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).
Improvement of headlamp efficiency by using clear bulbs and lenses instead of frosted ones.
| Identifier | ExFiles\Box 61a\2\ scan0218 | |
| Date | 31th January 1934 | |
| -> Hs.{Lord Ernest Hives - Chair}.. from C. C. to Hn.{F. C. Honeyman - Retail orders} WST 26/11/6. CL/I/31-1-34. HEADLAMPS. ---------- As you know, there has been a good deal of criticism lately of the efficiency of the headlamps fitted on both R-R and Bentley cars. My own car, 20-G-1V., was originally equipped with P80 Lucas headlamps having double filament bulbs which were not very successful as an anti-dazzle device. Moreover, certain difficulties arose because the bulbs were non-standard. Consequently, an opportunity arising to use up these lamps in another direction, I had my car fitted with a pair of RB.{R. Bowen}170.SED headlamps, such as we regularly fit on 20/25 cars, but with 48-watt bulbs instead of the more usual 36-watt bulbs. The bulbs were frosted as, of course, is standard. In spite of the more powerful bulbs I was disappointed with the illumination these lamps gave on the first long run after their installation. Before definitely condemning them, however, I arranged for the car to go to Lucas' own Service Depot. in London so that they might check up the focussing of the bulbs, etc. Lucas, on learning I was dissatisfied with the illuminating powers of the lamps, volunteered the suggestion that I should have new bulbs of the same power, i.e., 48-watt, but clear instead of frosted, and a pair of such bulbs were duly fitted. At the same time Lucas suggested that clear lenses in place of the standard semi-frosted lenses would effect a further improvement, but they were unable to supply off-hand a pair of such lenses. The first time I used the car on a long run at night with the clear bulbs demonstrated the very considerable improvement in illuminating power they gave as compared with the original frosted bulbs. The improvement was such that I arranged for Lucas to be asked why they did not fit clear bulbs as standard. It is appreciated, of course, that frosted bulbs are less likely to dazzle the drivers of on-coming traffic, but this is immaterial because when one meets another car one naturally makes use of the dipping reflectors as an anti-dazzle device and does not rely on the fact of the bulbs being frosted. | ||