SAFETY GLASS

Hauraki Plains Gazette, Volume 47, Issue 2671, 17 September 1937, Page 6

SAFETY GLASS

TESTS FOR WINDSCREENS RECENT RESULTS IN ENGLAND. 'ROUGHENED or a'rmourplate glass is used in a great number of cars sold to-day, for windscreens and frequently the side windows as well. Its strength is capable of withstanding the most surprising impacts. Toughened glass, however, is not entirely unbreakable. If struck hard enough in one spot the whole pane becomes Srlss-crossed with line cracks. Pushing at the pane will then make it fall into a heap of granules, not sharpedged, but something like sugar on a very large scale. Impaired Visibility.

This is one of the important characteristics of toughened glass, for if it is hit hard, enough by a flying stone or a stray rifle bullet—which actually has happened—to make it fall into its granulations straight away, the small granules will not cut the car’s occupants, even if they hit them. More frequently, when toughened glass is fractured in this manner, the screen remains in position, but is scarred all over by the fine cracks already referred to. This is the point which has worried many motorists and the matter has recently been discussed by drivers who want to know the effect on visibility. A representative of one of the prominent English motoring periodicals recently carried out a test to determine this point and the result seems to clarify the question quite satisfactorily.

To produce the granulated effect, an automatic centre punch was used. This is an instrument with a springloaded handle, steady pressure on which results in the spring giving a sharply-pointed punch a sufficient blow to cause an indention on metal.

With one man at the wheel of a car fitted with a toughened glass windscreen a speed of 50 miles an hour was maintained. Then a passenger pressed the automatic punch against the glass and, at the first blow, the granulated effect was produced. Able to Continue. The driver found that his view ahead w r as seriously impaired, yet not to such an extent that he involuntarily

swerved or applied the brake. Indeed, he was able to continue forward for a greater 1 distance than was necessary to bring the car to a halt so as not to stop close to a side turning.

Visibility to the near side was practically nil, as the driver’s line of sight

was then at an angle to the screen, but by peering through the centre of the screen he was able to see quite well enough to park quite close to the kerb. The journalist who made the experiment reported that there was no need to punch a hole through the screen hurriedly in order to see clearly to stop the car. The experiment was then tried on punching a hole in the fractured glass with a gloved hand. No glass particles cut into the glove, nor could any glass dust be discerned. The whole test was important in showing conclusively that this comparatively new form of safety glass, now in such wide use, is really safe in all circumstances.