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[I-A TECHNICAL TRIUMPH

2nd May 1947, Page 39
2nd May 1947
Page 39
Page 40
Page 39, 2nd May 1947 — [I-A TECHNICAL TRIUMPH
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Which of the following most accurately describes the problem?

• The .6-litre A.E.C. Oil Engine Gives An Exceptionally Fine Performance In a Chassis Incorporating All That is Best in Modern Passenger vehicle Practice. Driving is Almost Effortless

A feature of the Regent Mark III is the compressedair braking system, in which is incorporated a twostage control giving normal and emergency retardation according to pedal depression.

The foregoing represents far too sketchy a description for so fine a chassis, as there are sor many features representing the highest standard of engineering. I would, however, like to make. reference to the form of engine mounting adopted, as this is no doubt responsible for the almost entire absence of vibration transmitted to the chassis It is referred to as being of the A.E.C.. Metalastik floating-power type, in which the common axis of the front and rear rubber supports passes through the centre of gravity of the unit. Torque reaction is controlled by a series of serrations formed on the inner faces of the upper and lower circular clamps of the rear support, any tendency towards longitudinal movement during acceleption and retardation being checked by a link between the engine and its rear cross-member.

I was unable to check the gross laden weight, as the weighbridge at the works was temporarily out of action, but the ballast carried was made up of three 2-ton weights and others to a total of 6 tons 6 cwt. '1 qr. The chassis weight is 4 tons 7 cwt. 3 qrs., and this, plus driver and two passengers, made the total gross weight 10 tons 17 cwt. 3 qrs.

Our first test was for fuel consumption and the special test apparatus, which recorded fuel consumed in c.c., was filled and the engine allowed to run on this supply until the surplus above the " 0 " mark was used Using the mileage recorder on the vehicle, we ran for a distance of 10 miles, during which we consumed 3,800 c.c. of fuel, or 0.836 gallon.

This works out at 11.9 m.p.g. The time taken on the run was 20 mins., so that the fast average of 30 m.p.h. was achieved, the speedometer, for the most part, being in excess of 40 m.p.h., with a maximum of 48 m.p.h. Such a high speed is certainly not conducive to the best return in fuel consumption, and although the figure is good, there is no doubt that it could be bettered by adopting a lower cruising speed.

Effortless Travel at 40 m.p.h.

So easily does the A.E.C. engine deal with its load, and so beautifully sniooth are riding and transmission, that it was always difficult to appreciate that the road speed was around the " 40 " mark more often than not. The slow-running speed of the engine is rather important, having regard to the use of the Fluid flywheel, and it is not surprising that the A.E.C. unit is outstanding in respect of its idling characteristics.

In view of the effortless finger-tip gear-change of the preselective gearbox and the absolute minimum period of time taken in changing from one ratio to another, I expected some interesting figures for acceleration, and I was certainly not disappointed. The gears may have been " jumped " a little, but certainly not to the extent of causing discomfort, in attaining a speed of 30 m.p.h. from rest, and passing through the gears, in 20 secs. Travelling in the opposite direction, we took 2 secs. longer. During these tests 20 m.p.h wais reached in 9 secs.—acceleration indeed for a vehicle of a gross weight of nearly 11 tons.

The Regent Mark III engine pulls quite smoothly at 10 m.p.h. on top, and reached 30 m.p.h. in 20 secs. one way, and in 2H secs. in the opposite direction. The most impressive feature of the performance was that it was carried out smoothly and cleanly, the A.E.C. driver making his changes of gear ideally to suit the engine.

Driving, as we were, in the districts of Rickmansworth, Amersham and High Wycombe, we had many opportunities for fast running, and although riding on a chassis is not the most comfortable form of travel I know, in this instance I must confess that I had a most pleasurable ride. That the vehicle was fully loaded, and spring action, in consequence, would be softer, no doubt accounted in some measure for the disregard which the vehicle had for indifferent road surfaces. At the same time, no machine in which due consideration had not been given to correct weight distribution and spring control, could have handled so well or put up such a well-balanced performance.

" Gentlemanly " Braking The brakes were tested on a good stretch of macadam road having a covering of fine gravel. A mean figure of 49 ft. 6 ins, was obtained in braking from 30 mph., using only the foot brake. This figure gives a degree of efficiency of about 61 per cent., which is better than " very good," according to the Ferodo chart. Excellent as this figure is, it is more the gentlemanly manner in which the vehicle comes to rest that is praiseworthy— just smooth, rapid retardation.

After an interval for luncheon we checked the turning circle, using the car park at High Wycombe, and found it to be 57 ft. on both locks. The figure claimed is under 60 ft., so the machine is well inside its legal limit for turning radius.

For the hill-climb we chose Dashwood Hill, selecting the old road, which has an average gradient of 1 in 17.5 and a maximum stretch of 1 in 9. The length of the hill is 1,333 yds., but as we did not know the precise starting and finishing points it was futile to make a timed ascent.

Before reaching Dashwood we had tried the vehicle out on one or two really stiff climbs, but whilst they were steeper in respect of maximum gradient, the duration of the climbs was far too short to bring out the best in the engine.

Taking the atmospheric and cooling-water temperatures at the foot of Dashwood, we found these to be 65 degrees and 158 degrees F. respectively. We doubted the accuracy of the first, but nothing would induce the mercury in our thermometer to drop lower and so we accepted the reading. Starting away briskly, lAre were able to reach top gear for a short spell, but changed down to third at about 25 m.p.h. A characteristic of the A.E.C. engine is its ability to keep pulling without complaint at quite low road speeds, so changes have to be made—or it is policy so to do—by watching the speedometer.

Up 1 in 9 at 12 m.p.h.

We were able to maintain third gear for best part of the climb and on the approach to the 1 in 9 stretch a dab on the pedal at 20 m.p.h. set the engine revving in really healthy fashion and the climb was completed in this gear at about 12 m.p.h.

A check on the cooling-water temperature showed a rise of only 6 degrees. Whilst, as previously mentioned, we could not time-check the run, the climb took 2 mins. 30 secs, from a standing start.

Our run back to Southall was carried out at a smart pace, as the vehicle is quite happy around the 42-45 m.p.h. mark. At 30 m.p.h. the rate of travel seemed ridiculously slow, but open country, of course, does give this impression.

On the vehicle we tested the front springs, as previously mentioned, were provided with bump and rebound dampers, 'but, in due course, the patent A.E.C.type of torsion-tube stabilizer, as fitted on the rear axle, will be introduced. Such a stabilizer, of course, gives its maximum effect when the body is fitted, as in the case of a ballasted chassis the centre of gravity is much lower. The present arrangement yielded excellent results during our road test.

In all we covered 73 miles, and during the time I spent at the wheel I found the machine to be beyond adverse criticism. The preselective gear-change is as near the ideal as is possible of attainment with any type of fixed-ratio box. Apart from the effort required to turn the steering wheel, the physical demand on a driver of a Regent Mark III is practically nil. It is indeed a fine engineering feat.

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