The BAC

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Having seen an innocent little BAC light car wrongly described as an Eric-Campbell, both in a pictorial book about Brooklands (not mine!) and in a monthly contemporary, (the Benz it was towing in the Brooklands’ Paddock was also wrongly captioned as Hornsted’s great 200 hp racing car, whereas it was a smaller Prince Henry Benz) I feel that not much can be known about the BAC and that the time has come to put this right. . .

It surfaced early in 1921, at a time when so many light-cars and cyclecars were battling for sales in a large and difficult market. It took its initials from the firm that was handling it here, the British Automotive Company, with premises in Great Portland Street, dubbed “the street of cars”, not far from London’s Oxford Circus. The BAC was, in fact, almost identical technically to the Mathis, itself a good little car I have somewhere a silver rose-bowl presented to B S Marshall after he had won a Brooklands race in one of these Bebe Mathis but with 65 x 100 mm (1328 cc) engine, at 63 1/4 mph. The BAC was based on the 10 hp Mathis, and thus its engine was a small-four of 60 x 100 mm (1131 cc), of Edwardian concept, its side valves beneath big valve-caps, one per two valves, into which the sparking plugs screwed. Lubrication was on the rather unique system whereby oil was circulated not only to the engine, but to the multi-plate clutch and gearbox, by the fly-wheel. A Zenith carburettor on the off-side was gravity-fed from a pancake-like 7-gallon tank, its shape necessitated by the lack of space beneath the short aluminium bonnet, which had to be opened for replenishing. The timing case came to the level of the little fixed-head engine. (Mathis of Strasbourg was making 12 cars a day, so could presumably farm out its chassis).

Mathis specification was followed in the notable feature of a four-speed and reverse gearbox in unit with the engine and it seems that the body was wider than that on the French chassis. The BAC was distinguished by a slim R-R-like radiator and the spare wheel of the two-seater was carried flat on a shelf at the back, as on a Rhode. Internal-expanding brakes shared the rear drums, being separate for operation by pedal or rh lever. The gear lever was central, and half-elliptic springs endorsed the light-car status of the BAC, a further refinement being seven damping laminations in the front springs, ten in the back springs. When shown at the London Show in the winter of 1921 the price of the Mathis was £362 in chassis form, and the BAC’s agents hoped to sell a two-seater for £395. But by then it had a Peters power unit, with a bore of 62 mm, giving a capacity of 1208 cc, and the brake lever was now beside the gearbox, with its ratchet mounted thereon. In time for the Show 2-seater, 4-seater and coupé bodies were available, and £395 bought the last-named, £345 the 2-seater, the chassis selling for £300.

Certainly much had been done to publicise the BAC. For example, a workmanlike sports two-seater body was prepared for the earlier 8 hp model and Rex Mundy, the KLG plug competition rep, was loaned it for trials work. Noted for a healthy-sounding exhaust note, it did well in a Bournemouth trial, finding the chalk-surfaced Creech hill easy, and in the strenuous Scottish Light Car Trials of 1921 Mundy, still using a Mathis engine, again did well, the BAC being described as superbly handled, needing no attention apart from dusting, never being seen to steam, and unquestionably registering the best ascent of more than one hill notably the Inverfarigaig Corkscrew; free plugs forever for that reporter, I would think! Mundy gained one of the coveted gold medals, of which only ten were won, by the BAC, four air-cooled Rover 8s, a Calthorpe, two Jowetts, a friction-drive GWK and a Horstman.

A very stark sports BAC, with exposed bucket seats, a tiny low pointed tail, and very “French” front mudguards had it turned up in a recent VSCC Light Car event the body might well have been regarded as a replica, even a fake and a normal two-seater were entered for the well-supported 1921 ICC London-Manchester run; both these 8.9 hp BACs took gold medals. Such successes apart, when the great 1921 ICC 200 Mile Race at Brooklands, for cars of up to 1 1/2 litres, was announced, the BAC people took quite formidable steps to secure a good result. They secured the services of LG “Cupid” Hornsted, the famous pre-war driver of the 200 hp Benz at Brooklands, as a “works” driver, along with it Mundy, and their Mr WG Watson, in collaboration with MH Malaherb at the Peters Engineering Works in Belgium, set about designing a very advanced racing engine. (This link with Hornsted explains why a BAC was used to tow a racing Benz in the Brooklands’ Paddock).

The design which Mr Watson worked out was exciting – a proper sixteen-valve, roller-bearing racing power unit. Bore and stroke were 65 1/2 x 110 mm (1466 cc) and the inclined valves in a detachable head were operated from a base camshaft via hollow pushrods and rockers, each rocker actuating two valves: the exhaust rockers were machined from the solid and extensively drilled with lightening holes. (Enfield-Allday were also working on an ingenious 16-valve engine for the race; quite how the BAC valve-gear was contrived, if there was only one camshaft, is not clear to me). Camshaft, big-ends and crankshaft all ran on roller bearings, the disc-web crank being built up and the big-ends having two Hoffman bearings each, fed from the oil scoops. The con-rods were tubular, only 3/4 mm thick, with phosphor-bronze small-ends. The cutaway alloy two-ring pistons weighed less than 3 1/2 oz each, with the hollow gudgeon-pin. (They were described as “oval”, but this merely meant that they had vertical “flats” in line with the gudgeon-pins.)

The sparking plugs were central in the cramped combustion chambers, the carburettor fed through a two-branch manifold, and the sump had 13 cooling tubes running through it. A cone clutch took the drive to the 4-speed gearbox but otherwise standard chassis were to suffice, but with the brake gear faired over behind the back axle, the rear springs mounted within the side members to improve streamlining, and the frame stiffened by wood inserts in the front dumb-irons, and metal bed-plates and other stiffeners in the side members to obviate dash shake. Aluminium racing bodies were to be fitted, and petrol enough to do the 200 miles non-stop was visualised. The tyre size on the Rudge Whitworth wire wheels was 760 x 90 for 200 racing miles! All very exciting, for a small concern. Alas, though, time was running out. The engine drawings, not completed until June 17, were sent by air to Liege, where Peters were to build these advanced power units; the race was on October 22, so three months remained for their construction and installation — and then the engines were lost in transit to England!

Both cars non-started. And come the 1922 “200” no BACs. Had they been well placed in that first “200”, would there have been a production 16-valve sports BAC, I wonder? (We shall never know, and when a Capt Davis entered a 1373 cc. buff-coloured BAC with 73 x 82 mm engine for a Miss AML Northcott to drive at Brooklands in 1925 the fastest lap it did was a sad 60.37 mph, when the smaller winning Salmson turned in 86.46 mph. . .)

But the race set-back notwithstanding, and following an RAC-observed test at Brooklands when a BAC achieved 34,5 mpg for 27 miles at 27 mph on a 4.6 to 1 axle ratio, the 13 cwt two-seater climbing the Test Hill at 11.87 mph, BAC cars appeared again at the 1922 Show, now with Michelin disc wheels and in spite of a 300 lb return spring, the clutch was described as exceptionally smooth. But come the 1923 Show no BACs. . . A forgotten make, of which I doubt if a single example has survived. W B