First Performance
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Report of Road Test No. 259
THE NEW COMMER 4-5-TONNER
APACIOUS body, generous pay-load rating and ample ‘s.lpower are the main selling points of the latest Commer—a, maximum-load 30 m.p.h. machine offered at a figure that unquestionably represents good -value for money. .
This model was mtroduced just over a month ago, and full particulars of its construction, etc., were published in our issue dated April 23. Now we present a report of its performance on the road. It is named the LN5 and is described as a 4-5tanner. Available in a number of different forms, which were explained in that issue, the model was tested by us as a forward-control, longwheelbase chassis, shod with 34 by 7 times, which are offered alternatively to the standard 32 by 6 equipment.
To Combat Overloading.
The maker, Cominer Cars,Ltd., Luton; adopts the excellent system of fixing a maximum gross-weight figure for its vehicles, and in' the case of the machine submitted to us this limit is 7itons. It will be noted that, by -the time all personnel and testing paraphernalia were on board, we were, at the outset, 1 cwt. over weight.
In analysing the gross total recorded by the weighbridge (see accompanying table), an addition was made to the standard chassis weight for the larger tyres ; the generous allowance of 10 cwt. was madefor the body and cab, Which amount should necessitate no skithiiing or flimsy material. No less than 3Acwt. was credited to loose equipment, and yet over 5 tons remained to be reckoned as useful load.
Next in importance to weight capacity comes the available pay'. a28 load space. From the back of the cab to the end of the body the distance is 16 ft_ 11 ins.; this must be one of the longest-bodied vehicles in its class.
Ample power is:afforded by the 4-litre six-cylindered engine, which develops 80 b.h.p. ; thus giving the useful Power-to-weight ratio of 0.513 b.h.P. per cwt. Consumption braking,' controllability, etc., are all up to a high standard, thus ensuring a perfOrmance, in the broader sense, compatible with the machine's other attractive features. .
Running on ordinary commercial petrol, we tested the consumption rate over a course between the outskirts of Luton and a point, on the London side of Hatfield. On the outward run one gallon took us 12.1 miles, whilst, on the return, exactly 12 miles were covered on this quantity. This gives an average of 12.05 m.p.g.
An Arduous Route.
Our route followed the road that passes Luton .Hoo and runs through Wheathampstead, to join the Great North Road a mile or so north of Hatfield. It is rather narrow, winding, and undulating, including gradients which needed the use of third gear on four occasions—once for a considerable period. The return quoted compares well with, contemporary types of similar capacity and represents an advance on the figures obtained in the past.
This test completed, we drove to Offiey Hill, on the Luton-Hitchin ioad. Rising at the rate of 1 in 81 and about a quarter of a mile long, this acclivity constitutes a hard climb, and we estimated that first gear would be required. We were, however, mistaken, for the LN5 just succeeded in making the ascent in "second."
Our speed of approach was 83 m.p.h. At about 30 m.p.h. third gear was engaged, and soon afterwards the next lower ratio. As the slope stiffened, our rate of progress fell, touching a minimum of m.p.h. Had it dropped lower, first gear would certainly have been required.
In descending and on a subsequent ascent, the brakes and the clutch were tested both forwards and in reverse gear and found entirely satisfactory.
A characteristic of the Commer engine used in this chassis is its wide speed range. This, together with the choice of gears, enables fairly high road speeds to be reached in second and third ratios before the change-up is made. It also permits a high maximum road speed without an unduly high axle ratio: This good point is slightly offset by the fact that torque falls off rather earlier down the scale than would probably be the case were the engine-speed
range narrower. In spite of this, the power-unit continues to slog away steadily down to quite low "revs."
Proof of these statements is afforded by the accompanying acceleration graph, which shows a number of curves plotted from figures obtained during our test.
• Retardation tests were particularly interesting, in view of the new Bendix-Cowdrey brakes with which this model is equipped. A glance at the graph will reveal one most unusual fact—that the hand brake falls little short of the foot brake inefficiency, actually equalling, if not exceeding, it at speeds from 20-25
m.p.h.
Distribution of Braking Force.
As the hand brake acts on only the rear wheels, it would seem that too great a proportion of the pedal braking force is directed to the front wheels. Were more applied to the rear, it is reasonable to suppose that the difference between the hand alone and the foot alone would be greater. One would have expected, however, that the use of the lever in addition to the pedal would have shown a considerably greater improvement than is the case.
Another interesting point is that the curves seem to corroborate Dr. Steinitz's theory—outlined in our issue dated May 21—that the coefficient of friction between the tyre and the road is at a maximum at low and high speeds and at a minimum at intermediate velocities.
On the score mentioned, we make no criticism of the brakes, but point B30
to a way in which their already high efficiency might. possibly, be rendered even higher. We have, however, a minor criticism" to raise on another ground. When the foot brake is applied vigorously the vehicle tends to steer to the off side, despite the • fact that three compensators are included in the layout. We suspect streteh in the longer tension rod operating the near-side front brake. If this be the cause, the fault could probably be rectified by employing a stouter rod, or arranging the compensator centrally. There is, of course, a variety of other possible explanations not necessarily inherent to the design.
Apartfrom this slight tendency, the, machine steers well, and is easy arid pleasant to drive. To turn the
front wheels from full left lock to hard right, and vice versa, 3-1 turns of the steering wheel are required. This is about the average for the class, but the effort needed to pull the wheel around is a little above average. This may have been attributable to newness, the machine having run only about 300 miles at the time of our test. The vehicle can be turned in the reasonably small circles of 51 ft. on the left lock and 53 ft. on the right.
Goods chassis are built for hard work, and one does not, therefore, expect to find luxurious suspension systems. Moreover, if the springs be too soft, good cornering qualities may be impaired. In saying that we have driven over rough roads more comfortably in other comparable vehicles, we are not necessarily suggesting a fault in this Commer.
There is a last point that should be mentioned in connection_with weight and tyre considerations. With the oversize equipment used on our test (it is not far short of I cwt. heavier than with 32 by 6 tyres), the grossweight figure is higher, but the bodyweight limit lower. Therefore, for light, bulky loads and a big body, the standard-tyre equipment should be specified.
With a first-class all-round performance, built of high-quality material and constructed on really up-to-date lines, this LN5 is offered at a figure that represents splendid 'value and commands consideration.