Triumph 1924 SD 550 cc 1 cyl sv

Triumph 1924 “SD” 550 cc side valve single frame # 8850MS engine # 98177 OGH

The SD (Spring Drive) is a somewhat modernised version of the famous model H, which has grown out of the “Trusty” veteran Triumph. By the early twenties belt drive is losing its appeal to many motorcyclists, so Triumph designs a model with chain secondary

drive. With the “H” the power pulses of the low revving engine are taken up by the belt, with the SD this function is taken over by a strong spring fitted to the gearbox drive shaft.

The SD enters the catalogue for 1920; as the immediate post-war marked booms and then slumps again, the selling price of the SD goes from £110 to £140 in early 1921; in 1926 the price has gone down to £66 and 10 shillings. The last SDs are produced in 1927. For some years the SD is presented as Triumph’s top model; in 1922 that position is taken over by the new OHV “Ricardo” model. The SDs primary chain is protected by a well-engineered aluminium case and runs in an oil bath to minimize maintenance of chain and clutch. The sturdy 550 cc engine (bore x stroke =85x97mm) has lots of torque. Some new features for 1924 are the 5-inch internal expanding front brake and the forward mounted gear-lever; in the spring of that year a larger, tapered tank is introduced which increases the capacity from 1½ to over two gallons.

The machine on offer is a well-sorted older restoration. She comes with current Dutch registration and is fitted with nice aluminium footboards that were available as extras. The engine code OGH points to March 1924 as manufacturing month. Accessories comprise Lucas acetylene lighting system, rear view mirror and bulb horn.