Evening star., 1923-04-01
IDEAL HEADLIGHT
II FOUND IN TESTS
Bureau of Standards Reveals
Experiments to Show
N Proper Distribution.

A headlight which will brilliantly
illuminate the road ahead without
glaring in the eyes OF drivers coming
from the opposite direction is the
ideal of motorists. Several devices
now in extensive use accomplish this
object
The bureau of standards has been
making tests on automobile head
lights with a view 70 devisng simple
methods of testing lights on the road
and keeping them in adjustments, SO
they will give good distribution Of
light
a method OF testing is used which
requires nothing more complicated
than a screen of canvas or other suit
able material on which three lines
are drawn. One of these is horizontal
and at approximately the same height
as the headlights of the car; the other
two are vertical and as far apart as
the headlights.
Screen Twenty-Five Feet Away.
The car is placed al Il distance Of
twenty-five feet with its lights shin
ing on the screen. The region below
the horizontal line should be bril-
Iiantly Illuminated, with the illumi-
nation extending only a short distance
above and then fading TO an intensity
slightly greater than that obtained by
using DINNERS. Some light is re-
CURED in this region. hut should net
be bright enough to be glaring. The
bright light should not rise as high
on the sides as il does at the center.
In passing tests made at the bureau
it was shown that two cars using
good lenses could safely pass without
using DINNERS. The lights did not
glare in the eyes OF approaching driv-
eSs, yet they lit I'D the road beyond
the other car with sufficient brilliancr
TO permit the driver to see what was
there. When dinners are used. on
the other hand. the road beyond the
approaching car is left in complete
darkness. and not until he has passed
~ can the driver see what is thare.
A case is told Of where several
school girls were killed because of
this. They passed behind one car in
ffronsi1E fr0S5 Tb the re-, read : and one coming
down. In this case both cars were
using DINNERS. On another occasion
car smashed into a high curbing.
Desirable Types of Lenses.
Lenses of the best design appear 20
be made up OF rectangular or trian-
gular sections, and these will be
round slightly curved on one surface.
the axis of the curve being vertical.
and the top of the sections are thin
ner than the bottom
Certain types of refectors will give
approximately the same distribution
as these lenses, and with such a plain
glass is used.
Lenses of poor design scatter the
light in all directions Such lenses
DO not give sufficient illumination on
the road and are almost sure to give
q glaring light in the eyes Of an
preaching drivers. A driver should al
ways consult his police department
Detore buying a lens and obtain a
list of approved devices
tor OF or acetylene lights approved
types OF lenses are unnecessary and
u pain glass Is satisfactory. Such
HGhts do not usually give serious
glare.
Proper adjustment of the. headlight
Is or equal Importance with proper
design. The lamp must be in focus
In modern types this is readily ac-
com2lished by means of a screw on
tne IN eIi, oack OF the casing, where it can
sun on the market require the lens
TO be removed for adjusting, and this
type is, naturally, much more diff
cult to adjust
1t Is also necessary TO have tho
headlights properly aligned The
beams should be parallel and directed
straight in front of the car This can
be done by using the cross-lines on
.ne testing screen. the lenses being
taken off for the purpose.
1t is also very necessary that the
lenses be put in with the TOP up and
rlsht side out. Every good lens is
properly marked.
Urge Uniform Laws and Testing.
The desirability of having headlight
laws more uniform throughout the
country is shown by the fact that
many drivers travelling through sew
eral states have to carry devices for
use in different states Now that these
tests have shown what can properIy
be expected of a good headlight il is
hoped that these laws may be changed
Where necessary TO permit devices of
approved design to be used in all
states.
Testing by garages is also recon-
mended. and by the police in case of
alleged violations Of law. This would
require the testing device to be set up
at convenient points, and cars not
complying with the requirements
would be taken there and tested.
For most of this work a six-foot
square or cloth on portable frame
would do, the three lines being paint
ed on 1t. This could be set UP any
Where, and the cost would be only a
Few dollars
AS a reference tester to settle dis
puted cases. it would be desirable to
nave more elaborate set-up This
consists of a siX-foot square of beaver
board or similar material in which
four holes are made and small lamps
placed behind these holes with a
translucent screen in front. These
are so designed that if the light is
properly distributed the two above
the level of the headlights will show
bright and the other two dark
resting is particularly desirable, in
view OF the fact that lens originally
good may give a very poor distribu-
tion when not properly adjusted In
such cases. the test will show how to
correct the difficulty