THE CHAIN-TRACK MACHINE FOR TRANSPORT.
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The Renault Tank : Its Construction and Use, and Its Peace-period Modifications.
AS SMALL French Tanks are already being used for hauling barges on the northern and eastern canals of France, and are intended to be employed shortly, in a modified form, for forestry and agricultural work, there is more than a war interest in. these vehicles.
The " Whippets," as they are known in England, are the Renaults of France. The Tank idea appears to have originated in France, unknown to England. But the French Tanks did not appear until a few weeks after the English, and gave very indifferent results. In the opinion, of one leading French Tank officer, the only •good point about the first French Tanks is that they were copied by the Germans, who imagined that, as they had come after the British, they must be an improvement. Fritz accentuated all the bad features of the French Tank and got the worst article in Europe.
It was at this point that M. Louis Renault turned his attention to a light Tank, to carry two men, a driver and a gunner. These were produced in the autumn of 1917, and went into action early in 1918. In his factory at Billancourt, near Paris, Renault had a capacity for 12 Tanks a day, and, on the signing of the armistice, had actually produced 2450. In addition. to this, the Renault-type Tank had been built in other French factories, as well as in two Italian. and several American factories.
Fully equipped with gun or automatic rifle, the Renault Tank weighs 61,tons. It has a maximum speed of 4.9 miles an hour, and can climb a gradient of 45 degrees. The engine is of the four-cylinder block type of 9-5 rum, bore by 160 mm. stroke, and the machine can be handled with ease by two men.
The Renault Tank is divisible into three components—the armour-plated body, which carries the engine; the gearbox and the reducing gears ; and the
two frame members with their endless tracks. These "frame members ".are-mobile in relation to the body, for they pivot around the rear axle and move in guides at the,forward end.
There is very little that is distinctive in the engine. It is mounted at the extreme rear of the body, and has its starting handle preiecting through the tail of the Tank. (For war work this starting handle is not used.) The cylinder casting is of the L-head type, with enclosed valves. The crankshaft is carried in. three substantial plain bearings, and lubrication follows on general Renault lines, with the exception that the sump is dry. All the oil supply is carried in. lateral chambers cast with the aluminium base chamber, but having no direct communication to the interior of the engine. The oil is pump delivered from, these tanks to the bearings, and the overflow from the bearings is carried back by means of two pumps (one at each end of the base chamber) to the oil tanks. This enables the engine to operate at any angle without fear of seizing. • No water pump is fitted. The radiator is placed ahead of the engine, thus almost across the middle of the Tank, and is fitted with a fan, driven by a Dunlop motorcycle belt, which draws in air through' all the crevices of the armour plating and expels it vertically after passing it over the radiator tubes. In this way the radiator fan not only cools the water but ventilates the interior of the Tank. The engine has governor control which limits its speed to 1000 revolutions.
The _carburetter is a Zenith, fed from a petrol tank placed ahead of the engine. The excess fuel not absorbed by the carburetter passes to an auxiliary tank directly-above the engine, and when a certain pressure has been attained in this tank the excess returnee by means of a check valve, to the main tank. The auxiliary tank thus acts as a compensator and supplies the engine with fuel if the feed pipe from the main tank should break. The actual power developed by the engine is 30 h.p. at 1100 revolutions, 35 h.p. at 1300, and 39 h.p. at 1500 revolutions.
The main clutch is an inverted leather-faced cone, similar to the one used on Renault lorries. Power is transmitted through a four-speed-and-reverse gear sot, with gate change, to a couple of lateral cone clutches, of big diameter, lined with Ferodo. On each side of the engine base there is an aluminium housing containing a train of spur-reducing gears. The first driven pinion in each of the two trains of reducing gears is connected by means of an Oldham coupling • to the lateral clutch shaft. As there is separate control for the two lateral clutches, by withdrawing either one or the other, the whole train of reducing gears on either side can be immobilized. The total gear reduction is 114.5 on first and reverse, 56.3 on second, 34.3 on third, and 22.3 on fourth gear. The drawbar pull of the Tank is 11,090 lb. on first gear and 992 lb. on. fourth.
This general arrangement of engine and gear set makes possible a very compact engine-room ; the power is carried from the engine, forward through the main clutch and the gearbox to the two lateral clutches, then rearwards through the two trains of reducing gears to the main driving sprocket. Thus the total length occupied is equal to that of the engine and the gearbox.
Louis Renault claims a patent for his system of " caterpillar " or track-laying mechanism. This consists of a main frame with a sprocket in plain bearings at the rear, and a wood disc pulley with a metal rim carried in a fork at the front. By reason of the fork construction, this pulley is adjustable for lateral position. The endless track, which has a width of 13/ ins, with a length of 110 ins, in contact with the ground, is driven by the rear sprocket and passes around the wood disc at the front. The main frame members of each track-laying mechanism carry two sets of leaf springs on balance arms, and at the extremities of these balance arms are four bogies, the wheels of which run on the endless track. .
Provision is made for the automatic tensioning of the endless track. As will be seen from one of the illustrations, there is a channel-section beam pivoted in a bracket just ahead of the Main driving sprocket and held at the opposite end by means of a guide and a heavy coil spring. This beam is fitted with six rollers, which act as a support for the endless track for a length of about '78 ins. While this arrangement automatically takes up the slack in the endless track, permanent adjustment is provided for by reason of the idler pulley mounted in a fork.
Control of these Tanks is particularly' easy. The driver sits on a low seat—nothing more than a cushion on the floor—sat the forward end of the vehicle, and has to operate the three usual pedals of a lorry and a normal type of change-speed lever. The ignition point is fixed. As a precaution against the driver being wounded in the foot, there is a throttle control placed on the side of the Tank. There is no steering wheel, but in its place are two levers conveniently situated to left and right of the driver, by means of which the lateral clutches areaoperated. By milling on the left-hand lever the left-hand lafezal clutch is c30 withdrawn, and, in consequence, the train of reducing gears on that side is stopPed and the endless track is immobilized. There is a band brake on each lateral clutch drum. The first movement of the lateral clutch lever is to withdraw the clutch, and the second to apply the brake. Thus, according to the position of the lateral lever, the clutch can be slightly withdrawn, leaving a certain amount of slip, or it can be fully withdrawn and the brake applied so as completely to lock the endless track on that side. When travelling in a straight line the driver is concerned only with his three pedals. When he wants to turn he pulls on the lever on the side to which he wishes to go. The operation is easier than driving a lorry.
The protection of the Tank consists of bullet-proof plating varying in thickness from .3 in. to .6 in. As far as possible, vertical surfaces are avoided, for whenever the surface can be inclined or rounded the thickness of the walls can be decreased without danger. In the centre of the Tank there is a revolving turret mounted on ,ball bearings, within which there is either a machine gun or a 39 ram. cannon. The gunner either stands or sits on a girth within this gun chamber and can operate his weapon in any direction. The gunner thus has the -driver sitting low down ahead of him, and, on the opposite side, the radiator, followed by the gearbox and the engine.
The method of operating these Tanks was in companies of 20, of which one would be the commanding officer's Tank fitted with wireless telegraphy. About half the Tanks in each company are fitted with a maelnine gun and half with a cannon. Their most successful work on the Front has been the cleaning out of machine gun nests.
The total length of the Renault Tank is 161 ins. ; the width is 66 ins. ; and the track, measuring from centre to centre of the bands, is 56 ins. As the length of the Tank is not sufficient for it to span a trench, it is fitted with a curved tail, bolted in position. This gives additional length, but, at the same time, it largely facilitateil the operation of going into and climbing out of a shell hole or an abandoned trench. The tail prevents the nose of the machine bedding itself in the forward angle of the trench, and it gives a support against the rear wall when climbing out of a. trench or hole.
In t-he recent use of Renault Tanks for hauling barges, both the tails and the turrets have been removed, with, of course, a considerable reduction in weight. As BOOR as these vehicles are built specially for peaceful occupations, there will be a material further reduction, for the armour-plated body can be replaced by much lighter material. The mechanical features will not change in any respect, nor will the manufacturing methods be modified. At present the Tanks are built on rails, according to the method usually only associated with Ford ears. The body of the Tank is placed on a heavy carriage running on a central pair of rails, and is moved forward hour by hour as the various units—engine, clutch, gearbox, reducing gears, controls, etc. —are put in position. Flanking this central pair of rails are other sets on which the self-laying tracks are assembled, until they are ready to be connected up to the Tank body for which they have been prepared. Each day 12 finished Tanks move out of the assembly hall ;under their own power.