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).
Royal Automobile Club certificate of performance for 'Artic' Non-Dazzle Headlamps.
| Identifier | ExFiles\Box 61a\1\ scan0256 | |
| Date | 7th September 1926 | |
| (COPY) ROYAL AUTOMOBILE CLUB Certificate of Performance No. 638. (UNDER THE GENERAL COMPETITION RULES OF THE A.I.A.C.R. AND OF THE R.A.C.) “ARTIC” NON-DAZZLE HEADLAMPS. 1st September, 1926. This is to Certify that a pair of “Artic” Non-Dazzle Headlamps was entered for trial by Messrs. The Artic Fuse and Electrical Manufacturing Company, Ltd., of Birtley, Co. Durham. Description of Lamp.—The lamp consists of a body containing a parabolic reflector of the usual form, in front of which is fitted a frame, carrying a number of horizontal parallel slats, blackened on the upper surfaces and polished on the under surfaces. These slats are tilted slightly, so that the edges nearest the source of light are somewhat higher than the forward edges. In front of these slats is a moulded front glass of special design. The extra weight of a lamp fitted with the device and/or cover and above the weight of a standard parabolic lamp, was found to be approximately 2 lbs. The front aperture of the lamp was 6¾ in. When tested the lamps were fitted in the usual position on a car, their centres being 23½ in. apart and 27½ in. from the ground. Source of Light.—The actual candle-power of the bulbs was tested at a voltage of 12.26 (the voltage during the trial) with the following results:— Near-side bulb 24.3 watts | 30.7 candle-power Off-side bulb 24.2 „ | 31.2 „ } 61.9 total candle-power at source. Results of Test.—In order to appreciate the results obtained, it must be remembered that the ranges, widths, etc., are those at which the Standard Disc* can be seen, and that the illumination required to render the disc visible is the same as that required to show up a typical object on the road. The figures, therefore, represent the ranges, etc., at which a driver using these lamps, would pick up such an object. (a) Ranges and Corresponding Widths of Beam. Height from ground | Range (feet) | Width (feet) --------------------|--------------|-------------- 1½ feet... | 259 | 11 3¾ „ ... | 174 | 18 4½ „ ... | 125 | 21 6 „ ... | 92 | 14 8 „ ... | 79 | 11 (b) Side Illumination. Ranges at points 15 feet, 20 feet and 50 feet§ from the centre of the beam. Distance from centre of beam | Height from ground | Range feet -----------------------------|--------------------|------------- 15 feet... | 3¾ feet | 107 15 „ ... | 6 „ | 63 20 „ ... | 3¾ „ | 82 20 „ ... | 6 „ | 55 50 „ ... | 3¾ „ | 42 (c) Distance from the lamps at which the main beam appeared to meet the road ... 10 feet (d) Width of beam 150 feet from the lamps at 3¾ feet from the ground ... 26 feet (e) Visibility or otherwise of the disc placed 1 foot from the ground, 5 feet forward from the lamps and 10 feet to each side of centre of beam ... Visible (f) Dazzle.—The dazzle from the lamps prevented an observer, who was advancing towards them down the centre of the beam (eye-level 4½ feet), from seeing the disc placed 6 feet to the side of, and 6 feet behind the lamps, until he had approached to within 160 feet of them.† †The range at this height was 125 feet. § In addition it was found that the disc remained visible when moved down the 50 ft. line towards the car, until it had reached a point 8º from right angles to the car. Interpretation of Results.—To assist in the interpretation of these figures the following examples are cited: (1) A driver using these lamps, when approaching a pedestrian so dressed as to be seen only with difficulty, would be able to pick him out when 174 feet from the car, provided he was no further from the centre of the beam than 9 feet (i.e. half its width); (2) the driver would see a pedestrian stepping off a kerb into a road 30 feet wide when 107 feet away; (3) on approaching these lamps (eye-level of 4½ feet) blinding effect ceased when 160 feet away from them. (* The British Standard Disc, formerly known as the R.A.C. Disc, was used.) (Signed) F.{Mr Friese} P. ARMSTRONG, Secretary. (Signed) ARTHUR STANLEY, Chairman. Pall Mall, London, S.W.1. (Signed) GEO. W. WATSON, Chairman of 7th September, 1926. Technical Committee. (Copyright.) | ||