COMMERCIAL TRAILERS.
Page 18
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The Value of a Trailer Built for the Job. The Unsuitability of Converted, Disused Vans and Carts.
THE WAR has done much to. advance the claims of the trailer as a practical and efficient means of carrying additional load for a comparatively small increase in running costs. A few years ago, and for that matter, at the present time, too, the vast majority of trailers -which were in constant use consisted of nothing more or less than disused vans and carts which had very often spent their daily lives behind equine power. The mere substitution of a drawhaz for the shafts does not, however, transform such equipment into a gerviceable trailer for use behind a fast-moving mechanically-driven vehicle. Commercial-vehicle users, and more particlilarly steam-wagon owners, have been compelled in the past to use these makeshifts on account of the unavailability of a• trailer built for the job. When there are borne in mind the strains and stresses to which a hauled medium behind a power-driven unit is subjected, it will be readily admitted that if a trailer -is to withstand the arduous conditions of prolonged service it must.be designed with a view to securing utmost reliability and durability.
Horse Van and Commercial Trailer Loads.
Most horsed vans and carts of the type which are converted for use as trailers are rarely called upon to carry much above a 25 cwt. load. Yet, directly they have been transformed and certain necessary modifications have been made to enable them to be connected to their prime movers they may be called upon to carry anything up to 3 tons. It is very obvious, therefore, that such conversions must prove eventually to he totally unsuitable for trailing purposes.. The mere strengthening of parts of the structure simply accentuates its inherent weaknesses. The disused van or cart, although possessing the advantage of cheapness, has nothing; else to commend its use. The commercial type of trailer designed and built to withstand the conditions of modern road haulage, although more costly in the first place, will prove most economical and efficient in the end. Cheapness is not a standard of efficiency, and so-called economy in initial outlay may be dearly-bought by the use of such van and cart improvisations.
Of recent years several firms have sprung into being and commenced the manufacture of trailers specially designed for haulage purposes. One of them, to wit, Carrosserie Latymer (1915), Ltd., C44 of Pamber Street Works, Walmer Road, W. 7, have constructed a considerable number of trailers during the war for the conveyance of stores, aeroplanes and their parts, etc. We recently had an opportunity of inspecting first hand an example of the 2-ton and 4-ton types as manufactured by this concern. They closely resemble each other in design except that the former is of lighter construction throughout.
Dealing with the 4-tonner the main frame consists of two 16 ft. members of U-section channel steel 4 ins. by 2 his. hy * in., to which four cross members of the skim) section are securely gusseted with mild steel gusset plates. One member back and forward ends respectively, and two in forward part of main frame carry the wheelplate bed. The top bed of the wheelplate and perch pin is built up of II-section channel in the form of a crass gusseted with a heavy plate in centre 1 ft. sqnare, riveted to the main frame on the underside, thus forming a tie against all diagonal stresses in the main frame.
Two members afford support for the rear springs, and are riveted to all the angles supporting the flooring and also the main frame sides. Three lengths of mild steel angle of 3 ins. by 3 ins.
by in. dimensions are carried from the third cross member of the frame th the frame of the rear member, and are strongly gusseted to all the four cross members which are situated below the level of the main frame. Two 3 ins, by in. flat mild steel trusses are riveted to the outside of the side members and gusseted to vertical struts in the centre part of the main frame, and reach a point well beyond the squares formed by the cross members carrying the rear springs and the square carrying the wheelplate in the front of the trailer.
The under or fore carriage is designed to give a full leek, and is so constructed as to prevent any possible whipping or twisting tendency. It is built up of four members of 4 ins. by 2 ins. by * in. U-section channel steel constructed in the form of a square frame. This undercarriage is fitted with a wheelplate of 56 ins. diameter, which is securely bolted to the square frame.
Conventional laminated springing is employed, the specially-constructed spring brackets being attached to the fore carriage. Additional support is
afforded by angle brackets. A transverse spring is also embodied above the rear axle.
The brake which is employed is of the expanding band type, and takes effect on the rear wheel. It can be operated, of course, from the hauling medium by means of lever and steel cable.
The wheels are of steel disc pattern, and are shod with 880 mm. by 120 mm.
solid tyres. The overall length of the trailer is 16 ft., the overall width being 6 ft. 6 ins; the wheelbase is 11 ft., and the wheel track 6 ft. The height of the platform is 3 ft. 3 ins, from the ground. " As we have already said, so far as the more detail construction is concerned the 2-ton trailer closely follows the lines of design of the 4-tonner, except that it is of proportionately lighter build through
out. The dimensions of the 2-tonner are also slightly different, but apart from this feature and the fact that artillery pattern wooden spoke wheels are employed, the two types are very much alike. They both show in design a thorough understanding on the part of • the makers of the strains and stresses to vhich a trailer is often put. Stoutness of construction without the embodiment of unnecessary weight is a feature.
A Searching Official Test and Trial.
As ample proof of thin thoroughness of design and construction, we would quote from the engineer's report on one of the 4-ton Carrosserie Latymer trailers tested by the technical department of the Ministry of Munitions. The report runs as follows :— A 4-ton block of concrete was cast which occupied approximately 2 sq. yards of floor surface, and was placed in the
centre of the steel trailer. This was towed on to Wimbledon Common behind a four-wheel drive tractor, and, after ; going through a very severe test over all conditions of soil, it finally came to a soft place, and the trailer buried itself up to a point above its axles, and it came to an abrupt stop. The tractor was uncoupled, and a 30 ft. length of. 5-ton chain attached to the drawbar. After a series of flying runs it was eventually jerked out on to hard ground. It was then dropped from the surface of the common on to the hard road, a, distance of 20 ins. while travelling at a good pace. This test the trailer stood perfectly. Previous to this test the trailer and 4-ton block were given a 120 miles road test over byways in Kent, i'vhieh was thoroughly satisfactory.