Berliet TR 280 tractive unit at 32 tons gross
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by Trevor Long croft
Photographs by D. Ross
FRENCH truck manufacturer Berliet is at present establishing a UK dealer network and has already begun to market its TR 280 and TR 320 top-ofthe range tractive units here. Basically, the higher-powered 1 hd V8-engined TR 320 is offered for TIR or Middle-East operations, whereas the rhd TR 280 that we have just tested is considered a better proposition for domestic use.
One of the most attractive features of the TR 280 is its six-cylinder high-torque-rise engine, which provides an almost constant maximum horsepower between 1,400rpm and 2,200rpm—the engine's rated speed. Drive from the engine is transmitted via a single dry-plate clutch to the ZF nine-speed range-change gearbox and Berliet 13-tonne rear axle.
The test vehicle, a demonstration unit that has covered about 20,000km (12,400 miles), was coupled to a Crane Fruehauf 10m (33ft) platformskeletal semi-trailer and the outfit was loaded to the UK maximum, 32.5 tonnes (32 tons).
The Berliet covered the CM Scottish Trial route in one of the fastest times ever achieved, yet the fuel consumption returned equalled the 2.3km/1 (6.5mpg) average for the course. The cab must be one of the most luxuriously appointed that is available and drivers will like the high standard of trim and comfort and the general ease of vehicle control. The high-torque-rise engine in the Bernet provides an almost constant 180kW (242bhp) maximum power output (net installed: BS AU 141a) between 1,400 rpm and 2,200 rpm. Coupled with the very respectable 1,155 Nm (8521bft) maximum torque (net installed: BS AU 141a) developed at 1,300rpm, this output provides a performance edge over similarly rated engines having a more convential power curve.
Cruising speed
One of the best features of such an engine is the wide performance range it permits in each ratio, which effectively cuts down the number of gearchanges needed. On motorway there is rarely need to change from eighth (top) gear. High cruising speeds, often at the legal maximum 96krn/h (60mph) were easily maintained for long stretches while some of the lesser gradients, often requiring a lower ratio on other vehicles, were taken in the BerIiet's stride with the engine pulling quite comforably at 1,300rpm, maximum torque speed, or even below.
The gradients at Watford Gap and Keele were topped in eighth (top) gear, the Berliet dropping to lowest speeds of 70km/h (43.5mph) and 65krn/h (37mph) respectively. Only one gear was dropped for the long M6 Shan climb when vehicle speed fell to 53km/h (33mph) while the lowest motorway ratio, sixth, was required on the Shepshed "Slow Lorries" stretch when speed dropped to about 39km/h (26mph).
On A roads the Berliet nudges the 64km/h (40mph) speed limit with the engine spinning at a relaxed 1,300rpm. However, on slight gradients or on the fiat optimum acceleration from speeds below 64km/h (40mph) is achieved by dropping a gear to bring the engine revs back into the constantpower band.
On the steep gradients encountered on the northern sections of the test route the engine's versatility was quickly realised. The relatively few gearchanges required made for an unusually relaxed driving style over this, the busiest Dart of the circuit. The long climb from Moffat was scaled in 13min 26sec with the lowest ratio, fifth, being required for less than a minute. The short but sharp 1-in-5 Ridsdale gradient, which has thwarted many test vehicles, was covered in second at a lowest speed of 15km/h (9.3mph).
The full-pressure brake tests completed at the MIRA proving ground produced some very disappointing figures; the outfit took over 40m (130ft) to stop from 64km/h (40mph). Subsequent tests showed that the trailer brakes were not working correctly and that the tractive unit brakes were shouldering the weight of the whole vehicle. The trailer brakes were therefore adjusted before the road section of the test and the correct braking balance restored between unit and trailer. The brakes performed satisfactorily for the rest of the test.
The Berliet TR 280 was originally designed for twoline air brakes and so to conform to UK three-line regs the company has added a third line —a hand valve in the cab which actuates the trailer brakes only. Thus there are two valves in the cab, one for the park brake—lock actuators at the unit rear axle—and the other for the trailer brake. The latter is conveniently placed for the driver who I suspect may use it instead of, or as well as, the exhaust brake to control the speed of vehicle descent. Some Continental operators link the trailer brakes to the exhaust brake, and in my experience rapid lining wear results.
Ride and handling
The Berliet is fitted with semi-elliptic leaf-spring suspension with anti-roll bars at each axle and dampers at the front. These combine to provide an exceptionally fine ride with no pitch, bounce or roll being noticed from the driving seat. However, a slight vibration, which caused just the rear view mirrors to quiver, was noticed on odd occasions.
The ZF nine-speed rangechange gearbox will be new to most British drivers but it does not hold any mysteries. The six-speed gate is conventionally arranged except that the up-change sequence is accomplished by moving the lever towards the near rather than the offside as in most British vehicles. The gate is slightly offset, with odd ratios forward, even ones to the rear. The slot closest to the driver covers crawler and reverse gears, reverse forward of the neutral gate, crawler behind it. The remaining four positions are like that of a private car; once in fourth the upchange to fifth is accomplished by preselecting high range on the lever button and moving into first/fifth position in the normal way.
At first, it was disconcerting to discover that the slots between ratios on opposite sides of the gate were not straight, those for the even number gears being swept diagonally rearward towards the driver, Some care was needed when slipping the lever from either of the forward gear positions to the rear ones to avoid wrong slotting into second/sixth or even crawler. The bias away from the reverse/crawler plane is very weak, and it is very easy to overcome it without realising it.
The useful working rev range of the engine stretches from around 1,100rpm to the maximum engine speed, 2,200rpm. There are roughly 500 revs between adjacent gears, and typically upchanges were completed with the rev counter reading around 1,800rpm, down changes the others straightforwad. 1,200rpm. Once the gear positions are known the rev counter can be used to produce clean changes.