Novel Features in Cable-drum Trailer
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1::acticable overall length and a low loading level cornr achieve a high degree of manceuvrabilitv, the shortest bined with adequate ground clearance, was the object of the designers of the interesting 5-ton cable-drum trailer seen in the accompanying illustration. It was built recently for Barrow-in-Furness Corporation by R. A. Dyson and Co., Ltd., 76-80, Grafton Street, Liverpool, 8, and incorporates a number of unusual features.
It has Ackermann steering, it measures only 12 ft. long, exclusive of drawbar, and the platform height is 1 ft. 9 ins., whilst a ground clearance of 1 ft. is afforded.
Unlike most former Dyson cable trailers, this machine is equipped with 36 by 8 tyres on all four wheels and the main frame is straight, having as its basis 8-in. by 3i-in. angle side members. It is the use of Ackermann steering that has made possible a straight frame and short overall length combined with ample steering lock. • The Wheelbase is 7 ft. 9 ins., the lower platform is 7 ft. 10 ins. long and the winch section is 4 ft. 2 ins, in length.
A24 Under the forward platform are accommodated the linkage between drawbar and stub axles and the F. and J. vacuum cylinders by which the Girling brakes on the rear wheels are actuated. The shoes of these, incidentally, operate in 16-in. by 31-hi, drums. The brake cylinders or rather bellows are positioned vertically just in• front of the platform step and transmit braking force through a bell crank, the longer arm of which is attached to the lower end of the bellows, In addition to the vacuum line to the tractive unit, there is a cable for mechanical brake actuation from the cab. A hand lever across the front of the trailer, also, applies the brake for parking. There is nothing unorthodox about the steering layout. The extension of the. drawbar behind the vertical pivot is set at about 30 degrees towards the near side so as to be parallel with the off-side stub-axle arm to which it is coupled by a straight link. Motion is transmitted from the off-side front wheel to that on the near side by a track rod in the usual manner.
To prevent over-locking, a pair of fin, wire cables is provided. Each tethers the drawbar to one front corner of the frame so that it cannot swing beyond a given angle in either direction.
A point in connection with the loading ramp is of interest. It is provided with telescopic stays which do not have to be removed when it is desired to lower the ramp from the position in which it functions as a tailboard. All that has to be done is to take out a spring-loaded pin and let the ramp down with the winch. The stays simply extend and accommodate themselves appropriately.
The rear axle is, of course, cranked to permit the low floor which, incidentally, is flush with the top flanges of the frame members; it also permits a width available for cable drums of 4 ft. l0i ins, despite an overall figure not exceeding 7 ft. 6 ins. The track is approximately 6 ft. 5 ins.
Two screw-jacks are provided at the rear to steady the vehicle during loading. In order to enable the vehicle to be employed for other purposes besides cable carrying— transporting small excavators, concrete mixers, tractors, etc.—it is equipped with removable side boards.
It is clear that considerable ingenuity has been exercised in designing this trailer, and it shows that finality has by no means been reached even in such specialized spheres as this.