[The above image and following text is adapted from Unique Cars & Parts’s “Car Spotters’ Handbook,” and is reprinted here with their kind permission – Ed.]
After World War II ended, British car enthusiasts could once again seek out something spirited to drive. But these were still hard years, and money (and petrol) still hard to come by. Some could afford to splash large on the new (mainly pre-war) models, but others sought out the 500 c.c. sporting midgets.
One 1947 500cc model of note was the F.B., made by Frank Bacon. It remained as inexpensive as any that had been constructed since the war, its foundation being the chassis of an Austin Seven, which happened to be available at a microscopic price.

The Austin chassis was extensively modified, including changes to the brake gear, and a Rudge single-cylinder engine was installed. Unfortunately for Frank Bacon the engine was wider than the Austin’s chassis could facilitate. This was overcome by setting the frame so that its crankshaft was in line with what had been the gearbox of the Austin.
This meant that the engine had to be mounted higher than planned, so that it would drive down to a shaft at the correct level by means of a chain and sprocket. The engine sprocket had a spring-loaded cushion drive, the second sprocket was keyed to its shaft and the shaft mounted in bearings. This drove a reduced version of the Austin Seven flywheel, which was necessary only in order to preserve the Austin clutch complete in its housing. From there to the rear the drive was normal Austin Seven, and had a three-speed gear box which had been slightly modified to bring the gear lever to the desired position for the driver.

The suspension did not need further modification, although the rear shock absorbers were reinforced by most owners. Then the Austin steering gear was remounted with its column at a considerable angle to the chassis, in order to bring the steering wheel to the centre. There was a substantial bulkhead, and the usual small fuel tank which, because it was not much higher than the carburettor, was arranged to take air pressure supplied by a hand pump. A certain amount of thought was necessary to lead the twin exhaust pipes away on an easy curve to the side of the chassis, and the tails of the pipes were not far from the driving seat, but at least there was a curved metal plate that afforded some protection from frying the right butt cheek.
The 500cc F.B. was very light and neat, and could be provided with a complete body, primarily because the higher mounting had interfered with the lines of the bonnet, which had to be modified accordingly. But the essence of the whole design was that the expenditure was kept to the minimum. Bacon himself had the Herculean task of drilling all the holes necessary by himself with a hand brace.
This material originally appeared on the web at www.uniquecarsandparts.com.au.
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Additional image from www.500race.org