Description

A rare and fine Tachygraphe (French) or Tachograph in brass complete with dividers and case.

Signed “TACHYGRAPHE, E. de Louvencourt, Inspecteur de Chemins de fer de l’Est”, this instrument consists of a straight edge, hinged parallel rule, scaled vernier caliper/protractor with gradations from 0-100 and a pair of 4″ (10 cm.-small) dividers. 

By plotting distances from maps/charts/routes over time and/or speed over time, the variations/deviations of revolutions per minute (RPM) can be calculated using this unique instrument. 

Originally proposed and patented by Max Maria von Weber of Germany in 1835, the instrument is based on the Daniel Tachograph of 1844. With the advent of electricity, these instruments were re-invented and re-named as tachometers.

P.S. Engineering error in construction in that the vernier arc has to be manually assembled each time using a double pin location hole and screw. This could easily have been made as a folding arc but the case may have been too large/wide ???

The simulated sharkskin case measures 10 x 3 x 3/4 inches (25 x 7.5 x 2 cm.) with both eared C-hooks intact. (further stamped Louvencourt, S.G.D.C.).