Pulling its weight, easily
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The Seddon Atkinson 401 proved itself well able to operate at a gcw of 38 tonnes — indeed, Tim Blakemore felt it better suited to operation at this weight than at 32 tons. But this road test was far from trouble free
iEDDON ATKINSON has never leen a company to fight shy of natching its vehicles against its ivals in road tests, and the )1dham-based manufacturer as very keen to take part in ;Ivt's recent series of tests of 38onners (CM w/o March 13, 982). At first, the obvious vhicle to use seemed to be the ame Gardner-engined 401 as vas tested at a gcw of 32 tons CM w/e March 27, 1982). After ill, this tractive unit had already leen prepared, so there would De no delay; it had performed atisfactorily at the lower veight; and its design gcw of 40 onnes was certainly high icough.
But after some deliberation, Ind with due regard for the enpine specifications of the other vhicles involved, Seddon Atkin43n decided to wait until a more ilowerful 401 could be made ivailable. Few operators would question the wisdom of that decision, I feel. While our 8LXC had lived up to its reputation as one of the most fuel efficient engines on the market, it had been unable to provide the power required for fast, or even by today's standards, average journey times. It is clear that with an extra six tons or so to pull, this tractive unit would have been decidedly sluggish, especially over the hilliest sections of the Scottish route.
That is not to say that if and when the proposed increased weight limits are introduced every operator who runs at 38 tonnes will need at least 290hp, but surely that horsepower category will then become even more popular than it is already. Seddon Atkinson currently offers two engines of around 290hp gross in its 401 tractive unit range — the 14-litre Cummins E290 and the 12.17-litre Rolls-Royce 290L. It was the latter type of engine that powered this week's test vehicle.
The 290L is one of the younger members of Rolls' Eagle family of diesel engines: all in-line sixes with the same swept volume but with maximum gross power outputs ranging from 1 64kW (220hp) up to 254kW (340hp). The 220hp version is the only one that is not turbocharged, and 320 and 340hp versions additionally have air-to-water charge cooling. "L" tuning (meaning that the engine delivers maxi
mum power at 1,9 0 0 —1,95Orpm instead of 2,100rpm) is
available for the five most powerful variants. As is so often the case nowadays, the installed retail prices of these engines are much more a reflection of "market forces" than any actual production cost differences. A 401 with a 290L, for example, costs some £1,650 more than one with a 265L, while a 320L engined version will set you back a further E1,500.
My initial impression of SNE 71X was that perhaps it had been fitted with a 320hp rated engine by mistake, though it definitely did not have charge cooling! It pulled its 38 tonne burden that well.
The engine was certainly in peak condition, having been well run in up to 43,000km (27,000 miles) as we began the operational trial, and having just been fitted with a new turbocharger because Rolls-Royce's engineers had discovered in a pre-test check that the old component's boost pressurewas below par.
If changing the turbocharger was the main reason for this engine's sprightly performance then I would thoroughly recommend the same course of action, a little expensive though it may be, to any operator whose 290L is inexplicably off colour.
The first indication of how strongly this engine pulled came on M1RA's twin horizontal straights where the Seddon Atkinson reached 80km/h (50mph) from rest in times that many 32tonners would have difficulty bettering. Undoubtedly, swift acceleration was aided by the remarkably fast gearshifting that was possible with this vehicle's Fuller Roadranger gearbox. Like the engine it was nicely run in and gear selection was like the proverbial knife through butter.
Every 401 I have driven has impressed me with the standard of its Fuller installation but this one was the best yet, giving a consistently good, almost effortless and smooth action throughout the three day test.
Furthermore, the ratio steps of the RT09509A behind the 290 Rolls felt even better suited to 38 tonnes operation than they do to 32 tons. At the higher weight, for the best acceleration, every gear (except crawler) was used when changing up, though in normal circumstances on the road it was often possible to skip one or two ratios in the low range.
By no means all our specific tests at MIRA went as smoothly as the acceleration runs. Indeed, this particular 401 chassis was dogged by a number of niggling defects, some of which came to light on the first day.
The service brake performance was unexpectedly poor and improved hardly at all when the slack adjustment was taken up a little and the tests were repeated with warm brakes back at MIRA on the third day. Seddon Atkinson informs us that when the vehicle was returned to Oldham the braking system was checked and the cause of the problem was found to be a sticking piston in the footbrake valve.
We are grateful to Vee And InLine Diesels, the Seddon Atkinson distributor who responded so promptly to our call for assistance when this 401's flasher unit failed, again at MIRA. The technician who brought and fitted the new unit found himself with more work than he had expected when during his visit the starter motor also failed to operate. One of the leads to the starter solenoid was badly corroded and had broken away. It was an easy enough job to reconnect it but this incident, on a new vehicle, served to demonstrate how exposed the solenoid's terminals are. It is clear that they need some protection from the elements.
This 401 was something of a rogue chassis. Even the power steering was not up to the usual impeccable ZF standard. There was a noticeable pull towards the nearside, probably attributable to a misalignment of axle and suspension rather than any defect in the steering box, and also an uncharacteristic vagueness occasionally in the "straight ahead" position. The ruts on the nearside lane of the M6 northbound at its northern end caused more feedback of movement to the steering wheel with this vehicle than with any other 401 I can remember.
It is interesting to compare this vehicle's performance over the Scottish route with that of the Rolls-Royce 290L-powered 401 which was tested last year (CM w/e November 21, 1981). The overall average speeds of the two tractive units were almost identical, being in fact marginally faster for the 38-tonner. At 32 tons gross the Rolls 401 used 102.49 gallons of diesel to complete the 736 miles whereas the 38-tonner used 108.39 gallons, giving overall average mpgs of respectively 7.19 an( 6.80.
One of the conclusions to IN drawn from the earlier test we: that the lowest available ratic (highest geared speed) of 4.44:' for the International Harveste RA-57 single reduction rear axIE was the most suitable for gen eral UK operation at 32 tons, be hind the 290hp engine an overdrive gearbox. At 38 tonne gross the higher (lower geare( speed) ratio of 4.78:1 as fitted t( our test vehicle is clearly the bet ter choice.
None of the vast variety o road conditions provided by tho Scottish route revealed an serious deficiencies in this 4131' transmission matching. Then were odd occasions on cartel( gradients where exactly the righ ratio was not available but this not uncommon. On Carter Bar for example, the Rolls woul( quickly pull up to maximun power in fourth gear but couli not quite hold on to fifth, witl the result that I had to switcl between these gears a numbe of times. But as our hill climl chart shows, this had little detri mental effect on the time climbs.
The maximum geared spew it 1,950rpm with this axle ratio is 106km/h (66mph) and at a road >peed of 60mph the engine was milling strongly with the ta;hometer indicating 1,750rpm. 'Jo downchange was needed for (eele hill on the M6 and Shap as climbed in seventh (direct).
For operators who regularly sun fully laden up long notorway gradients such as ;hap or the M18, or the M1 bank it junction 23, and who hope to )e able to do so at 38 tonnes in he future, then the thirteen ;peed Fuller gearbox must be an )ption well worth considering at ts extra price of £360. That cost ;hould soon be amortized by the ;aved fuel and shortened jourley' times resulting from the iseful additional ratios it profides.
At 40 mph in top gear overdrive) the engine speed vas down to 1,150rpm, well beow the peak torque speed of 1,300rpm, but still pulling Arongly. One of the 290L's virues is its willingness to be dri ven at low speed when necessary, extending in practice what on paper is quite a narrow usable rev range.
This 401 was the first one we have tested to be fitted with the option of a Kysor radiator shutter as well as the standard Dynair thermostatically controlled fan. It is impossible to say exactly what effect this had on fuel consumption, though of course by allowing the engine to reach its operating temperature more quickly, it certainly should have helped. One secondary advantage of the shutter which I appreciated was that it led to the heater, and so the demister, becoming effective very quickly first thing in the morning.
On the first two days of this test the weather conditions were moderate in every respect and so were similar to those prevailing during our previous tests of 38-tanners. But on the third day it was really a mixed bag of weather with some sunshine but a lot of rain, and on the last sections a very strong southwesterly wind. This wind must have adversely affected fuel consumption, though as the results table shows, the consumption over the last two stages was nevertheless quite creditable.
The rain on the final day made me acutely aware of the problem of mirror fouling on this 401. Spray from the wheel nuts was splashing up directly on to the face of the nearside mirror and that meant that over muddy sections of road the mirror became almost useless within a matter of minutes. It seems to me curious that apparently the best solution to this recurring problem is still the primitive one of tying a length of cloth to the mirror arm.
Summary A number of niggling faults on this particular 401 spoiled what was an otherwise convincing demonstration of its ability to operate more than satisfactorily at a gcw of 38 tonnes. The overall average fuel consumption, despite the unusually high wind on the last day, was second only to that of the Volvo F12 in the group of vehicles so far tested at 38 tonnes with this tilt semi-trailer, and its average speed was on a par with many 32-tonners.
Like the lveco 170F30T, this 401 with its multi-leaf road springs had noticeably firm suspension with the relatively high axle loadings and it was obvious that the suspension seat was having to work hard.
A lasting impression of the Seddon Atkinson, and indeed all the vehicles I have recently driven at 38 tonnes is that it is actually better suited to operation at the higher weight than at 32 tons.
If I had to compile a short list of drive line specifications to suit 38 tonne general haulage operation in this country, then this 401's would definitely be on it. But I would give serious consideration to the option of the thirteen-speed Fuller.