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A MIGHTY ANT

20th April 1951, Page 96
20th April 1951
Page 96
Page 97
Page 96, 20th April 1951 — A MIGHTY ANT
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IN THE

By P. G. TUCKER How Britain's Most Powerful Tractive Unit, which Can Attain a Speed of 28 m.p.h., is Erected at Basingstoke ONE of the biggest and most powerful tractors ever to be made in this country is the Thornycroft Mighty Antar, which was described in great detail in "The Commercial Motor" dated March 3 last year. Its advent followed consultations between engineers of the Iraq Petroleum Co. and the Thornycroft designers. An order was placed for a prototype in March, 1949, and in December of that year it was completed and ready for testing. The first production vehicle was shipped in April, 1950.

The tractor draws a Crane 50-ton semi-trailer and the gross laden running weight of the whole outfit may be up to 100 tons. A number of these machines is now being operated by the oil company, which is using them for the transport and stringing of 560 miles of pipe from Kirkuk to the port of Banjos, on the eastern Mediterranean coast. This project has for its objective 1,500,000 ton-miles of transport a month, the route being over desert tracks and sandy wastes with climbs rising to 3,500 ft. above sea level. in the winter, 20 degrees of frost are not unusual, and in the summer the shade temperature rises to 120 degrees F. or more. wheeled rear bogie with doublereduction gear in each axle, power-assisted steering, and airpressure braking. The unladen weight is 151 tons and a speed of 28 m.p.h. is obtainable on the overdrive. A gradient of 1 in 21 can be surmounted.

The main and auxiliary gearboxes and many other items are manufactured at the Basingstoke works of Transport Equipment (Thornycroft), Ltd., whilst some components, developed by specialist manufacturers to Thornycroft requirements, are supplied ready for assembly in the chassis. The first operation is the drilling of the individual frame members and their assembly. Although the side members are 111 ins, deep and in. thick, there is a full-length secondary channel fitting into the main member, to which it is held by welding the edges of the flanges at intervals.

Additional strength is given to the frame structure by a bolted-on flitch plate running between the forward rear-spring mounting and the rear front-spring mounting. In the region of the bogie assembly there is a reinforcement plate measuring 9 ins. deep by in. thick. When the deepsection dual cross-members, with their heavy diagonal bracings, have been added, the finished frame forms a basic structure of immense strength.

The next stage in assembly is the erection by fitted bolts of the numerous brackets, such as those for the bogie springs, torque-reaction members, brake relay gear, silencer, compressor tank, pedal assembly, and so on. After these have been attached, the front springs are added and the front axle, complete with its wheels, is manceuvred into position. Then follows the steering-gear assembly, including the hydraulic gear which provides power assistance.

The chassis is now getting towards the self-supporting stage, for after the bogie springs have been fitted. the bogie axles, complete with their wheels, are placed in position. Then follows considerable detail fitting as the torque members, radius arms. brake cylinders and linkages gradually assume their operational status.

As the various units are added, electricians and pipe fitters start to couple up the complex system of wiring, together with the oil, air and fuel pipes. While the bogie assembly is being built up, other members of

the crew install the power unit, which is received at the works rigidly mounted in a sub-frame. This subframe and special parts, such as manifolds, sump, pipes, etc., are manufactured by the Thornycroft concern, and are supplied to the engine builder in order that the unit may be tested complete with all auxiliaries in place.

Thus, ultimate assembly amounts to little more than dropping the engine, complete with its sub-frame, on to the rubber-bushed supports at the front and rear, and coupling up torque-reaction arms on each side. The design of the mounting ensures that a minimum of vibration is transmitted to the chassis, in that a line joining the front and rear supports passes through the centre of gravity of the engine After the engine has been installed, the gearbox unit is swung into position. This unit comprises the main and auxiliary gearboxes, clutch, flywheel and jack-shaft, compressor, two starter motors and dynamo. An extension of the flywheel housing carries a built-in fan and leading rearwards from its cowling are two air ducts running to the clutch housing. Thus there is always a powerful stream of cool air which keeps clutch and gearbox cool.

Before entering the assembly shop I toured the machine shops, more particularly to trace the evolution of the gearbox unit. 1 saw the gears and shafts in various stages of manufacture and was impressed by their sizes when compared with normal heavy-vehicle types.

An extensive range of machine tools was being employed, including such machines as Maag gear-tooth grinders, Orem spline grinders, Matrix thread grinders and a Churchill Red Ring gear shaver. The latest Hydroptic B Genevoise jig borer is used on the production of main and auxiliary gearbox cases.

An examination of the individual gear wheels revealed that high degree of finish which is characteristic of the chassis maker's products.

Although I am dealing with the assemblâ–  of the Mighty Antar. I feel that this slight digression is not inappropriate, because, as I have already mentioned, the gearbox unit is built throughout in the Thornycroft works.

After the gearbox unit has been installed. the two tubular propeller shafts, with their needle-roller universal joints, are fitted. These shafts, which are interchangeable, have an intermediate bearing carried in a substantial housing bolted to the chassis frame The scuttle, complete with electrical equipment, instruments and wiring, is now brought to the assembly shop and lifted into position in the same way as other unit assemblies. To minimize heat transference into the cab, this scuttle is built up of two spaced plates with a layer of asbestos packed tightly between. The cab floor, which is built as a unit, is similarly treated with sprayed asbestos.

With the addition of wings, the two radiators, two fans, front guard, two 100-gallon fuel tanks, and the cab, a Mighty Antar is nearing the stage where its rear wheels will revolve under power from its engine.

Despite the size of the machine, its assembly is carried out with no more concern than a standard product.


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