• A wide range of single-axle dollies for rapidly converting
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semi-trailers into self-contained drawbar trailers has been introduced by the Primrose Third Axle Co Ltd, Blackburn, Lancs.
The Primrose dollies are available in 7.5-, 8.5-, 10-, 16and 20-ton load ratings. The 16and 20-ton models are for low-speed work off the road on private sites such as docks. They are longer than the road models, measuring 9ft from towing eye to kingpin pivot instead of the 711 10in, of the ordinary range.
Two patterns of drawbar dolly are available and there is no price difference between them. With one arrangement, the fifth-wheel coupling which engages the semi-trailer kingpin, oscillates on trunnions on a rigid chassis. With the other, the fifth-wheel plate is fastened rigidly to the chassis, which then has a hinged tow-bar. The type with the hinged A-frame for towing has the advantage of being easier to couple at various heights. It is also stable in a longitudinal vertical plane. The A-frame is constructed of 2+in. square steel tube.
Whatever the model, the axle is sprung on leaf springs and located by rubber-bushed radius rods. The brakes are cam-expanded by air-pressure diaphragms. On the 7+ and 8+-ton dollies the brakes are 6in. wide. For 10-ton rating either 7in. or 8fin.-wide brakes can be specified. The 8-fin.-wide brakes are standard on the 16-ton and 20-ton models.
The Primrose Cushionride suspension, in which the radius-rod located axle is suspended simply on big hollow-rubber cylinders, is available optionally.
Any make of fifth-wheel can be specified. A load-sensing valve in the braking system is recommended if the operator aniticipates towing the dolly by itself. Three-line braking with the necessary connections is included in the price, which, net from Primrose, is 1629 for the 74Tton, £671 for the 8+-ton, £705 for the 10-ton, £985 for the 16-ton and £1,038 for the 20-ton.