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Fighting Winter on the Motorway
Page 110
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Three Manufacturers • Producing Special Chassis for High-speed Gritting and Snowploughing on the New LondonBirmingham Road
Ykeep the new London to Birmingham motorway clear for traffic in all weathers, the Ministry of Trangport are developing gritting and snowplough vehicles which will be capable of performing at speeds of 30 m.p.h. and over.
Two types of chassis are being built: eight-wheelers able to carry 14 tons of gritting materials, and six-wheelers with a slightly lower payload capacity. All the vehicles will be fitted with specially designed spinner-distributor bodies, for use with grit or salt, produced by Atkinsons' Agricultural Appliances, Ltd., and will have front mounting brackets for straight or V-shaped snowplough blades.
The original Ministry requirement for the gritter chassis specified a 6 x 6 design. Both Atkinson Vehicles. Ltd., and Douglas Equipment, Ltd., set out to. produce vehicles to this configuration. Atkinson's prototype was complete and had been tested successfully when it was decided to run the gritters at 24 tons gross weight. Therefore, they had to have four axles to conform to regulations.
Design Altered
Thus the original Atkinson 6 x 6 vehicle was extensively altered and converted to an 8 x 6 layout. Douglas have proceeded with their 6 x 6 design, attempting, by the use of a petrol engine and lighter components, to provide nearly the same payload as the eightwheelers within a gross weight of 20 tons.
Atkinson's 8 x 6 chassis is novel in that only the front axle of the forward pair is driven, the propeller shaft passing over the second steering axle. It is thought that this is the first vehicle to have such a layout, which is also a feature of the chassis being produced by Scammell Lorries, Ltd.
The Atkinson is powered by an A.E.C. 11.3-litre engine developing 165 b.h.p. at 2,000 r.p.m. The drive is taken through art 18-in.-diameter single-dry-plate clutch to a Z.F. AK6/75 six-speed constant-mesh G8 gearbox with an overdrive sixth ratio of 0.71 to 1. A power take-off on this unit drives the compressor for the vehicle's braking system, which is of direct-airpressure type on the rear bogie and air-hydraulic on the front axles.
Coupled to the main gearbox is a Z.F. V.G. 500 auxiliary and transfer gearbox. This unit provides an additional low ratio of 1.85 to 1 for the main transmission in addition to straight-through 1 to 1 drive. It also incorporates a torque-splitting device todivide the drive between the front and rear axles. A power take-off from this box provides the drive for the conveyor belts fitted in the gritter body giving a power take-off speed proportional to road speed.
Open propeller shafts from the auxiliary gearbox drive the two 7-in.centre overhead-worm rear axles and the spiral-bevel-drive double-reduction front axle. Single Trakgrip tyres are fitted all round, with 12.00-20 in. (14-ply) on the front wheels and 14.00-20 in. (22-ply) equipment at the rear.
Clearance has been left to allow the fitment of chains which will be provided but, it is hoped, not be found necessary. They can be expected to last for only 8-10 miles at speed.
Necessarily, the frame of the 16-ft.-71-in. wheelbase chassis is robust to withstand ploughing loads and possible collisions with kerbs and similar obstacles when working. It is a conventional ladder-type structure with 1347in.deep side members in 4-in.-thick material having 3-in.-wide flanges.
The balance-beam-type rear bogie is mounted on a sub-frame, as is the second steering axle. Hydraulic power assistance is provided for the steering, and the steering servo and the grit-spinner motors are powered by separate engine-driven hydraulic pumps.
Following the same general configuration as the Atkinson, Scammell's 8 x 6 design is powered by the Leyland 0.680 11.1-litre oil engine. This unit produces 160 b.h.p. at 2,000 r.p.m. and drives a Scammell six-speed constant-mesh gearbox through a 161-in.-diameter clutch. The gearbox has an overdrive top ratio of 0.715 to 1 and incorporates at the rear a separate two-speed transfer gearbox. This unit splits the drive to the front and rear axles and provides either 1 to 1 drive or a reduction ratio.
Like the Atkinson, the forward driving axle is a double-reduction unit, whilst the two axles in the rear bogie, which is of walking-beam-type, have overheadworm driving heads of 9-in. centres.
The vehicle has• power-assisted steering and an air-pressure braking system. Again, Trakgrip tyres are fitted all round, but in this case 12.00-20 in. (14-ply) at the front and 14.00-20 in. (18-ply) at the rear.
The Scammell 8 x 6 has chassis-frame longitudinals 12 in, deep in --in.-thick material with 3-in. flanges. At the forward ends they are reinforced to support the snowplough attachment frame. A theoretical top speed of over 40 m.p.h. should be reached by the 17-ft.-9-in.wheelbase vehicle fully laden.
20 Tons Gross
The Douglas 6 x 6 chassis being built will operate at 20 tons gross weight. They are of 15-ft. wheelbase and have Rolls-Royce B.81 petrol engines developing 196 b.h.p. at 4,000 r.p.m. The primary gearbox is a Rolls-Royce fourspeed, automatic unit incorporating a fluid flywheel, and this unit is coupled to a 1.4 to 1-ratio single-speed auxiliary gearbox and a two-speed transfer box dividing the drive to the front and rear axles and providing additional transmission ratios of 1 to 1 and 3.89 to 1.
The steerable front axle (power steering is fitted) is a spiral-bevel unit, as are the two axles in the fully artictilating real' bogie. Brakes are air-hydraulic at all wheels and 9.00-20 in. (14-ply) tyres arc fitted all round.
Douglas are also manufacturing chassis to carry Rolba. or AEB.1 rotary snowplough heads. These vehicles now have a 130 -b.h.p. petrol engine as the prime mover and a 165 b.h.p. Rolls. Royce petrol engine to drive the ploughing head. The remainder of the chassis was .fully described in The Commercial Motor on April 10, 1959.
As an adjunctto the gritting vehicles the Ministry are to acquire two sweeper. collector trailers from abroad. These an Streicher and Faun machines which an towed by tipping lorries into which the dischargetheir sweepings.