The R.AUCU Tests of Headlights.
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An Interesting Series of Photometric Trials in the Grounds of the Crystal Palace.
In our last issue, we published a list of the. entries which had been made for the Royal Automobile Club's tests of headlights. These tests have now been carried out successfully. On the nights of Monday and Tuesday last, the entrants submitted their lamps to the adjudication of a number of the members of the Technical Committee of the
: Capt. R. K. Eagnall-Wild, R.E., Messrs. G. H. Baillie, Mervyn O'Gorman, A. G. New and Dr. W. Watson' F.R.S., with, as usual, Mr. J. W. Orde as general organizer. The trials were held
ou the Firework " terrace at the Crystal Palace, and they commenced at 10 p.m, each evening—after the fireworks had " gone off," it is well to note.. Amongst the interested spectators, we noticed Mr. Worby Beaumont, Major Lloyd, Supt. Bassom, and a representative of Mr. John Burns from the Local Government Board.
The avowed object of these Club tests was " to encourage the use of efficient headlights," and the means adopted to secure this result was the careful compilation of data concerning the "dazzling effect," the range of illumination, the horizontal dispersion of the beam, and the absence of back reflection of over 40 examples of the workmanship of various makers—newcomers, or established.
The range of illumination and the horizontal dispersion of the beam were carefully ascertained, by means of a simple form of photometer. Along a stretch of gravelled road, facing the Palace, an exaggerated form of tape measure was extended ; this was 100 yds. in length, and boldly marked in yards. At one end of this strip was placed a focussing screen, on which a black vertical bar was prominent directly over the line of the tape measure; at the other end, a timber balk was placed across the measure, in order that a car might run exactly up to its position with facility ; between these two points, a small wheeled truck, carrying the photometric device, was adjustable.
The photometer in use consisted of about 2 sq. ft. of white blotting-paper,
upon which were marked with grease a number of small stars. This screen was illuminated from behind, at a fixed die
tame, by means of a 1 c.p. electric lamp, and, in the first place, was placed exactly facing each headlamp which was tested. The whole truck was then wheeled directly forwards, or backwards, until the stars first began to show on the surface of the screen owing to the balancing, at 3 ft. above the road surface, of the brilliancy of the opposing illuminations from the headlamp and the photometer lamp respectively. At half this distance from the lamp under test, further records were taken, in a similar manner, to the right and left of the centre line, at heights of 3 ft. and 4 ft. 6 in., in order to ascertain the extent of the horizontal dispersion of the beam. The decision as to the actual balancing of the two forms of illumination on the screen of the photometer, when the stars were first discernible, rested with Capt. BagnallWild, who acted as chief " star-gazer."
The " dazzling effects " were tabulated from optical observations that were made by Mr. Mervyn O'Gorman, who conscientiously located the " dazzle " over the top of a 4 ft. 6 in. broomstick along a line ruuning parallel to the tape measure and 6 ft. to its off side. It was his duty to note the distance, along this line in front of the headlamp, at which its light began to prevent him from seeing a black device on a brown screen, which screen was fixed 6 ft. behind and 6 ft. to the off side of the said headlamp. This screen was faintly illuminated. We trust Mr. O'Gorman did not suffer unduly from excessive fatigue of the retina towards the end of the tests after midnight. Slight errors in this respect would not be of importance, but it is, at least, open to question if a tired eye would not be more easily " dazzled " than a refreshed one? We do not essay to state in which sense an error might occur.
Other features of these trials were the interesting comparisons that it was possible to make between gold-backed and silver-backed mirror lenses, and the eclipsing effect of various patent antidazzling devices. The measurements taken on the same lamp, with and without the screening device in operation, showed in many cases most remarkable differences. The petrol-oxygen lamp's illuminating powers were stupendous.
Comprehensive as were these tests, we. in all seriousness, suggest that it would have been most advisable to have devised some scheme whereby marks might have been awarded to those acetylene installations giving rise to the least offensive odour. One of the principal objections of many people to the use of acetylene lamps is their occasional objectionable odour from leakage, and careless tilling or cleaning. During the trials, with so many lamps under way, the state of the atmosphere at times was almost unbearable. Why inducements to abate this undoubted nuisance shauld not have been offered at such an excellent opportunity it is difficult to explain.
It was originally anticipated that the proper testing of each lamp would occupy at least half-an-hour, and that part of the trials would have to be conducted in September next, but, chiefly owing to the careful and skilful preparations made by Mr. Orde's technical staff, under the control of Mr. H. H. Gregory, few lamps took longer than 10 minutes. There will. therefore, in all probability, be no need for further tests at a later date. Excellent weather conditions prevailed on both the Monday and Tuesday evenings. The rules provided that all the lamps entered should be presented for trial, mounted on a car or suitable stand.
The Club will issue a certificate of performance for each lamp, but as the avowed object of the trials was, primarily, the acquisition of useful data, the marks which are awarded will not, in all probability, be published. We now mention a few of the special features on some of the lamps.
Bleriot Ltd., of 54, Long Acre, W.C. was represented by a No-glare acetylene lamp, an electric lamp, and the new petrol-oxygen lamp. All these gave powerful illumination, that from the last named being produced by a beam something like 350 yds. low:.
The Badger Brass Manufacturing Co., of 32-34, Featherstone Street, E.C., entered several of their Solar lamps. The special short-focus lens mirror, its method of mounting, and the means provided for its accurate adjustment, are some of the features to which the makers draw particular attention.
S. Smith and Son, Ltd., had two handsome acetylene headlamps in the trials ; we reproduce photographs of them herewith. Both lamps were of the self-contained type, and capable of holding 13 oz. of carbide. In each case, a gold-plated reflector was fitted behind the light, and the larger 7i in. lamp also had a goldplated parabolic reflector in front.
Dunhill's London, of 359-361, Euston Road, were represented by one of their new lamps to which the name " Dreadnought " has been gvien. Amongst the special features claimed by the makers are the very simple nature of the design. the provision of special filtering des-ices and the accessibility of all the parts for cleaning purposes. This lamp, which was tested on a stand, gave good results during Monday's test.
Brown Brothers, Ltd., of 22-34, Great Eastern Street, E.C., had two of its wellknown Autoelipse acetylene headlamps tested amongst the first batch on Monday night, and the complete control of the projected beam, by the simple lowering of the eclipsing shutter behind the burner, was effectively demonstrated in the trials. it is interesting to note that this particular make of headlamp has found groat favour with most of the large companies for their fleets of private-hire cars; another special application is instanced by the number of these lamps which has already been supplied for use upon motor mail-vans and fire-engines. We illustrate the " Autoclipse " on the preceding page. It deservedly enjoys a large sale amongst supporters of THE COMMERCIAL MOTOR. The makers offer a week's trial to intending purchasers.