Details of an Interesting Development in Air-Cooled Construction.

READERS who are under the impression that the famous ” A.B.C. ” car has ceased to exist from a manufacturing point of view, will be interested to learn that Messrs. A.B.C. Motors, Ltd., of Waltonon-Thames, are still engaged in the production, and that a much improved Super-Sports model is now being handled by Messrs. Ward & Co., of 51, Upper Richmond Road, Putney, S.W.

As the new A.B.C. differs considerably from those of the earlier type, it may be excusable to depart from our usual practice and give a few technical details, though normally these fall within the province of the makers’. catalogue.

A Remarkable Power Unit.

The power unit of the A.B.C. is a twin cylinder horizontally opposed air-cooled engine, with a bore of 96.1 mm. and a stroke of 91.5 mm., with a cylinder capacity of 1,326 c.c. For taxation purposes the horsepower is rated at 10.37, thus coming in the l 1 tax, but when fitted with light aluminium alloy pistons and twin carburettors, this remarkable little engine is capable of developing no less than 40 h.p. at 3,500 revolutions per minute.

Air cooling has been adopted for many reasons, but chiefly with a view to producing a simple and reliable machine with a very high performance. We are informed that during a special test to discover the limit of heat under which the A.B.C. engine would run, the cylinders of the test engine were enclosed in a box to prevent heat radiation, and though the heads were actually allowed to become red hot, the dynamometer showed that there was only a reduction of 5 per cent. of the normal power developed and, furthermore, none of the parts showed the slightest ill-effect on being dismantled.

Records of performance prove that the A.B.C. can be relied upon to work on its lower gears at high speeds for hours on end, and as far as hill climbs are concerned this make has many Gold Medals to its credit in Trials where such hills as Porlock, Lynton, Beggars’ Roost, Blue Hills Mine, Kirkstone Pass and the Nailsworth Ladder have been included.

Technical Details.

Bearing the above facts in mind, let us look into some of the mechancial details and we find a very high degree

of technical knowledge is combined with first class workmanship to produce a small but extremely efficient power unit. The cylinders which were formerly made from bar steel, are now of cast iron, this having been adopted to secure more silent running and freedom from such distortion as is bound to exist in some degree when steel is used.

Thanks to the lay-out of the engine and the disposition of the cylinders, it is possible to use a very short and extremely solid crankshaft, in which whip is practically impossible. This component is carefully balanced and is mounted on ample roller bearings. The connecting rods, too, are of very substantial construction, the bearings taking the form of double roller races of the non-adjustable pattern, possessing a very high degree of durability. The bearings for the gudgeon pins are of larger diameter, the gudgeons themselves being made from a special alloy steel and are hollowed out for the sake of lightness. Lightness combined with durability are the chief characteristics of the aluminium alloy pistons, each of which is fitted with two rings.

The employment of roller bearing big ends is of great benefit to the owner-driver, for it has been proved that these will give a mileage of 30,000 miles without showing any appreciable traces of wear, which contrasts very forcibly with the ordinary type of plain bearing.

With regard to lubrication, the wet sump in the bottom of the crankcase has now been discontinued and in its place a square tank is fitted underneath the sub-frame, from which the oil is pumped to a double adjustable sight feed on the dash. From thence the correct supply of oil is forced to each cylinder and back again into the supply tank to be used over again. The position of the tank ensures the oil being kept cool under all conditions and the consumption has been increased to 1,200 miles per gallon. This modification eliminates one of the minor troubles with this make of car which consisted of oiled plugs on the off-side cylinder. Incidentally, the improved lubrication system enables the engine to be run for at least 5,000 miles without need for decarbonisation.

Improved Valve Mechanism.

The old valve rocker gear has now been entirely re-designed, with the result that all the moving parts are provided with increased bearing areas and the cross thrust associated with the old type has been entirely eliminated, thus the valves can be kept in proper adjustment without attention for long periods The rods and rocker gear are also enclosed and are lubricated continually by a thin film of oil from the crankcase, which is blown through the tubes enclosing the rods to every part of the mechanism. This improvement eliminates a greater part of the noise of the engine, which formerly constituted one of the objections to the type.

Another detail making for silence in operation is the adoption of skew gearing for the timing wheels, three of which only are employed and by increasing the width of the wheels, the ringing noise has been overcome.

Clutch Details.

The clutch which is enclosed in the flywheel, consists of a single steel driving plate of large diameter, held between two Ferodo rings, the advantages of the type being a very light engagement, facilitating a quick change of gear, reliability and requiring no attention. In driving the car I was particularly struck by its sweet action and ease of manipulation.

An Unusual Type of Gear Change.

The gear box, which is a separate unit mounted on a substantial sub-frame, is noteworthy by reason of the unique form of gate control adopted. The gate itself is of the vertical type, similar in principle to that originally used on the Vinot Deguingand car, but the entire mechanism is enclosed within the gear box casing. To move the selector from one gate to the other, the gear lever is given a vertical movement, which, though strange at first, soon becomes quite easy to operate and possesses quite a fascination of its own. As with all other details

in this well-built chassis the gear box is of particularly substantial construction and has four speeds, of which the ratios are as follows :—First gear, 13.7 to 1; second gear, 9.45 to 1; third gear, 6.5 to 1; and top gear, 4.5 to 1. The reverse ratio is 18.36 to 1.

All the shafts run on heavy duty ball and roller bearings and the gear box has a central control lever.

A Substantial Rear Axle.

The rear axle by which all A.B.C. cars can be immediately recognised is a very substantial piece of work and is fitted with spiral bevel gears, the propeller shaft being enclosed in a torque tube, provided with triangulated torque rods. The axle is notable for its quiet running and ball and roller bearings are fitted throughout.

Some Details of Performance.

So much for the general features of the new A.B.C., now let us give a few personal experiences as to its performance, some idea of which can be gathered when it is mentioned that the following speeds are obtainable On the different gears. On first speed it is possible to rev, the engine up to give a speed of thirty miles per hour. On changing into second, forty miles per hour can be reached. On third, the speed increases to fifty miles per hour, whilst a good ” sixty-five ” is easily attained on top gear without any fuss or flurry.

After having tested the speedometer with a stop watch and finding it reasonably accurate, we tried an acceleration test on a piece of good ‘evel road, when by using the gears it was possible to get the car going at 55 m.p.h. in the astonishingly short time of 14.2 seconds.

This test was made on the way out to our test route, which includes a section of a well-known testing ground for motor-cycles and includes a section of rough winding roads, liberally sprinkled with nasty little gradients. As a hill climber it can only be described as marvellous and, indeed, took on third gear a hill for which a change down into second is necessary on many cars boasting greater horsepower.

One can effect remarkably quick changes of gear after the unfamiliar method of gear operation has been mastered and one of the great fascinations of the gear box is the ease with which a real ” slip change” can be effected. By getting the car into a fast stride on third gear and keeping the accelerator pedal hard down, a slight touch on the clutch and a quick flick of the gear lever will permit of an instant engagement of the top gear dogs, without the slightest diminution of way on the car.

In the matter of silence, the A.B.C. does not compare very favourably with some of the more quiet fourcylinder light cars, but one must remember that it is a special type and its performance is so attractive that one is quite willing to sacrifice a little in the way of silence.

One is conscious all the time of a very pleasing reserve of power, the springing is quite good and the body work, though of the sporting variety, gives ample comfort.

Altogether the A.B.C. is one of the most fascinating cars we have driven for a long time and it should certainly make a very strong appeal to those who desire a fast and reliable little Sports car, built on sound engineering lines.