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The First Effects of "30" Limit on Bodywork

15th November 1957
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Page 52, 15th November 1957 — The First Effects of "30" Limit on Bodywork
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Fewer Light-alloy Bodies at Glasgow Show: Plastics Maintain Their Popularity: New Methods of Construction

By P. A. C. Brockington, A.M.I.Mech.E. NEARLY a generation has passed since bodybuilders who cater for operators of medium-weight vehicles have been able to display their products at a national exhibition without regard to the critical weight restriction imposed by the 20-mph.. limit for vehicles of over three tons unladen. The limit gave weight reduction an artificial value, and the Glasgow Show may mark the unobtrusive start of a new era in the battle of body design principles.

Although the weight of a body structure is still critical if it is the main factor in determining the taxation class of the vehicle, raising the limit has given bodybuilders a new freedom to develop up-to-date designs. From now on, the gain in payload provided by a low-weight body will, in most cases, be matched against its relative cost and durability; the shadow of the weighbridge is no longer a deterrent to the adoption of a progressive feature.

There are fewer light-alloy lorry bodies displayed this year than were exhibited in 1955, . and about the same amount of plastics is employed by bodybuilders in the goods bodies on show. According to the report of one standholder the majority of operators who formerly purchased aluminium-bodied pantechnicons now have a decisive preference for timber framing, but all the concerns displaying aluminium platform bodies can produce evidence that many users of "borderline " vehicles fitted with this type of structure have not been influenced by the speed-limit change.

Of significance in the case of a pantechnicon builder is the view that employing a plastics roof affords sufficient elasticity to accommodate severe chassis-frame flexing, and

c16 he recommends that in future all aluminium-framed van bodies should be fitted with a glass-fibre roof assembly. This may be indicative of a trend to reconcile the claims of the two materials by employing both in the same structure to their best advantage.

Of the many unsatisfactory light-alloy platform bodies built over the years, trouble in service has mainly been the result of haphazard design or of applying the mistaken principle of stiffening the underframe locally to give a. rigid structure. This concentrated the stresses caused by chassis flexing, and often resulted in rivet failure or fracture of the members.

Relatively simple structures that can accommodate chassis distortion by distributing the stresses uniformly tend to be somewhat heavier than the rigidly braced type for agiven nominal load capacity, but can be built at a lower cost because of the attendant saving in labour, charges.

The Show has provided the opportunity to test bodybuilders' reaction to the possible benefits to the body designer of an air suspension system with a -constant-ride characteristic. I regret to say that few concerns have yet given the subject much thought. One bodybuilder, however, believes that it wouldoffer a great advantage if vehicle makers exploited ks merits by producing a rigid chassis rather than one that was essentially part of the

suspension layout. Rumours of apparent reliability which may be heard on other stands indicate that at least one of the leading makers of rigid four-wheelers is embarking on a long-term project with this objective.

A notable departure from standard practice is represented by the light-alloy platform body being shown by A. C. Penman, Ltd., Dumfries, which is mounted on an Albion Chieftain chassis having a hardwood-framed cab with woven glass-fibre panelling. This body has a cross-planked floor of back-to-back channel members, the sections being assembled with self-locking bolts, arid 9-in, longitudinal runners are provided, together with timber packing pieces which are inserted above and below the runners. Cantilever angle-section members are bolted at their outer ends to the body raves and welded to cross-bearers at their lower ends. The bearers are fitted under the longitudinals and act as compression struts,

Prolonged Tightness

Cadmium-plated high-tensile bolts for the floor and raves mate with Simmonds shakeproof nuts, which, it is claimed, do not require retightening for an indefinite period if they are initially checked after the vehicle has covered 500 miles. The total weight of the body is about 5 cwt.

Displayed by the S.M.T. Sales and Service Co., Ltd., Fountainbridge, Edinburgh, 3, a Bedford 3-ton longwheelbase chassis with 'a Homalloy light-alloy platform body is one of a number of vehicles with bodies of the same type to be supplied to Glasgow Housing and Works Department. Sustained interest in aluminium construction is reported on the stand, which is indicative of the proven merits of a simple design giving uniform stress distribution.

The constructional methods employed by Alloy Transport Sections. Ltd. are based on a somewhat similar prihciple. An interesting example of this company's products is a light-alloy drop-sided body exhibited by Lamb's Garages, Ltd., Dundee, and mounted on an Austin forward-control oil-engined 4-ton chassis. Both bodies are of bolted construction.

Possibly of greater potential significance to operators than any other recent development in the use of light alloys is the display by G. E. Neville and Son, Ltd., Mansfield, Notts, of a demonstration shell evolved for vans and containers. This is based on a modified form of the Neville section employed for dumper and tipping bodies and comprises a structural component that combines the function of a frame member and external panel, the easy assembly of which reduces labour costs and facilitates replacement. Moreover, the body or container may be increased or reduced in length by adding extra sections or removing some of the existing ones. The high modulus of elasticity of the metal, combined with a novel type of interlocking joint, enables severe flexing to be accommodated. Each 12-in, standard extruded section is rolled to the required shape of the sides and roof, and the sections are held together by cadmium-plated bolts with self-locking nuts.

Sections comprise an end-flanged member with three integral stiffening ribs, the flange faces being grooved to provide a continuous .V-register on the inside and space for a rubber sealing strip on the outside. Torsional stresses are resisted by the V-registers, so that the bolts are relieved of shearing stresses; the scaling strips give effective waterproofing and prevent seepage when a sealing solution is being applied to the inside.

When insulation is required it is housed in a timber frame at a sufficient distance from the sections to form a small cavity, which improves the insulating properties of the assembly and provides a means for renewing a section without disturbing the material. It is claimed that 17 sections of a body can be built up in eight hours by a skilled worker and an apprentice. The superstructure is mounted on top-hat frame members.

By employing a 20-ft. by 7-ft. by 6-ft. insulated lightalloy container shown by the bodybuilders John Gibson and Son, Ltd., Leith, Edinburgh, 6, the operator will be able to deliver fish from Wick to Glasgow, a distance of 300 miles, which represents a valuable extension to his normal range. At the Show the container is mounted on a Leyland Comet chassis.

Third for Fish Transport

This is the third container designed for fish transport to be completed by the concern in three months, and has a number of special features. These include insulation of the sides with Onazote to a depth of 3 in., which is extended to a point mid-way between the floor and the roof, the remainder of the sides and the roof being insulated with 1soflex. Timber spacers are used to separate the lightalloy angle-frame longitudinals from the exterior panels. The uprights and roof members are of top-hat section.

An Austin-based Gibson pantechnicon displayed by Moir and Baxter, Ltd., Comely Bank, Edinburgh, 4, is typical of the concern's practice of employing plastics corner panels for the Luton extension and timber framing braced with

diagonal members. Glass-fibre corners have materially reduced body maintenance costs.

Refrigeration in the Gibson container is applied by placing dry ice on the fish boxes. In contrast, three ice compartments are fitted below the roof at the front of the Litex light-alloy meat container, shown by the Central Motor Co., Calderbank, Airdrie, which is mounted on the Alloy Transport Sections body of a Dennis Condor 12-ton forward-control chassis.

The ice compartments are of the standard mesh type and are loaded from the front of the body after the withdrawal of wooden plugs. They are reached by mounting a special platform on the cab. A hinged cover plate is louvred to give ventilation when ice is not being used.

Prototype of a batch of 30, the light-alloy baker's body built by Croft Bodybuilding and Engineering Co., Ltd., Gallowgate, Glasgow, is constructed of light-alloy frame members and plastics panels, which include the roof. The body is mounted on a Thames 4D chassis having a 13-ft. 1-in. wheelbase.

Front sliding doors 5 ft. 6 in. wide give access to the interior from both sides, and a two-section tailboard, combined with a counterbalanced door, affords entry from the rear, both tailboard sections being fitted with steps. At the forward end, a three-quarter-width light-alloy cupboard with a door on the near side is provided for the salesman's stock, and on the off side narrow racks of light alloy are fitted which extend the full length of the vehicle.

These are for loading the smaller trays. The larger trays are mounted on wider racks facing outwards on the near side. Frame members and racks are held with Aero seIflocking nuts which give freedom from flexing troubles.

Durability Demonstrated

A display of special plastics interest at the 1955 Show was the Seddon wood-framed cab with glass-fibre panels and roof, and, according to representatives of Moodie and Co., Colston Road, Bishopbriggs, the cab has demonstrated the durability of the material over the past 2-1 years. The standard plasvics cab is seen at the Show fitted to a Seddon Mk. 15 oil-engined chassis with a 20-ft. platform body. Formation of bubbles in the material and difficulty in providing a good base for the paint have been the only troubles since production was started, and these have now been overcome.

Another well-established structure incorporating a plastics material which proves the durability of glass fibre is the B.R.S. standard parcels van body of 700-cu.-ft. capacity being exhibited on an Austin normal-control 5-ton chassis by Lamb's Garages, Ltd. This van has been designed to reduce body maintenance to a minimum by employing extruded-aluminium frame members, resin-bonded-plywood pillar-stiffening members and a reinforced glass-fibre transparent roof riveted to light-alloy roof slicks.

Scientific combination of light-alloy and plastics materials. in the production of goods-vehicle cabs is exemplified by the Bowyer cab fitted to the Guy Formidable, displayed by Guy Motors, Ltd., Wolverhampton. This is based on a main frame of light-alloy sections, to which the panels are Pop-riveted, and a double-skinned plastics roof. The cab is flexibly mounted at four points.

Twin Roller Shutters .

Of the small number of mobile shops at the Show, the most original design is a travelling grocers' shop exhibited by T. M. Erskine and Co., Inchinnan Road, Renfrew. It is mounted on a Karrier Bantam 2-ton chassis. Built to the special requirements of The City Bakeries, Ltd., the shop has twin roller shutters on both sides, the serving counter being located on the near side and tray racks on the opposite side. A gangway between the counter and the racks is entered through a sliding door in the cab bulkhead.

This arrangement enables empty trays to be exchanged for full ones in a few minutes and delays at the concern's depot to be reduced to a minimum. A three-section compartment at the rear of the vehicle is available for storing trays.

Also designed to the customer's specification, the stationers' van, shown by Westfield Autocar Ltd., Westfield Avenue, Edinburgh, is fitted with roller shutters on both sides and at the back, whilst loading can be performed, if necessary, through sliding doors at the rear of the cab. Packages of stationery are loaded in the van according to size and delivery order, and the multiple doors obviate the movement of parcels other than those which are being unloaded. The van is based on a Morris 2-ton chassis powered by. the B.M.C. 3.4-litre oil engine.

Matching the capacity• of a dumper to the type of load carried can be an all-important factor in the economy• of operation, and a special example of this practice is provided by the 15-cu.-yd. body displayed by A.C.V. Sales, Ltd.. Berkeley Square. London, W.1. The dumper is based on an A.E.C. Mammoth Major six-wheeled chassis and is the ninth vehicle to be added to the fleet of the Scottish Land Development Corporation, Glasgow, for use on the Kinglassie open-cast coal site. Vehicles of 15-cu.-yd. capacity are employed for light, bulky materials, whilst similar chassis equipped with 10-cu.-yd. bodies carry coal and other heavy loads. An Edbro twin-ram underbody lifting gear of the power-return type can raise a loaded body to 700 in 15 sec.

An important detail of the dumper is a safety arm, mounted at the back of the body on the near side, which is pinned to a bracket on the chassis to hold the body in the raised position when the mechanical components are being serviced.

The degree of resistance of plastics materials to repeated abrasion has been the subject of speculation for some time, and although the plastics floor lining of a wooden-bodied drop-sided tipper exhibited by Transport Equipment (Thomycroft), Ltd., Bishop Street, Glasgow. C.3, is an experimental fitting (specified by a local coal merchant) it is expected to outlast steel linings. Mounted on a Swiftsure 11-ft.-wheelbase chassis, the body is raised by an Anthony Hoist lifting gear.

Based on glass-fibre material, the lining is covered with rayon and has an overall depth of in. The body has a capacity of 51 Cuyd.

A new addition to the concern's standard range of lifting gears, known as the EP.1400 type, is displayed by the Spenborough Engineering Co., Ltd., Heckmondwike, Yorks. This is a single-ram gear designed for front-ofbody mounting and incorporates a sling-type cputrigged stabilizer fitted between the trunnion mounting of the tube extensions and the steel channel-section sub-frame.

Great interest was aroused among operators of doubledeckers by the news that Edinburgh Transport Department would be following the example of Ribble Motor Services. Ltd. and the Potteries Motor Traction Co., Ltd. by employing front-entrance vehicles of this type. This has attracted many extra visitors to the stand of Leyland Motors, Ltd., Leyland, Lancs. who are exhibiting a Walter Alexander 30-ft. by 8-ft. 72-seat front entrance doubledeck body mounted on a Titan PD3/2 chassis equipped with fully automatic transmission.

The door is operated by a hydro-pneumatic mechanism and can be controlled by two sets of switches, one in the cab and the other in the ceiling above the platform. A recessed window in the lower-saloon bulkhead is open to the cab on the off side and facilitates direct communication between the driver and the passengers. The height of the first step is 17 in. from the ground and the remaining step is 12 in. higher. An unobstructed entrance about 3 ft. wide is provided.

A Clayton heatee located under the canopy discharges warm air through two vents in the bulkhead (one of which directs the flow towards the stairway) and to a third vent at the front of the upper saloon. Heated air is also supplied to the cab interior and to demisters arranged at 450 in the lower corners of the windscreen. Details of saloon fittings include plastics treads, held in light-alloy channels, and Cronapress bell strips.

Introduced as a last-minute innovation, the winding handle of the destination blind is connected to the mechanism by a universal joint at its upper end and rotates in a bush, housed in the bonnet, at its lower end. The crank is immediately above the bonnet and within easy reach of the operator. The grille, wings and front panels are of glass fibre, thus saving 2 cwt.

Visitors are left in no doubt that the grille, bonnet and left front wing of the Daimler CVG6 double-decker chassis exhibited by Transport Vehicles (Daimler), Ltd., Coventry, are made of plastics. In contrast to the sheet-metal parts of the cab floor and so on, the glass-fibre components are unpainted and provide an eye-catching feature.

Numbered among a variety of Continental luxury coaches, the Plaxton 37-seater based on an Albion Aberdonian chassis is notable for its striking colour contrasts, twin roof-mounted horns and twin electric fans at the sides of the windscreen. This vehicle is displayed by Millburn Motors, Ltd., Millburn Street, Glasgow, N.1.


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