Interessante argomento :http://en.wikipedia.org/wiki/Railroad_chronometer







The rise of railroading during the last half of the 19th century led to the widespread use of pocket watches. Because of the likelihood of train wrecks and other accidents if all railroad workers did not accurately know the current time, pocket watches became required equipment for all railroad workers.

The first steps toward codified standards for railroad-grade watches were taken in 1887 when the American Railway Association held a meeting to define basic standards for watches. However, it took a disaster to bring about widespread acceptance of stringent standards. A famous train wreck on the Lake Shore and Michigan Southern Railway in Kipton, Ohio on April 19, 1891 occurred because one of the engineers' watches had stopped for 4 minutes. The railroad officials commissioned Webb C. Ball as their Chief Time Inspector, in order to establish precision standards and a reliable timepiece inspection system for Railroad chronometers. This led to the adoption in 1893 of stringent standards for pocket watches used in railroading. These railroad-grade pocket watches, as they became colloquially known, had to meet the General Railroad Timepiece Standards adopted in 1893 by almost all railroads. These standards read, in part:

"...open faced, size 16 or 18, have a minimum of 17 jewels, adjusted to at least five positions, keep time accurately to within 30 seconds a week, adjusted to temps of 34 °F (1 °C) to 100 °F (38 °C), have a double roller, steel escape wheel, lever set, regulator, winding stem at 12 o'clock, and have bold black Arabic numerals on a white dial, with black hands."

Railroad employees to this day are required to keep their watches on time, and are subject to spot checks by their superiors at any time. Failure to keep their watches on time can lead to disciplinary action, due to the gravely serious safety issues involved.

Additional requirements were adopted in later years in response to additional needs; for example, the adoption of the diesel-electric locomotive led to new standards from the 1940s on specifying that timekeeping accuracy could not be affected by electromagnetic fields.

e gli orologi delle ferrovie statali?

Per chi non lo sapesse, visto che siamo in tema, fu proprio l'espansione delle ferrovie a rendere necessaria l'adozione dell'ora legale mondiale.