Triumph Pre-Unit Twin, 2020

Description

Aesthetics and Engineering: Pre-1970 Motorcycle Engines Series

Motorcycles entered the public zeitgeist in the early 20th Century as basic, affordable transportation.  They were quickly adapted to the new sport of motorcycle racing, be it oval speedway/flat track/dirt track, tourist trophy on public streets, race tracks, trials, dirt bike and desert racing.  Motorcycle design was driven by the need to increase speed, keep weight low, maintain a narrow profile, and provide adequate suspension.

Between the two World Wars, the evolution of engine designs took on an aspect of engineering aesthetics as with rare exception motorcycle engines were fully visible.  In America, as the original marques declined to just Indian and Harley Davidson, and finally just Harley, the brutish 74 cubic inch vee-twin cylinder reigned supreme, first with finned flathead engines, followed by the “Knucklehead”, “Panhead”, and “Shovelhead” designs all related to the valve train. In Europe, an especially England, the big single cylinder “thumpers” followed by the side-by-side twins of a dozen manufacturers were highly popular.  These engines were elegantly shaped and stylishly black with polished aluminum and a highlight of chromium to offset interesting external engineering features.

The Triumph pre-unit twins were produced from 1938 to 1963.  The designation “pre-unit” refers to the separation of the gearbox from the motor.  In 1964 and later models, the motor casing extended to incorporate the gearbox.  Triumphs were very popular in America up until the introduction of the Honda 4-cylinder bikes.