Rotation is transmitted from the shaft whose speed is being recorded to tachometer shaft A through shaft B and bevel gears 1 and 2. Hinged to shaft A are levers 3 and 4 with weights 3' and 4' at their ends. When shaft A rotates, the centrifugal force spreads weights 3' and 4' and sleeve 5 is shifted to the right together with lever 6. Motion is transmitted simultaneously to hand 7 (through lever 8, segment gear 9, rigidly attached to lever 8, and pinion 10) and to pen 11 (through gears 12 and 13, gear rack 14 and slider 15). Slider 15, carrying pen 11, moves along guides 16. Drum 17 is driven at constant speed by clockwork. Spring 18 returns levers 3 and 4 to the initial position. Thus the angular velocity of the shaft being tested is simultaneously indicated by hand 7 and recorded on drum 17.
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