ROAD AND WORKSHOP by Handyman
Page 38
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Headlamp Setting
FREQUENTLY on a night journey car drivers flash their lamps at approaching goods vehicles. Yet, in most instances, the heavy vehicle is travelling on dipped headlamps. It is difficult to be quite certain of this until you are almost past the approaching vehicle and this tends to cause ill-temper between car and lorry driver. The lorry driver so treated will often retaliate by promptly blinding the lower-seated car driver will full headlamps just to prove that he was already dipped. He may pile it on further by letting the other man have the benefit of two 60 W foglamps also. This is a dangerous state of affairs and there is no place for it under present-day road conditions—but it happens frequently. Even a normally considerate driver can be, annoyed to the point of retaliation. Towards the end of 1963 the number of requests for a headlamp check, together with reports of regular flashing from cars, was enough to merit a closer look at this problem. Thirteen vehicles were concerned. At first the lamp checking failed to produce a single fault, yet the evidence was enough to show something was wrong, with reports of flashing several times per night.
The regulation requires that all lamps used as headlamps shall be incapable of causing dazzle at a greater distance than 25 ft. at a height of 3 ft. 6 in.—or lamps must be so constructed that the beam can be deflected downwards or to the left. or both, to prevent dazzle. Therefore, it is the dipped headlamp position that we must examine.
To return to the 13 vehicles. Eight were sent along to the agent, who returned them in each case with a note reading "satisfactory ". This was, however, considered far from satisfactory and the situation was further examined. Eight of the machines were tractor units and five were long-wheelbase four-wheelers. It began to appear significant that no rigid eight-wheeler had offended. The next step was to again examine all 13 vehicles —this time fully loaded.
Once loaded, both tractor and I.w.b. promptly sat down several inches at the rear with no appreciable drop at the front. Other than one I.w.b., the tractors were the worst offenders—with a variation of 40-7° when loaded. This brought the dipped beam very close to full headlamp position. The one I.w.b. had its regular load of 3-ft.-diameter cast water pipes with all flanges over the end of the body—this was giving a 9° lift to the dipped beam and the full-ahead beam was far too high. As a result it became the practice to set the lamps of these vehicles when loaded and rely on the fact that there was little mileage covered unloaded after dark. On the flat vehicles the type of load carried was the main reason for trouble. On heavy tractors some consideration was given to the fact that recent alterations had been made to
the rear tyre equipment—while enjoying the benefit of more rubber to spread the load over the rear of the chassis was sinking a fraction more than desired, thus spoiling the headlamp settings.
When there is no headlamp setting device available, and a wall or stand is used and marked off at the correct height and distance, a useful tip is to incorporate ordinary red reflectors at the required setting points.