Surrey's Severest Hills Tackled with
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THERE are now in the Dennis range four distinct models based on the original 40-45-cwt. design. Three of these were exhibited at the 1933 Commercial Motor Show, and the fourth has only just been introduced. A full description of the 40-45-cwt. model was published in this journal dated September 29, 1933, and a road-test report of the Ace 20-seater appeared on November 10, 1933. The six-wheeler and the latest addition—a four-wheeler—are of the same pay-load capacity, but, to distinguish them, their maker de
scribes them as the 31-tonner and the 70-cwt. chassis respectively.
The new model is built to constitute a machine with what seems to be the maximum load capacity compatible with first-class performance, really adequate equipment and good durability in the 30 m.p.h. £30-tax class. As a chassis it weighs 41 cwt. ; thus a substantially made cab and lorry body can be added without the 21 tons being exceeded. It may even carry a light van body and yet come within this limit.
Priced at £400, this chassis, judged
ANEW
in terms of value for money, would seem, when its likely life is considered, to be a proposition hard to improve upon in its class, or, indeed, among commercial vehicles of all sizes and capacities.
To refresh the memories of our readers, we will recapitulate certain important features of the design and, in doing so, mention some of the points of difference between the new model and the smaller prototype.
A prominent characteristic of the four-cylindered 3.77-litre engine is its high low-speed torque, 30 b.h.p. being developed at 1,000 r.p.m. Its bearings are unusually large and the compression ratio is on the low side, whilst a point that probably contributes more to its good performance and durability than might at first be expected is that the camshaft is driven from the flywheel end.
With the axle set so far back as it is, better aceess to the engine could hardly be gained, and good weight distribution is afforded. Lubrication of the clutch and Withdrawal gear is automatically pro' vichfl by the engine." The gearbox • has plain spur gears, with a tooth ' formation that renders them almost noiseless. The complete unit is rubber mounted. As on the smaller chassis, -Laycock rubber-bush-type -universal joints are employed behind the gearbox and centre bearing, but the third coupling is a Spicer needle-roller universal joint.
The interest of the rear axle lies partly in the fact that the crown wheel backs against the differential housing, thus avoiding the restrictions imposed upon tooth width in conventional practice without the sacrifice of •ground clearance.
A point of difference is found in the brake gear, the Dewa.ndre-Lockheed vacuum servo system with hydraulic transmission being used. The steer
ing gear, so far as the stubaxle assemblies are concerned, resembles the 40-45-cwt. design. The chief feature of interest is that the swivel pins are within the hub, their axes being centre lines of the wheels, giving true centrepoint steering and permitting an unusually large angle of steering lock.
In setting out to test this machine we had in mind the thought that, in modifying the original design to allow a considerably larger load to be carried, the performance might have been unduly affected. Accordingly, the hill. climbing tests to which we subjected it and the roads we included in our route were of a much more exacting nature than usual. The Dennis, however, succumbed to no trial to which we put it. Instead of revealing weaknesses, the steepest gradients and most trying road conditions served to stress its good qualities, and we admit that there were times when, we were glad to think that we were aboard such a roadworthy machine.
From the bottom of the valley in 1343 which lies the road from Guildford to forking, several lanes climb steeply up to the high ground above on the north side. Up one of these, which has a gradient of 1 in 5, we drove the Dennis, stopping on a sharp bend for a restart test. Approximately one-third of a mile was traversed in first gear. The engine throughout had plenty of power in hand 'and the restart was made with absolute ease. At the summit the temperature of the cooling water was found to be just over 200 degrees F., the air temperature being slightly below 60 degrees F.
Thence a roughly made grass track, narrow, tortuous and steeply undulating, was followed. It deserves to be classed as quite unsuitable for commercial vehicles and was, to our knowledge, recently included in a motor trial. Emulating the sporting motorist, we took it at a fair speed, although at times there was barely width for the 70-cwt. chassis. The ease of control and security of the machine generally were thus given an opportunity of manifesting themselves. One of the accompanying pictures gives a good impression of the conditions.
This lane brought us out on to the Leatherhead-Guildford road, but, with some further hills in mind, we turned the Dennis towards the former town, 'striking off shortly afterwards to the right again towards' Polesderi Lacy. The ascent negotiated here was made in third and second gears, the lowest speed recorded being about 10 m.p.h. Then we dropped down a 1-in-41 gradient known as Blagden Hill.
This constitutes a severe brake test, because; prior to the steepest gradient, a long gradual descent is made, during which all the brake drums have time to get hot. Not the slightest difficulty, however, was experienced at any part and, on the
1-in-41 section, a stop was made and a-restart up the slope carried out in reverse. Here, again, the excellence
of the design was demonstra led, and drivers will appreciate that this test is certainly a severe one.
Subsequently, we tried the Dennis on the well-known Ranmore hairpin, where the hill is at least 1 in 5. The long, rising approach was negotiated on its earlier stretches in third gear at 19 m.p.h.; later, as the hill became steeper, the speed dropped to 15 m.p.h. when second gear was engaged. As the hairpin was approached, our speed fell to 12 m.p.h., then 10 m.p.h. and, finally, to 7 m.p.h.; first gear was used until the summit was nearly reached By the time we had again descended to the low road to Guildford, we were entirely satisfied that only conditions of indeed abnormal severity would prove beyond the powers of this machine.
The next tests were of fuel consumption, acceleration and braking ; the results of these are shown in the accompanying table and graphs. The first consisted of a return run from a point near the Dennis works on the Guildford-Godalming by-pass to the centre of Esher and back. This route includes the hills on both sides of Cobham, that on the Esher side of the Fairmile, and Esher Hill itself. The distance was 25.2 miles, and the speed averaged 26 m.p.h. Exactly 2 gallons of petrol were consumed, giving a consumption at the rate of 12.6 m.p.g. In view of the power and acceleration of the engine, this figure must be considered entirely satisfactory.
Acceleration tests provide definite figures, but in this case they failed to reveal much more than our earlier trials had brought to light. Quick gear changes can be easily made and the engine has marked liveliness, combined with excellent pulling power at moderate speeds.
For both the foot and hand brakes we have nothing but praise. No improvement in retardation was shown by employing both controls simultaneously. The manceuvrability of the machine is good. The turning circle was found to be just over 41-ft. on either lock, and the ratio afforded by the steering box to give good controllability with moderate effort.
Finally, the appearance of the machine deserves a word of commendation. We consider it to be one of the best-lookers on the road, and that this view, and our opinion of its capabilities and desirable qualities generally, are shared by many others Is evidenced by the demand that the company is experiencing for it.