PROPER FOCUSSING.

Hawera Star, Volume XLVII, 24 March 1928, Page 14

PROPER FOCUSSING.

ELIMINATION OF GLARE.

The following interesting article on the elimination of glare from motorcar headlamps by proper fbcusing has been supplied by General Motors, Melbourne.

Motor headlights are so easily adjusted that the motorist is rendering an injustice, not only to himself, but to fellow drivers, by not obtaining the full illuminative qualities and preventing glare. It is impossible for a driver to get maximum road illumination from glaring headlights, because part of the light rays are projected into the air at a comparatively high distance from the ground, where they are naturally of no value to the driver and a source of annoyance to the passing motorist. Once the theory of the reflector is understood, it is simple to adjust the bulbs in the reflectors for correct focus

If all lights were correctly focused and tilted slightly downward there would be no necessity for dimming lights, as the light rays would all strike the road, and any that reached the eyes of another motorist would be too weak to cause annoyance. The method of correctly focusing a headlight can be easily explained. First be certain that the device’ for moving the bulb backward and forward in the reflector is free from rust and properly lubricated. Usually this adjustment is made by means of a screw, the head of which is accessible from the rear of the headlight. Make certain that the bulbs used are capable of adjustment in the lamp to which they are fitted, by using the lamp recommended bv the car manufacturer.

if it is necessary to purchase a bulb in an emergency, the position of the nlament witn relation to the prongs on the side of the base is as important as tiie voltage and candle-power. To focus, p.ace the car on level ground about, 20 feet from a light-coloured manic wall, and remove the headlignt lenses unless they are plain glass. Disconnect or cover up one lamp and test each separately, escrow the bulb iorward as far as it will go, and a black spot wid appear in a ring ot light on tne wall. Then screw tne bulo back siowiy until the black spot just disappears. Next screw the bulb still iurtner baciv anti the black spot reappears in a ring of light.

finally screw the bulb forward again until tne spot just disappears, and the .amp is correctly iocused. Results other than these indicate that the bulb is unsuitable. if the filament is shaped like a letter V the lamp socket should be set with the V in a horizontal plane. Tne purpose of the V is to make the beam of light cover more road surface.

The top of the light beam on tho wall should be no higher than tho top of the lamp of the car. The latest cars have an adjustable bracket for raising or lowering the light beam, but on older models it is sometimes necessary to slightly bend the headlamp brackets to' get the beam down where it belongs, which is about four feet high at a distance of 25 feet. After both lamps have been adjusted the lens may he replaced and the driver can rest assured that his lights will not glare.