Exceptionally Light Semi-trailers of unusual design
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EVERY WHERE. the search for new forms of construction which will permit the building of lighter vehicles
is being carried out. This applies particularly in countries where the taxation of such vehicles depends wholly or to a great extent upon their unladen weight. Thus legislation exercises a tremendous influence upon design—in some cases it is retrogressive, in others it tends to advance construction, and in connection with the reduction of unladen weight the latter applies.
Holland, chiefly because of the boggy foundation upon which so much of it is constructed, is carrying most of its bigger loads on articulated six-wheelers, but owing to the exacting requiremeats in that country as regards trailers, its neighbours were unableto meet the demand, and for this reason Holland has turned to the manufacture of trailers and semi-trailers, one of the principal constructors lacing Mr. Van Donnie, Junr., of Van Doorne's Trailer Factory ( D. A.F. ) in Hit id hovel].
One of the reasons why Mr. Van Doi). rne turned to the construction of light trailers was the encouragement given by Mn J. Harms Tiepen, Editor of Bedrijfsauto, the cornmercial-vehicle weekly of Holland. Mr. Tiepen's idea was put forward not so much with a view to lessen taxes as to redace petrol consumption and enable bigger, loads to be carried on comparatively weak roads where wheel pressure is strictly limited by law.
In addition, Holland, last year, introduced a law by which a graduated tax was levied on the unladen weight of trailers. Up to this time, when the Minister of Finance, fixed the rate of taxation on trailers, no notice had been taken of the heavier weights.
The trailers are made in. various capacities and patterns, but the essential is a frame with one central main girder which carries the whole of the load. Its capacity is due, in the first place, to the enormous tensile strength of the material employed ; next, to its box section, and, finally, because there are no openings or protruding ends where cracks might begin.
The frame can be made as wide as required, because the pressed-steel brackets are electrically welded to the main girder, whilst light channel-section sides serve for the securing of the coupling member and the coachwork, at the same time carrying the wood floor members.
At the front, the main girder carries a vertically mounted tube, which contains the hydraulically operated front support. The tube is connected at the other side with a head which increases in width until it assumes the shape of a
saucer containing the controls for the front support and the automatic connectors for the compressed-air and lighting leads. The saucer, with its coupling pin, also constitutes the upper part of the coupling between trailer and tractor. The bearing surface between this saucer and the one on the tractor is very large, and coupling and uncoupling can be effected entirely from the driver's seat. That part of the coupling on the tractor is mounted on heavy rubber blocks and is so pivoted that it is possible to couple or uncouple the parts in any position.
An hydraulic pump supplies the means for operating the front support, so that the trailer can be lifted to any required height. Should it sink on any marshy surface, the pump can be used for raising it sufficiently high to enable coupling to be carried out. The rollers on the support are steerable and rise automatically free of the ground when couplingt' is effected.
Experience has shown that many trailers in Holland are overloaded, and if it were not necessary to take this into consideration the dead weight of the frame, etc., could be• reduced by a further 25 per cent.
One hundred trailers of this type have already been supplied in Holland alone within a. few months and, so far, no breakdowns or abnormal irregularities have been reported. '
There are 5-ton trailers, Ci metres long and 2 metres wide, which, inclusive of wheels, tyres, mudguards, etc., weigh only 1,025 kilos.; similar trailers with U-iron frames weigh 1,950 kilos. In another, case, a 12-ton trailer,
8 metres long and 2.20 metres wide, weighs only 1,975 kilos.; a trailer of similar capacity built with a U-iron girder weighs 4,100 kilos.
Special attention has been paid to the method of suspension, and our illustrations show types with two wheels and four wheels. One view indicates how the ends of the springs actually bear upon the vacuum-brake cylinders. In one design, in order to facilitate the changing of the inner tyres, each axle bearer can revolve on its own axis, after removing the safety bracket, thus permitting the inner wheel to be brought to the outside. In the compound axle construction, each of the four wheels has an independent spring.
We understand that the licence for the construction of this trailer in France has been taken up by M. Pilot, a well-known manufacturer of tipping gears, etc.