AT LAST the Bedford TM3800 test! Our original test met
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with gale force winds throughout the whole of the second day which made the results meaningless when compared with those of previous tests.
So we persuaded Bedford to let us have the truck again for a re-run of the Scotland-England leg, and this resulted in the shortest ever round-trip journey time. Disappointingly, however, the overall fuel consumption was on the high side at 47.4Iit/ 100km (6.0mpg).
The TM range was introduced in 1974 with the 3800 being
the top of the range (as far as the two-axle trucks are concerned) at a design weight of 38 tonnes (37.4 tons). Like its smaller brother, the TM 3250, a Detroit Diesel two-stroke. engine is featured but, in this case, it is a V8 design which produces 221kW (297bhp) which puts it into competition with such trucks as the F88 Volvo, Leyland Marathon and the 111 Scania.
New ground
• A two-stroke engine is not exactly a common feature, but the Bedford also breaks new ground in the transmission by using a ten-speed Spicer splitter box. At present it is the only truck in Europe with this particular gearbox although it is rumoured that the proposed T45 from Leyland will use the same unit.
Rounding off the drive line is a hub-reduction axle made by SOMA in France.
In the past, the two-stroke TMs have been criticized for poor fuel consumption and Bedford has not disputed this, claiming that the main strength of the Detroit Diesel lies in its durability. Now that the first TM3250 trucks to be sold in the UK are reaching the ri.uarter million mile mark, this claim
seems to be borne out.
It can be seen from the accompanying results table that the engine prefers full load work to part throttle running. On the first day, the motorway sections were completed with competitive results as far as fuel consumption was concerned and at very high average speeds. This enthusiasm for hard work was also illustrated by the fuel figure for the severe Rochester to Neville's Cross section where the TM recorded one of the best ever results.
On the part throttle sections of the 50mph Al, however, it was a different story. Although the engine seemed perfectly happy running at around 1,200rpm, this was not reflected in the fuel consumption which, at 451it/100km (6.3 mpg), can only be described as poor for this section.
The Bedford test was fated with bad weather and the last leg comprising the southward run on the M1 was again covered against a strong headwind so the motorway figures were not in the same league as those of the northbound run
Fuel consumption
• Overall the Bedford returned a fuel consumption of 47.414/100km (6.0mpg)which does not exactly put the GM truck into the honours for good fuel consumption when compared with its competitors or with the average figure of just over 6.7mpg for the Scottish route recorded over the past three years.
There is more to a truck's performance than fuel consumption however.
Round trip journey time is becoming more and more important to many operators meaning their drivers can confortably get back to base without an overnight stop. In this category the Bedford excelled by returning the fastest ever average speed for the operating trial route and in an effortless manner.
Two other "plus" factors must be mentioned in connection with the TM. One is the ability to couple (legally) with any 40ft trailer regardless of
continued overleaf The VS version of the Detroit Diesel engine produces 221kW (297bhp) at 2,100rpm. It is unusual in that it operates on the two-stroke cycle.
king position and the other is the price. At £16,887 as tested, the TM3800 has just got to represent value for money in anyone's language.
In ride and general handling it was impossible to fault the truck. The suspension absorbed all the irregularities thrown up by the constant road works on our route and this factor coupled with the excellent suspension seat (Bedford's own design, based on Chapman components) meant that the Bedford gave me the most comfortable Scottish test I have had in a long time.
Steering
• The steering with its recirculating ball design and integral power assistance was precise on the corners and absolutely rock steady in the straight ahead position. In these days of more and more motorway running, this last feature is an extremely important one for combatting driver fatigue.
I was very impressed with my first experience of the ten-speed Spicer. Rapid half changes could. be made easily and the same applied to whole ratio changes provided a hefty blip was given to the throttle.
On most sections of the route used half gear changes but, on the steeper sections, full changes were advisable.
The Detroit would pull well down to around 1,400rpm, and then to make a clean whole ratio change, it was necessary to blip the engine right up to ,2,50Orpm.
The combination of this box and over 290 horsepower proved to be one of the better transmission matchings available on the UK market. At 32 tons gross, the 3800 is not exactly overstressed so the bottom two ratios of the Spicer could effectively be ignored. On level roads I used third for starting followed by fifth, using the splitter from there on.
Apart from the unimpressive fuel consumption, there were two, lesser, features of the TM which I did not like. One concerned the noise from the big Detroit which at high revs sounded like a diesel engined 38-tonne Suzuki motorbike. The Bedford engineers claim that it meets all the existing and proposed regulations on noise but in spite of this I found it (subjectively) to be a noisy brute.
The other point concerned the amount of room in the cab. Our test truck had the full width cab and I was surprised to find just how little of that space is available for the driver. The Detroit Diesel being a vee design makes for a wide hump in the cab which doesn't help, of course, but it was mainly the comparative lack of leg room which I found irritating.
Braking tests
• On the braking tests, the results were excellent with the Bedford being among the best we have tested on this score. Stopping in a short distance is one thing, but the Bedford managed it with a complete lack of fuss or rubber smoke.
We ran into a rather unusual situation when we did our customary hill starts.
On the 1 in 4 gradient the park brake held the truck, but the tyres didn't so we ended up sliding gently backwards with the wheels locked leaving a smear of rubber on the road. Some violent juggling with the brakes and the clutch enabled a successful restart to be made on this gradient in spite of the conditions.
The TM cab can be tilted hydraulically to a maximum angle of 60 or alternatively it can be locked in one of a number of intermediate positions. Before the cab can be moved the gear lever must be telescoped down into its housing to clear the cab floor. Tilting is not necessary to routine level checking, however. By opening the two hinged front panels, access to the oil and water can be achieved easily.
Summary
• My overall impression of the TM was of a comfortable well-engineered truck which is more than competitive in price — at £17,307 (including fifthwheel) it is a couple of thousand cheaper than most of the equivalent opposition. It is a pity that our test did nothing to argue against the thirsty reputation the two-stroke TM has developed.