Did you know the state of railway signal lamps back in the 19th century?
The advent of the electric incandescent light was regarded as the future during this time (1881). However, most of the material was still necessarily on oil lamps. While it is noticeably true that lamps have made slow progress in terms of design, it should be made known that lamps are simple, elementary devices that are not improved for reasons of practicality.
There are in fact, types of lamps that remain in use for more than a decade which have not been modified (Welsbach incandescent mantle caused fuel lamps to be of equal brightness or brilliance as the electrical one.) The significant change that was taking place at that time (1881) was the replacement of vegetable and animal oils by mineral oils. This change was seen as a significant and more economical improvement in illumination.
For earlier railway systems, Admiralty-like candles used at sea were already obsolete for railway use mainly because they don’t burn long enough and are not bright enough. The brightness of the flame was due to the incandescent particles of carbon created when the flame’s heat decomposed the oil. A luminous flame is produced by illuminating gas’ heavier constituents. Natural gas at present day only has pure fuel which is useless for illumination.
Limited Use Of Hydrocarbon Due To Cost
Vegetable oils were the main lamp oils used in Britain at the time while the US railways used lard oil. Whale oil proved to be very costly as that time. Petroleum paraffin oils or hydrocarbon had been introduced to Britain by Young, who distilled the illuminants from oil shale near Edinburgh or oil from wells near Nottingham. And because this superior illuminant comes with a high price tag, it was seldom used on railways.
Kerosene As A Cheaper Alternative
While American kerosene was cheaper, the problem was its being more explosive and as such would not be advisable for railway use. Vegetable oils continued to be used in head and tail lamps, and for carriage lighting for some time.
The Need To Improve Lamps Used In Railways
In great need for improvement was the optical system of railway lamps but because of economic issues, progress had not been made. The traditional lamp was considered a little better than a common stable lamp. Its light was little concentrated by a cheap bull’s-eye lens which described most lamps for the railways.
The short life and unreliability of incandescent lamps with carbon filaments have caused electric lamps not to be used for signaling for many years. Faure lead-acid battery was thought to be of use in place of the old oil reservoir but batteries do not have the energy density of fuels, so it never materialized. Improved incandescent lamps became the railways’ reliable light signaling instrument.
Change To Red, Green And Yellow Lights
In 1881 white light was used as the color of safety but because of the confusion with other white lights they were changed to green fifteen years later. The segmented lens called Fresnel lens, borrowed from nautical signaling was just introduced into the market. The invention of the searchlight signal in the United States where colored spectacles are mounted on a separated relay armature selected yellow, red, or green light to be projected by a single optical system. A hand lantern with red, white or green lights displayed at the press of a button became a best-seller in 1881.
Do you know of other facts surrounding railway signal lamps?