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Graham Montgomerie tests the Rolls-engined. .
Page 75
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Page 78
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ONE ENGINE which has recently been attracting a great deal of attention from operators is the Rolls-Royce Eagle 265L, so it was with particular interest that we embarked on our test of a Seddon Atkinson 400 fitted with this power unit.
The interest was more than justified by the impressive results returned by the lorry with an excellent overall fuel consumption of 38.7 lit/100km 17.3mpg) allied to a high average speed for the Commercial Motor Scottish operational trial route.
Our test truck was similar in specification to the one we tested at the time of the 400's announcement but with two important exceptions -the Rolls-Royce engine and the Eaton axle.
The Mk III version ofthe Eagle 265 was designed to
meet a minimum . power-to-weight ratio of 7bhp /ton
for operation in the 34136-ton-gcw category.
The "L version is "derated" as far as maximum engine speed is concerned. but careful turbo
charger. and injection pump • matching has ensured that the maximum power of 197kW /265bhp) has remained the same. Torque, however, has been increased slightly from 1,047 to ,1,090Nm 1772 to 800Ibft).
• Normally, Seddon Atkinson • 400 Series are fitted with the group hub-reduction axle but, fo.r the moment at least, a ratio • suitable for motorway use is not available -hence the move to the Eaton axle with its 4.56 to 1 ratio.
Low-speed economy
• The main point of interest in our operational trial results is always fuel consumption, and,in this particular area the Seddon. Atkinson excelled with an overall .fuel consumption of 38.5Iit /100km 17.3mpg).
The best figure ever recorded over the present CM route was 37.71it/100km17.5mpg) for an 8LXB-engined Atkinson over five years ago, and for some time during the 400 test it looked as if this result might at long last be beaten. motorwwing park brake meant that the brakes would release only with absolutely full tanks. And this Problems with a badly stickmeant that every time the park • brake was applied I had to rev the engine hard to build the air up quickly so we could get moving.
fuel
The problem got worse during the course of the test so I abandoned using the park brake at all except at essential times. Thus with this extra unnecessary running, the 7.5 mark was not reached, but the figure we did get still puts the Rolls-engined SA in with the best of them as regards economy.
With its 4.56 to 1 axle ratio, the •lorry cruised happily at the motorway speed limit with 1.,800rpm on the clock. Under these constant speed conditions the fuel consumption figures were consistently into the. mid-sevens and these results were achieved at very high average speeds, as a glance at the results panel will indicate.
On A-roads, however, the
vehicle was not quite so happy and this again was a direct function of the overall ratio. Top gear in the Fuller box coupled to the 4.56 axle meant that the Rolls was turning at around 1,200 rpm at 40mph. Now this was fine on a perfectly level road, but as soon as a gradient arrived -however slight — a downchange was required as there was just not the necessary flexibility in top gear for this sort of running. As a motorway. machine, however, the gearing could not be faulted.
It is difficult to assess the effect of the axle ratio on the stiff Rochester to Neville's Cross section as much of this is covered in the low range of the gearbox anyway, so any extra down-changes were not quite so obvious.
What was obvious and could be easily measured was the fuel consumption which, at 52.3 lit/100km i5.4mph), was more than acceptable for these road conditions.
Hill country use • In hilly country, off the motorways, it was necessary to keep a careful eye on the rev counter. With the maximum torque being produced right down at •1,200rpm, the Rolls was quite happy lugging away at this speed and several times I was ready to make a downchange which eventually was not needed as the engine just kept hanging on.
The only problem was that this could be carried to extremes. so if a change was finally necessary, I had to go down two as one gear alone would just miss the peak of the torque curve.
My overall assessment of the lorry's mechanical specification is that it is an excellent motorway machine, but for mixed roads something between the Eaton's 4.56 and the highest Seddon axle ratio of 5.05 to 1 is necessary.
Normally, one would expect a turbocharged engine to run at a fairly high engine speed if only to keep the turbine speed up and most tc units bear this out with the average speed being around 2,600rpm. The L version of the 265 has none of the normal characteristics of a turbocharged engine.
I have already mentioned its low-speed performance, but one other area worthy of comment was noise. At no stage during the test was I conscious of any turbocharger whine which is so irritating on many vehicles because of its pitch. At low road speeds there was a fairly pronounced "rumble" from the engine but it never became a nuisance.
Hill climbs
• At the MIRA proving ground, I was rather surprised to find that a restart was possible on the 1 in 5 gradient as I had expected this to be beyond the Seddon Atkinson's capabilities.
Now that the Devil's Beef Tub climb out of Moffat is lost to us, because of a recently imposed axle weight limit, our only timed climb is Carter Bar on the Scotland/England border and, here too, the ability of the Seddon Atkinson surprised me.
In fourth gear (fifth if you count crawler as first) the truck went up at a steady 29 km/ h (18mph) with no dithering about between one gear and another as is often the case on this hill. The time taken for the climb was 5 minutes 18 seconds in comparison with the lower powered Cummins 250 version of the 400 which took nearly 61/2 minutes.
As always with Seddon Atkinsons the ride comfort was excellent, but this time with one important exception, although this was not the fault of the lorry itself. The trailer had been loaded in such a way that the majority of the test load was situated in the middle of the trailer and, on bumpy roads, the trailer was flexing so badly that it tended to lift the drive axle. Thus on bumpy roads the ride of the Seddon Atkinson /Crane Fruehauf combination was atrocious.
Under motorway surface conditions and speeds, this characteristic was not nearly so noticeable.
.Brake tests
• When we carry out braking performance tests at MIRA, a reasonable standard to aim at is around 100ft from 40mph. On a dry track the Seddon Atkinson took 34.7m (114ft) which is about the norm. No exhaust brake was fitted on this particular vehicle but, except on the steepest of hills, one was not really necessary as the engine speed in sixth and seventh gears stayed fairly constant on the overrun thus avoiding driver use of too many dabs on the brake pedal to control the speed.
The cab of the Seddon Atkinson is now too well known to need a great deal of description. Suffice to say that the oil level is checked after lowering a hinged front panel while the water level can be inspected in the header tank at the rear of the cab.
The cab itself tilts hydraulically to a maximum angle of 60 affording excellent access for maintenance, planned or otherwise.
Summary
• Although hampered by the recent strike, Seddon Atkinson has been producing over 200 vehicles per month in the 400 Series as a trip along any motorway will confirm. The Rolls-Royce 265L version will, I feel, increase Seddon Atkinson's market penetration still further if only supply can meet demand.
With a fuel consumption of 38.5 lit/100km (7.3mpg) allied to an overall average speed of 69.5km /h (43.2mph) the truck put up one of the best all-round performances ever recorded over CM's Scottish test route.
In these days of ever increasing awareness as to the effects of aero-dynamic drag on fuel consumption I wonder how much we lost owing to the Seddon Atkinsdn's headboard.
As tested, the 265 L-engined truck costs £16,150.