THRE ISTAR
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ATTRACTION
The Mercedes-Benz 1834 tractor/drawbar range was launched on to a pre Euro-1 European market early in 1992 as part of Mercedes' low-emission vehicle (LEV) range. As befits the model that superseded the successful 1733, the1834 has become the best selling model in MercedesBenz (UK)'s heavy truck range.
That's not too surprising as this no-frills, yet high-tech tractor—tested here in its airsuspended LS guise—is aimed squarely at the British market.
Mercedes' SK/Powerliner 2 range differs considerably from the company's offerings of the mid-eighties. As well as the LEV engines, the range comes with Mercedes' own G180 gearbox with a weight-saving aluminium case in place of the steel ZF casing. The revamped cab was already in place, and with other weight savings in a number of other areas the Powerliners soon lost their heavyweight reputation.
Other innovations include the 45,000km oil change interval and factory-fitted automatic chassis lubrication. Costly but lightweight aluminium air tanks remain a rarity Further improvements are planned for the SK range this year (CM23 December 1993) in the run up to a new cab in 1996 (see vehicle news). Mods will include partial electronic engine management for Euro-2, a revised dashboard and a centre-lift twin-steer chassis.
Our test truck came with the optional ASR traction control system, a relatively heavy sliding fifth wheel and a third passenger seat.
The standard 1834LS comprises a doublebunk sleeper-cab on a 3.6m-wheelbase 4x2 chassis which, like the cab and driveline, is produced in-house. A 3.8m wheelbase is optional.
Our truck had a 3.44:1 drive axle ratio to run at 96krrilh (60mph)—M-B(UK) is still considering a move to the optional, 3.77:1 ratio to suit the new 90krn/h (56mph) limit, The change has been made on the lower powered 1831 (CM 3-9 September 1992) but this truck was registered before the 1 January cut-off so we tested it at the old 60mph motorway limit.
The vee-six 0M441LA engine is an updated version of the vee-six which was launched in the late eighties. The 1834 uses the same block as the 1831 but its 142mm stroke increases the capacity from 9.6 litres to 10.96 litres. It is a particularly efficient six-pot version of the charge-cooled vee-eights used further up the power band. The short engine is particularly well suited to day-cab chassis: drawbars and tractors pulling long-pin trailers benefit from a tidy cab rear.
The 0M441LA develops 250kW (340hp) at 1,900rpm with a healthy 1,450Nm (1,0701bft) of torque at 1,200rpm measured to EC 881195. Injection is purely mechanical. All LEV engines are charge-cooled; the vee configuration calls for twin turbochargers and twin exhaust brakes.
Behind the engine lies an air-assisted, hydraulically operated single-plate clutch and Mercedes G155 16-speed synchromesh gearbox. EPS electronic control does away with the bulk of a conventional gear linkage.
A short propshaft takes the drive down to IsrIerc's own hub reduction drive axle which is air-sprung with VVabco electronic height control. The front axle is steel-sprung: anti-roll bars are fitted front and rear with the usual shock absorbers, All heavy trucks now benefit from the Bendix steering box progressively introduced across the range since late 1992. (CM 18-24 June 1992). Vague Mercedes steering was an irritation for years, which was not helped by the old dustbin-lid-size steering wheels.
The old LS7 steering box had a fixed ratio of 21.8:1; the new design varies from 19.3:1 (low power assistance) in the straight-ahead position to 23.0:1 (high power assistance) on full lock so the driver gets more help on tight turns. This avoids over correction and makes the steering wheel more sensitive to road conditions. It also needs less maintenance.
The new box has allowed a further reduction in steering wheel size, from 520mm to 500mm. Mercedes is following the trend toward smaller, more car-like steering wheels typified by Volvo. In Norway Mercedes has test marketed heavy trucks with the small T2 van steering wheel, making it a possible innovation for this year's update.
In adverse conditions during CM'S 1,180km, three-day test the 1834 returned the best and worst fuel consumption in our comparison group. On the A-road/dual-carriageway section, despite headwinds, it came top of its class. But tall gearing and possibly slower gearchanges took their toll on the hills and its overall figure of 38.4lit/100krn (7.36mpg), while by no means bad, was beaten by all three competitors, who enjoyed the benefit of better weather.
The 1834 is slower and slightly more economical than the 1844 tested last year; it romped home well ahead of the old 1831 on the A-roads and in its overall result. Its hillclimb times are also reasonable in its class. Overall journey times were well on track, though weather conditions led us to err on the side of caution. Indeed we might have been forced to cancel our test if not for the 1834's ASK which proved its worth by maintaining traction on icy, snow-dusted roads. On some hills we would probably have been beaten without it.
With full air management kit, a sliding coupling, the extra seat and a full tank the 1834 tipped the MIRA scales at 6.9 tonnes. We've weighed similar chassis without as many extras at 6.5 tonnes: both figures compare well in the market. CM's seven-tonne tri-axle Fruehauf test trailer gave the Merc a payload of 24.1-tonnes, which is well up with its rivals..
As we discovered with the 1844 the new steering works well, both in a straight line and round the bends. The new box has certainly taken the dead out of dead ahead. It's slightly lighter and more crisp, giving better feedback to the driver.
The variable power assistance is smooth enough to go unnoticed and the smaller steering wheel is a definite improvement. Mercedes has succeeded in giving its heavy truck range the same steering quality as can be found in the 0404 coach and the rest of the industry.
The steel and four-bag air suspension combination comes as standard on most UK-spec tractor chassis. We've reported before how we found the ride spongy and a bit dead, and the 1834 ran true to form despite the appearance of an Isringhausen driver's seat.
Handling is also unexciting. This remains the solid base we've come to expect from 0 411Mercedes. A bit stodgy in the damping department perhaps, but like the 1831 the 1834 limits roll well when cornering. The relatively low-height Powerliner cab also keeps cab roll down. Hefty anti-roll bars are fitted front and rear on all the Mere's. These restrict chassis movement and help keep the ship in trim. Overall the truck feels a lot better, but it all down to that steering box.
Cab access is OK even if the illuminated steps are narrow, but in this respect the Powerliner is beaten by recent products from Iveco Ford and Leyland Daf. Once inside the driver enjoys a full range of ergonomic adjustments including a tilting, telescopic steering column. The large, ungainly EPS control unit continues to clutter the engine cover but otherwise cross-cab access is not bad.
The Isri seat has a sliding base and quick deflation switch. Like all new seats that come along it took us a little time to feel our way round it. The nearside window and nearside main mirror are electrically controlled and heated. Most controls are grouped together in a single stalk on the column's right side; various other switches are scattered across the dash in no particular order but they're in easy reach. Our only real complaint about the dash is the layout of the heating/ventilation controls. You can figure them out eventually, but the agency driver boarding his fifth truck of the week will struggle.
The cab is well put together. The trim wears well and it's all fairly easy to clean. Two bunks are fitted as standard; they're both quite hard and could be wider;.in this narrow L cab there's no end-of-bunk wardrobe. Folding the top bunk and reaching the underbunk storage space could keep drivers entertained for hours. However the abundance of cargo netting will keep almost anything in place and the cab is blissfully devoid of the wraparound dashboards that use up so much space. A built-in hot water Webasto night heater warms the engine and cab through the regular heater/cooler circuits.
The 1834 sits at the base of Mercedes' 38tonne line-up. The 1831 is plated for 38 tonnes, but most fleets will employ its talents at lighter weights on diminishing loads, supermarket and one-way deliveries. The 1834 is much more a haulage machine.
Equipped as it is there's little outside of a coupling to be added before putting it to work. Payload is good and fuel economy acceptable. The list price is rather high, but most Mercs are sold through fleet deals with discounts. These can include part or full contract maintenance which offer the high parts prices much lower, at least for those buying in numbers!
Small fleets are up against it where individual parts prices are concerned, but the automatic chassis lubrication and 45,000km servicing intervals could offset this with fewer trips to the workshop.
The ASR traction assist system, which is an option off the back of the standard ABS system, could be well worth its £750 price tag We certainly thought so when it helped us wade through slush laden roads in Scotland. Increased power in recent years certainly makes ASR worth a second look, particularly on three-axle tractors.
by Danny Coughlan