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Date of manufacture: around, ca: 1900
This portable rev counter has a wooden handle at one end. The tip of the other end is pressed against the end of the shaft whose revolutions are counted. In the middle there are two wheels. When the bottom wheel turns once, the top wheel moves one tenth of its circumference. The edges of both wheels are divided into 100 equal parts. Each tenth division is numbered.
The lower wheel is labelled: DIZAINES (tens). Its divisions are numbered clockwise from 0 to 9 on the inside and counterclockwise from 0 to 9 on the outside. The top wheel is labeled: CENTAINES (hundreds). Its divisions are numbered counterclockwise from 0 to 9 on the inside and clockwise from 0 to 9 on the outside. A spring disengages the wheels to allow zeroing. A mark on the back of one wheel reads: A. Sainte / Paris, and two more marks: AS linked and anchor.
By counting the number of revolutions on the shaft of a steam engine and knowing the steam pressure and the properties of the engine, steam engineers could calculate the power of the engine. A. Sainte patented a device for this purpose in 1877 and exhibited it at the World's Fair held in Paris in 1878.
Measurements: 11.5 cm x 5.2 cm
Excellent almost new condition, in its original box, but two pieces are missing. See the images to get a correct idea.
It is sent by certified mail with a tracking number. 67394159
