Matching the Body to the hi
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AN ESSEX BODYBUILDER GIVES HIS VIEWS ON FIVE TYPES CONSTRUCTION FOR A LUTON Vi IF a goods vehicle operator requires a special custombuilt van body for mounting on a standard chassis, he is faced with the major problem of deciding vi hat types of material should be employed in its construction with due regard to weight and cost factors and to the probable life of the body., In this article, Mr. T. E. (Tony) Osborne, a director of R. W. Osborne and Sons Ltd., Saffron Walden, Essex, gives some expert advice on the subject based on an assessment of the advantages and disadvantages of five types of construction applied to a Luton van body of a given capacity. Although the concern specializes in the building of dairy bodies, production covers every type of pantechnicon, box van and platform body. The general policy of the company is to employ materials best suited to the user's requirements.
Mr. Osborne takes the hypothetical case of a haulage contractor who seeks advice regarding the supply of a special Luton van of 900-cu.-ft. capacity mounted on a standard 3-ton chassis with the maker's cab. The vehicle is to be used for the carriage of television receivers (or similar finished goods), but it will also be employed for local furniture deliveries and general work. A pleasing appearance is essential and a normal singletone colour scheme is specified, lettering being restricted to the cab. Facilities are required for floor movement of palletloaded television sets.
A low-slung tailboard is necessary to facilitate certain types of furniture delivery and, because the vehicle operates in a rural area, provision will have to be made for overhanging trees. It is therefore decided that the van shall be of the rectangular box type with a razor-edge cant line, which will afford the maximum loading space for given box dimensions and be resistant to tree damage. The final specification stipulates a body length, excluding the Luton extension, of 14 ft. 6 in., a height of 8 ft. 3 in. and a width of 7 ft. It also includes a flat floor (to accommodate the pallet-loading rails) and a roller shutter at the rear.
Having established the suitability of these dimensions and features, the problem remains of the most appropriate type, or types, of material to be used in its construction. In five specimen quotations, covering bodies mainly constructed of timber, aluminium, steel and plastics, and also a composite type, Mr. Osborne outlines the merits and deficiencies of each type and these are weighed against first cost.
Taking the case of a timber body, Mr. Osborne points out that this can be produced at the lowest cost and that it can he fabricated by a small bodybuilder. His quotation relates to a body with a hardwood frame and cross bearers, aluminium side panels of 18 s.w.g., a plywood-clad roof, covered in duck cloth, a tongued-and-grooved timber floor and a timber-lath rear shutter. The basic cost of such a body would be £490 unpainted, and extras would include Plymax panels and Joloda tracks, which would add £15 and £25 respectively to the quotation. Total cost would, therefore, be £530.
Advantages in favour of timber constructionapart from its low first cost—include ease of repair, the avoidance of "sweating" (which would damage the high gloss finish of the television sets) and freedom from drumming. Given fair treatment the body would have a useful life of six years, which is a42 more than the life of the average 3-ton chassis between full overhauls.
If soundly constructed the basic weight of the body would be around 19-20 cwt., and this might increase the unladen weight of the vehicle to
more than three tbriS. The duckcloth roof would be easily damaged by contact with overhanging trees.
Referring to aluminium construction, Mr. Osborne emphasizes that the light-alloy body is a "job for the bigger specialist, who is reasonably expert in fabrication methods ". Framed in extruded-alloy channel and top-hat sections with alloy gussets, assembled with bolts or rivets, clad throughout with 16-s.W.g. haid-alloy panels and fitted with a 1-in, tongued-and-grooved timber floor and an aluminium shutter at the rear, the cost ofan unpainted body would be about £630. In this case, fitting of the Joloda tracks would be complicated by the use of alloy cross bearers and the cost would be increased to £28, giving a total of £658. Estimated weight of the body is 14-15 cwt. and Mr. Osborne observes that a life of seven tb eight years would cover its higher initial cost.
In addition to its weight-saving advantages, the aluminium body would be virtually free from corrosion and would ha% e a higher scrap value. Moreover, the alloy roof would be resistant to damage by overhanging trees.
Costly to Repair
Dealing with accidental damage, Mr. Osborne states that, contrary to much-publicized opinions on the subject, aluminium bodies are relatively difficult and costly to repair. Special sections are not always available from stock and are very costly when ordered in small quantities. Condensation would have to be avoided to obviate damage to the television cabinets in the example considered, and this would necessitate lining the interior with hardboard or plywood, which would add some £20 to the cost.
The quoted cost of the steel-framed body, fitted with Joloda tracks, is about £553 and the specification includes a cladding of 18 s.w.g. alloy sheet, a 1-in, timber tongued-and-grooved floor, and tailboard and a timber lath shutter. A steel underframe is specified, constructed of 0.125 in. channels, the sides and roof framing being of 16 s.w.g.
This quotation shows that the steel body offers a worthwhile weight saving (1-2 cwt.) compared with the timber type at an overall cost increase of only £38. Repairs would, however, offer greater difficulties (unless bolted construction were employed) and the steel framing would promote condensation. The body would tend to drum at critical engine or road speeds and efficient insulation would be required between the aluminium and steel to avoid rapid corrosion.
Of the different forms of plastics construction that could be used for the body, Mr. Osborne selects the one-piece moulded type for a quotation, based in colour-impregnated inner and outer plastics skins bonded to a rigid centre core. An underframe would be formed of bonded-in steel and timber fillets which would give strength to the structure and would be used as holding-down brackets. One-piece moulded construction could also be employed for the rear flexible shutters.
It is considered that the overall body weight would be about 24 cwt. and that the total cost would be at least £680. No painting would, however, be necessary, the body would be free from condensation and drumming and the roof would not be easily damaged by trees. The panels would be resistant to light accidental impacts and conventional types of glass-fibre kit could be used for repairs. In the event of a major accident, however, highly-specialized techniques would be required to repair the damage.
Finally, Mr. Osborne outlines the constructional features of a composite body that might represent the hest compromise between the various body types mentioned. Complete with pallet-loading tracks the cost of the body unpainted would be approximately £578 and it would weigh 17 cwt.
According to the specification prepared by Mr. Osborne, this composite body is mounted on hardwood longitudinal runners attached with U-bolts to the vehicle chassis members which are locally packed with hardwood blocks. The cross bearers arc constructed of 0.125-in, press-brake-folded channels and are attached by steel brackets to hardwood pillars reinforced with mild-steel strips. Hardwood is also used for the cant-rails, bottom side rails and intermediate rails, and the sides are clad in aluminium-faced plywood glued to the framework. In the case of the roof 6-mm. resin-bonded plywood is glued to the main structure externally and is overlaid with 18 s.w.g. aluminium sheet.
A section of 2-oz. glass-fibre mat measuring 12 ft. by 3 ft. is used as a translucent roof panel, and an alloy roller shutter is fitted above a hardwood-framed drop-tailboard. Body flooring is I-in, tongued-and-grooved board treated with a preservative.
The cost of this body would, Mr. Osborne emphasized, be only £63 more than that of the timber body and would be comparable with the cost of the steel-framed type. Moreover, the timber main frame would offer "ample toughness" and the preservative would obviate deterioration over an extended period. Resin-bonded phenolic glue used for the plywood would remain effective indefinitely. The roof structure would have more than adequate strength and the body would be free from drumming and condensation. At an extra cost of £80, the body could be panelled in colour-impregnated glass fibre and a one-piece plastics roof could be employed, which would obviate painting for the life of the van.
"There can never be a complete answer as to which is the best constructional material," Mr. Osborne adds as a postscript, "the answer lies in selecting materials to suit the application with due regard to the proven merits of established materials and to the challenge offered by modern techniques and innovations." P.A.C.B.