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Boxvan trailer aids tractor testing

26th December 1981
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Page 29, 26th December 1981 — Boxvan trailer aids tractor testing
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A BRACE of Seddon Atkinson 401s came our way this year — one with Cummins and the other with Rolls-Royce power. First off the mark in February was the Cummins-engined vehicle, and coincidentally it was the first to go round our Scottish route with our boxvan trailer.

As the range numbering suggests, the new series is de veloped from the 400-Series which is to continue alongside the 401.

There was a definite American influence in the unit's styling exemplified by the tall air-intake stack, cylindrical aluminium fuel tank, and 1H embossed lift-up door handles.

The original basic steel cab structure of the 400-Series is re tained, but there are significant changes which are aimed at keeping its weight to a minimum.

Contributions to weight saving come from aluminium fuel tank, two-leaf parabolic springs without anti-roll bars and a lighter steering box from ZF.

Extensive use of SMC (sheet moulding compound) for the cab's front panelling and grille, wings, the covering for the bumper and the air dam has also trimmed off the pounds. And 1H's RA57 single-reduction rear axle, familiar as an option on the 400-Series, is also considerably lighter than the hub-reduction axle it replaces.

With a full tank of fuel and the Cummins E290 engine, our test vehicle weighed in at 6,538kg (8 tons 8cwt 2qr). • The change to the braking system of the 401 compared to the 400-Series is the use of Rock well S-cam foundation brake assemblies for simplicity of design and the ease with which they may be serviced and maintained.

The diameter of the brake drums has been increased by 25mm (lin) to 419mm (16.5in) with a marginal increase in the tractive unit's total braking frictional area.

Standard gearbox for the Cummins, Rolls-Royce and 8LXB-powered 401s is the Fuller RTO 9509A with overdrive top gear. The direct-top version with the C set of ratios is offered as an option and is standard when the 6LXC Gardner engine is specified.

The about-face gearchange pattern of the 400-Series has gone on the 401 by fitting the gear-lever mounting above the engine, so that it does not tilt with the cab.

Gear selection on the 401 was much more crisp and positive than on the last 400-Series we tested and is now of a similar standard to the Fuller installation of Fodens or Ford.

An overdrive top gear ratio of 0.74:1 matched to the optional "slow" rear axle ratio of 4.78:1 gave our 401 a geared road speed of 103km/h (64mph) at 1,900rpm engine speed (at which maximum power is developed).

The extra frontal area of the van compared to a flat trailer seemed to have little or no effect on the Seddon Atkinson's performance, either on the track or on the road. Keele Hill on M6 was taken without dropping out of top gear and our overall average speed was 65.94 km/h (41.01 mph).

Returns of 5.42mpg over the hilly A68 section showed that the 401 was never in difficulty. The lowest gear needed on the steepest section was third (counting crawler as first).

One of Seddon Atkinson's major aims with the 401 was to appeal to the driver, and it seems to have been successful.

The contoured base and squab of the driver's seat gives support and comfort and stops the driver sliding forward.

The position of the gear lever in relation to the seat is just right, as is the park brake lever which has been repositioned so that its action is now forward and back.

Action of the air-assisted clutch is light but not insensitive and the same may be said for the ZF type 8043 steering.

We decided that just aboul every criticism that was made ol the 400-Series has been answered by Seddon Atkinson with the 401. Improved corrosion protection, self-adjusting clutch, conventional gear-change pattern, side-mounted turbocharger for Cummins engines, repositioned clutch fluid reservoir, repositioned park brake lever — these are all features that will please 400-Series operators.

A kerb weight as low as that ol the 401 is an attractive feature for any operator, and even the most demanding of driverE would be hard put to complair about the cab comfort.

If there is any fly in the 401 ointment, it is its price which. model for model, is about £2,00C Second of the Seddon Atkinons was the Rolls 2901 lowered 401. It used 465.9 litres 102.49 gallons), an average conumption of 39.29 lit/.100km 7.19mpg), and its overall averge speed was 64.67km/h 40.23mph). It would be conveient if from these figures we oncluded that the Rolls-Royce ngine is more economical but ot capable of maintaining as igh an average road speed as le Cummins.

The 401's differential ratio was ifferent from the earlier one, riving through a 4.44:1 ratio nd the Cummins through a .78:1 ratio.

Both vehicles had the Fuller oad ranger RTO 9509A. On each ill climb the Cummins powered 01 was faster.

If, on the other hand, we cornare the two Seddon Atkinson's tage-by-stage fuel consumeons, the Rolls-powered model /as always ahead, except for le long section between Hamil)ri and Rochester.

It was over the easiest, and the nighest sections of our route :let the Rolls-Royce engined 401 id particularly well on fuel conJmption: 5.99mpg over the A68 action between Rochester and eville's Cross and 10.05mpg ver the next easy section be veen Neville's Cross and Dar ngton. The Rolls-Royce 290L ngined sleeper cab 401 is 150kg 131 lb) lighter than the same ahicle fitted with the Cummins 290 engine.

The 290L cannot match the 290 for maximum torque, but le Roils engine seemed in a 'ay more driveable.

We decided that whichever igine is fitted to it, the 401 is an npressive tractive unit.

The 290L powered version is £400 less expensive than the E290 version and the RollsRoyce engine's other main advantages are its light weight and first-class fuel economy.

Our attempt to test an ERF BSeries fitted with a Rolls-Royce 265L was thwarted by heavy snow in the Scottish border regions early in the test year. Coupled to a Fuller RTO 9509A nine-speed box and driving a Kirkstall Forge axle, we were able to get results of 42.5 lit/100km (6.65mpg) from MIRA to Forton then 40.7 lit/100km (6.94mpg) on the other motorway section to Gretna.

Along the A74 and up to Hamilton Services, the ERF pulled in 40.13 lit/100km (7.10mpg) and our final recorded figure down to Rochester was 40.65 lit/100km (6.95mpg). Naturally we were unable to record any further fuel figures as the test had to be aborted at Carter Bar.

However, later in the year in sunny July, in fact we got our hands on another B-Series unit, this time powered by the latest 14-litre Cummins engine, the NT250.

Before the actual road test began, the ERF was impressive. The uncoupled unit weighed in at just 5,969kg with the fuel tank three-quarters full and a 30kg fuel flowmeter on board, putting it among the lightest of the 36tanners. Cummins' slimming exercise has brought the net dry weight of the NT250 down to 1,123kg (22 cwt)a reduction of 63.5kg (140Ib) compared to the NT240.

Some of the weight-saving components on the ERF are: a cylindrical aluminium fuel tank; Kirkstall's D66-8-15 rear axle; a pressed steel clutch cover in place of a cast iron one; and tapered-leaf springs all round (an option to semi-elliptic multileaf). The specific tests were good with the park brake holding without difficulty on the one in four test hill and the fully laden tractive unit pulling away from rest on that gradient.

Using every gear (except crawler) in the nine-speed Fuller gearbox, it was not difficult to accelerate quickly with the NT250-powered unit.

On the road itself and long motorway inclines in particular, the pulling strength of the NT250 was evident, reflected in fast journey times.

Overall fuel consumption was good, too, with the ERF returning 40.24 lit/100km (7.02mph) overall at an average speed of 67.22 km/h (41.78 mph).

A distinctive feature of all the NT240-engined vehicles we had driven before had been the vibration at maximum torque but this particular bug seems to have been almost completely ironed out in the NT250.

A feature of the ERF which impressed us particularly was the effectiveness of the exhaust brake. When its rocker switch is put on, the exhaust brake operates automatically whenever the throttle is returned to the "no fuel" position. If the throttle or clutch pedal is depressed, the circuit is opened and the brake can no longer operate.

We felt that putting Cummin's latest and lightest 14-litre engine with ERF's lightweight tractive unit is a natural development, giving outstanding fuel economy, journey times and an unusually good payload.

WITH THE ARMITAGE report being at the forefront of most people's mind during this year, we decided to try a back to back test of vehicles at 38 tonnes. We reckoned that as the Mercedes 16.28 and Leyland 16.28 closely matched each other, spec h spec, they would be a naturE However, Mercedes declined 1 join in.

Leyland, though, was happ enough to run a Roadtrain at 2 tonnes gcw around our norm. Scottish test route and als agreed to let us test a Cruiser the same time at its design con bination weight of 34 tonnes.

We used CM's usual tanden axle trailer for the Cruiser an the same Al Trailers tri-axle ti that was used for the 40-tonn test, for the Roadtrain. Thus w ended up with the first ever te: of vehicles in this country rur fling at the weights recoilmended by Armitage for twc axle tractive unit/two-axle sem trailer and two-axle tractiv unit/three-axle semi-trailer conbinations.

Our test of the Cruiser at 3 tonnes proved Leyland's conf dence in it to be well foundec The only mechanical differenc between a 34 tonne and a 32-to Cruiser is the gearbox bot Fuller nine-speed models, tot. 950Ibft rated in the former an 600Ibft in the latter. The bigge gearbox adds about 100k, (220Ib) to the tractive unit's unIE den weight.

All Cruiser models use th 11.1-litre TL11 engine with an A suffix for the two heavier model and a D-suffix for the 28-tonner. nstalled in the 16-21 the modly turbocharged engine, deaped from the well-known )-Series, is rated at 156kW igbhp) at 2,200rpm giving it a vver to weight ratio of only kW/tonne (6.24bhp/ton) at 34 Ines.

tVith this power the Cruiser I not exactly fly over every hill, t never was it in any difficulty, an between Rochester and ville's Cross.

Dyer the gentler 40mph secns of the route, the Cruiser's ;I consumption edged ahead its more heavily laden runig mate and the 34-tonner was a about able to hold its own average speed.

3ut motorway sections were other story, with 28 tonnes of 'ni-trailer and payload and the Id resistance of the Crane Jehauf van having much more an effect on the lowerwered tractive unit and fuel nsumption and journey times ffered.

t seemed on motorway secns that the Cruiser had to uggle to reach 60mph and Id that speed.

k strong throttle return spring ide it difficult to hold the pedal ainst its stop and could irritate iriver on a long run, and the avy clutch action could be a urce of irritation on urban deery work.

_ow noise and a good ride :re features of Cruiser. At a ady 50mph in top gear we aasured 75.5 to 76.5 dBA at ; driver's ear, and while we uld not take measurements at mph at MIRA because the user would not pull at that eed on the proving ground ck, we reached 60mph on the 3 and noise increased very le, Tested at 32 tons, Roadtrain ffered cab nod and we excted the Cruiser, with a orter wheelbase (2.884m) and simpler cab mounting, to be )rse. Although the ride was

firm it was never uncomfortably so, and had no cab nod.

On level ground the Cruiser would move off with no trouble in second and usually the next ratio could be skipped, using fourth and all the ratios in high range.

Our test vehicle was fitted with the lowest available ratio of 5.524:1 in the Guy hub-reduction range, yet it restarted with ease on a one in five gradient.

Maximum geared speed of the Cruiser was 104km/h (65mph), and fuel consumption over the whole route was 43.13 lit/100km (6.55 mpg) at 59 km/h (36.72mph).

The two most obvious external differences in appearance between Roadtrain and Cruiser are the absence of a grille in the front panel on the smaller unit and single headlight units in the place of pairs. The smaller cab looks to us even more aesthetic than Roadtrain and, the absence of the grille leaves more scope for signwriting.

Roadtrain by contrast looks a much bigger vehicle and easily capable of handling the 38 tonnes gvw which we tested it at.

Three engine options are available for the 1628 Roadtrain, the most powerful of which is Leyland's own TL12 turbocharged Flexitorque diesel, fitted to our vehicle.

The cab was designed to give optimum clearance, and would allow coupling with inches to spare using any of the three fifth-wheel positions of 483mm (19in), 535mm (21in) or 610mm (24in) and a kingpin position of 1,200mm (48in), Entry into the cab itself presents no problem, grab handles are placed within easy reach from the ground, and two wide steps are staggered so they can be seen from inside the cab or when getting in.

A small steering wheel, adjustable for rake, is located above the dashboard, housing a very neat and comprehensive instrument panel. The park brake and heater controls are also housed on the facia.

We found that forward visibility is unimpaired by the header rail, while the bottom edge of the front screen is located well below facia level.

The ease with which the 1628 handled 38 tons was very pleasing. As expected, acceleration was marginally slower than when we tested Roadtrain at 32 tons, but only when moving away from rest did this become apparent on the road.

During normal A-road running it was not difficult to keep Roadtrain moving at a speed in keeping with other road users.

On the motorway sections, 60mph could be maintained for long spells. Along the M6 gearchanges were rare and even over Shap a drop of only one cog was needed.

Inevitably the A68 section between Rochester and Neville's Cross proved both the matching and operation of the gearbox. Using the splitter, down changes could be made very quickly, avoiding any loss of impetus on hills and gearshift engagement was reassuringly positive.

The impression of an exceptionally firm ride may have been influenced slightly by the setting chosen for the suspension seat. Anti-roll bars fitted to both front and rear axles kept the vehicle on an even keel. On this test there was no evidence of cab nod — a point of criticism during our 32-ton tests.

In-cab noise levels were low. We recorded between 73.5dBA at 40mph and 77.5dBA at 60mph.

Fuel consumption of 43.7 lit/100km (6.46mpg) was over 1.25mpg less than Roadtrain tested at 32 tons, coupled to a flat-bed trailer.

On a one in six gradient at MIRA the park brake held the vehicle facing both up and down with the facia-mounted lever becoming more acceptable as the test continued over three days. On a one in five incline the vehicle just managed to restart. The park brake, however, only held when facing down the slope.

The service brakes, spread over five axles, gave short stopping distances and highpeak decelerations without locking any of the wheels on a dry road surface.

Both engine power to weight ratio and the matching of the driveline components made for easy tireless driving, but we found the gearbox splitter control extremely noisy.

ALTHOUGH the implementation of Armitage may help those operators needing extra weight capability, it does nothing for those requiring more volume.

More and more of these operators are resolving their difficulties with the use of drawbar outfits which take the maximum advantage of the 18m (59ft) overall length limit, and can give a larger cube than is possible on a single 12.2m (40ft) trailer.

Our test of a DAF 2300 DHU 4x2 coupled to a Crane Fruehauf drawbar trailer showed some of the,benefits and disadvantages of operating such an outfit.

The A-road speed restriction of 30mph for this type of vehicle was a daunting prospect with over 700 miles to be covered in two and a half days.

Although top gear could be used on downhill and level sections, where there was little load on the engine, it pulled much better in 7th turning over at about 1,600rpm at maximum torque. But when road speed was lost, it was often necessary to take two gears at the one go.

By the time we reached the motorway at Cannock we were 20 minutes down on a normal journey time. On heavily trafficked two-lane roads, this slow rate of progress was an obvious hazard to other road users.

Motorway driving was much more in tune to modern motoring with the vehicle subject to the same limitations on speed as any other 32-tonner. With a geared speed in excess of the limit, it pulled at about the 60mph mark along the flat but quickly dropped by as much as 10mph at the sight of any hill climbs.

A better overall performance might have been achieved if the vehicle had been specified with the alternative slower 5.03 to 1 drive-axle ratio which gives a geared top speed of 91km/h (57mph) and a slight improvement in gradeability.

The overall consumption of

37.17 lit/100km (7.6mpg) was )etter than the average for ,ehicles with a 5.2kW/tonne 7.18bhp/ton) power to weight atio. With DAF's air suspension, he rear axle was located and rttached to the chassis frame by wo twin-leaf springs, pivot haunted at the front and lropped towards the rear. A evelling valve on each of the :hassis aided coupling to the railer and avoids the need for a eparate lifting system for loadng and unloading the denounts.

The trailer had no anti-roll bar iut was equipped with chains to imit roll. During motorway runling, a continual shunting rnoion was most noticeable from yithin the cab and at speed teering corrections became acentuated by the trailer.

On twisty roads the air susiension allowed a fair degree of oil.

Braking was never a problem hroughout the whole of the Durney. The pedal gave an ,veniy progressive response without becoming heavy.

Although there was sonic indiation as to what might happen without Maxaret, the vehicle always came to rest in a straight ne.

Straight brake pipes, and not he Suzie type, are used to, onnect the trailer. In the event if a breakaway, the loss of air iressure would be sudden and ne application of the trailer 'rakes immediate.

As for the exhaust brake, it vas more noisy than effective, rut used in conjunction with a we r gear it found some use on n g descents.

The 2300 has been around ince 1977 and externally the ab has stood the test of time tell. Detailed changes have eon made to interne) trim and air ducts, and so on, but it has basically remained similar. The larger steering wheel gets in the way of the gear change, and heater controls in the centre of the dash are at arm's length.

Steering is light enough and with large treadle-type brake and throttle pedals, and comfortable suspension seat, driving becomes relatively untaxing. We measured noise levels of 76dBa at 30mph.

Entry is low and made easier by two well placed wide staged steps, a floor without a door lip and a large grab handle.

Cab tilting of 60° gives access to the turbocharged chargecooled 8.25 litre DHU power unit, while daily oil checks and water can be carried out with the cab down.

Although the park brake works on the drive axle only, it held the vehicle stationary on a one in six gradient, the steepest on which the 2300 could make a restart.

Drawbar combinations offer up to 20 per cent larger platform area than can be achieved with maximum-weight articulated units, but we thought the following points may prove to be operational disadvantages: • A heavier unladen weight detracts from the payload potential unless the weight/volume ratio is compatible.

• The existing 30mph speed restriction, peculiar to this type of vehicle, slows journey times and is a major disadvantage — unless routeing can maximise the use of motorways.

• Air suspension and demount systems can offer a high degree of flexibility in loading and delivery, but leaks in the air system can lead to some unusual difficulties.

• DAF's cab is in need of a major face-lift in order to maintain expected levels of driver environment. • Some form of brake control for the drive axle is essential to vehicle stability.

• The engine unit provides adequate power for operation at 32 tons gvw, but daily service points can be improved.

• Rationalisation of speed limits would reduce any hazard caused by the vehicle's overall length.

• The market for drawbar combination is growing at about 24 per cent a year and is expected to result in about 300 registrations in total this year.

WHEN VOLVO offered CM a used tractive unit under its Golden Opportunity scheme, we said: "Yes, but we'd like to choose our own."

After visiting three truck dealers, we selected the Volvo F7 in preference to the more powerful F10 or 12, it had a long list of faults to the cab, engine, rear axle, brakes, tyres, cooling system and exhaust.

Like all Golden Opportunity Volvos we were assured that all faults would be put right to Dpt test standards, on this occasion by J. R. Duffield and Son of Norwich. When we saw it next it certainly looked good, but to check its mechanical condition we asked the FTA to conduct an "A"-vehicle inspection report.

A two-hour inspection found several minor faults, but fewer than would be expected with a new vehicle. Over the CM Scottish test route the two-year old vehicle confirmed the fuel consumption we had obtained with a new vehicle by returning 35.05 lit/100km (8.06mpg) and at the same overall average speed but with a flat-bed trailer. Three springs fitted to the throttle return instead of two gave it a snappy action but made for a heavy throttle pedal.

Rear brakes had been relined and front drums deglazecl but there had not been time to bed them in so we left the braking tests until after the road section. However, when we tried it under full braking a slight imbalance from the rear and judder from the front led to deviation of the unit and stops from 30 and 40mph were aborted.

Hill climbing on the road had been no problem but at MIRA the F7 could not be persuaded to restart from rest on a one in six gradient.

A lack of power steering assistance at engine idle speed, noticed by the FTA inspector, persisted throughout the test and was only cured later by Duf field's with a new steering be Duffield's and Volvo Trucks we aware that we were going to te the vehicle and it was prepar( to a generally higher standa than might have been expect( with a new vehicle.

For those who want Volvi but can't afford a new one, ti Volvo used vehicle warran scheme is probably the next be thing.

THE NATURALLY aspirated 11. litre in-line six-cylinder engir rated at 117kW (237 bhp) fittE to MAN's 16.240 FTN 4x2 tra tive unit surprised us with i fuel consumption.

Tested back in July it knockc the E290 SA 401 off the top the pile, returning 41.2 lit/100km (6.85mpg).

It is also a very quiet engin Cab interior noise levels we among the lowest we ha\ recorded with any tractive un yet the design has virtually r mained unchanged since 1969.

A maximun torque output I only 862 Nm (636Ibft) 1,400rprn must be considerE modest for a vehicle designe for operation at 38 tonnes.

When driven over our te route at 32 tons the vehic showed similar journey times I those of more powerful vehicle

A constant-mesh gearbox the standard specification for U machines. The ZF AK6-90 si. speed model with GV90 splith has a total of 12 forward ratios., restart-was possible on a 1 in test hill at the MIRA test tracl but like MAN's of the past th park brake would not hold on a in 6.

The S-shaped gearlever positioned close to the steerin wheel and the gate is the revers of the conventional pattern witl the most used, 5 and 6th ratio: farthest away from the driver.

Provided due consideration

ven to engine and road eeds, silky changes can be de moving up and down the x — but double declutching is sential.

The multileaf spring suspenm is harsh and the rubber ountings and telescopic mpers on the cab fail to iso.e the driver from the bouncy le.

Location of the controls for the Iht switch and the exhaust ake make operation of both fficult. It is a long stretch ross the cab to the lights so lection of either sides or iadlamps is a matter of luck. The MAN is not alone in havg poor exhaust brake performice, but if the button were not aced so close to the seat it )uld be more easily used.

T FIRST SIGHT the 1628S Merdes-Benz appeared very miler to the 1626 it replaces, _it a closer look uncovers a Duble-c hanne I section chassis ame which is shallower than efore. Combined with new ree-leaf parabolic springs, the ame height has been lowered y 120mm (4.7in), which is aimed to make it possible to 3rry an 8.5ft high container on 2.22.5 tyres and remain below le European height limit of 4m 13ft 1n).

With most trailers there hould also be room to fit full 'kid guard over the drive-axle /heels.

The braking system has also een modified with automatic lack adjusters and cooling of le compressor.

Our vehicle was fitted with the ptional 5.22 to 1 rear axle ratio nd powered by the M-B )M422-1 naturally-aspirated V ngine; its power output is 06kW (276bhp) and torque 040Nm (767Ibft).

Running at 32 tons, the Mer:edes gave the impression that it :ould climb the side of a house. iowever, journey times were on he slow side. Running at 40mph showed the vehicle was at its most economical with the rev counter smack on 1,400rpm. Overall it returned 6.56mpg. Including two crawler gears, the ZF 55-111 GP splitter box has 18 forward gears.

The Mercedes philosophy of drive-train optimisation gives the driver a close ratio box and a wide, usable rev band from 1,100 to 2,300rpm so that full power can be used for hill climbing. However, low engine speed is there for economy at cruising speeds as well.

The ride quality of the 1628 would be difficult to improve upon. The chassis and cab suspension isolates the driver from the humps and bumps of the worst road conditions. The cab is really comfortable even allowing for the fact that the Bremshey suspension seat did not need to work at all.

A large steering wheel and liberal power assistance made the steering feel light.

Although the test showed the 1628 to be a good all-rounder, it did not stand out in any one respect. However, the fuel consumption is_ very good for a naturally aspirated unit; most of our best figures are obtained with powerful ti...rbocharged units..

HAD CHANGES been made to the weight regulations, Leyland would probably have included only two models in its Cruiser range at 28 and 34 tonnes. But, as things are, a 32-ton model is needed and it differs from its heavier counterpart in one important aspect.

The Leyland Cruiser 16.21 (32 tons gcw) beneath the skin has a Fuller's RTO 609 nine-speed constant-mesh range-change gearbox carried over from the previous model and has a lower torque rating than the box used at 34 tonnes.

This is recognised by the marginally higher gearing, particularly in the lower ratios, but has identical seventh (direct top) and overdrive top of 0.74 to 1. Many other components also have Buffalo origins, but the chassis, although using the tried and tested all-bolted straightsided ladder design with reinforced flitching, now comprises light but tough high-tensile steel.

Outwardly the cab is based on the T45 concept using the C40 shell. Here it was 305mm (1ft) narrower than on the Roadtrain, though.

The inside is divided into two by the shallow intrusion of an engine cowl and a driver's toolbox doubles as a footrest for the passenger. Front, side and rear glazed panels makes the cab environment light and give good all-round visibility.

On the outside two wide staggered steps give a sure foothold whether entering or leaving the cab.

A power to weight ratio of 4.7kW/tonne (6.5bhp/ton) form Leyland's TL 11A turbocharged engine is less than generous and is reflected in both acceleration and journey times.

A maximum geared speed of 103km/h (64mph) allowed a motorway cruising speed of 96.5km/h (60mph) for only short periods where neither wind resistance nor gradient proved too great. A more typical rate of progress was around the 92km/h (57mph) mark.

Over the most severe terrain along the A68 south of Edinburgh, the engine's high torque was not enough to compensate for the lack of power. Constant gearchanging was needed to overcome slight inclines.

The thermostatically controlled radiator fan rarely came into operation except at high speeds on the motorway and when working hard on the hills.

Ironically this is just the time that the 7.46kW (10bhp) or so absorbed by the fan could be best used to propel the vehicle. Using to drive the fan only when needed, saves fuel, and over the 735-mile test route contributed to the Cruiser's consumption figure of 41.6 lit/100km (6.78mPg).

Imperfections of braking distribution came to light on the test track. Braking from 48km/h (30mph), both the drive axle and the trailer axles locked up leaving the steered wheels still rotating.

From 64.3km/h (40mph) the vehicle reacted more violently and the brakes had to be released to bring it back into line despite the vehicle's high brake specification which includes load sensing.

So often, even with new factory-prepared vehicles, the device does not prevent the drive axle brakes from locking, usually through maladjustment. What hope, then, has it of working safely in service?

Weighing about 305kg (6cwt) more than the Buffalo, the Cruiser gives the operator more for his money — but less potential earning power.

The new cab updates Leyland's standards at 32 tons while mechanically it continues with proven components, but it is expensive when compared with imported models built for operation at 32 tons.

After our test Leyland returned the Cruiser to its workshop and found that the maximum-speed fuel stop had been incorrectly set, resulting in a 14 per cent loss of power effectively reducing the engine's output from 210bhp to around 185bhp. With correct settings, overall journey and acceleration times should improve, but fuel consumption would be similar.

IVECO was later than most in turning to turbocharging and it was not until this October that the first of its sleeper-cabbed tractive units became available in Britain, equipped with the new engine.

The 170 F30-1is plated for 44 tonnes and is powered with a 223kW (300bhp) 14-litre unit to give a massive 6.8W/tonne (9.38bhp/ton) at the UK limit oi 32 tons.

With so much power at hand, one expected that the comparatively light work load would result in good fuel ,consumptior results like those of other power. ful machines. While it did no. live up to expectations, it re turned a creditable 41.7: lit/100km (6.77mpg) at a fas average speed of 65.7 km/h (40.9mph).

Top-gear slogging ability firs became apparent over the A7, where limited to 40mph con

sumption was much healthier at 35.01it/100km (8.07mpg"). On the flat sections the big Fiat engine readily pulled overdrive top at about 1,250rpm while a flick down into direct top more than coped with quite considerable gradients such as the long steep bank on the M18.

Turbocharging the 14-litre engine has provided about 30 per cent more torque, which is where its main advantage lies. There is little to be gained except bigger fuel bills by revving the engine above the green sector of the tachometer, which extends from 1,100 to 1,750rpm.

The IVECO cab has been around for quite a while but gives nothing away to its competitors and has what is arguably the best Fuller installation of all.

Gear-shift movements are short, very positive and wholly reliable and might only be improved by the inclusion of a clutch brake to ease selection with the vehicle stationary.

The biggest disadvantage of the Fiat's specification is its relatively high unladen weight, perhaps inevitable for a vehicle designed for the Italian maximum weight limit.

Along with IVECO we shall be watching to see how well the competitively priced 170 F3OT sells, as a guide to how big the market for 300bhp tractive units is in Britain.

THE MERCEDES-BENZ 1625, a slightly lower powered replacement for 1626, returned the best fuel figures of any 32-tonner with a van trailer, this year, at 7.33mpg.

The OM 422 111 engine is a derated but larger capacity version of the OM 402 now rated at 184kW (247 bhp) with a torque of 432Nm (687Ibft). Externally there is little difference to distinguish one from the other, but internally both stroke and bore are increased.

If the driver follows the manufacturers recommendations he will let the engine work down to just below 1,200rpm before changing down and over the 40mph sections of the route the engine was always working at 1,400rpm or less.

Fitted with a ZF 55-92GP eightspeed gearbox matched to the standard rear axle ratio at 4.205 to 1, the taller 13 to 1 deep crawler ratio allowed a restart gradeability of 1 in 4 while the remainder gave a good spread to match engine characteristics.

The park brake held only on 1 in 6.

At the legal maximum speed of 60mph the tachometer needle .rose just above the economy zone. The double-h-gate was difficult at first but with practice rapid changes soon became easy. The Hi-Lo range-change dash-mounted indicator lamps need to be brighter for day-time use.

This sleeper-cab tractive unit is attractively light with a ready for the road kerb weight of 6,350kg (6 tons 5 cwt) which includes fifth wheel, normal in-cab equipment and a full 300-litre (66ga1) tank of fuel. It also couples to a 12.2m (40ft) semitrailer comfortably within the 15m legal permitted length.

Inevitably the short wheelbase has a detrimental effect on ride. However, there was no unpleasant pitching or rolling.

Despite it having slightly less power, we believe that drivers will find this Merc an easier vehicle to drive than the 1626, especially over A-road running. units a year in 1979 to little more than 6,000 this year.

Within this group the 32-ton machine has gained a larger share of a diminishing market, and now reprAents about 17 per cent of total sales.

Bedford's 3250, which we tested, has a kerb weight of 5,191kg (5.1 tons), so payload capacity is there for the taking if it can be used. Bedford employs high-stress steel in the construction of the chassis, which although strong is also light.

The drive axle, rated at 11 tons, is built by RUBA under licence in Hungary. The narrow, low Day cab's overall width of 2.13m (7ft) allows an internal dimension of 1.92m (6ft 4in), is made of steel and tilts to 60°.

A Fuller RTO 609 nine-speed gearbox has been used since was first introduced in 1974 but now to match the new engine it employs a lower set of ratios with a direct top gear in preference to the overdrive.

So-called because of its colour, the 8.2-litre Blue-Series diesel in a turbocharged form produces maximum power of 155.5kW (208.5bhp) at 2,500rpm and a torque of 689Nm (507Ibft) at 1,600rpm. Although producing well above the minimum power-weight ratio requirement of 4.4kW/tonne (6bhp/ton), the torque output is some 20 per cent less than is generally available at this weight from other manufacturers, but nevertheless manages to produce similar tractive effort at the wheel.

A modest hill restart performance was only to be expected but the park brake was more than adequate, for the same 1 in 6 gradient and, releasing quickly, allowed a positive take off with the help of high revs but with little fuss.

Maximum speed around the mid-sixties was comfortable for cruising at around the legal motorway limt when on level going. The green sector of the rev counter extends from 2,500rpm, at which maximum power is achieved, downward to 1,200rpm, well below the 1,600rpm at which maximum torque occurs.

However, the engine does r -down to this speed without sl ging to give a road speed about 30mph. Maximum torc equates to about 40mph in gear and the wide rev ba makes for easy driving , and clueing the frequency of g changes.

Stiff hill climbing over the section needed the use of ev, forward gear in the box on s eral occasions.

Clutch flare on downvw changes resulted in a slow tz up of drive, and an initial loss road speed and engine revs.

However, gear selectioa positive, so all changes could made with confidence when vehicle was working really hz If there is a criticism to be rm it is that the gate is too free.

A fuel consumption of lit/100km (7.27mpg) is w good, and come second to I of the Mercedes. Both driver i dual passenger seats, shapec, provide support, remained ccl fortable throughout a long dE drive and took out much of jarring from what w sometimes a bumpy ride.

In-cab noise has been redul and is in part due to the quic turbocharged Blue-Series gine designed to meet impe ing EEC legislation. We recon readings of 72dBa at a ste 40mph and 76dBa at 60mph v a hand-held Cirrus meter.

Entryto the cab is high, steps in front of the steered c and a grab handle located on the A-post make the climt easy one. Dismounting is I sure as footholds cannot be s€ from within the cab, and a lir the door opening makes it d cult to remove dirt from the f well.

Running here at well under 32-ton limit, the vehicle carrie. payload well in excess of tons, and at £19,833 the seemed to be none to match on price.

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