E n 583 tractive unit at
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By Graham Montgomerie
photographs by Dick Ross IT'S KNOWN by the Foden computer as 04A 032 C25 OS— it has a 3.12m (10ft 3in) wheelbase, Cummins NHC-250 engine and the S83 glassfibre cab. It has been some time since CM tested a vehicle of this make, so it was nice to be behind the wheel of a Foden again, and to find that it put up an acceptable performance over our Scottish route, and this despite bad weather on the return leg.
Mechanical details
Compared with the other users of proprietary power units, the Foden has more home-built components for the rest of the specification. The rear axle is still the worm type, which must be one of the most well-proven truck components in existence by now, while the eight-speed gearbox is also familiar to drivers and operators. Calling the gearbox an eight-speed unit is rather a nonsense as it still possesses the same set of cogs as the old 12-speed, so the driver can use it as an eight-speed unit ' according to the Foden recommended shift pattern or search around to find a few extra ratios to fill in the gaps. Actually, the eight-speed layout is well spaced and little performance is lost by using it as such.
The new S83 cab is similar in appearance to the S80. The major difference is the addition of steel reinforcements to strategic areas of the fibreglass construction, notably the hinge-mounting points and the bulkhead. The cab can be described as "functional" or "old-fashioned" depending on your point of view; certainly in some areas the latter view is more likely the reaction to it. I am thinking in particular of the cab entry, where the Foden still relies on the use of a step ring on the wheel.
The cab is well laid out, but is made gloomy by the amount of black trim.
The gear lever fell easily to hand with the range-change/ overdrive switch situated in the top of the lever itself. The pedal layout was satisfactory in most circumstances so far as I was concerned, but I would prefer a different combination of pedal angle and throttle spring for motorway operation.
The cab visibility was very good, especially to the rear, owing to the first-class twinmirror system which Fodens use. But in the wet there was a large unswept area in the centre of the split screen assembly. I wonder Fodens do not fit electrically operated wipers instead of the present air system.
The secondary/park brake controls are more complicated than usual in that a springloaded safety catch blocks the park-brake position so that applying the parking system is almost a two-handed job.
Performance
The wide ratio spread of the Foden gearbox should allow the truck to tackle any conditions likely. to be encountered by the average operator. The top gear of 0.77 to 1 gave a top speed of 66/67mph while the bottom gear with a 12.25 to 1 ratio made an easy restart possible on the 1 in 5 test hill at MIRA. it would almost certainly have gone up the 1 in 4 as well, but the proportions of the trailer and the layout of the test hill meant that we would have grounded the landing legs at the top.
The Foden cruised effortlessly at around 2,000 rpm near the maximum legal speed. The engine seemed unobtrusive, I think partly because the higher than usual wind noise tended to cover up the engine's contribution.
Acceleration was adequate for normal operation, but a trifle disappointing when related to the power output of the Cummins engine. However, the upward gearchange was relatively slow, which partly accounts for this. Under normal road and traffic conditions the gearchanges were excellent, but during the maximum acceleration runs at MIRA it
proved impossible to hurry the change—a situation aggravated by the slow die-down of the Cummins power unit. Surprisingly, the worst change of all was the range change from fourth into fifth via the epicyclic section. This needed a pronounced pause in the middle of the change to ensure a positive first-time engagement. On flat roads this was no problem, but on hills when a fast upward change was advisable it proved to be a handicap—the more so as fhe delay worsened during the test.
On Carter Bar, crossing the Scotland/England border, we carried out a timed climb, Average gradient is about 1 in 13 with several sections much steeper than this. The slow change between fourth and fifth caused problems on the hill and, on one occasion, the gear did not engage at all compelling me to make a very rapid two-gear downchange before the truck stopped completely,
Fuel consumption
Down changes were no problem at all: a quick blip on the throttle ensured clean and rapid changes at all times. On hilly roads the unofficial "extra" gears came in very handy indeed with third overdrive (to use the old 12-speed nomenclature) proving invaluable. I must say I cannot comprehend the thinking behind the marketing of the gearbox. It has 12 speeds, so why not call it a 12-speed box? The days of the separate rangechange lever are long gone and the present three-position switch on the gear lever is simplicity itself to use. And sooner or later drivers are going to use the "missing" gears anyway.
Over the past couple of years the average fuel consumption for all the heavy trucks tested over our England -Scotland-England route has given a par for the course of 6.5mpg. The Foden with its overall fuel consumption of 44.31it/100km (6.4mpg) was only just below average in this respect. Throughout the test the consumption was consistent; only the severe A68 section gave a high figure, but then all the trucks tested by CM are thirsty on this section.
The average speed related to this fuel consumption figure was slightly distorted owing to patchy fog on the second day on Al and the top end of MI. Thus while the average speed of 63.9km/h (39.3mph) for the 700-odd miles long test route was still perfectly respectable, it was not truly representative of the Foden's capabilities in this area.
The first day of the road section was completed in perfect weather in 8 hours 35 minutes—some six minutes faster than the Seddon Atkinson 400 with an identical power unit, It was only on the second day that the weather intervened to pull the average down,
Braking
The Foden's braking was very good indeed especially when viewed against the performance of some recently tested trucks. The secret of the short stopping distances recorded lay again in the balance between the trailer and the tractive unit.
From 40mph, the stopping distance was 31.7m (104ft Iin) which it achieved with a remarkable lack of fuss and no obvious wheel locking. The combination also pulled up straight with no deviation whatsoever.
General handling
The steering of the Foden, courtesy of a Burman integral system, was very light, making life easy for the driver in tight manoeuvres. In Jedburgh, on the way to Carter Bar, the main street was littered with doubleparked delivery vans and I was grateful for the easy steering as I put it from one lock to the other to get through. On the other hand, the small number of turns from lock to lock (4D made it a very "nervous" truck to drive at speed as it was far too easy to over-correct.
On the Staffordshire section of M6, the nearside lane is now very badly grooved by heavy traffic, and this affected the Foden when crossing lanes and overtaking. In a situation like that, I initially found myself putting on too much lock to prevent the truck being deflected by the grooves. But it proved easy to adapt to the steering.
The ride was not particularly good on roads with good surfaces, and on long undulations or equally spaced expansion joints an uncomfortable pitching motion was caused. Paradoxically, when the road surface was bad, the ride improved relative to the conditions, but even so, it still bounced the driver around.
Most of the motion seemed to originate around the fifthwheel coupling, and at times it felt as though the trailer was flexing, and literally lifting up the rear of the tractive unit. I wonder whether a set of darn
Above: The latest 883 cab tilts to 45 degrees for engine access. The handle for the hydraulic pump is alongside the radiator.
Below : The instrument panel can be easily read apart from the rev counter, much of which was obscured by the rim of the wheel. The bank of contact breakers is to the right of the steering column.
Maintenance and accessibility
The Sg3 cab is tilted hydraulically. This is not in itself unusual, but the siting of. the pump alongside the radiator is not common. The radiator itself tilts forward after removing two locking pins and the cal instrumentation includes a warning light which is illuminated if the cab safety locks arE
not secured properly.
The dip-stick and oil filler are situated behind a removable panel under the driver's seat. It is no encouragement to check the oil when one has to slacken off four wing-nuts and remove a panel to do so.
The water level in the radiator is checked via the hinged front panel.
The fuses for the Foden electrical system are of the contact-breaker type which can be reset once a problem has been corrected. The fuse bank is conveniently situated under the instrument panel to the right of the steering column and the individual fuses are all clearly labelled.
The old problem of hooking the top radiator hose out of the way when the radiator is returned to its normal position after tilting has been removed by the addition of a middle support which prevents the hose being trapped.
Summary
It was unfortunate that the bad weather delayed us en route as the performance until then had been good—certainly the equal of the opposition with this sort of power to weight ratio.
The fuel consumption was marginally above the norm for the 728-mile round trip, but was still satisfactory.
The slow gear change from fourth to fifth is—hopefullylimited to this particular test vehicle, and not an indictment of the Foden gearbox, which in all other respects showed up very well.