New Tandem-axle Semi-trailer
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COLLOWING experience with proto-I types which have been in service since the beginning of the year, Merriworth (Engineering), Ltd., Dartford, Kent, now offer a tandem-axle semi-trailer. This employs leaf-spring suspension with the rear shackles of the springs on both sides connected to each other to prevent axle hop. Other features include the use of Glacier DU oilless bearings throughout the suspension and a new design of landing gear manufactured by Merriworth themselves.
Rubery Owen axles with Girling twoleading-shoe brake units at each wheel are employed. The standard brake-shoe width is 5 in., but 7-in.-wide shoes can be fitted if required. The joining of the rear shackles of the springs is by a long. square-section tubular member to which upward extensions of the shackles are attached. Rubber buffers on brackets located inside the frame side-members at the front and rear of the connecting link prevent excessive movement.
As with the single-axle semi-trailers produced by Merriworth, the all-welded chassis frame uses 15-in.-deep pressedsteel side-members made by Rubery Owen, Ltd., with tubular cross-members and triangular-section tapered outriggers. The side rails are special E-section extrusions welded to the outriggers. Also following the practice With the singleaxle units, the tandem-axle model is available with the Merriworth Auto-fifth automatic coupling gear or a standard S.A.E. king-pin for fifth-wheel couplings. Construction of the chassis frame is the same for either, and an Auto-fifth coupling or a king-pin can be fitted in the locating hole in the centre of the front support pad. This means that if an operator needs automatic coupling to suit his current tractive units he can change to fifth-wheel coupling, if this is requ:red later on, without much expense. Another feature of the Auto-fifth coupling is that the bearing surface of the turntable is the same diameter as with the fifth-wheel coupling.
. When sold with a fifth-wheel coupling —for a I6-to-17-ton load—vacuum, air pressure and vacuum or air assisted hydraulic braking are available. If vacuum or air-pressure, cam-operated brake shoe units are fitted. When sold in the automatic coupling version—for loads of around 12 tons—brake application is through a plunger in the centre of the turntable and a vacuum or air servo is incorporated to provide extra effort at the tandem master cylinder fitted.
In addition to the Glacier DU bearings—these are of a composite material incorporating a fluorocarbon plastic (P.T.F.E.)—used for the suspension bushes, it is expected that in the near future pad inserts of pure P.T.F.E. will be incorporated at the turntable. A number of semi-trailers with this feature are said to have been in service for some time with excellent results.
The support legs of the new Merriworth landing gear are screw operated and have two-speed gearing as standard. The main castings are of light alloy and the legs are of square-section tube. Bracing members are of 'squareor rectangular-section tube.
Standard platform dimensions of the semi-trailer are 25 ft. long x '7 ft. 6 in. wide and the list price is £1,250. Lengths of 26 ft. and 27 ft. are also available. It is expected that the 'unladen weight of the -unit will be in the region of 3 tons 2 cwt: in its production form...
COMPUTERS FOR COMMUTERS
ACOMPUTER may be-used to bring about a freer flow in road traffic. Mr. Marples, the Minister of Transport, said last week that he was investigating with the Road Research Laboratory the possibility of using one of these machines for the continuous processing of traffic data to permit the coordinated contrel of traffic over large areas.
The Minister noted that an electric computer would be used to analyse data on traffic flow for the comprehensive survey of London's traffic now being made by consultants on behalf of his department and the London County Council.