A New A.E.CThe Crocodile 18-tonner
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THE accompanying illustration shows one of three similar machines that have just been built by the Associated Equipment Co., Ltd., Southall, Middlesex, for Pickfords, Ltd. It is specially constructed to carry a concentrated load of 18 tons, but its chassis dimensions are such
that, when transporting loads that do not cause the gross weight to exceed 22 tons, the vehicle falls within the maximum legal limits and may be licensed as an ordinary lorry.
Its unladen weight is 7 tons 16 cwt., and the overall length is 30 ft., whilst the layout ensures that, when normally loaded, each wheel supports an equal share of the gross weight,
It will be observed from the picture that the centre portion of the frame is dropped, the height above ground level being actually 2 ft. This has necessitated employing special construction to withstand the exceptionally heavy stressing thus caused.
To afford the maximum loading space, the front and rear bogies are positioned as far apart as possible, the distance from the front axle to the rear-bogie centre being 23 ft. 3 ins. Each of the main side members of the well is formed of a pair of 12-in. by 31-in. rolled-steel channels, set back to back and reinforced by flange plates above and below.
At the front the structure incorporates pressed-channel side members, which are 15 ins, deep where they join the attachment to the well, whilst over the rear bogie, side members similar to those of the well are used.
Every practicable precaution has been taken to ensure strength at the junction points of these three sections of the frame, sturdy gusset plates and angle-pieces being freely employed. There are, moreover, transverse bolsters at the ends, which, in conjunction with outriggers from the centre portion, carry channels at the sides of the dropped platform. These afford support when the lorry is being loaded from the sides.
With regard to the general layout of the chassis, an A.E.C. oil engine is installed. This has six cylinders of 115 mm. by 142 mm. and develops 110 b.h.p. at 1,700 r.p.m. Power is transmitted through a standard fourspeed gearbox, modified to suit an auxiliary gearbox, which gives additional low forward and reverse ratios.
At 1.000 r.p.m., the road speeds range from 1.8 m.p.h. in low first gear to 12.7 m.p.h. in direct drive. In reverse the auxiliary gearbox gives a speed of 1-5 m.p.h.
A heavy I-section stamping forms the first axle, whilst the second is machined to rectangular section from the solid. The rear axles incorporate one-piece steel casings. Both are driven by worm gears affording a reduction of 10-k to 1, and between the final drives there is a third differential. Torque reaction is resisted by a flexible plate mounted below the axles.
In the braking system there are Incorporated two vacuum-servo motors and master hydraulic cylinders, one of the latter being mechanically controlled by the pedal. They actuate brakes on all eight wheels. The hand lever operates on the four driving wheels. No fewer than 672 sq. ins, of frictional area are afforded by the complete set. All wheels are shod with 12.75/20 low-pressure single tyres.