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).
Comparing slot illumination versus glass edge illumination on Bentley instrument boards.
| Identifier | ExFiles\Box 138\2\ scan0226 | |
| Date | 4th May 1933 | |
| X231. To Wor.{Arthur Wormald - General Works Manager} from E.{Mr Elliott - Chief Engineer} c.c. Sg.{Arthur F. Sidgreaves - MD} Hs.{Lord Ernest Hives - Chair} By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Wst. (Sg{Arthur F. Sidgreaves - MD} and By are struck through) EV.{Ivan Evernden - coachwork} By/RD. (EV{Ivan Evernden - coachwork} and By/RD are struck through) re Bentley Instrument Board. By arrangement, a meeting of Hs{Lord Ernest Hives - Chair}/Wst. By/RD. EV{Ivan Evernden - coachwork} and E.{Mr Elliott - Chief Engineer} was held at the Works last night, to compare the instrument illumination of Nos. 1 and 2 Bentley chassis. The large instruments, namely, the tachometer and speedometer on the former are fitted with slot illumination, the remainder being merely flood lit, whereas the second Bentley is fitted with glass edge illumination all round. The slot edge illumination when first received was thought by those who had had the opportunity of viewing it in the dark to be very good, but owing to No. 1 Bentley being hurriedly despatched to France and no other sample being available, it was necessary to arrive at some decision as to what should be instructed for production without being able to make a direct comparison, and so it was decided that the glass edge illumination as supplied on the second Bentley would be the safest plan to follow, as our experiments with the slot system on RR. patches had not yielded the same satisfactory results as glass edge. Last night's experiments confirmed beyond all doubt that the decision aforementioned was a wise one. The slot lighting on No.1. Bentley, although giving a brilliant effect on the dials is far from even as regards the distribution of the light, but its main objection is the large quantity of light which escapes into the driving compartment, and which would be particularly distressing to the occupant of the passenger's seat. The driver also, in the case of a tall man, would be subjected to considerable glare from the two lower slots, which would materially interfere with driving vision. The glass edge illumination of the big instruments on No.2. Bentley, although not perfect, has not these objections, while the small instruments when all fitted with the correct dials will be very satisfactory. It should be realised that it is not an easy task to obtain even distribution of light on very large dials when the instruments themselves must necessarily be crowded | ||