Atkinson Make a Desert Giant
Page 71
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DESTINED for work in the oil lands of Saudi Arabia, a new Atkinson 6 x 6 vehicle, the Omega, has just been completed. Although intended for specialist duties, the design is such that, with few modifications, it could form the basis for a general crosscountry or heavy tractor chassis.
The power unit employed is the RoilsRoyce C6.SFL, a six-cylindered supercharged oil engine having an automotive rating of 250 b.h.p. at 2,100 r.p.m. The main gearbox is the Wilson self-changing model RV30, giving eight forward speeds and two reverse. The auxiliary box has been specially designed for this model by Atkinson Vehicles, Ltd. Clayton power steering is employed. Drawbar pull is 45,000 lb. either forward or in reverse.
Wheelbase to the centre of the rear bogie is 20 ft. 2 in., whilst the measurement from the rear of the cab to the end of the frame is 17 ft. 8 in. The rear track is 7 ft. 34 in., overall width outside the tyres, 10 ft. 6 in., and front track 6 ft. 84 in.
When laden, the frame height above ground level is 4 ft. Frame members of 11-in. section are employed and the chassis is of bolted construction throughout. The front bumper is connected solidly to the frame and there are utility hooks and towing pirates at front and rear.
The tractor has an all-up weight of approximately 15 tons and it will form part of a heavy articulated outfit to which any number of additional trailers may be attached. It is expected that the running will usually be over open country with a soft, sandy surface. Tyres of 16.0020-in. (10-ply) are being used at present; recommended pressures are 25 p.s.i. on the road and 18 p.s.i. for sand.
A 30-gal. radiator with 1,500-sq.-in.
frontal area is provided. This incorporates Withnell tubes and, as specified by the customer, is of all-welded steel construction to suit the desert water. A
condenser tank draws off the steam and liquefies it if the radiator water boils.
Two 25-gal. fresh-water tanks are carried. Before being dispatched the Omega will be equipped with an air cleaner incorporating the new Purolator dry elements.
The range of forward ratios for the eight-speed gearbox is 0.68, 1.022, 1.446, 2.195, 3.09, 4.64, 6.57 and 9.98 to 1; the reverse ratios are 11.53 to 1 in low and 2.53 to 1 in high. With the Wilson fluid coupling is incorporated a specially fitted airdisplacement fan.
The main gearbox and auxiliary box are separately mounted with a propeller shaft between them. The auxiliary box has a high ratio of 1.1 to 1 and a low ratio of 1.6 to I. By the action of a solenoid air valve the selection of the low ratio automatically engages the frontwheel drive.
Changing up brings an instant response in the main gearbox, but, as set at the moment, there is a 2-sec. time lag on the change down. By means of an override knob it is possible to cut out the delay when it is desired to drop into neutral.
On the model that has just been completed air brakes are applied to the rear wheels only. The hand brake is assisted by a limited air pressure, so that in the case of its locking, depression of the pedal will release it.
The range of instruments in the cab includes a low-air-pressure safety warning device. It is also equipped with a highwater-temperature and low-oil-pressure safety reactor which can be arranged either to give warning at the appropriate time or to shut the engine down to idling speed.
The eight-wheeled rear bogie is a specially modified Kirkstall hypoid design with epicyclic hub reduction, giving a 10.18 to 1 ratio. The Kirkstall front
wheel-drive hypoid double-reduction axle is of the same ratio. Semi-elliptic springs are employed.
All-steel construction is used for the cab, which is insulated with Fibreglass and has graded tinting to the windscreen to counteract glare. Both windscreen and ,windows are heatproof and shatterproof.
Driver and mate are accommodated on Chapman ventilated seats mounted on pedestals hydraulically adjustable to suit the individual. The foam rubber of each seat is enclosed in a special canvas bag so as to preserve it from deterioration by the ingress of sand. Tygan is employed for the upholstery and door panels.
The 450-gal, fuel tank can be checked by means of a dipstick, mechanical gauge or electrical gauge. As the tank is filled the fuel passes through six replaceable paper filters that are fitted in such a way that illicit abstraction is impossible.
A Darlington S70 winch with fin. rope is fitted. All winch controls are located in the cab, the fuel tank being cut away in such a manner that operation is in full view of the driver. Two spare wheels are carried and are lifted by a hand winch.
The front-wheel drive is air-selected and the full power take-off is manually selected.
Atlas dry-charge batteries have been supplied for use on this vehicle. The full incidental equipment includes air-brake connections at front, and rear, a built-in Lyre inflator, air-operated windscreen wipers, air horn and electric horns.