FODEN/YORK
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32-TON-GROSS
ARTIC by Tony NA/ Ming m mechE IT IS unusual to find a 32-ton-gross artic that is able to restart fully laden on a 1 in 5 gradient. Yet this is what the Foden 4AC6 /34 did on test by CM, even though gross output, to BS AU141, of its Cummins engine was only 205 bhp. This standard of gradient-climbing ability results partly from fitting the Foden 12-speed gearbox which has a bottom ratio of 12.25 to 1. And the useful spread of gears in this box gives the vehicle a better-than-expected performance on the road.
It is doubtful if the Cummins NHK 205 diesel will be powerful enough for a 32-ton model designed to meet the future power-to-weight regulations proposed for this country. It is likely that for each gross ton, 6 bhp in the "installed" condition (net) will be required; and taking into account the power losses due to the fan, the generator, exhaust system and so on the NHK 205 is unlikely to give the necessary 198 bhp net to the British standard.
However, the characteristics of the power unit and the 12-speed gearbox gave the Foden /York outfit a more-than-satisfactory performance for such a vehicle, showing again how arbitrary is a simple power-to-weight limit. The outfit coped well with the arduous part of the 731-mile operational trial route used for this test and it gave acceleration times normal for British maximum-gross artics previously tested by
CM.
. Braking was very good. Not that stopping distances were startling—the average from 30 mph was just over 69ft.—but the Foden and the York semi-trailer have well-designed, wellbalanced systems which resulted in good response to brake pedal operation and no wheel locking on the maximum-pressure stops. The stopping distances were well up to the standard expected nowadays of maximum-gross artics and the York semi-trailer played a good part in this. The 69.3ft. which it took to stop from 30 mph represents an actual efficiency of 43.5 per cent (the peak reading on the Tapley was 69 per cent) and the brakes on the trailer were clearly giving the optimum effort. There were only very slight trailer-tyre marks on the road for the last few feet of the stops.
Light steering
The "feel" of the brakes gave confidence when driving the test vehicle but I cannot say the same for the steering. Fodens use a Burman box with power assistance by a Davies and Metcalfe hydraulic ram. The steering was very light but it was very easy to over-correct and this gave the outfit a most disconcerting over-steering character.
It was difficult initially to keep to chosen line and it took me at least 1 miles of driving before I could feel confid and was able to anticipate the point which I had to bring the wheel back to • opposite end of the "play". There v rather too much free movement in • wheel, it seemed, accompanied by rubbery feel and while the difficulty N not so great at motorway speeds, on ot roads one had the feeling of "aiming for gap" rather than steering the veh precisely when a vehicle was coming in opposite direction.
I had expected to have some trouble v the steering, for when I travelled passenger for the first 56 miles of operational trial before taking over for stage from M1 up to Gretna, Charlie L( of Fodens was doing more "sawing" of wheel than is usual in a person experien with a vehicle make. I am quite sure ti was something wrong with the partici vehicle we had and that this was not inherent fault. The Foden had covered c 1800 miles before my test and it may h been that something was sticki Eventually one became used to the steel but it still demanded above-aver, concentration.
There was also something not quite ri with the transmission of the test vehich rating and racking which seemed to be oming from the gearbox at speeds over bout 45 mph became progressively worse luring the run. The cause may have been a 'caring that was below standard but it never eached the point where real concern was aused or where it was felt that we should Lot be pushing the vehicle so hard.
The drive from the Cummins 205 bhp ngine in the Foden is through a 7in.-diameter single-plate clutch (with intered-iron facings) to the 12-speed box .nd there was always a good, smooth ake-up of the drive. Many people imagine hat the Foden transmission has rather a omplicated change but I disagree entirely. le only odd thing about progression hrough the box is that fourth gear in the pw ("underdrive") range comes out of equence. It is in fact possible, unless articular circumstances make it undesirble, to leave out fourth in "underdrive" hogether. And then the change is oerfectly straightforward using first, second ind third in the underdrive range followed oy the four ratios in the main box engaged n sequence with the intermediate and high. Itudliary gears as a normal splitter irrangem ent.
I found it quite easy when starting off on he flat to begin with bottom gear engaged n the main section and the intermediate ratio in the auxiliary gearing in use and then use the gearbox as a normal eight-speed splitter unit. On slight up gradients, restarts were made in second or third gear with underdrive and from third to first in the main box in the intermediate range.
Gearbox range It is unlikely that the full range of the gearbox will be utilized at all frequently in normal operation. We used bottom low on 1 in 5 slopes but managed 1 in 6 restarts with second low. The change action of the Foden was smooth though a little heavy, but this could have been due to the newness of the components. With only little experience well-synchronized changes could he made and reliable changes in the auxiliary section of the gearbox were possible.
For all the tests, including the operational trial, the York trailer carried a payload of over 22 tons and it would have been exactly that figure if the gross weight had been just 32 tons (we ran slightly over). The first day of the long run went very well, with commendable average speeds on the motorway. Average speed dropped markedly on the trunk roads such as A5 and later in the day on the twisting and relatively hilly section across the Tweedsmuir Hills, but this is to be expected
with a vehicle having only just a little more than 6 bhp per laden ton. Nevertheless, the Foden made an extremely good overall average of 39.7 mph for the 376 miles from Hemel Hempstead to Pathhead and completed this long distance in less than 9.5 hours. The motorways contributed a lot to this good time, especially as Shap is now bypassed by the extension of M6. But the new part of the motorway is not as flat as the rest and there is a particularly hard climb from the A65 junction. From this point there is a long 3.85-mile drag with only a short stretch of flat and downhill running before it is uphill again to the A684 junction. For the first time, details were taken of this 3.85-mile climb which extends to the marker post bearing the number 412/4. This gradient was covered in a time of 7min 42sec in which third/direct was the lowest gear needed and the minimum speed was 18 mph.
On the second day the more severe hills of A68 brought average speeds down still more and over the worst part we recorded 19.8 mph where the hills are really severe. The pleasure at reaching Al after the hard work of A68 was marred by very bad weather and from this point there was heavy rain which made driving particularly difficult, especially at high speed on the motorways. Even so, the average speed on M1 was not greatly different from that achieved on the way to Scotland.
The first of the hills timed on the second day of the test was Carter Bar and this 1.8-mile gradient was begun at 40 mph, but speed soon dropped to between 12 and 15 mph for the most part. Having used second /direct for the general gradient of between 1 in 13 and 1 in 14, first /direct was needed for the steeper 1 in 9 part near the top, where road speed was 6 mph. At the summit second/direct was again engaged with a speed 15 mph; total time for the climb had been 8min 14.7sec.
Some difficulties with engagement when changing into the lower gears with low range engaged were experienced when the really steep hills on A68 were reached. On the 1 in 6.5 pass West Woodburn and on the 1 in 6 near Ridsdale stickiness in the linkage when changing into second prevented it being completed before we catne to a halt. The road surface was running in rainwater at the time and straightforward restarts were prevented by whedspin but by reversing a short distance down the slope we moved off satisfactorily in bottom gear with the rear axle differential lock engaged.
Having been prepared for low gear changes-in advance, the climbs of Riding Mill and Castleside were completed smoothly. At Riding Mill which measures 0.6 miles we were making 6 mph at the bottom in fourth/low and on the climb second /low was the lowest gear needed with the minimum speed of 5 mph. At the top changes of up to fourth/low were made and the speed was 11 mph, the time for the climb having been 5min 2sec. On the longer Castleside which measures 0.8 miles the 1 in 5.25 gradient needed the same gear as the 1 in 5 of Riding Mill and the minimum speed was the same at 5 mph. At the summit of the hill speed was 15 mph in second /direct and the climb had taken 5min 47secs.
After we had reached Al it was all plain sailing except for the very bad weather. A fuel fill-up just after we had picked up Al showed that a low figure of 4.3 mpg had resulted from the severity of the A68 but when on Al the figure rose to 7.8 mpg. This is lower than I would have expected and the Foden did not appear to be running as well as it had been on the previous day but any suspicions were eliminated on M1 when as well as satisfactory speeds the consumption wasup to standard with 6.7 mpg.
AN-steel cab The heavy rain brought to light a fault in the sealing of the cab and a fair amount of water entered through the rubber seals around the windscreens. Apart from this the all-steel cab proved well designed and well insulated even though one had to speak rather loudly to converse when running at high speed. Both the driver's and the passenger's seat were set rather high from the cab floor and in the case of the latter which is fixed at its height to clear the battery located underneath, my feet would not reach the floor when sitting on the seat normally. This may have been the reason why the seat cushions felt hard and uncomfortable after three or four hours in them. There is good visibility all round in t Foden cab and the model is well equipp with mirrors, having a flat and a cony type on each side. On the front corners the side of the screens there are curv deflectors which helped keep spray off' t mirror glasses. They were very good in tl respect and the mirrors did not get muddi up as they often do with a flat-front cab. adequate area of each screen is covered 1 the wipers on the Foden and the model well equipped with instruments which a visible through the top half of the two-spo steering wheel.
As well as a speedometer, the instrume panel contains water temperature and pressure gauges and two air-presst gauges; it would also have been advantage to have had an engine rev count to enable the very best to be obtained frc the engine and gearbox. The control les for the auxiliary section of the gearbox mounted on the right-hand side of the da and the secondary brake system control on the left. On the lower part—on t left-hand side—there are the light switct while a stalk from the right of the steeri column carries the dipper switch and he button.
The Foden has a single-pull handbra lever mounted low down on the left-ha side of the driver's seat, operating I transmission brake at the back of the axle In the form tested the Foden tractive uu which is designed for a gross weight of tons although limited at present legislation to 32 tons in this country, earn a price of £6491.