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).
Reprinted article from 'The Motorist' magazine reviewing the 'Bicolour' fog lamp screen.
Identifier | ExFiles\Box 61a\3\ scan0157 | |
Date | 30th November 1935 guessed | |
Reprinted from “THE MOTORIST”. FOG LIGHTING approached from a NEW ANGLE WE have tested a number of appliances and fittings designed for making fog driving easier, and of those of which we have either seen details or tried, this one, Bicolour, represents the fifth different principle. One of the first we tried consisted of a small spot-light type of lamp giving an intense, extremely concentrated beam of white light intended to penetrate fog by sheer power of light; another was on the colourfilter principle. Another of which we have details but have not yet actually tried, consisted of a golden-tinted reflector with a clear bulb and lens; there are also tinted bulbs; but Bicolour is the only means yet brought to our notice in which the light is both tinted and deliberately diffused for penetration. The manufacturers of Bicolour claim that only a completely diffused light can actually penetrate fog. We agree that there is some basis for this claim, as it was stated in our December issue, under the heading “Driving in Fog,” that we had made reasonably good progress through thick fog on a long journey by using the dipped and diffused beams of head-lights fitted with double filament bulbs. The effect was advantageous. We found that Bicolour certainly did diffuse the light in a very useful manner and the palely-tinted light did penetrate fog, although the fog on the day the light was tried was not very dense. It was, however, thick enough to give an indication of the benefits of the Bicolour screen. The manufacturers also claim that with Bicolour visibility up to 25 yards in the worst fog can be obtained. Well, that is a pretty big claim. We have not yet experienced the worst type of fog this year, but we did get a light of extraordinarily long range in the moderate fog mentioned. After driving and finding the Bicolour effect very useful, we stopped the car, and noted the distances at which objects could be seen on a cross road. At 45 to 50 yards range objects could be seen as rather indistinct bulk. At 30 to 40 yards the objects became distinguishable, and at 25 to 30 yards they could clearly be seen. We should expect proportionate results in thicker fog. Although it seems that Bicolour is meant to be used in fog with the head-lamp or lamps dipped, we recorded the above results with the one dipping head-lamp in its normal, long-distance, position, and the other lamp disconnected. The diffusion of the light would be advantageous in clear weather preventing dazzle, when in the normal position, and giving a wider beam of more useful radius when the lamp is dipped, also reducing the contrast in beam length generally observable between normal and dipped lamps. With the car stationary, we could walk in the beam of the light towards the car without being dazzled. The principle of Bicolour is, as stated, a combination of tinted filtering of the light and diffusion of the beam. Bicolour consists of an unbreakable screen, semi-circular in shape, with a long and short slot cut each side concentric to the diameter, and moulded on a base of what appears to be wiremesh of approximately one-tenth of an inch square apertures. The filter tints the light, and the wire mesh diffuses the beam. The screen is fitted to the upper half of the headlamps, and is held in place by the pressure of the lamp rim against the edge of the reflector. There are three rubber pads on the edge of the Bicolour screen to assist in retention of the screen. Fitting is, obviously, a simple matter of taking off the rim and lens, placing the Bicolour screen in position, and replacing the lamp rim and lens. It is our intention to amplify these remarks when we have had the opportunity of trying this fitting during denser fog. Incidentally, we tried an experiment with the two screens. We fitted both screens in one headlamp, thus completely covering the diameter of the lamp and disconnected the offside lamp. This gave a reasonably good effect, but was not so good as when only the upper half was covered, showing that the diffusion and subsequent mingling of the tinted rays from the upper half of the reflector with the clear rays from the lower part of the reflector were of greater lighting value. Please turn over | ||