New Trailer to Work in Mine
Page 58
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When this lever is fitted to the rear • bogie the trailer can he accurately steered by hand, withvery little effort,. to assist the front bogie around sharp corners.
TYPICAL of the wide variety of trailers for special purposes which can be made by Carrimore Six Wheelers, Ltd., Great .North Road, North Finchley, London, N.12, is one 'which has just been designed and built to the order of Imperial Chemical
Industries, Ltd.
This is for use in a mine at Billingham-on-Tees, where a special mineral rock is extracted. In order to go down the mine shaft the trailer had to be built in halves, split along the longitudinal centre line. It has been assembled at the maker's works, but will have to be taken apart again and then reassembled at the bottom of the mine.
The trailer is double-ended, and can be operated equally well in either direction. Two unusual features are the method of applying the brakes, and the means for steering the rear bogie by hand.
Rock-cutting machines are to be carried between the mine face and the overhaul works at the foot of the shaft. These machines, known as joy loaders, run on caterpillar tracks and are winched on to the trailer by detachable loading ramps. They can be up to 30 ft. long, running on a 7-ft. 4-in. wheelbase.
Consequently, the trailer has to have a flat, unbroken surface, with ample space for the load to overhang at each end, and this surface has to be as close to the ground as possible.
The load platform is 13 ft. long and 9 ft. 8 in. wide. Its framing is entirely in mild-steel channel sections, which, except for the bolted joint down the centre line, are all welded together. Each half of the platform has three longitudinal members 13 ft. long, of which D12 the outer two are of 10-in. by 3-in. channel and the third is 6-in. by These are connected by short sections of 6-in, by 3-in, channel, in four sets each of 10, .
. The floor is in two layers of hardwood, each 2 in. thick, and at rightangles to each other. These sit on top of the intermediate 6-in, channels, but are flush with the surface of the main 10-in. channels.
Maximum load to be carried is 20 tons, which may have to be concentrated on any part of the platform.
The trailer runs on two bogies, each with a turntable wheelpiate 4 ft. in outside diameter and 3 in. wide.
No road springs are fitted, as the trailer will not have to exceed a speed of 5 m.p.h. It will, however, have to traverse very rough surfaces, so each bogie runs on four in-line wheels on two short axles, which oscillate about a fulcrum beam. The wheelbase is 9 ft.
Each wheel has twin 20 by 6 solid tyres, of which there are 16. Every wheel it fitted with Girling 14-in. by 24-in. two-leading-shoe hydraulic brakes, which will hold the trailer on the 1-in-8 gradients found in the mine.
The brakes on each bogie are applied
independently by means of a hand wheel. An ingenious mechanism is used for this purpose. It was thought that too much physical effort might be applied to the hand wheels if they were coupled direct to the hydraulic cylinder, and that this might be enough to burst the fluid pipe.
Effort is therefore transmitted through four heavy coil springs of 11-in, mean diameter. These are 15 in. long when closed and will extend to 211 in. The maximum load that the set of four will transmit is 1,375 lb. A further pair of coil springs acts as a return pull-off.
The trailer is to be towed by a 'Ruston-Bucyrus TID14 Bull Grader. As the mine roadways are only 18 ft. wide and include many right-angle corners, it is essential that the tractor and trailer combination should have maximum maneeuvrability, and that the trailer can be towed from either end.
For this reason, each bogie can be locked solid, or locked in a position which allows only 15° of steering, or unlocked to permit unlimited steering. With one bogie locked and one free, the trailer can turn in its own length.
The bogie at the front is always in the free position, and a conventional drawbar is fixed to it. While the trailer is travelling on reasonably straight roads the steering of the rear bogie is locked solid, but it is locked in the semi-free position when a sharp corner is reached, or when shunting before loading or unloading.
In this position a 5-ft. pedestrianoperated lever is fixed to the bogie. This pivots in a sliding block of phosphor-bronze, arranged so as to give a leverage of 6 to 1, which affords an overall leverage of 20 to 1.
For loading and unloading a screw jack is placed under each corner of the main platform. The loading ramps are 15 ft. long overall, each being in two sections supported by a portable stool.