Norton Commander (motorcycle) Norton Commander (motorcycle) The Commander was a Norton motorcycle with a Wankel rotary engine. The first Norton Wankel motorcycle was the 1987 air-cooled Classic, built as a special edition of just 100 machines. It was followed by the air-cooled Interpol 2 model. The Commander was a liquid-cooled successor to the Interpol 2, liquid cooling being adopted for greater power and reliability. The Commander's final-drive chain was protected by a full enclosure. Some cycle parts (such as front wheel, forks & brakes) were bought-in Yamaha items. Two types of Commander were built. The P52 was a single-seat model equipped for police
Tuning fork Currently, the most common tuning fork sounds the note of A = 440 Hz, the standard concert pitch that many orchestras use. That A is the pitch of the violin's second string, the first string of the viola, and an octave above the first string of the cello. Orchestras between 1750 and 1820 mostly used A = 423.5 Hz, though there were many forks and many slightly different pitches. Standard tuning forks are available that vibrate at all the pitches within the central octave of the piano, and also other pitches. Well-known tuning fork manufacturers include Ragg and John Walker,