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The light weight, day cabbed TM3800 has shown what a
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low power 38 tonner can do, given the right gearing. Tim Blakemore reports after three days behind the Bedford's wheel.
FOR THREE DAYS in August a Cummins LT10-powered Bedford TM set about destroying the CM 38 tonnes fuel-economy record held since April by Seddon Atkinson's Gardner 8L-CT engined 401.
When the Seddon Atkinson became the first 38-tonner to notch up 7.00mpg over the 737-mile Scottish operational trial route, I had expected that to become a long-standing standard. How wrong I was. The TM3800 not only used fully four gallons less diesel than the 401 in pushing the record way up to 38.86 lit/100km I7.27mpg), but it also managed a remarkably good overall average speed for a vehicle with a power to weight ratio of only 6,4bhp /ton.
An overall average of 40mph can be considered the bogey speed for the Scottish route both for 38-tonners of 290hp and above and for 32-tonners of around 250hp. The net installed power output of the Cummins 10-litre engine in the Bedford chassis is a modest 180kW (241hp) to the BSAu standard. However as the operational trial results show, if the TM had been hauling 38 tonnes alongside many of its 290hp rivals over the same three-day period, it would have been no more than a few minutes behind most of them at the end. Indeed, comparing the Bedford again with the 287hp Gardner engined Seddon Atkinson, it can be seen that the 240hp TM's journey time was nine minutes shorter.
Much of the credit for the TM3800's performance must go to Bedford's engineers for their careful choice of gearing for the L10-engined models.
A 5.43 to 1 rear-axle ratio (standard for this model) behind the overdrive-top Eaton Roadranger gearbox gives the 11R-22.5-shod TM a maximum geared speed of only just over 62mph at 2,100rpm.
For many modern engines, most certainly including the "Big Cam" Cummins 14-litre models, such
Top picture: Though geared for a maximum of only 62 mph, the LT10 engined TM maintained surprisingly high average speeds over difficult motorway sections and still returned fuel consumption figures well on the right side of 7.00 mpg.
Left: The TM used four gallons less diesel than any other 38-tonner so far tested to Scotland and back. Calm weather over two days helped, but most of the credit must go to Bedford's choice of gearing — ideal for the high revving 10-litre Cummins. Design gcw: ested gcw: Payload as tested:
£27,326 excluding 5 (including £750 for fi. wheel installation 38,000kg 137.4 tons. 38,000kg 137.4 tons: 25,356kg 124.96 ton
Overall average fuel consumption: 38.86Iit /1C 17.27mpg) Overall average speed: 64.9km/h 140.37mph Power to weight ratio at 38 tonnes: 4.7kW/tor 16.4 bhp/ti
short gearing would be a recir heavy fuel consumptioi motorway speeds, but our n make it clear that the L' different in this respect.
One of the engine's r attributes is that it does not rE a disciplined right foot for its to obtain high mpg. The opti speed for fuel consumption, p and torque, says Cummin 1,700rpm and both theory practical experience show th short-stroke 10-litre can be r 1,900-2,000rpm without becc at all thirsty.
Moreover, a comparison of results with those obtained fr higher geared, L10-pow vehicle (the Seddon Atkinson larch 19, 1983) indicates that, limits, the faster the engine ade to run the better is its rmance.
e 301, a pre-production .1, was tested at 32.5 tonnes Overall average fuel Jr-notion was 7.20mpg and II average speed 40.94mph. a bare figures, by no means or a 32-tonner pulling CM'S semi-trailer, underline how essive was this TM's ,mance. Closer scrutiny of the sets of test results, always nbering that the TM was ng over four tonnes more ad than the 301, provides
evidence for commending )rd's engineers on their ig selection, The 38-tonner's 0-50mph mean acceleration time, for example, on Mira's twin horizontal one-mile straights was only 5.3 seconds slower than that of the 32-tonner while there was virtually no difference between the two vehicles' 30-50mph acceleration times.
The closer ratio steps of the Seddon Atkinson's 10-speed splitter Dana Spicer gearbox must have helped to give it a small advantage over the short, steep Carter Bar and Blackhill climbs. But, surprisingly, over the longer, more gentle, constant gradient of the M18, the two vehicles' hillclimb times were within one second of each other.
As you would expect, the lighter vehicle forged ahead over the toughest section of our route, the 53.1 miles of hard road between Rochester and Neville's Cross, averaging more than one mile per hour more than the TM as well as
recording a better fuel consumption.
One other difference between these two L10-engined vehicles is worthy of mention, though some allowance has to be made for the fact that the Seddon Atkinson was a pre-production model. 1 refer to the in-cab noise level, which was noticeably lower in the TM. Little, if any, of the gear noise which was evident in the 301 could be heard in the Bedford and our formal noise meter checks confirmed that this vehicle's noise level at a steady 60mph to be as low as 75-76dB(A) compared with the 301's 79dB(A).
Unlike TMs plated above 38 tonnes which have twin-wedge foundation brakes, the lighter models have single-wedge components, but just like the heavier models, or at any rate all those which have been presented to CM for test, this test vehicle's braking performance was generally of a high standard,
All out full-pressure track tests were free of drama and the rolling road test revealed a normal front/rear split with adequate braking effort on eachaxle.
However, one aspect of this TM's braking was not up to the same standard and suggested that the front axle's brakes had to work too hard. A strong smell of hot brake linings became apparent as we neared our Neville's Cross fuelling point at the end of the gruelling A68 section, which involves a number of quite severe descents as well as hard climbs.
There was no sign of loss of braking efficiency owing to fade, but I would not have liked those front linings to have become any hotter. This overheating was particularly surprising since I had been making full use of the more effective than average Cummins rotary valve-type exhaust brake, which, though fitted to our test vehicle is not yet readily available because Cummins, it seems, is still not entirely satisfied with its long term performance.
I am now convinced more than ever that some form of retarder is highly desirable for 38-tormers.
Another, much more minor, difficulty we had with the TM's brakes during this test was that a connection on a gauge pipe routed behind the dashboard persisted in working loose, indicating perhaps that either more careful routeing or more extensive clipping of the pipe is necessary.
Although the weather was generally very kind to Bedford on this occasion, we did run into some heavy rain on the M6 on Day 1 and this highlighted a deficiency of the TM mirrors. They fouled up very quickly and without any mirror heater to help disperse the water the only way I could rm decent rearward vision w continually wind down the w and wipe them.
The mirror arm mounting need improving. This wai second TM I have driven thi which had arms that moved adjustment whenever the were slammed.
This test gave me the oppor to compare the ride and ha characteristics of a short-whei TM with the longer, sleeper-c. Detroit Diesel-engined model we tested earlier this year (Cu 30). Not surprisingly, the cabbed model pitched notir more than the longer unit without the optional front ar bar, the amount of roll we: greater, but by and largt TM3800 maintained Bedl reputation for producing tr units with no unpleasant ri handling traits.
However, the driver's seat c TM created entirely the wronc of impression. The padding SE to be inadequate and it impossible to remain comfortE it for more than an hour or a
I was much more favoi impressed by this Bedf behaviour in traffic. The Cam power-assisted steering accurate low-speed manoeL easy and the gearchange always crisp and reliable. I some earlier TMs I have driver model also had a nicely a clutch brake which could be upon to give trouble-free firs engagement. However, maximum pedal load of 20kg the clutch action is a little c heavy side.
Summary
In summing up the TM2 outstanding features, one hardly fail to be impressed vehicle I tested offers a attractive blend of superlativ economy, excellent pa carrying ability and reasc quick journey times from a cost, comfortable day-cab tr unit built by and enjoying the sales support of one of the vs. largest vehicle manufacti Quite a package. LOY is showing examples easy access Localiner and ler bodywork this year. ocaliner has been built on a Tasker straight-frame trailer destined for in-town iry work with Scottish and astle Breweries which aloperates nine vehicles of h an overall length of 1(25ft 10.5in) it provides for :ernal width of 2.46m (8ft , which is achieved by the pf aluminium side door ; front and rear and an indiate curtain which folds irds to clear the load.
lloy's grp air flow equipis fitted to the front bulkand a Whiting wide-slat 1r gives access to the rear. aluminium roof structure • orates six tubes carrying straps which terminate at gs set into the 22mm i) thick Lydney plywood
le racks beneath platform ;aye a capacity for a mixed 140 CO2 bottles.
4.26m (14ft) Linkliner is based on a .Ford Cargo rigid chassis. Measuring
: The Linkliner body from y mounted on a Ford Cargo hassis.
1.9m (6ft 3in) high it has an internal width of 2.2m (7ft 3in) and a side aperature of 4m (13ft 1.5in).
The front bulkhead and roof are of alloy construction while a Henderson wide-slat shutter door is used at the rear. An 18mm (0.7in) Wisamant floor has a 25.4mm (1n) raised angle chock to clear the side doors when opening.
Cargo control is provided by one 152mm (6in) mesh-webbing net and a reinforced transverse curtain housed in a continuous longitudinal track which allows them to be set to suit the load.
Boalloy claims a unique transverse locking system operating on both side doors at the same time with a one lock closure. An independent lock is fitted to the rear shutter.
YORK is exhibiting a variation of its established Thermovan refrigerated semi-trailer which will allow two metric pallets to be loaded alongside each other. Originally announced back in 1979, the Thermovan is ATP Class C approved.
This year the first thin-walled tandem axle Thermovan trailer, designed for 38-tonne operation, includes several features to maximise its load-carrying capacity.
Also on show are other components produced by the York Group including the Airpoise lifting tag axle conversion unit.
Designed as a family of air suspensions it can be supplied in single, tandem or triaxle form, with or without the lift facility.
York's self-steering axle for trailers is on show for the first time and its staff will be happy to explain how easily it can be fitted to a trailer and how it will minimise tyre wear.
The York low profile sliding Big D fifth wheel can be set to move over 450mm (181n) along the length of the tractor chassis within only 212mm (8.25in) above the level of the subframe. The new slider enables operators to keep tractor fifthwheel heights within closely defined tolerances and prevent adverse braking conditions being created with the wider spread tri-axle bogies now in use.
York Trailer's air disc brake was shown at Frankfurt but it is the first opportunity for most British operators to see it in the metal.
Developed jointly with Eaton, it is suitable for axles with up to 10-tonne capacity. It is no longer necessary to remove the drums to check lining wear — the pads are easily replaced by removing two locating pins and in some instances it can be done without the removal of the road wheel.
York says it still has some field trials to complete before the disc brake will be made commercially available.
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CRAVEN TASKER's folding neck low-loader has detachable subframes and optional wind-up kingpins. The 42-ton model on show built at Cumbernauld is constructed from four I beam members shaped at the rear to form a low bridge over the wheels.
The front end is tapered with large pivot pins to enable the drop section to be hinged hydraulically to form a continuous sloping deck for loading and discharge of the cargo. Specially tapered locking wedges are incorporated to prevent the exces sive movement often assoc with this type of trailer.
In operation, the tractivE can be uncoupled by rele the subframe preventing ti gress of dirt and grit der between the fifth wheel semi-trailer rubbing plate.
From the company's Gar factory, south of the borde 38.2cum (50cuyd) 9.1m Taper tipper. Measuring 1 (5ft 6in) at the front end it higher than a conventi 34.4cum (45 cu yd) parallE died unit. But with a pri chassis frame the centre of ity is lower and stability braking is improved throur ter axle weight equalisation A grp panelled Task vai been developed to satisfy