Automobile Experiences in the Great War.
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A Paper Contributed to the American Society of Automobile Engineers by W. F. Bradley, Our Special Correspondent in Paris.
(Continued from pa.ge 475.)
The non-skid device consisting of a circumferential chain, lodged in the space between the dual tires, has not been a great success„ for the available space is too narrow to allow of a heavy chain being fitted, and breakages are frequent. The same objection applies to the type consisting of a circumferential chain placed between the dual bands, with transverse ribs at regular intervals having one surface in contact with the tread of the tire and the opposite face in contact with the road surface. The chain uniting these ribs has always proved too weak.
Short lengths of chain, hooking from the outer to the inner face of the rim, across the tire, fitted amoug others to the Pierce-Arrow trucks, are fairly aatisfactory. The lengths being independent, the breakage of any one does not affect the efficiency of the device. -Experiments were made with the same trucks with a caterpillar attachment secure,d to a flange bolted to the wheel felloe. This device was quite unsatisfactory. After a truck became bogged it was MIpossible to apply the attachment, and if used over, a made road it broke the chains or bent the steel shoes in such a way that they could not be used a second time. In the case of some of these trucks, carrying a heavy load of armour and an anti-aircraft . gun, it was found that if the ordinary chains would not take them through, nothing else would. Thus these ehains were always kept on when operating away from roads.
It is surprising, however, how soon a set of chains will be eaten up if used over a hard macadam road or a granite surface. A few seconds are sufficient to reduce a set of chains to individual links and portions of links under certain road conditions. Thus the necessity arises for a quickly detachable device, so that it can be taken off immediately a hard road surface is encountered. It should also be pointedaout that the ordinary chain devices are not applicable to chain-driven trucks, the clearance generally being insufficient between the road wheel and the pinion to allow a chain to be attached. It is not necessary to .describe what happens when an anti-skid chain
• breaks away and mixes itself with one of the driving chains.
A device adopted as the result of practical experience in the field consists of an endless chain passing round the road wheel (fitted with dual tires) and around a loose pulley some distance back of the road wheel. A spring-controlled bell crank arrangement operates on the pulley and maintains a sufficient tension on the chain. On greasy roads and mudcoated granite surfaces this was a most effective nonskid device, and one that gave little trouble through breakage. It was found to be useless, however, on soft earth. Under these conditions theahain refused to revolve with the driving wheel, and the whole thing became embedded.
The problem of securing traction has not been confined to rear-wheel drive trucks. Four-wheel drivers have had to face the same difficulties, although. of course, in a different degree. The most difficult feature has been to find a device that would prove satisfactory under all circumstances.
Metal Wheels Being Adopted.
One of the most important developments of the war is the adoption of the all-metal in place of the wood wheel. Although the wood wheel may continue in use for some years on commercial trucks, and possibly will not be abandoned for touring car purposes, it is already doomed for army trucks. The primary objection brought against the wood wheel is that,even if well made of good material in theifirst instance, it requires attention from time to time to keep it in proper condition. Thisaiefect is most apparent when trucks have to remain out of doors day and night, indeed on all occasions except when in the repair
shop. Another, objection is that if the vehicle catches fire—and the enemy's guns are constantly on the
search for convoys working back of the lines—the wheels are liable to be destroyed, and it becomes a difficult matter, if not an impossibility, to get the truck away. With metal wheels,it is nearly always possible, when the fire has burned itself out, to tow the vehicle home. Apart from the body, it is surprising how little a burned out truck will suffer in its essential organs.
Practically no army trucks are now being built in Europe with wood wheels. All the various makes of
trucks supplied to the Royal Naval Air Service for use in France in a short time had their wood wheels changed for those of the steel disc type. Generally when replacements become necessary cast-steel' or disc wheels are substituted for wood. A small number of American bucks have been changed in this way. .
For trucks of 3 ton capaCity and upward the caststeel wheel of the. spoke variety is extensively employed by French and Italian makers, and also by the British. The latter, however, are also partisans of the disc type. For the lighter unit % such as light
trucks on twin pneumatic tires and motor ambulances., the steel disc wheel has made a remarkable jump into favour. These pneumatic shod wheels can be detached by removing four to six nuts.
four studs and nuts, adopted by some makers,
are considered an insufficient attachment. Six should be a minimum. The detachable wire spoke wheel has
not been given a more extended application, although it has held its own on touring cars used by staff officers.
Rubber Tires Used on All Wheels.
Not many,years ago the French nailita,17 authorities were inclined to'favour the use of steel tires, particularly on the driving wheels. The retsults were not satisfactory, the initial economy being more than offset by the greater cost of upkeep and the difficulty of operating the vehicles on greasy granitepaved roads. The war has proved the,necessity of using rubber on all trucks and on ail wheels.. Block tires, for which manyaclainas were made at one time, have not proved satisfactory. The alleged advantage of being able to replace a block if one gave out has not been substantiated. One reason is that the new block always has a greater thickness than the worn unit it has to replace. All kinds of tire troubles have developed, and, moreover, kinds unknown under peace conditions. Mileage has dropped very low, and many trucks in the north of France are not averaging more tha,a 1500 miles on a set of band tires. On some of the heavy gun ears 800 miles is considered a fair average, and la00 miles excellent service. These, however, are special vehicles having a load of seven tons and more,. obliged to operate in a fire-swept zone not negotiated by any vehicles other than thelightitwo-wheeled carts c55 of the Army Service Corps. One section of PierceArrow five-ton trucks doing ordinary transport service in France averaged 5000 miles on a set of tires, but 4000 miles can be considered a fair,aver,age.
It has been suggested that the rubber used during the war is not equal in quality. to that of peace times. There is nothing substantial in support of this contention, however. It is true that some damage is done by improper press work. The hydraulic presses to be found in all the repair depots are often in the care of men who cannot be considered experts and who shorten the life of a tire in the fitting process. Tires do not perish principally by having their tread worn down. They chip away laterally ; they come away from their base, sometimes for their entire circumference • and generally they wear unevenly. On all the cambered roads of France the inner one of dual tires carries the greater portion of the load, and,
• of course, wears down before the outer one. It is worth suggesting that some means of equalizing wear • be devised ; a detachable and' reversible wheel separate from the bearing housing, would make it possible to get the full life Out of a.pair of bands, instead of having to scrap both when only one is worm
An engineer officer connected with one of the PierceArrow convoys, who was troubled with this uneven wear of tires, often followed behind the trucks on a low sidecar. The road consisted of a centrally-paved strip, 10 ft: wide, with the outer stripacomposed of a mixture of mud, and more or less broken stone. When passing other vehicles it was necessary to run with the right-hand wheels in the mud, the left-band side. of the body then being a foot.higher than the righthand side. Under such conditions it was possible to see daylight under the outer of the dual tires, showing that the wear was all on the tread of the inner tire. It was also noticed that the standard equipment for front wheel tires was insufficient for the rough roads near the front. When dropping into shell holes and bumping over obstructions it was common tie see chunks of rubber born out of front tires, mush-1g them to be withdrawn from service more frequently than the rear ones. •
The experiment was therefore made of fitting wider front tires and narrower rear ones. In the place of the original set of 36 by 5 front and 40 by 6 dual rear, the engineer had fitted 36 by 6 front and 40 by 5 dual rear. This change was satisfactory, the mileage being greater and the cost less. There was less tendency for the front wheels to bog, and drivers said that road shocksat the steering wheel were less. The angle of wear for the inner tire was reduced, the outer one taking the load sooner owing to the narrow tread. The tendency to skid was also considerably reduced.
Body Sizes and Construction.
The body dimensions fixed for French trucks and confirmed by war use are a platform of 138 ins. by 67 ins, with removable sides 24 ins. high. The driver's seat must be 55 iris. wide. The hoops carrying the canvas top have to be of sufficient stiength for each of them to carry a load of 660 lb., the central hoop receiving 1300 lb. This allows wounded men on stretchers to be broughteto the rear when trucks are returning after delivering supplies, which was done extensively during the series of battles for the possession of Verdun. Owing to this specification the hoops are generally of steel and are fitted with rings. Many of the American trucks supplied to the Allied armies had a prairie schooner type of body, with a single top covering the load and the driver. This was a mistake, as the driver was left without protection when thenature of the load necessitated the removal of the top. Also with no division 'behind them, the men on the front seat were in the Position of a person in the mouth of a draughty alley. It is essential that the two tops be independent, and that there be a vertical division just back of the driver's seat. Drivers need much
058 more protection than is given on the standard commercial vehicle. This protection has not been given by American makers. The drivers have therefore provided it themselves. _sometimes with peculiar results. The British have a preference for a permanent driver's cab with side doors and canvas extension above the dash, so that in bad weather only the upper portion of the driver's head is exposed. The roof of the cab carries a rifle .rack. This arrangement is satisfactory, particularly for English weather conditions. It is a primary condition that the rear wheels must not break the uniformity of the body platform. On this account the body is raised a little.above the frame members. Advantage should be taken of the lateral overhang of the body to fit stout lockers alongside the frame members. This has been done in many cases to provide storage space for the regulation spares the
truck must carry. Few makers appear to have realized, however, that a couple of men having to live
and eat aboard the truck also need spares, and that no space is provided for their storage. This could easily be remedied by fixing additional lockers alongside. The construction of these boxes should be strong and door hinges should be at the top—that is, the door should open upward.
Although special vehicla are provided for the rapid transportation of troops, all trucks are liable to be called upon for this work on occasions. It is thus desirable that the body should be so designed that it can receive either a couple of longitudinal seats down the. centre and about 6 ins. apart or transverse seats. The accommodation required is of the most primitive nature, and, the fittings should not interfere in any way with the normal service of the truck. The brightly-tinted yellow or sandstone canvas tops supplied with many American trucks are a danger under European war conditions. The correct tint is gray, or blue-gray, or better still variegated with blue-gray as the dominant note.
Uses of Form-wheel-driven Tractors.
Practically all the ordinary transportation of the Allied armies is done by rear-drive trucks. The fourwheel driver is doing special work and does not usually come into competition with the two-wheel driver. In other words the two-wheel-driven truck is the moat satisfactory and the most economical type for the general transportation of feod, ammunitien and men. The four-wheel driver first came into use five or six years ago when the French army sought to abolish the use of horses in the haulage of its heavy field pieeeteFor this work it was impossible to consider the ordinary truck, for the artillery rarely operates along main roads, and in the majority of cases has towork on no roads at all. What was required, therefore, was a tractor capable of hauling the guns to all positions open to horse teams, and of doing the work fastee than it could be done by horses. The abolition of horses for haulage of the guns also implied the abolition of horses for the transportation of munitions; thus the tractors had to be capable of hauling trailers loaded with shells to any position that might be taken by the guns. The problem has been a difficult one, for it was not by any means sufficient to duplicate the points of application of the power in order to obtain a vehicle that could travel over any kind of country and mount any kind of obstacle. The difficulties met by ordinary trucks when obliged to abandon main roads also had to be faced by the four-wheel-driven tractors. The difference is that the four-wheeler's real work begins when the going is 'such that the ordinary truck would have ceased to be of any use. A large amount of experience has been acquired in the use of chains, paddles and caterpillar bands for the road, wheels in order to allow these tractors to operate under all kinds of cross-country conditions. The results, however, have been sufficiently satisfactory to ju-stify the belief that the horse-has ceased to he necessary to the heavy artillery batteries. (To be continued.)