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).
The design and function of the Trippe Lamp for optimal performance in fog.
| Identifier | ExFiles\Box 167\1\ img010 | |
| Date | 2nd September 1935 guessed | |
| THE TRIPPE SAFETY SPEED LIGHT CO. LTD. LIVERPOOL. 3. THE TRIPPE LAMP IN FOG. It has been established that the densest fog does not reach below 12" from the ground, and at 24" it is considerably less dense than at higher levels. Visibility at ground level is normal at all times, despite the densest of fog. Provided that any light used can be located in such a way that none of the free light from the filament, or the reflected light from the reflector systems can be prevented from rising above, say, 18" from the ground, trouble from refraction and diffusion caused by the moisture globules, can be completed avoided. Working on these lines, as the TRIPPE reflector system already makes it, impossible for there to be any upward-going reflected rays, a cowl has been produced and included, which effectively cuts off the upward going rays emanating from the filament itself, which do not strike the Reflector system normally at all, as in sketch below. - Location of Cowling. Free Rays area. The area shaded indicates the allocation of the mask on the bulb, and it will be moted that only light which is not either utilised on the reflector, or goes in an upward or forward direction, is masked, and the area so covered is exceedingly small, compared to the lit area of the reflectors. The nett result is that if this Lamp is mounted suitably, i.e. as close to the ground as practicable, say, 18" or below, and aimed for the beam to be parallel with the ground, there is no light projected from this level throughout the path of the beam. As this automatically obviates the trouble normally caused by glare and diffusion, the whole power of the light can be utilised at all times, irrespective of conditions, the use of coloured screens or other palliatives being both undesirable and unnecessary. In order to enhance this effect, a special lense has been developed which has the effect of spreading out the beam into a fan, and making the cut-off extremely sharp. This wide ray, as opposed to the usual expedient of concentrating the ray, gives adequate illumination at the side, while maintaining enough ahead light to avoid running into obstacles seen too late. | ||