A NEW 10-tor
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LORRY-TRAILER OUTFIT
tested on the road
0 UR standard road test of the new Armstrong-Saurer model described in brief in this paper on January 20 has now been completed. It took the form of a 268.3-mile journey from the Newcastle works to Barnet, near London, and, despite bad weather and a vehicle that had covered only 145 miles on the road we made an easy journey and obtained good results in regard to hill-climbing, acceleration, general power, flexibility and braking.
The fuel consumption (measured over 237.6 miles) worked out, however, at the rate of only 7 m.p.g.
This was due to the newness of engine and chassis, the snow and floods on the roads, and the inclusion of numerous halts for acceleration and brake tests, etc. Altogether there were 29 halts. For this reason another test was made when the outfit had covered 2,500 miles. On a 41-mile journey including an exit from congested London we obtained 8.75 m.p.g. It was a dry, warm day and the cooling-water temperature at the end of the test was 188 degrees F.
The Durable, intended to carry 5 tons and to draw a_ trailer carry ing a further 5 tons, has been developed from the Diligent 5-tonner. It cannot be called a modification of the Diligent, however, because the changes made are major ones. In place of a four-cylindered 60 h.h.p. engine it has the BLD six-cylindered 85 h.h.p. engine, as in the Dauntless four wheeler for maximum legal loads. It also has the bigger clutch and gearbox, whilst the super-gearbox, giving eight forward speeds, is a standard fitment —and most valuable for trailer work. A double-reduction axle is adopted.
The lorry is definitely not intended to be loaded to the legal limit of 12 tons gross, and has lighter springs, frame and rear axle than the Dauntless, which is built for that work. A Durable for work without a trailer is available, this having a 7.14-to-1 axle ratio. Hauliers familiar with the Diligent will have an idea of what to expect from the Durable, judging from the above differences in design.
The outfit, as we tested it, with trailer and 10-ton pay-load, attains 20 m.p.h, from rest in 33 sees., against 23 secs. without trailer and against 25 secs. for the Diligent with super gear.
It climbed a gradient of about 1 in 121 (Croxedale Hill, 14 miles north of Darlington) in second gear at 8-9 m.p.h., and on a steeper gradient held 5 m.p.h. (1,300 engine r.p.m.) in the same gear. To note that there are still two lower ratios available, giving respectively 3.38 m.p.h. and 2.38 m.p.h. at 1,200 r.p.m., and that at this engine speed the maximum torque of 281 lb.-ft. is developed (output 64 13.11.p.), is to realize the reserve of power and climbing ability that is provided. Digswell Hill, south of Welwyn, was climbed in third gear at 13 m.p.h.
On level roads the super fourth gear permits the engine speed, at the legal limit of 16 m.p.h., to be kept down to 900 r.p.m., at which the torque is practically 280 lb.-ft. This results in fuel economy and long engine life.
The four-speed gearbox (central ball change) gives light operation, and to change to or from super gear in any of the four main ratios is as easy as pressing a horn buttonand as quick. The driver is encouraged, therefore, to make full use of hi4, gear change and thus keeps the engine speed within its range of high efficiency.
We cannot help thinking that even for drivers experienced with the type the expense of an engine revolution counter would be justified by the accuracy of gear selection which it would ensure. Having eight gears,
one really would appreciate the addition of such an instrument.
• The Knorr compressed-air brake system is the next most outstanding feature of the Durable, as of other Armstrong-Saurer models. The reservoir pressure, shown on a dashboard dial, can be adjusted by a knob according to the degree of adhesion afforded by the road surface. Even on a wet day we found 100 lb. per sq. in. not excessive, and the powered retardation is most reassuring. It, of course, calls for no effort by the driver.
Should there be a leak (more than the compressor can replace) a red. light will appear so soon as pressure has dropped to 25 lb. With the engine stopped we found that the reservoir gave 18 good applications and three fair applications (30 lb.20 lb.). The brake layout on the outfit tested is given in the accompanying data panel, whilst the graph shows that we tested it both with and without the trailer brake coupled, also without the trailer. Secure parking is provided by the hand brake, even on 1 in 6 gradients.
The steering (Armstrong-Saurer worm and segment) is very light and not noticeably self-centring, except at well towards full lock. The springing is secure and resilient and • benefits from the Silentbloc bushes. The controls are all easy to reach, and before the mate's seat is a screw-brake gear for trailers that are not Knorr equipped.
A front towing coupling and rear trailer hook (sprung) are part of the standard equipment. The Dyson trailer followed steadily, but there was some thrust—due, one would normally say, to insufficient spring movement of the towing hook. We are inclined to think, however, that an unsprung hook with a bushed pin —providing a non-extensible coupling—would prove more comfortable. This warrants investigation.
All the accessibility features of the Diligent are found in the Durable. The use of Silentbloc bushes for all spring mountings and for the exposed universal joint reduces the points of chassis lubrications to so few that grouped nipples are unnecessary.
As regards the running of the BLD engine, its characteristics are familiar to our regular readers. It started from cold instantaneously after a 30-second use of the heater plugs and ran smoothly and without visible smoke all day. Thermostatic control of the radiator shutters helps to preserve the right temperature.
The cab of our Durable was, we learned,, to lc* modified to reduce the weight, and we think that this opportunity might be taken for making the floorboards and dash a better insulator of the engine warmth and sound. The ArmstrongWhitworth all-steel body, by the way, seems to be a sound job ; it was first seen at the Scottish Show last November.
The Durable is a robust, simple and efficient machine deriving important advantages from the super gear and the compressed-air brake, and is a useful newcomer in the 5-6ton unladen-weight class. It will be a great pity if hauliers nullify the designer's good work by attempting to carry on it such loads as those for which the Dauntless is intended.