From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Comparative tests on the power of light of various types of head lamps.
| Identifier | ExFiles\Box 61a\1\ scan0011 | |
| Date | 19th October 1914 | |
| From Exp. Dept. Copies for: J.{Mr Johnson W.M.} R.{Sir Henry Royce} Da.{Bernard Day - Chassis Design} Na.{Mr Nadin} X.1357 Wor{Arthur Wormald - General Works Manager}/Hy{Tom Haldenby - Plant Engineer}31/L191014. Oct. 19th. 1914. X.1357 Report on comparative tests on the power X.1369 of light of various types of Head Lamps. The test described below does not necessarily prove which lamp would be the best to drive by on the road, but at the same time a lamp which does not give good results in these tests could not be a really good driving light. The tests were made by photometry similar to the grease spot test, but instead of a grease spot we used a screen made of a piece of Bristol board. A small star shape aperture was cut in the centre of the board and a piece of white tissue paper was pasted on each side covering up the aperture. We used as a standard of light a small "F" type C.A.V. head lamp fitted with a 12 volt 24 C.P. Lucas Osram bulb. This standard of light was fixed 10 feet from the screen and focussed on the star shaped hole. The lamps to be tested were mounted on a trolley at the other side of the screen and moved about until the star was rendered invisible due to the light on each side being equal. The distances were taken and are recorded in the tabulated list attached hereto. The results only give the power of the central beam of light and one must bear in mind the nature of the x 1357. | ||