therefore, important to go warily when endeavouring to obtain finality of design.

There tire two or three British makes of 15-cwt. van which meet military requirements, but the number of this class of vehicle is relatively small.

Regard.ng the subsidy scheme, there are now eight manufacturers in possession of the subsidy certificate, and in a year or to sufficient numbers of the subsidy vehicle will be available to guarantee mobilization requirements. There is an intlic tiou that, were the subsidy discontinued, the British ype of 30-cwt. lorry would develop in a direction unsuited to military requirements.

Where good roads are available, the British heavy lorry carrying 3 tons or more is second to none, but to meet the requirements of performance it will be necessary to employ four-wheel drive right away, and the semi-tractor type, capable of carrying a proportion of its load and hauling the rest, appears to be the most satisfactory.

It is apparent that we cannot rest content that in time of war the British Army will be better situated than, or even as well situated as, other armies with regard to the types of mechanical transport vehicle -and the numbers available. It is, of course, probable that no difficulty would be experienced in making extensive purchases of suitable vehicles of foreign make, but it is undesirable that such a course should be pursued.

The War Office is conscientious in its support of the home motor trade, but, curiously enough, the efforts of British vehicle manufacturers to include foreign-made components has at times to be resisted. It is desired to call attention to the merits of the rigid six-wheeler driving on at least four wheels. This design would appear to possess a unique merit in that it has advantages for commercial purposes under good road conditions, whilst meeting military and Celonial requirements as regards cross-country performance. It is the only recent development which does this, all others tending to improve road worthiness at the expense of military or Colonial worthiness, or vice versa. There is one important point in connection with the suspension system of the rigid six-wheeler which should not be overlooked, and that is the securing of equal pressure to each of the four driving wheels under any condition of torque reaction or road irregularity. The designs illustrated show one method of overcoming this difficulty with semibogie construction, by taking thetorque reaction direct to the main frame and also providing that when the driving axles are standing at different angles to the frame, looked at from the rear, no twisting of the springs occurs. The advantages of the six-wheeler are valuable and should permit of privileged legislation at home in connection with the vehicles possessing them.


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