The 500cc two valve two-port OHV Model TT was developed by Victor Horsman, a Brooklands racer and tuner. His design replaced the previous Riccardo Model R.
This two-valve design would be the basis of Triumph engine design until Val Page’s models in 1934. Between 1923 and 1926, Victor Horsman developed and raced his own version of an overhead valve cylinder. By 1924, he had also built a new frame geometry. With displacement variations of this engine of 498cc, 596cc, 599cc and 607cc, Horsman broke many British and World solo and sidecar speed records during 1923 and through to 1926. It was not long before Triumph approached Horsman and negotiated the acquisition of his design for £1,500. Triumph immediately announced that they would be putting the famous ‘Victor Horsman’ Triumph into production. Thus, in October or November 1926, they commenced the production of what was debatably Triumph’s most-successful sporting Vintage Triumph. It was certainly Triumph’s first modern motorcycle that offered a 500cc two valve, two-port, OHV Model TT. The Model TT continued for the 1928 season, unchanged apart from a Doherty quick-action twist grip being a standard fitting and the fuel tank changing, with all other 1928 models, to the new colours of black with saxe blue (sky/pale blue) panels. Also, the previous nickel-plated wheel rims became gold-lined black. Most Triumph models had their flat-tanks replaced by saddle tanks for 1929, and the Model TT was no exception and was renamed as the Model ST (Saddle Tank). It is believed that approximately 450 model ST's were produced, unsurprising really considering the economic situation and that these were bound for competition. Courtesy Webbs NZ