A SUCCESSFUL LIGHT CHASSIS..
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Details, Details, of the A.F. Commercial Chassis to Carry a Total Load of 30 cwt., together with Notes on its Road Performance.
WE were recently afforded an opportunity of making a short road and hill-climbing test of the A.F. light commercial chassis manufactured by the Austrian Automobile Manufacturing Co., and marketed in this country by British Austro Daimler, Ltd., whose offices are at 112, Great Portland Street, London, W.1, and works at Grove Park, Edgware Road, Hendon, London, N. W. 9.
Some 200 of these chassis are now in active operation in this country, and that they have proved efficient and economical in service is shown by the fact that the call on the spares department is practically negligible, and, actually, in only two instances have any serious camplaints been made, and, on investigation, it was then found that the troubles experienced were due to -neglect.
• 'The proof of the pudding is in the eating, and we were not surprised at the service rendered when we went through the details of the design and examined the component parts, all of which show remarkable care and finish, all important gear teeth being ground— a refinement which is not always found in a commercial vehicle. Even hidden parts are machined all over or brightfinished in a manner which would, in some works, be considered far too costly as a commercial proposition.
The power unit is a four-cylindered inonobloc with the cylinders cast with the top half of the crankcase, which also carries the main bearings. The dimensions are 80 mm. bore and 110 nun. stroke, the power developed being '24 b.h.p. at 2,000 r.p.m., with a maximum of 27 b.h.p.
This engine is exceedingly lively, and the vehicle drives with an acceleration and ease of control akin to that of a private car, this being assisted by the fact that it runs on pneumatic tyres, 820 mm. by 120 mm. twins at the rear and singles of the same size at the front. Four forward speeds are provided by the gearbox, and-the ratios appear to be so arranged that the steps are not too abrupt, and we found, on taking the wheel, that gear changing was a matter of great simplicity.
The exainple we tested was fitted with a an body, but carried no load. Its anaxirnum speed was such that during most of the time the engine had to be throttled down, and several private cars we encountered were overtaken with the utmost ease, particularly on Broekley Hill, near Hendon, which was ascended on third gear at something over 25 m.p.h., our only criticism was that, being rather long in the leg, we found the accelerator pedal slightly too close to the seat.
The valves are arranged side' by side and are interchangeable, and the ignition is by a Bosch instrument. Carburation is attended to by a Pallas device, in which the jets can be removed almost instantaneously. This carburetter is of the triple-diffuser type. Ignition is controlled by a lever on the steering wheel. The engine runs very silently and is well balanced. An interesting feature is that if the oil supply is lowered to a dangerous extent the ignition is cut out. The lubricant is force-fed to the three main bearings and through the crankshaft to the big-ends, from which it is conveyed through capper tubes to the small ends. Silence is assisted by the adoption of !helical timing gears—bronze working against steel, whilst the dynamo is positively driven by an aluminium pinion. The design of the oil pump is unusual. It is of the semi-rotary plunger type, the rotary movement opening at closing the ail parts as required.
Cooling is effected by a honeycomb radiator, through which the water is circulated therrno-siphonically, the cooling being assisted by a fan mounted on an eccentric spindle which provides a means of adjustment for the fiat belt.
A point regarding the radiator is that it is removable -without breaking the bottom rubber joint, the water jacket connection being secured by a central bolt.
Three-point suspension is employed for the power unit, and the drive is taken through a multiple flat plate clutch; with an adjustable spring, and running in oil, to a compact gearbox suspended from two channel-section cross-members, and which is notable for the very short shafts which are employed. Cast with the gearbox casing' is an extension to the rear which encircles the brake drum and :provides a bearing behind it. This also is unusual, as, in most chassis, the shaft on which the drum is carried overhangs its bearing.
Aft of the gearbox the drive is totally enclosed, the axle casing being formed in pressed-steeL halves, which are extended to form a torque tube, at the front end ef which is a torque ball head which takes the place of the usual fork found in certain axles of this type.' Within this ball is a eardan joint with hardened steel dies and a large bearing area.
The loco-type foot brake has its shoes faced with . bonded asbestos fabric, the operation being by means of face cams, and the' final drive is through straight bevels, a bevel differential, and stout differential shafts on to which the sun 'wheels and Wad wheels are secured by keyed tapers.
The axle is of the half-floating type, the differential shafts being carried at their outer ends in large ball bearings. Internal-expanding shoes are employed in the rear-wheel drums. These are protected from the entry of dirt and water and are non-compensated, so that, in the event of one brake rod failing (which is unlikely, as these are of ample proportions), the whole of the braking power is not lost.
Steering is effected through a worm and nut gear, and the stub axles are centrally pivoted, -whilst the springing is effected by semi-elliptic springs all round, those at the rear being particularly Mug.
, A noteworthy point is that all the plates are ground on their faces to provide an even vibration-damping effect. The lighting is on the single-pole system' with a 1.2-volt accumulator, and on the dash is a neat switchboard with easily removable fuses for the various circuits. Other points of interest are a quickly detachable ball joint for the carburetter connections, an adjustable hot-air device, and.a stoutly constructed Antovac ptavided with a screw cover which can be removed complete with the float, balance weights, etc.
The wheelbase is 9 ft. 11 ins., which is 5 ins. longer than that previously employed, andthe overall chassis length is 15 ft, 4 ins. The chassis weight with "tyres is 20 cwt.
There are certain points in the design and the materials employed to which we have not yet referred. For instance, the cylinders, which are combined with the top half of the crankcase, can be removed together with the crankshaft, leaving the base in position. By this arrangement the alignment of the unit in relation to the other parts of the chassis is not disturbed. This not only promotes efficiency, but saves a considerable amount of time. All the gearwheels are constructed of special alloy steel, and elsewhere throughout the chassis material of excellent quality is employed. The steel disc wheels afford ample strength, but are not heavy.
Of particular interest, in view of the cases of running backwards which have recently occurred, is the sprag. This, however, is of the ordinary drop type with a forked end, the hook for the retaining cable being situated at the right of the driver's seat just behind the control levers. Many of these chassis are in use as • 14-seater coaches, one type of which we illustrate. This vehicle complete weighs 36 cwt., and it is of a type which should comply with the stringent regulations now imposed in many districts on motor coaches.
The price of the complete chassis is £295.