AMERICA'S ARMY LORRIES.
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Details of the Light 15-cwt. Class AA and 5-ton Class B Military. Vehicles.
IN OUR LAST ISSUE we drew attention to the "Liberty ',' lorry, as the 3-ton • War vehicle now being built for the U.S.A. QuartermasterGeneral's department is colloquially called.Mann.fa-cture of this unit now being in full swing, attention is being devoted to the two other vehicle's entering the American war lorry programme—the class AA 25 cwt delivery van and class B 5-ton lorry respec
tively. . .
This 15 cwt. vehicle is probably the most important of the series of these officially-designed Motor vehicles. Although elaborated essentially for the Quartermaster-General's Corps, and for which large numberii will be :required, it will. also be extensively utilized by theNavy Department, Marine, Signal and Medical Corps, and last, -but not least, by the Postal. Authorities as well. ' In fact, at the present moment, it is difficult._ to say whence the demand will be heaviest—the Medical or the Postal. The first named is to receive precedence in respect of 3500 vehicles, but the second-named is to be supplied With 400(1 lorries during the year to meet the demands of the new parcel post routes which have been. evolved thriiugh the States east of the .Mississippi, The circumstance that this Vehicle would have to figure prominently in the medical service played a. farreaching influence upon its :design. • The necessity. to render the chassis adaptableto ambulance service 3mposed the introduction of a torque arm and .radius rods, although in the two.heavier classes .of lorries the final drive selected is the Hotchkiss, in which torque and propulsion are taken through the rear springs. By confining the Mission of the springs to the carriage of the body and live, load, the designers concluded that the primary essential of an ambulance vehicle; namely, easy riding, would be more effectively
assured. ,
Generally considered, the lines of the 15 cwt. vehicle follow thoSe of the other two and heavier models, 'although there are one or two outstanding features demandingmore than passing notice. The fourcylinder engine is of the detachable head type, and is fitted with dual ignition and hot-spot manifold. • The Bosch magneto, _Kenny distributor and water pump driven by one longitudinal shaft are on the left•side of the engine—looking from the driving seat—while the governor and generator are oit the opposite side. One salient feature is the incorporation of an elec7 trio starter, whence this model differs from its two heavier brothers. Another radical departure from general practice is the design of the crankcase, which is such as to perinit the use of 4 in.: by 5 in. cylinders as selected for military service, or smaller cylinders of 31 in. by 5 in. to meet Post-Office requirements: The reason for this arrangement is that the latter departfuent considered the military power unit of .42 h,p. to be in excess of its needs, and, as this vehicle is to become the standard light vehicle for parcels-post serVice, the provision for interchangeability was made. Accessibility of all components is a prominent feature. Three-point suspension is adopted for the gearbox, this following somewhat novel lines. The front point resembles -a trunnion type bearing, while the two rear .supports may be said to follow semi-universal lines. This disposition of the gearbox is such as to permit its easy removal without disturbing the .clutch, the .drive from which to' the gearbox is transmitted through two fabric universal joints. Another little refinement, facilitating the removal of the gearbox, is the mounting of the brake lever on -a special bracket carried on the gearbox cover. This can be easily and quickly released when it is desired to bring the. gearbox adrift. As with the heavier trucks, the gearbox
-is provided with a large-sized side spout through which it may be readily charged with lubricant from beside the ear, the withdrawal of a plug being the only preliminary to the operation.. On the right-hand 'side of the gearbox is a tyre pump. To secure easy riding special attention has been devoted to the springing arrangements. The rear springs are unusually long-54 inches—and are built up of 11 leaves. This arrangement cuts the frame overhang at the rear spring bracket very short. Seeing that these vehicles are likely to be called upon extensively for towing, the frame is well braced at the corners to absorb the strains of the towing-hook. The class B 5-ton lorry is. generally conceded by American critics to represent the culmination of native effort in heavy-vehicle design as expressed by the Societv of Automotive Engineers by whom it was elaberatect This, again, is composed throughout of standardized parts. The two experimental vehicles have been completed and are being submitted to searching mechanical test and examination.
The frame is of the pressed channel section type constructed of open hearth steel, tapered at the front for lightness and to provide ample space for the reception of the radiator.
The gearbox is supported fore and aft by a heavy forged and tight-pressed steel transverse member respectively, the former serving also as a support. to the four-cylinder 4.1 in. by 6 in. engine. The motor is given a three-point suspension, as is also the gearbox. Four forward, speeds and a reverse are provided. In order to give the 18 in. ground clearance demanded,
at a point midway between the front and rear wheels, the main and counter shafts are set in the horizontal. plane with the long gearshaft above to the left. The final drive is the Hotchkiss.
The dash is so designed as to carry one half of the petrol supply in a tank placed thereon, the. balance of the supply being carried under the driver's seat. Lubrication has received attention. All spring bolts, shackle pins and brake-rocker shafts are oiled• upon the capillary system with wicks drawing the oil from large-sized pockets, which only demand charging at monthly intervals,integral with the bracket castings to the bearing surfaces. Seepage ensures. the leaves of the springs receiving their required supplies of lubricant. The wheelbase is 160i ins:, the maximum lengstkin
the original specification having been increased by 44 ins. This revision was made to ensure the proportion. of the load on the rear axle being kept below 90 per cent. The tyres are of the pressed-on type—the original demountable wheels were tdiscarded in the light of experience deriv,ed from the battle front. By this modification a saving of 400 lb. in weight has been secured. The rear wheels are shod with 40-in. twin tyres in lieu of the original 36-in, specified, it being discovered that the amended size of tyres not only gave 2 ins, further clearance but enhanced adhesion. superior rolling on bad ground, lower fuel consumption, higher tyre mileage and an increase of 11 per cent. in vehicle speed for a given engine speed. The use of castor wheels on the tailboard represents quite a new line of thought.