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Fig. 274.—Simple Methods of Eliminating Headlight Glare.
the term most frequently used to express the blinding effect of pov ful headlights. Perhaps the best definition yet given is the following: “A glaring light is one which interferes with the acuteness of vision of adjacent objects.” Glare is due chiefly to the ultra violet rays of the spectrum. It has therefore been proposed to use a yellow lens or front glass on head lamps, which absorbs the ultra violet and blue rays and transmits only red, orange, yellow and green rays. This special glass used for the purpose transmits the red and other rays with very little absorption, hence the total radiation is not materially reduced. Another fact to be taken into account is that the red rays penetrate farthest through a misty or foggy atmosphere, as is shown by the fact that the sun when rising or setting always appears red. Hence the penetration of the beam of the headlight is not much, if any, diminished by the yellow glass.
Methods of Reducing Glare.-By using two bulbs in the headlights, a larger one in focus and a smaller one out of focus, as in the Gray & Davis lamp shown at A, Fig. 274, both an intense light for country driving and a subdued, non-glaring light for city driving can be obtained from a single lamp without any shading device and without waste of current. This arrangement gives the car the equivalent of both head and side lights, reducing the side lamps to the small bulbs.
Another principle which may be employed for preventing annoying glare is that of making certain portions of the front glass of such form that they will disperse the rays falling upon them, rather than transmit them without deflection. Thus by making the top half of the glass of grooved or corrugated form the top half of the beam will be broken up and only the bottom half remain, and the lamp can then be so adjusted on its bracket that no part of the beam rises more than a certain height above the road surface. This principle of limiting the maximum height of the shaft of light works all right on level ground but it is ineffective when a car approaches the crest of a hill, which is one of the critical conditions in night driving. In such a case it would certainly be better if the driver had some means at his command for instantly reducing the intensity of the projected beam. Sometimes the lamp is provided with a frosted glass, having only a small portion of clear glass as shown at B, Fig. 274.
An early method of dimming electric headlights consisted in reducing the voltage applied to them, either by connecting the two · lights in series across the battery or by introducing a resistance in the circuit. Connecting the lights in series is advantageous on account of the current economy resulting therefrom. There is one objection to it, however, namely, that in case one filament breaks,
Fig. 275.—Miscellaneous Fittings to Use in Connection with Electric
Headlights to Reduce Objectionable Glare.
both lamps will go out instantly and the driver, therefore, will be enveloped in more or less darkness. This, however, is a less serious matter in city driving than it would be in country driving, because of the street lighting.
Another dimmer consists of a shade of translucent material, as depicted at the bottom of Fig. 274, similar to a window shade, which is rolled up in a tube above the lamp when not in use and is drawn in front of the lamp by means of a cord connection to a foot-operated device when it is desired to dim the lights. When the foot pressure is removed from the pedal a spring automatically rolls up the curtain in the tube.
The method shown at A, Fig. 275, involves the use of a lamp with a readily movable reflector which can be moved out of focus with respect to the bulb for city work, or where the anti-glare laws are stringent. When the searchlight effect is wanted it is very easy to bring the reflector in focus again. A foot-controlled form of dimming switch is shown at B. This is intended to be placed under the toe board, having the plunger project through where it can be easily depressed. Such devices may work either by interposing a resistance in circuit or by coupling the lamps in series momentarily.
The Amco auto light deflector, outlined at C, is a small white enamel reflector that is snapped on the lower side of an electric bulb. It deflects all light rays to the upper half of the lamp reflector from which they are cast outwardly and downwardly, as at Fig. 276, and eliminating all glare. By this principle the strength of the light is not decreased, the road being as well illuminated as before.
The Amco auto light deflector adequately meets all laws governing headlights and has been highly recommended by experts. The Department of Motor Vehicles of the State of New Jersey is one of the latest indorsees.
The use of shutters or curtains naturally suggests itself, and a number of dimmers of this class have been brought out. The NoDaz, shown at D, Fig. 275, consists of a series of translucent screens which normally stand parallel to the axis of the beam of light so as not to obstruct the light, but upon pushing a button which energizes an electro-magnet, they are placed at right angles to the beam of light, thus placing a curtain of translucent material in front of the lamp. The apparent source of light is then a circular plane of considerable diameter, which gives a mellow, diffused light claimed to be sufficiently strong for driving at ordinary speeds and unobjectionable to other road users. The operating mechanism consists of a small solenoid placed out of sight close to the screen.
The Aderente, illustrated at Fig. 275, E, is a non-blinding device which is so arranged as to cut out the glare and at the same time have many of the rays of light thrown directly ahead of the car in order to illuminate the roads. According to the manufacturer the device is not a dimmer, but rather increases the power of the projected light by deflecting the rays to the road which
would otherwise be thrown upwards or in a straight line ahead of the car, thereby blinding approaching pedestrians or drivers. The device is attached to the lamp door, and although made of metal, is said to have the appearance of cut glass. It does not require adjustment and does not
have to be touched Fig. 276.—Illustration Showing How the Use
whether the car is beof Shields Under the Lamp Bulbs Reduces Glare by Deflecting the Light Rays to the
ing driven through the Ground.
city streets or in the
country. As the device is attached inside the door, it should not require frequent cleaning.
Electrical Alarms.- The old style hand-operated bulb horn has given way to the more easily actuated electrical signals since the use of electrical current has become general in the modern automobile. These signals operate on two principles: they may be the buzzer type, as shown at Fig. 277, A and B, or may be of the form having a mechanically actuated diaphragm, as shown at C and D. The buzzer type horns actuate the diaphragm by magnetic attraction just as an electric bellhammer is actuated by the magneto. In one form the diaphragm is attracted directly by the magnet, in the other, shown at B, the sound-producing element is vibrated by a plunger rod attached to an armature. The mechanical type in which the diaphragm is moved by a ratchet wheel is