_q 1r BY LES OLDRIDGE, A.LR.T.E., A.M.LM.L
Page 78
If you've noticed an error in this article please click here to report it so we can fix it.
Trailers (2)
FOLLOWING on from last week's discussion of the permitted lengths and widths of trailers, it now seems logical to deal with their permitted weights.
The maximum total weight of all trailers drawn by a locomotive must not exceed 40 tons (Regulation 69, Construction and Use Regulations). Drawbar trailer/rigid vehicle gross combination weight must not exceed 24 tons but if the trailer is fitted with power-assisted brakes which remain effective when the drawing vehicle's engine is not running and the driver has a low-pressure warning device then the total combination may gross up to 32 tons. A drawbar trailer is considered individually for purposes of calculating its permitted weight and is treated in the same way as a rigid vehicle following the same weight/axle spacing limits. Axle weights limits are either nine or 10 tons. Trailers fitted with overrun brakes must not exceed 34 tons.
The distribution of weight for trailers is laid down in Regulation 75 of the C and U Regulations. The weight transmitted by more than two wheels to any strip of the road surface contained between two parallel lines on that surface at right angles to the longitudinal axis of the vehicle must not exceed: (a) less than 3ft 4in. apart 11 tons; (b) less than 4ft apart but 3ft 4in. or more apart 16 tons; (c) less than 7ft but 4ft or more apart 18 tons.
Coming now to the brakes required on trailers one finds the regulations are complex. First let us list the trailers where no brakes are required. They are: trailers under 2cwt unladen weight, land implements, .land implement conveyor trailers used for street cleansing which do not carry a load other than the necessary gear and equipment, a broken-down vehicle drawn by another vehicle in consequence of the breakdown; certain agricultural trailers and trailers carry ing gas-producing plant to provide gas for the drawing vehicle which is either a goods vehicle exceeding 2 tons unladen weight or a public service vehicle.
The exception made for broken-down vehicles is particularly useful for commercial vehicles with air-operated brakes which are likely to be inoperative when the vehicle is being towed without the engine running.
The provisions concerning trailers which require brakes are divided into two categories, those manufactured before. January 1 1968 and those made on or after that date.
Trailers manufactured before January 1 1968, and, incidentally, every agricultural trailer of any age, must have a braking system able to act, when being drawn, on at least: (a) Two wheels in the case of a trailer having not more than four wheels; (b) Four wheels if the trailer has more than four wheels; (c) Half the wheels if made after April 1 1938 and so constructed that (i) the brakes can be applied either by the driver or attendant (who may be carried on the vehicle or trailer) and (ii) the brakes can be set to prevent two at least of the wheels from revolving when not being drawn irrespective of whether the trailer is attached to the towing vehicle or not.
The provision in (i) does not apply if the trailer is fitted with overrun brakes.
The regulations for vehicles registered after January 1 1968 are more stringent. They must have an efficient braking system: (a) capable (when the vehicle is being drawn) of being applied to all its wheels by the driver using the braking system of the drawing vehicle designed to have the highest braking efficiency; (b) so constructed that in the case of failure of the system brakes can still be applied to at least two wheels of the trailer or to one wheel of a two-wheel trailer; (c) include a parking brake capable of being applied to at least two wheels by a person standing on the ground, to be maintained in operation by direct mechanical means and capable of holding the trailer stationary on a gradient of 1 in 6.25.