Let's start off by dispelling a myth spread across many Triumph books. The Model H was not the 1914 to 1918 dispatch riders machine for that period of World War One. The Model H was not available until February 1915, and therefore when Siegfried Bettmann received an order from the War Office for 100 machines on the Saturday in xxx it was 1914 models which were available for collection on the platform of the Coventry railway station on the Sunday evening, and those, and following such orders, were what the despatch riders rode until the superior geared Models H became available.
The Model H was Triumph's first model with a gearbox, where gearboxes should be mounted, although not having one of their own manufacture a Sturmey Archer 3-speed box was used.
Some Triumph books say that the Model H was named after Charles Hathaway who designed it. Well, Hathaway would have designed it, for he also designed the earlier models (not Mauritz Schulte, who was NOT an engineer), but it was only logical to be the H model (actually designated Type H) for the Types A through to G had preceeded it and H was the next letter of the alphabet!
Certainly well beloved of WW1 dispatch riders, but they did not coin the 'Trusty' term for Triumph had been advertising their "Trusty Triumphs" from very early in 1910.
Catalogued for the years 1915 to 1924.
Much more substantial than earlier models, and as it was such a 'step up' from those earlier models is claimed to be the reason why the Veteran Class terminated at the end of 1914.
550cc side-valve, 85mm bore X 97mm stroke.
3-speed Sturmey-Archer countershaft gearbox.
Chain drive to gearbox, then belt to rear wheel.
Popular as a solo mount, and with a sidecar due to the engine capacity.
Major changes occurred for 1920 models with a stronger big-end, the addition of a shock absorber on the crankshaft, changed cam profiles,the gearchange lever became frame mounted and the frame was fitted with sidecar mounting lugs.
For 1923 models a larger fuel tank increased the capacity from 1½ gallons to 2 gallons.
Approximate production was 45,000.
Models H still survive in Australia, Belgium, Britain, Finland, France, Denmark, Germany, Holland, India, Italy, Malta, New Zealand, Norway, Spain and South Africa.
For more details, technical information, performance figures, and much more, you really need to refer to the booklet I have written covering these models.