CM tests new Volvos in Sweden's snow
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by Tony Wilding
• Some of the reasons for Volvo trucks being designed the way they are, were provided on a test run made in Sweden this week with a range of current Volvo models. These included examples of the new 89 Series, two of them running with trailers at a gross combination weight of 50 tons.
On roads made rough and difficult with packed snow and ice the need for good suspension, light steering and well-designed brakes was highlighted in particular. And because so much concentration is needed to control a heavy vehicle in conditions which exist in Volvo's home market for most of the winter there is obvious advantage in giving the driver a comfortable, quiet cab with heating equipment adequate for temperatures well below freezing.
The test run made by the Volvos was from Are in the north of Sweden, close to the Norwegian frontier, to Uppsala 45 miles north of Stockholm. The journey was made in two stages-181 miles to Sundsvall along E75 on Monday and 201 miles to Uppsala on E4 on Tuesday. As the run was mainly intended to show the European commercial-vehicle journalists who took part just what conditions were like for vehicles operating in Sweden during the winter, results comparable with those from normal CM truck road tests were not produced. But reasonably accurate figures were obtained for fuel consumption.
These appear in the accompanying table and the results can be of value provided it is taken into account that engines were left idling for a fair time at the start of each day to get temperatures up, and that the vehicles were each driven by a number of different journalists, some of whom had little experience of heavy truck driving.
Certainly, it is more than likely that better fuel consumptions would be obtained by an experienced driver over normal British roads. And yet the figures were not too bad. They ranged from 10.4 mpg for the 16-ton-gross F86 to the commendable 4.7 and 4.9 mpg for the G89s running at 50 tons gross. An F89 at 38 tons gave 6.1 mpg, which is what one would expect of the old F88 and, in fact, this latter model produced 5.1 mpg at 44 tons.
Use of the 330 bhp 12-litre turbocharged diesel in the 89 Series as compared to 260 bhp in the 88 should not necessarily worsen fuel consumption therefore, although there' was over 1 mpg difference between 22-ton-gross 88 and 89 six-wheelers-8.8 mpg for a normal control 88 and 7.6 mpg for a G89. There is no doubt that this result was because drivers did not adjust their driving techniques with the higher power-to-weight vehicle.
There were very bad road conditions for the first 130 miles of the run with the surface covered in thick ice under a layer of packed snow which was broken up in places, often to reveal large patches of ,glistening ice.
It was with some trepidation that I took over a 38-ton F89 truck-trailer outfit for the first 65-mile stage but, encouraged by success at controlling the vehicle when following advice from the Volvo driver, I quickly built up to a running speed of between 35 and 40 mph to average 29 mph over the distance. Except for about 20 miles where it was narrow, hilly and winding, the road was of reasonable width and gently undulating with few difficult bends. By the time I took over a G89 running at 50 tons gross, my confidence had increased• sufficiently to produce an average of 36 mph over the next 68-mile stage.
On the second day road surfaces were much better. For much of the way there was still snow and ice on the road but there was
usually at least a clear strip in which the wheels on one side of a vehicle could be kept and there were some long stretches free of snow, it was always necessary to pay full attention to the conditions however, "driving" well ahead of the vehicle to avoid having to brake suddenly. Even if the road appeared safe there was a lot of black ice to contend with, especially in the early morning and late afternoon.
I started the second day in a G89 50-ton combination and averaged 32.1 mph over 35 miles. Then I had the chance of seeing how the less powerful F88 handled at 43 ton gross weight. Although there was not so good a performance as with the trucks, having the 330 bhp engine, a good average speed could be maintained by proper use of the Volvo SR61 sixteen-speed gearbox; I made 37.4 mph over 50 miles.
For the last stages of the run I had a couple of the "babies" of the convoy-G89 6 x 2 rigids running solo at 22 tons. With 330 bhp these vehicles could be kept in top gear at an easy 50 mph all the time except in towns arid on the more severe hills. Average speeds were 42.7 mph over 56 miles and 47.4 mph over 60 miles.
The main overall impression from the test run is the absolute ease of driving the various Volvos despite the fact that truck and trailer combinations at high gross weights were being driven in conditions abnormal by British standards. We hear a lot of support for suggestions that double-drive bogies are needed for gross
weights of over 36 tons or so. The test convinced me that such support is unfounded-all the vehicles had single drive. On some parts of the run, tyre adhesion could hardly have been lower yet it was only when a vehicle was being driven inexpertly that adhesion was lost.
In the same way that the need for braking had to be anticipated, so had the possibility of traction difficulties. When I was coming to ice-covered gradients the Volvo staffrnan acting as my "co-driver" would lean across and switch in the differential lock--and sometimes the bogie-lift as well-to add extra weight to the driving axle. We never had a problem. But I did come to grief once when leaving a parking area with a 50-ton combination. There was solid ice covered With packed snow and I failed in two attempts to get over a short gradient at the exit. I handed over to the Volvo driver and he moved out smoothly and with no trouble at all although appearing to use no special technique. Clearly a driver with experience of "feeling" the adhesion is needed.
I would rate single drive with differential lock and load transfer facilities higher in the particular conditions encountered than double drive with free axle and inter-axle differentials. I was told that Swedish drivers and operators would not buy the latter layout and 6 x 4 chassis are used only where very heavy loads-100 tons and over-are involved. And then it is not for traction but to divide the torque having to be supplied by the engine and gearbox for such weights.
The test was made with outside temperatures down to -15deg C (+ 5deg F) which was warm for the time of year by normal Swedish standards. There was therefore more cab heating than necessary. All six vehicles I drove gave an excellent ride, and had responsive brakes and light and positive steering-both of these factors were essential for safe control in the road conditions. The alteration to a short control lever for the gear change on the 89 series was found very worth while. The layout on the 88 is acceptable but the new design has cut out the "stretch" and springiness with the long lever. All four "heavies" I drove had the SR61 gearbox-the basic Volvo eight-speed range-change synchromesh box with ratios doubled by the addition of splitter gearing. With 16 ratios engine speed could be kept at just the right level-between 1600 and 2000 rpm-for best performance on all types of terrain; there was no trouble through not knowing which ratio was engaged.