Standard Oilers Perform Well Under Military Conditions
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WHEN, in May last, the War DepartVV meat held a series of trials of standard 4-6-ton petrol engined vehicles, another set of trials was contemplated in the " not-too-distant future" to embrace oil-engined vehicles. Last week (as reported in The Commercial Motor on July 27) such a trial took place, the tests being planned on the same lines as previously, so that an exact comparison could be made of the relative merits of the two types of power unit.
A representative of The Commercial Motor was present on both occasions, and from observations made—quite apart from the methodical collection of data by the military authorities—the performances of all the machines entered by the various manufaCturers can be described as being remarkably good. 'When it is realized that standard vehicles were set to climb such hills as the old Horseshoe Pass, near Llangollen, and Bwlch-y-Groes, near Dinas Mawddwy, in Wales, and that they were all successful, the outstandingly good performances can be better understood.
The Object of the Trials.
The trials were not held for the purpose of finding the ideal machine, but were undertaken in order , that the military authorities might be able to assess the value of commercial vehicles under service conditions. As we have already indicated, the trials showed conclusively that the normal products of any of the prominent British manufacturers would do everything that , might reasonably be expected.
Although rated at 4-6-ton capacity, the vehicles were loaded with only 3 tons, as, for military purposes, notably that of bridging, the heaviest useful load carried in the field is restricted to the amount quoted. It was thought that four-wheeled 4-6-ton vehicles of minimum tare weight should be quite suitable, as the power-weight ratio would be high (with the 3-ton load) and, with low gear ratios, to enable hauliers to use a trailer, would produce a vehicle which, it was hoped, would give a performance sufficientto meet military needs.
Standard Vehicles for Abnormal Conditions.
Naturally, there are problems of adequate engine cooling and tyre adhesion. The British Army might have to • operate under widely divergent conditions, such as in mountainous countries, or in a desert, and the possibility of having to use vehicles designed primarily for work in temperate climes complicates the issue. As the whole basis of the trials is to assess the capabilities of standard vehicles, manufacturers were requested to equip their engines with cooling systems " as sold to the public."
Regarding tyre equipment, it may be mentioned that the War Department, in the past few years, has concentrated on the production of somewhat special forms of tread on low-pressure tyres. Research has shown that certain patterns afford the greatest possible degree of wheel adhesion when used across country and that they give good riding comfort and road worthiness on " made " surfaces.
Such tyres, however, are not likely to be itt popular demand, and so the vehicles participating in the trials were shod with tyres as sold to purchasers in the ordinary way of business. The performances under these conditions have been assessed and the vehicles examined with a .view to ascertaining whether the general design permits of ready substitution of the largersectioned special-tread tyres, which are known to give optimum wheel adhesion.
The .Competing Machines.
Two Albion lorries, one equipped with the • Gardner L.W.-type sixcylindered power unit and the other with the Gardner four-cylindered model. were entered, likewise a couple of A.E.C.s, one having the company's own six-cylindered engine and the other a four-cylindered type. Crossleys were represented by three machines, two being Beta models, one having he Crossley V.R.6 engine and the other the V.R.4 pattern, whilst the third was a Delta chassis powered by the small Crossley four-cylindered unit known as the V.54.
A Leyland Beaver with the maker's six-cylindered engine and a Badger with a Leyland four-cylindered unit were also entered, along with two Guy Warriors, one of which was powered by a Gardner five-cylindered L.W.-type engine and the other by a fourcylindered unit. The Armstrong Saurer concern entered an Active fourcylinder model, whilst a Karrier and Maudslay each had a Gardner fourcylindered engine and a Thornycroft Taurus was powered by one of the company's six-cylindered units.
The first test consisted of a climb of the new Horseshoe Pass, near Llangollen. This is a steady and relatively easy climb, although the hill is, 3.6 miles long. It rises 269 ft.. per mile and has an average gradient of 1 in 19.6 and a maximum incline of 1 in 6.69. In a long cjiimb such as this, the effect of a slight-1 fference in engine-to-rear-wheel
reduction might make it necessary to climb, say, two miles on first' gear, instead of "second," so that a wide diversity in times might be anticipated.
The next event, a climb of the old Horseshoe Pass, with its average gradient of 1 in 8.15 and a maximum incline of 1 in 4.4 was another proposition altogether. For one thing, the hill is only slightly more than a mile long.
Exhausts Free from Smoke.
All the vehicles climbed the hill with ease and it was noticeable that, despite the full-load conditions under which the engine would. be working, there was hardly a trace of smoke from the exhausts.
From the private user's point of view this indicates the advances that have been made in oil-engine design.
• A cross-country test, in which two slopes had to be negotiated, one with a maximum gradient of 1 in 8 and the other with a maximum incline of 1 in 3.7, followed, and all the machines performed creditably.
The piece de resistance in the whole trials was the climb of Bwlch-y-Groes, the well-known and little-used test hill rising from Dinas Mawddwy. This hill is 1.62 mile long, rising 704 ft. per mile, with an average gradient of 1 in 7.43, and a maximum incline of 1 in, 3.5. The vehicles were stopped and restarted at two points on the hill, where the gradients are approximately 1 in 5 and 1 in 4 respectively, both foot and hand brakes being tested to determine their capacity to hold the vehicle.
The climbs were undertaken in a howling gale with the wind blowing directly up the hill, so that the conditions were the worst possible from an engine-cooling point of view. Despite these adverse conditions, there was little evidence of boiling.
Results of the Engine-cooling
Tests.
A summary of the results of the engine-cooling tests—the only results available—shows that on Bwkh-yGroes 0.2 of the entry were (a) within the' W.D. temperature difference of 100° F., 0.4 were (b) within the commercial temperature difference of 123° F., and 0.4 were (c) not fit for the tropics.
On the Old Horseshoe Pass, the proportions were (a) 0.467, (b)0.333, (c) 0.2, whilst on the NewHorseshoe Pass they were (a) 0.267, (b) 0.533, (c) 0.2.