Recently acquired----This speed indicator was installed on most French steamengines by the end of WWI
All such devices were speed recorders as well as speed indicators. The record was kept on a paper tape that could be unrolled and examined at the end of a run to provide evidence of the speeds attained on the journey. Accidents had occurred on lines with steep gradients and sharp curves, and it was expected that speed recording would lead to better control of train speed. Some French railways provided bonuses for keeping time and for economy in fuel use, and it was suspected that such incentives might lead to excessive speeds at times. Knowing that one's performance could be examined was a strong motive for keeping within the speed limit.
The most popular speed recorder turned out to be the French-designed Flaman recorder, in which the tape was driven by the locomotive wheels at the scale of 5 mm per km. The speed was determined by integration, as in the Hausshaelter recorder, but with intervals of 3.6 seconds. The integration is performed by a ratchet wheel driven by a square cam, so that the wheel moves forward four spaces for each rotation of the cam. The action is the same regardless of the direction of travel. Another shaft, driven by the clock, controls the resetting of the ratchets. The scale of the speed curve is 0.4 mm per kmph, and the range of the recorder is 0 to 130 kmph. This is the lower curve on the chart, showing speed as a function of distance, v = v(s).
This item is 2 feet tall and weighs about 80 pounds.