SOME IMPRESSIONS OF A 1927 A.C. (ACEDES).
By THE EDITOR.
BY the courtesy of the manufacturers we recently enjoyed a very pleasant week end on a 16-40 h.p. 6-cylinder A.C., fitted with a commodious threeseater body. Needless to say the A.C. could not possibly be described as a sports model, as the photograph shows, but we suggest that by virtue of its performance, this 2-litre car deserves consideration from the sporting driver who desires to indulge in fast and unostentatious driving. As we took over the A.C. at Thames Ditton we could not suppress a feeling of secret amusement at the thought of Motor Sport purring about in such an eminently *respectable and comfortable vehicle. We were immediately impressed by the air of quality embodied in the
A.C., a feature which one expects at the price payable for this model. This air of quality originates from the superlative finish, the attractive lines of the coachwork and the high class upholstery and detail work throughout. Other items of information gleaned from a preliminary inspection were that balloon tyres were fitted, while strange to say no front wheel brakes feature on this model, save as an extra. This latter may appear to be a serious defect in these advanced days but our experience, as will appear below, showed that the brakes left little to be desired.
The A.C.-Six chassis combines some extremely advanced points of design on lines which are acknowledged to be sound, and some unorthodox features, which are apt to involve the A.C. enthusiast in fierce argument with rival owners.
In the first place the six cylinder engine has hemispherical shaped combustion spaces with inclined valves, the latter being operated by a chain driven overhead camshaft. The chain drive for the camshaft is provided with a patent automatic tensioning device which effectually prevents any variation of the valve timing when the chain becomes worn. Another interesting feature is the method of mounting the valve guides in the cylinder head on seatings having a hemispherical contact surface. The guides are a loose fit on these seatings, being held in position by the tension of the valve springs ; the advantage of this system is that if any distortion takes place as a result of the temperature of the engine, the valves are still able to seat
themselves correctly, and are not forced to remain in one position, as they are with fixed valve guides.
The point on which the A.C. defies modern practise is the use of a 3-speed gearbox incorporated in the back axle. Whatever theoretical disadvantage there may be in the back axle-cum-gearbox lay-out, it is only fair to the A.C. exponents, to admit that so far as our own experience goes, no evil effects of the arrangement could be detected. With regard to the lack of a fourth speed forward, the A.C. gear ratios are so admirably chosen that the car has a road performance at least equal to, if not better than, many more expensive 4-speed cars, with less happily chosen ratios. It is just conceivable, however, that the rather high bottom gear of the A.C. might cause trouble if some really frightful hill of the motorcycle
trial type were to be attempted. However, this contingency is so remote that the simplicity of the 3-speed gear is amply justified.
Remarks on the gearbox, such as the above, require qualification in the case of the 6-cylinder A.C., since undoubtedly much of the success of this car, with three speeds, is due to the extraordinary flexibility and liveliness of the engine. Many engines are capable of high revolutions while others can develope great power at slow speeds, but few, if any, combine both qualities to such a degree as does the A.C. To descend to actual flexibility figures, a mere snail’s pace could be indulged in on top gear, say about 3 m.p.h., and from this speed, still on top gear, 40 m.p.h. could be reached in 20 seconds. This phenomenal top gear acceleration is doubtless aided by the comparatively light weight of the whole car, and is quite the equal of many cars of a similar engine capacity, using the gears.
If the gearbox of the A.C. was used, a similar change in velocity could be accomplished in exactly half the time, i.e., 10 seconds.
These figures prompt one to believe that it would be possible to show a clean pair of rear mudguards to many real sports cars, provided road conditions did not permit sustainedspeeds of more than 65 m.p.h. The last named figure was attained several times on arterial roads, during our test, but when driven on the track at this speed the front wheels tended to develop a slight shimmy.
This fault was very slight and never occurred on the road, but was probably caused by the tyre pressures being unsuitable for the bumps of the track. On second gear 45 m.p.h. was easily attained, though the engine aperformance did not necessitate this style of driving to any extent. On 1st gear 25 m.p.h. was possible, and the same remark applies again. At engine speeds corresponding to half a mile an hour each side of the 41 m.p.h. mark, on top gear a very definite engine vibration was felt—causing a noise somewhat reminiscent of a supercharger. It must be emphasised,
however, that owing to this period being kept so closely to one speed, it could not be described as a nuisance, as it was quickly passed through when accelerating or decelerating.
The clutch was extremely light and smooth, being designed to prevent any possible damage to the transmission by even the most careless driver. As a result a certain amount of care had to be applied to the operation of the accelerator pedal at times to prevent clutch slip. This only occurred when the car was driven in an exuberant manner on the gearbox and could easily be overcome with a little care.
As previously mentioned, only rear wheel brakes were fitted to the car under review. A certain amount of force was required to operate the foot brake but we found that, descending a slight slope at 30 m.p.h., on a wet tarmac surface, we could bring the car to rest in 35 yards. The wheels we locked part of the time but the figures are distinctly good and compare favourably with some of the cheaper F.W.B. systems. The car was remarkably comfortable, both from the point of seating position and. upholstery and as to ease of driving. Steering was light and reasonably certain, while the gear change was easy though the actual gate was inclined to be noisy.
Petrol consumption during a week end of fast driving was approximately 20 m.p.g.
Nothing more remains to be said of this car, which is undoubtedly near the top of its class for reliability, comfort and elegance, combined with a performance which is by no means despicable.
For the driver who requires something faster, the engine design allows certain modifications to be easily carried out, such as a racing camshaft and specially balanced crankshaft with high compression pistons. Engines incorporating one or both of these modifications are obtainable at a higher price, known as the 16-56 h.p. and the 16-66 h.p. models respectively, the latter being capable of some 85 m.p.h.
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