The 1930s were difficult years for Douglas. The Douglas organisation was sold to a group of investors in 1932 but its financial problems persisted, leading to a further change of ownership in 1933. Production was at a standstill in the early part of that year, with dealers offering unsold 1932 models at discounted prices. New models were announced for 1934 and 1935, but in June 1935 the company changed hands again, this time bought by the British Aircraft Company. Models were re-branded as ‘Aero’, but little development occurred between 1936 and the end of motorcycle production in 1939.

Douglas S6 motorcycle engine, 19301930 – S5  1930 saw the introduction of new side-valve models of 500cc and 600cc, designed by racer/designer Freddie Dixon. The Douglas S5 and S6 models were smooth, quiet and flexible, and gained an excellent reputation for reliability. Note the finned oil sump, BTH pancake dynamo and updraught carburettor with butterfly choke control.

Douglas L3 motorcycle, 19301930 – L3  Douglas introduced shapely saddle tanks during 1929, but the rest of this 1930 L3 350cc machine still looks very ‘vintage’. Oil is held in the finned sump visible below the engine. Acetylene or electric lighting was offered; this machine is fitted with a battery and BTH headlamp.

Douglas A31 motorcycle, 19311931 – A31  As the Depression worsened and sales fell, Douglas introduced new lightweight models to take advantage of the under-224 lb road tax category. The 1931 A31 side-valve 350 offered a high specification at a low price – a chrome-plated tank and full electric lighting set (missing on this example) for just £41. The wet sump of the L3, above, has been replaced by an oil compartment in the tank, reducing cost and weight.

Douglas G31 600 OHV Motorcycle, 1931Douglas G31 600cc OHV Motorcycle Engine1931 – G31  A rare sight – a G31 600cc OHV machine, beautifully restored and believed to be one of only eight in existence. This, and its 500cc sibling the F31, were only made in 1931-2 and were superseded by the lighter K and M models below. Note the grease nipples  for the rocker spindles and the fully-enclosed carburettor with rear-facing grille for the air intake. While most ’30s Douglases have their front brake drum on the left, these OHV models have the brake on the right, as shown here, with the speedometer drive on the opposite side. These models also, unusually, have their transmission on the right hand side.

Douglas E32 motorcycle, 19321932 – E32  The Douglas E32; a new name for a familiar model. The S6 and T6 of 1930 became the Models D and E in 1931 and all models acquired tartan borders to the tank panels. Like other machines in the range, the gearbox position of this 1932 E32 model is fixed; primary chain adjustment is achieved by moving the engine backwards or forwards. The draw-bolt is visible at the front of the sump casting.

Douglas K32 motorcycle, 19321932 – K32  New for 1932 were a pair of overhead-valve machines of 350cc and 500cc – the K32, shown here, and M32. With short-stroke engines and the lightweight frame of the smaller side-valve models, Douglas compensated for the greater length of the OHV engine by positioning the gearbox above the rear cylinder – allowing the kick-start lever to be more easily operated by hand!

Douglas D33 motorcycle, 19331933 – D33  This D33 596cc side-valve ‘Touring Sports’ model has a fashionable tank-top instrument/switch panel but is otherwise similar to the 1931/32 machines.

Douglas Z1 motorcycle, 19341934 – Z1 Powerflow  Years before Kawasaki’s legendary Z1, the 750cc Douglas Z1 ‘Powerflow’ of 1934 offered lusty rather than scintillating performance! Based on the proven 600cc model, now termed the Model Z, the Z1 differs from earlier models in using a Lucas Magdyno, visible beneath the tank.

Douglas Bantam motorcycle, 19351935 – Model X Bantam  The UK’s under-224 lb reduced road tax category was replaced in 1932 by a new under-150cc tax classification. Douglas introduced a Villiers-powered 148cc 2-stroke for the 1933 model year, but fitted a 150cc 2-stroke engine of their own design from 1934. Featuring full engine enclosure and leg shields, the Bantam was offered with flywheel magneto – the Model X, for £24, or as the Model X1 with full dynamo lighting for an additional £3. This Bantam is from 1935, the last year of production.

Douglas Endeavour motorcycle, 19351935 – Endeavour  The star of the Douglas stand at Olympia, London, in November 1934 was the 500cc Endeavour – Douglas’ first transverse twin. The gearbox and single-plate clutch are built in unit with the engine, and drive the rear wheel via a shaft. To reduce tooling costs, the crown wheel and bevel assembly in the rear hub was sourced from Morris Motors. The press loved it but, at £72-10-0, the public were more sceptical; records suggest that relatively few were built.

Douglas 250 Aero motorcycle, 19361936 – Aero 250  In June 1935, Douglas was purchased by the British Aircraft Company and from 1936 most models were designated ‘Aero’. This 1936 Aero 250 model followed Douglas’ conventional layout, but with a front frame now constructed from straight tubing. Note the twin filler caps; oil for the dry-sump engine is contained in a compartment in the tank where, it was claimed, the petrol kept it cool.

Douglas Aero 600 motorcycle, 19381936 – Aero 600  The 1936 Douglas Aero 600 was little changed from the 1935 model  – note the vintage-style inverted handlebar levers and four-speed hand gear-change. The petrol tank acquired a stylish new insignia, however, with a winged ‘Aero’ design, adopted during 1936. The Lucas headlamp is not original.

Douglas Aero 600 motorcycle, 19381938 – Aero 600  As the ’30s closed, the Douglas range was looking dated – this 1938 DC38 Aero 600, now with a lozenge-shaped tank badge, still features hand gear-change years after most manufacturers had introduced foot-change gearshifts. Even bargain-basement prices – a new Aero 500 was available for just over £37 in 1937 – could not restore Douglas’ fortunes, and with the advent of war in 1939, the Bristol factory was turned over to defence contracts.