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25th October 1974
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awics

Aluminium for economy?

A BIG increase in payload—or a SUBSTANTIAL reduction in fuel consumption: this is the promise offered by a new era of aluminium construction

IS it worth it? Will it last? What about age-hardening and fatigue?

These are the sort of questions that are being asked about the aluminiumframed semi-trailer, notably by visitors to the recent Earls Court Show who took an interest in the exhibits on the Welford Truck Bodies stand and who had a close look at the Alexander tandem-axle unit coupled to a Fiat 0M55 displayed in the demonstration park.

The same questions could be in the minds of those who have heard stories of bigger things to come in the lightweight field such as tractive units with aluminium frames, cabs, wheels and axles, not to mention gearbox casings and engine blocks.

The potential saving in the ease of a big semi provided by an aluminium chassis frame is, say, a ton and, perhaps, as much as three times as much if aluminium were used to the fullest extent throughout a heavy articulated outfit. For a vehicle carrying a bulk load the weight saved could be exploited to reduce engine size (and to use a lighter transmission) and thereby to improve fuel consumption and cut tyre costs.

How proof of chassis durability can be obtained is the outstanding question. Proof is a long-term process that should be based on a service mileage running into hundreds of thousands. Step forward Mr. Tom Jones of Joseph Jones and Sons, Ystradgynlais, Swansea. "It's a marvellous design", says Mr_ Jones of the aluminium chassis construction of four Duramin semitrailer coil carriers which he has been operating for eight to ten years.

"There's been no age-hardening of the chassis members, and they spring back to their original level when the load is taken off, which contrasts with steel members which take on a permanent sag after a while. So the extra flexibility of the aluminium doesn't matter."

Mr. Jones's oldest aluminium "coiler" was purchased in 1964 and was recently scrapped, after covering well over 400,000 miles, for reasons other than deterioration of the main members, which apparently are still as good as new.

Having an unladen weight of 3.35 tonnes (3 ton 6ewt) two 1964 Duramin 8.5m (28ft) coilers were originally rated at 24.4 tonnes (24 tons) gvw and could carry approximately 2.03 tonnes (2 tons) more than a comparable steel-framed semitrailer. And this payload advantage was also provided by two Duramin 9.75m (32ft) 3.86-tonne (3 ton 16 cwt) carriers acquired in 1966. The vehicles are now rated at 28.4 tonnes (28 tons) and 27.4 tonnes (27 tons) respectively and the outfits are operated at 32.5 tonnes (32 tons) gvw.

Although advances in steel construction have materially reduced the advantage if comparisons are made with more modern steel vehicles loss of benefit is then less than 50 per cent M and G 10.06 m (33 ft) and 10.97 it (36 ft) steel-framed coilers have unladen weights of 4.42 tonnes (4 tons 7 cwt) and 4.93 tonnes (4 tons 17 cwt) respectively.

The only structural troubles have been rivet loosening in the stressed aluminium floor at the front end and. in the case of the oldest vehicle. disintegration of the coil wells. Six tractive units are employed in conjunction with 15 semi-trailers, and coils are carried for the British Stee. Corporation.

On a proportional basis the current benefit to Mr. Jones from operating aluminium coilers is small compared with the weight advantage offered by the Welford Engineering Urb-a-tic aluminium-framed brewery semitrailer, as displayed at Earls Court and now in service in the Bass Charrington fleet. Equipped with Dunlop leaf/air suspension, the trailer has a rated unladen weight of 1.0 tonnes (1.87 tons) and coupled to a Bedford urban tractive unit it provides a payload advantage over a conventional counterpart (according to Bass Charrington) of better than 0.864 tonnes (17 cwt).

The first of six similar vehicles ordered by the company has been in service for three months and equipped with bars the trailer has an overall weight of 2.13 tonnes (2 tons 2 cwt), the weight of a typical steel trailer of the same type being more than. 3 tonnes (2 tons 19 cwt).

Design weight unladen of the outfit is below 5.1 tonnes (5 tons) while it is plated at 13.2 tonnes (13 tons) gvw. The outfit has been endurance tested on the pave at MIRA over 36 laps in a joint exercise with Allied Breweries, but an official report on the vehicle's condition has yet to be released.

A number of references to the potential advantages of aluminium were made by Roger Denniss, group fleet engineer of Bass Production Ltd, Burton on Trent, in a paper on the American trucking scene read at the CM Fleet Management Conference last month. In his final comment Mr. Denniss stated a conviction that there was a growing market for

light-weight aluminium-framed 4 x 2 and 6 x 4 tractive units in Europe, and earlier he claimed that the aluminium cab was regarded in America as "the best proposition to counter corrosion and to minimize unladen weight". .

Mr. Denniss has since told CM that two years ago no manufacturer was interested in building a lightalloy trailer or in other advanced applications of aluminium. He forecast an increase in fuel price to 68-78p per gal in the fairly near future and said that the cost penalty could be offset by the more extensive use of aluminium including, as a possibility, the production of lightalloy front axle beams, which his company has fabricated (experimentally and unsuccessfully) from aluminium tubes.

A saving in fuel consumption is envisaged by Mr. Denniss as the most important potential advantage of employing aluminium because it would enable the same payload to be carried by a vehicle powered by a smaller more economical engine.

British Leyland says that technicians of the truck and bus division have made on-the-spot investigations of light-alloy applications in America and Europe and are fully clued-up on current developments. Forward planning does not specifically include the design of a production model with a high aluminium content. For the time being, at least, production policy will be based on the current policy of employing the most suitable type of steel for appropriate components.

It is said that a number of UK rigid vehicle makers have definitely planned production of an aluminiumframed vehicle. But a hard core of pro-steel advocates regard aluminum as one of those things that have gimmick value rather than solid worth.

Ford claims that an extruded aluminium side-member would not be significantly lighter than a hightensile-steel equivalent and that the low relative cost of malleable or nodular cast iron in Europe militates against the use of aluminium forgeings for smaller components, which reportedly would be five or six times as expensive as cast-iron parts.

American practice

In some reviews of American practice it has been. emphasized that the use of aluminium for truck frames is favoured in that country by strictly limited rear overhang.

In the UK an overhang of up to 50 per cent of the wheelbase is common and this concentrates stress at a point behind the rearmost rear spring bracket. In contrast the highest loading of short-overhang American trucks is ahead of the rear hanger bracket of the front spring. The load is therefore more &evenly spread over the frame member and the lower strength modulus of aluminium is less serious factor in the design of th vehicle. Moreover, the 8-ton axl weight limif in the majority American states gives greater scor for exploiting aluminium to the bet advantage; and of related significane the design of chassis and suspensior is such that bump through to tr chassis is disallowed, whereas sonr UK designs provide for bump throug with the use of rubber auxiliat suspension units. And a lower pric differential between steel an aluminium also favours aluminiun Employing aluminium forgings fc smaller components would, it is sait involve high capital investment new production equipment.

That substitution of aluminium fu steel enables the weight of the chass frame of a maximum-load serr trailer to be reduced by about a to is confirmed by Alcan Boo Extrusions Ltd of Banbury. But the design were based on the op mum application of the latest produ tion techniques, weight saving cou be increased to around 1.6 to according to Alcan technicians.

The French Benalu compai concentrates entirely on buildii aluminium trailers and is one of number of European manufacture who have achieved a saving of tl order. Designing for aluminiu involves the production of a memb having a flange thickness which considerably greater than the nom thickness, together with a thinn web, in the interests of weight savir and Alcan says that it is much easi to do this with aluminium than wi steel. Employed extensively aluminium trailer makers in Germa France and Belgium, HE17 zinc all has properties which reduce loss strength in weld areas to a minimui

Alcan estimate

According to a recent estimate Alcan, the increase in cost when 32.5-tonne (32-ton) gvw semi-trai is built with an aluminium chas frame is £278, given that the mar facturer is tooled-up for producti in fair quantity. This is based on net sale price of £2,508 (for a pt form vehicle) compared with £2,2 for a steel trailer. The cost of steel assumed to be £1521 ton, whi represents a saving over aluminium E602/ton. Cost of manufacture pl profit and so on is quoted at £538 steel and £646 for`aluminium.

Referring to American practi, Alcan points to the aluminit options offered by the White Tru company which give a weight savi of well over a ton in applications a three-axle rigid. These include I frame, cab, radiator and grille, ge; box casing, wheels and brake drur rocker beams, fuel tanks and r( bumper.

Tags

Organisations: Earls Court
People: Roger Denniss
Locations: Ystradgynlais

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