Triumph 1924 SD 550 cc side valve combination frame # 336253 engine #94110
The SD (Spring Drive) was in fact a somewhat modernised version of the famous model H, which had grown out of the “Trusty” veteran Triumph. By the mid-twenties belt drive was losing its appeal to many motorcyclists, so Triumph designed a model with chain secondary drive.
The primary chain is protected by a well-engineered aluminium case and runs in an oil bath to minimize maintenance of chain and clutch. The powerful 550 cc engine (bore x stroke =85×97) has lots of torque.
The machine is equipped with three speed Sturmey Archer gearbox, 26×3 beaded edge tyres and full electric Lucas lighting, an expensive accessory in those years.
The stylish sidecar is a “ Whitley” .
This SD combination is a fine example of high quality twenties British motorcycle technology .