In the brief sketch already given of the principal trials and manœuvres in which motor transport has figured, some indication has been afforded of the attempts made by the British Government in this direction. The most consistent, and probably the most successful, efforts have however been made by our neighbours, the French, who have for this special purpose given much encouragement to the development of internal combustion tractors driving all four wheels. The movement dates back about three years, and owes its origin to the need for hauling 155 m/m siege guns along roads and across country. The first type of tractor produced to meet the requirement was the Chatillon-Panhard. The weight of the first type with full load was in the neighbourhood of 22 tons, and more recently efforts have been made to evolve lighter types weighing about 14 tons with their load, the belief being that these rather smaller machines would be of great general utility. Some very important trials in this connection took place in France early in 1914, four types of tractor participating, namely, the Latil, the Schneider, the Chatillon-Panhard and the Renault. The first-named is a development of the Latil type of lorry, in which the engines drive the front wheels, and the whole power plant is concentrated on to the fore carriage, the back wheels and the platform being really nothing more in principle than a two-wheeled trailing vehicle. An extension of this system involves the use of three differential gears, one for each pair of wheels, and a third as a balance gear half way along the vehicle from which the drive is taken fore and aft through longitudinal shafts and worm gearing. All four wheels are steered as well as driven.
In the Schneider, the drive is taken from a gear box containing two sets of sliding gears through cardan shafts to the front and back axles, and alternatively, when required, to a capstan enabling the engine to haul through the medium of a wire rope. In the Chatillon-Panhard, the transmission is so arranged as to involve no universal joints, and only one differential gear. This is mounted on a transverse countershaft, and the power is taken to the wheels through bevel gears at the ends of the countershaft, and four diagonal shafts driving in their turn auxiliary shafts upon which are bevels engaging with similar bevels on the wheels. The Renault is a very simple machine of its type. The drive is taken fore and aft from the gear box by cardan shafts leading to differential gears on the front and back axle. Either one of the differentials can be locked when desired to help the machine to find its way out of difficult positions. Yet another machine which is available to the French Government, though it did not take part in the trials mentioned, employs electrical machinery in place of the usual mechanical transmission gear. The engine drives an electric dynamo, which supplies current to four electric motors, one for each wheel. On the whole, the French four-wheel driven tractors have performed very well under severe tests, and it is stated that approximately 300 tractors of one or other of the types mentioned are available for military service, though it is possible that this estimate is somewhat exaggerated.
“The Autocar” illustration.
A KRUPP MOTOR GUN-CARRYING LORRY, SHOWING THE RAMPS UP WHICH THE GUN HAS BEEN HAULED SERVING ALSO THE PURPOSE OF HOLDING IT SECURELY IN POSITION.
For the rapid transport of light artillery various special machines have been devised, providing either for the carriage of a gun upon the platform of a motor lorry, or for the construction of a gun-carrying vehicle forming one complete unit. In this branch of development the Germans have shown the most initiative, and Krupps have got out several interesting designs. In all of these strong motor lorry chassis are used. A usual system is to fit, by hinging to the back of the chassis, strong ramps up which the gun may be hauled, either by the power of the motor engine or by other means. When on the platform, the gun wheels sink into depressions formed to take them and also bear up against shaped vertical stops. When the gun is in place the ramps are swung over, and are so designed that their ends can then be conveniently attached rigidly to the vertical stops, the ramps themselves also bearing against the gun wheels and holding them quite secure; or in an alternative method, the ramps are arranged to grip the axle of the gun carriage.
Special designs are for motor vehicles capable of a good turn of speed, and arranged to carry guns especially intended for fighting against aeroplanes or airships, and consequently so arranged as to allow of their muzzles being swung up until the gun assumes a vertical position.
Other special arrangements of motor vehicles are those providing for the carriage of machine guns, but this type perhaps comes more properly under the title of an armoured motor car.