1928 was the second year that the OHV 680 accounted for the bulk of the Brough factory output, with 100 produced along with 35 SS100s and just 19 SS80s. The Side Valve 750 and the 5/15 were still in production, probably accounting for a maximum of another 50 machines. Records for these two models are missing so numbers are estimated.
The SS100 for 1928 was now fitted with the JTOR JAP engine producing an estimated 50 brake horsepower. The Sturmey Archer gearbox had evolved into the ‘super heavyweight’ box at George Brough’s insistence. The 50bhp produced by the engine was too much for the standard gearbox which had been designed for much earlier engine performance.
The Bentley and Draper spring frame was introduced sometime in 1928. 9 bikes out of a total of 35 were fitted with this frame. Technically it was very advanced and offered the rider unheard-of comfort. Unfortunately, the pillion rider did not share this comfort, in fact it made pillion riding very uncomfortable. Interestingly a centre stand was fitted to about half the 1928 springers. This was not continued and it could be speculated that it did not work very well.
The SS80 had minor changes such as a separate oil tank rather than the split petrol and oil tank of the earlier models. The trademark twin filler caps remained as they would on all models until the end of production in 1939.
The OHV 680s saw an engine change in that the pushrods were now enclosed for the first time. The seal on the top of the pushrods and the earlier rocker arms was via a convoluted rubber bellows. This was one of the less successful modifications, the rubber failed very quickly. This meant that the top of the engine became very oily.
The 5/15 and side valve 750 continued unchanged, neither of these bikes attracted the following of the buying public. It is thought that the bulk of the entire 5/15 production went to the Meyer brother’s Austrian agency in Vienna. There are fewer than 10 5/15s surviving worldwide.
Following the failure of the 1927 V four George Brough embarked on another four cylinder Brough using an engine produced by Motosacoche a Geneve specifically for Brough. This was an inline side-valve 900cc air cooled four running a compression ratio of 5 to 1 through a three-speed gearbox and a bevel gears giving a chain drive to the rear wheel.
Famously the bike was built but a conrod broke on test and fractured the crankshaft. The bike was displayed at the Olympia Motorcycle show with a wooden crankcase. The project did not progress any further.
There was a remarkable world record set for the fastest one-way kilometre at Arpajon of 130.6mph on the ‘works scrapper’. This was an out an out racing version of the SS100 with a special frame and minimal cycle parts. This engine was producing well over the 50 bhp of the standard engine.
(Text courtesy Miles Soppet with the assistance of Dave Clark -