ON BEAM SAND BEEMERS
The Sunbeam story and pictures in RC161 were interesting. The writer suggested that BSA based the Sunbeam on a BMW R75. I personally have my doubts about this, as the R75 had a rigid back end incorporating all that wonderful Zündapp transmission. It may be that the earliest BSA / Sunbeams were also rigid framed. My contention is that BSA got hold of a BMW pre-war model, the one with plunger rear suspension and BMW telescopic forks. Many of that model were made as solos and sidecar haulers (with no sidecar drive) for the German army.
Studying the frame and suspension of the pre-war BMW will show you the post-war BSA / Sunbeams. The frame was a copy of the pre-war BMW, and the plungers from that pre-war model provided BSA with plungers for their entire range of motorcycles until 1954 when Small Heath produced their own ( jolly good) swinging arm frames, leaving the plungers to continue in service on the Sunbeam range and the small capacity BSAs until the C12. The Ariel Colt was basically a 200cc BSA C11 in what looked like a frame from a BSA Bantam, but with the (BMWbased) plungers. If Small Heath had more money, they could have also copied the BMW final drive for the Sunbeam, rather than relying on the peculiar (for motorcycles) Daimler / Lanchester rear ends. This made the ’Beam something of a parts bin special, and fitted it with an Achilles’ heel!
The Bantams and Sunbeams were built in Redditch so it’s no surprise that BSA used the same mist green on both makes.
Another throwback to the pre-war BMW from which the Sunbeam grew was the adoption of ‘meat hook’ handlebar levers, with the control wire running inside the handlebars. This was not carried over to the developed Sunbeams, no doubt due to production costs. And like the BMW from which it was copied, the Sunbeam also had ‘clean bars’ with the choke control fitted to the side-mounted Amal instrument. The BMW probably had a rotating air filter housing on the centrally mounted air intake for the carburettors – the rotation of the cover cut-off air intake made a good ‘choke’; similar to that fitted on my post-war BMW R69 US, but a non-standard item.
The red and green warning lights BSA provided on the ’Beams was a direct copy of what they found on the BMW headlamp, except in that application the red light was for charge and the green light was for neutral. The cantilever saddle of the S7 was a direct copy of the German saddle on that pre-war design. And yes, the S8 with British-type single seat gives a much improved ride compared to the British dual seat option. The S8 was never offered with the superbly comfortable, fully adjustable ‘German’ single saddle of the S7.
Ironically, the final version of the BMW 250/300 single, the R27, had its engine and transmission hung in the frame just like the non-vibe set-up used by BSA on the Sunbeam. Making the shaky R26 into the rubber-hung R27 allowed the happy owner to squeeze an extra 1000rpm out of the engine, adding greatly to the road-speed. Those post-war, Earles front-forked Bee Ems came with a close ratio set of gears, with the addition of a fourth gear like an over-drive. That clever ‘geared’ handlebar throttle control allowed for very precise slow running, much admired by police outriders. The Sunbeam had a conventional ‘British’ twistgrip.
Ah, happy memories of my black Sunbeam S8 shaftie. The engine castings of any Sunbeam engine are worthy of serious study – so very much like a modern car engine – and an item of beauty. And that cast aluminium silencer: a lovely, gentlemanly sound… a cracker! David Bullivant, member 1638
I’m pretty sure that some folk will dispute how much was directly ‘copied’ from one marque to another, in any circumstance. There are inevitably some obvious engineering solutions which best suit the materials and tolerances of the times, so we shouldn’t be too surprised to see them popping up simultaneously in different places. There are, after all, only so many ways to skin one cat! Rowena