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).
Principle and fitting instructions for an anti-dazzle bulb.
| Identifier | ExFiles\Box 166\4\ img241 | |
| Date | 4th January 1939 guessed | |
| THE PRINCIPLE THE BULB consists essentially of two light points controlled from the same circuit, and supplied in such a way that two distinct light centres are formed. These two light points are sheltered one from the other so that the rays from each point fall on no more than half of a parabolic reflector positioned behind them. Thus by virtue of the optical system of the bulb, when mounted in a parabolic reflector, the whole of the reflector service is used, but all light is projected forward and downward in the plane of the lower half of the lamp. A frontal cowl on the glass of the bulb is used to mask off direct rays from the visable filament where these would not otherwise fall on the reflector surface. In this way, when the lamp is mounted in a vertical plane, the light given is ABSOLUTELY ANTI-DAZZLE - and conforms fully to the Ministry of Transport's Anti-dazzle Lighting Regulations. NO DIPPING - NO DIMMING. THE INSTRUCTIONS The anti-dazzle bulb contained in this carton is scientifically designed to perform in a certain way, and will do so with every success if used as we advise below. PLEASE FOLLOW THE INSTRUCTIONS CAREFULLY. 1. Insert the bulb so that the arrow points upward to the word "Top" on the cowl when in-position. 2. Cover the top half of the lamp glass lense with paper or handkerchief, etc. 3. Adjust focus of lamp until a spot is obtained on a wall or door some 30-ft. away. 4. Uncover lense and put final adjustment on focus, which should be a substantially flat-topped beam. 5. A fluted glass on the lamp is preferable for best effect but is not essential. 6. It is advisable that the whole lamp should be checked to ensure that it is aimed in a horizontal or slightly downward direction. 7. The above instructions apply both to headlamps, or any auxiliary lamp. When the Rode Bulb is fitted as above, the back half of the filament illuminates the lower half of the reflector only, and the front half filament the upper half of the reflector, and the combination projects a substantially flat top beam. The lamp so adjusted will give a light that conforms to the Minister of Transport's Regulations for prevention of dazzle, and will give adequate driving light in all conditions and in fog. | ||