Some AC History
The presence of two vintage racing ACs at the August VSCC Prescott hill-climb, as reported last month, prompts a few words on the subject. Willoughby's two-seater has the Anzani-pattern side-valve engine and a replica long-tailed body of the kind used on several ACs at Brooklands and elsewhere. Incidentally, it is so well done that it proves a good replica to be more acceptable than a chopped-about original, whatever the purists may say.
The other AC, which was confined to the Paddock with "traditional troubles", is Mrs. Hewitt's ex-Joyce sprint car, making a welcome re-appearance after having gone to ground for many years, our man DSJ being nominated to drive it. This car is a special racing model, composed of extremely interesting mechanical items at both ends, with nothing very much in between. By this I mean that the engine is a true tool-room job, of advanced but odd design, and that the back axle is equally unusual.
Indeed, with its 16-valve bronze head, chain-driven single-overhead-camshaft, external oil and water pumps driven by exposed chains, and twin distributors for the dual coil ignition system, twin carburetters, this is a decidedly fascinating piece of machinery. The back axle, consisting of a single tubular shaft, both ends exposed, with inboard brakes and the ¼ -elliptic springs mounted close together on the front of the bevel-drive casing, is likewise unique. The front axle is wider and also sprung on ¼ -elliptic springs. The track-rod is ahead of the axle; there may be no connection but it is interesting that S. F. Edge was responsible for both Napier and AC cars and that Napiers had the steering track-rod in front of the axle. So did most London taxis, but the reason here was no doubt the small turning-circle demanded by Scotland Yard regulations . . . .
To revert to racing ACs, the car Robbie Hewitt has unearthed was built during 1924, at a time when the make held all the records in its Class. The AC was, in fact, the first 1½-litre car to exceed 100 m.p.h over the half-mile, then for a mile, then for a full Brooklands lap, and in 1922 it had accomplished this for the hour run, with J. A. Joyce in the cockpit. So many different engines and chassis were used for racing and record-breaking by AC that it will be a courageous man who attempts to sort them out. However, the special racing models, like the Hewitt car, stemmed from the drawing board of John Weller, in preparation for the 1914 RAC Light Car Race, which was never held, due to the war. The design, with an 8-valve head, was revived for the first JCC 200 Mile Race at Brooklands, three ACs of this advanced conception, with streamlined track bodies, starting. All of them retired. In the 1922 "200" two 16-valve cars started but retired, but at the end of that year Joyce used one of the 200 Mile Race 16-valve engines in the old Harry Hawker long-wheelbase AC to put the coveted light car hour record at over 100 miles - actually 100.39 m.p.h. In 1924 his record was broken by a supercharged Darracq, so Joyce took the AC, which was not blown, out again and set a new hour record, of 104.19 m.p.h This was an outstanding achievement, even if the Darracq had taken its record during the "200" with other cars on the Track and held to a set speed, whereas Joyce had Brooklands to himself. This AC was then giving about 55 b.h.p. on a mild petrol/benzole mixture.
By this time the short-wheelbase sprint car which Jenkinson should have driven up Prescott this year had been built, single and two-seater bodies being made for it. It was modified extensively in 1925. Joyce made FTD at Porthcawl, Brighton, Brentnor, Colwyn Bay, Bexhill and Kop and in 1925 twice broke the Brooklands Test Hill record. These were good performances but the 16-valve racing AC engine could hardly be called reliable. When I said that DSJ was experiencing "traditional troubles" at Prescott I was thinking of the many retirements from races suffered by this type of AC. Joyce had seven unsuccessful attempts at getting the hour record in 1922 (although tyres were partly to blame) and his first bid in 1924 failed, nor did the car manage a second run. The engines, which originally had cast-iron heads (with a steel head tried. I believe, in 1923) were prone to overheating and porosity. Raymond Mays raced a special version in 1925, modified by Amherst Villiers and supercharged with a Villiers blower, the engine being converted to dry-sump lubrication, using a scavenge oil-pump driven from the nose of the supercharger, as Villiers was to do seven years later on the Birkin blower 4½ single-seater Bentley - see page ???. This AC was a complete fiasco. However, Joyce did finish 3rd. in the 1923 200 Mile Race in spite of much tyre trouble, and 4th in the 1924 "200" beaten only by the "Invincible" Darracqs, using the 16-valve engine.
The Joyce sprint AC seems to have been retired after 1925 but in October 1930 it turned up at Southport, which, like Brooklands, was a haven for old racing cars. The entrant was A. J. Aked, who had a garage nearby. The body was again a sketchy single-seater and knobbly tyres were used on the back wheels to aid grip on the sand. Before the war Aked again retired the car and it wasn't seen again until it was brought out at Prescott this year. It was involved in an accident at Southport, because the "water tower" radiator filler, another feature AC shared with Napier, has been wiped off'. It is good to know that this interesting AC has escaped being incarcerated in the Aked Motor Museum and that its engine, of which the Sydney Smith rocking valve guides and Weller timing-chain tension are other unusual features, is very much as Joyce knew it.
Incidentally, exactly how many of these 16 valve engines were made it is impossible to say, for by 1924 this type of AC single-seater was offered for sale new, priced at £1000 but I would think that there must have been about half-a dozen of them, of which that in the Hewitt car seems to be the only survivor. - W.B.