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Formidable but thirsty

6th April 1985, Page 37
6th April 1985
Page 37
Page 38
Page 39
Page 37, 6th April 1985 — Formidable but thirsty
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Keywords : Overdrive

FODEN vehicles are individually specified to a customer's operation. This entails holding a wide range of driveline options; there were 17 engines and 11 gearboxes on offer for 38 tonnes gross combination weight use alone. Now the company has introduced another ingredient to the mix.

The latest choice is a new generation 12-speed gearbox from Eaton, exclusive in Britain to Foden for the rest of this year, which incorporates a fourposition gate, with three splitter gears in each one. Eaton says that the new gearbox, which is being built in France at St Nazaire, will provide low life-cycle costs with an expected 800,000km (500,000 miles) before a major overhaul.

I am sure that it will add fuel to the synchromesh versus constant-mesh debate because of the speed and ease of gearshifting with it.

Our test vehicle had an impressive build specification. It was powered by the 254kW (340hp) gross, turbocharged and charge-cooled 340Li RollsRoyce (Perkins) engine, driving through the new overdrive (TS0-11612) constant-mesh box.

As an advocate of the 6x4 drive-axle configuration for tractive units, Foden fitted the vehicle with Rockwell SQ100 tandem-bogie axles. Many operators mistakenly believe 6x4 units are heavier than 6x2s, so Foden chose rear axles with aluminium drive heads and other weight-saving items, such as the Kenworth torsion-bar suspension and aluminium wheels, fuel tank and air reservoirs. And the 340Li engine is 155kg (3cwt) lighter than the Cummins NTE350.

Let's compare the test vehicle's 7.43 tonnes ready-for the-road kerb weight with the 7.68 tonnes of the Volvo F10.26 (CM, April 28, 1984), the 7.71 tonnes of the Scammell 20.32 (CM, October 27, 1984) and the Seddon Atkinson 301's 7.28

tonnes (CM, February 2, 1985). All these are 6x2 models, and

were tested with the same Crane Freuhauf tandem-axled and curtain-sided test trailer.

It does seem to prove Foden's point on the 6x4's kerb weight. However, payload po :entia I has to be kept in )erspective with the much iigher capital outlay that ac ;ompanies these tailor-made rucks. The Seddon Atkinson 01 6x2 at February's prices ;ost around £4,500 less, with he Scammell and Volvo 6x2s n very similar price brackets.

Powered by the highly repuable Rolls-Eagle 340Li diesel, he vehicle looked to be cap ible of putting up a fairly quick ind fuel-efficient performance.

:ven the Foden engineer who iccompanied it expected somehing above 43.46 lit/100km 6.5mpg).

So we were unprepared for le poor results that we did ob )in: 46.54 lit/100km (6.07mpg).

his worked out at about seven er cent below the figure ex ected, or approximately 36.4 tres (8gal) more diesel used ver the entire 1,184.6km (736.8

Most of the 38-tonne vehicles tsted on our Scottish route roduce some of their best fuel ?turns between the Nafta sta tion start point on the A5 near Nuneaton and Hamilton Services, south of Glasgow on the M74. Fuel consumption here was well below the seven plus expected and it remained proportionately consistent, even on the tough A68 section between Carter Bar and Consett.

Thick fog in the morning in the Borders spoilt Colin Sowman's photographic work, but allowed him time to notice that the Foden's exhaust was smoking badly.

After we had corn pleted the road test, Rolls-Royce service engineers found no fault on the engine itself, but Foden engineers later discovered that the throttle actuating lever on the fuel injection pump did not have a sufficient arc of travel.

The Foden spokesman believed that the final adjust

ments made. before releasing the vehicle as a demonstrator had compensated for the lever's inability to move its full angle, with the result that it had over-fuelled across the entire speed range.

This has not yet been confirmed, but it seems a likely explanation looking at the consistently high fuel usage over the three days.

However, during the test I found Eaton's new gearbox a revelation, although it was not until the second day that I began to appreciate its full capabilities. Foden says that it normally takes two hours of concentrated use for a driver to get the hang of it, but driving on the A5 and M6 to Gretna Green allowed few opportunities to refine my technique on the first day.

The main body of the Twin Splitter gearbox is virtually the same as that of the conventional Fuller twin countershaft unit, but the splitter gearing is permanently attached to the output shaft.

There are four (forward) gear lever positions and each one has two splits. These are selected using the button on the gear lever to give a total of 12 ratios.

When a gear is pre-selected, the original one is held by means of a special sensor and blocking assembly. When torque is removed by releasing the accelerator, or by using the clutch pedal, this unit ensures that the original gear is released and the pre-selected one engaged.

Compound gear changes can be made using the clutch in the normal way, but after a short time, this can be carried out using only the accelerator. Towards the end of the test, I only needed to use the clutch for moving off.

Driving away from rest on level ground could be accomplished easily using third, fifth, seventh and then each ratio up to 12th. Several hill starts in Edinburgh required a modified pattern of first gear, with a skip shift to third, or second to fourth.

Working uphill called for nimble fingers when stick and skip shifting down the box, but once the knack had been acquired, it became very gratifying.

Changing up on severe hills can be done very quickly by using the upshift brake. The clutch pedal has to be fully depressed, which ensures that the air control system slows down the primary gear train and allows rapid synchronisation.

My climb up the notorious West Woodburn, Kiln Pit Hill and Blackhill gradients on the ABS between Rochester and Consett, were among the easiest I have made owing to the new gearbox and crisp RollsRoyce acceleration. Carter Bar was climbed in a very fast time and without the use of the clutch pedal. The price and the weight of the new box are very similar to those of the 13-speed Roadranger.

Foden's S10 double-bunk sleeper cab is well appointed and very comfortable, with Isringhausen air suspension seats, electric passenger window and Eberspacher heater. Heated wash/wipe mirrors, variable sweep wind screen wiper control, reversinc alarm and a quality radio wen all included in the overall price. Normal manoeuvring 01 roundabouts and at junction produced very little roll; eve cornering at reasonable speed had little effect.

The overall quality of the rid was a little on the soft side. 0 good roads this was fine, ix on poor surfaces cab mow ment became pronounced. Thi could well have been caused b the long 4.08m outer axl spread and the fact that th chassis is really designed fc the higher kingpin offsets 1.02m (40in) and upwards.

The steering felt very pos tive, giving a good feed back t the wheel and the kerb to ker turning circle of 13.8m (45.3f bears comparison with th Volvo F10 6x2's 13.62m (44.4f1 Scammel 20.32 6x2's 14.31 (46.8ft) and the Seddon Atkii son's surprising 17.0m (55.7fit).

Braking power was first clas reflecting well on the asbesto free Enduramid brake lininc which are fitted as, standar The Foden pulled up straigl and true on the track, witho any sign of locking. The retr, gate exhaust brake was less ir pressive, however.

Foden's high roof S10 cE has been developed to a hiç standard and goes a long wi towards making long-haul wo less strenuous. Noise levels a down to a reasonable levi too.

Summary The combination of Rol Royce 340Li, Eaton Twin Sp ter, Rockwell SQ100 twin-boi axles and torsion-bar susp( sion sounds form dab enough. Nevertheless the fi consumption figures were po whether or not they we caused by a poorly servic fuel injection pump. And fuel a very important element operating costs.

At £40,000 this superbly Ix machine represents a fair-siz capital investment which neE to be accompanied by worthwhile return.


People: Colin Sowman

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