Unusual devices

Our friend Alan Underwood is near to completing the restoration of a

1919 4hp Douglas, fitted with the Bristol maker’s own carburettor.

The device has slides shaped like tiny, bottomless well buckets, which appear to work on the tight wire/ closed carburettor practice. Thus, with the carburettor levers opened fully the slides are positioned to shut the instrument off, progressively closing the levers lowers the slides to open their respective chambers.

You can only shudder to think what happens if a cable breaks, as this will fully open the chamber and off you go! But there is a valve lifter, so the ‘quick thinking’ (good luck with that!) needn’t go too far on full throttle…

Then, like London buses, as if one unusual carburettor isn’t enough, Chris Sawyer acquired the accompanying JES instrument with his recently bought JES lightweight project. How does it work? Well, I haven’t a clue, but it looks as though there’s a cooperation between a chamber plunger which opens the main jet and semi butterfly-like flap. A fan-shaped sprayer is involved too.

The Douglas-made carburettor, as fitted to Alan Underwood’s 1919 model.

Mystifying JES carburettor, fitted to the company’s own lightweights.