COAST. I ARTILLERY JOURNAL, - Air Defense Artillery

Velocity Measurements with the Universal
Measuring Camera
By DR. ING. HANS RUMPFF
Translated by Colonel George Ruhlen, U. S. A., Retired
THE necessity for measuring the initial velocity of every possible
shot at firing exercises away from proving-ground establishments
has been acknowledged by the artillery in recent years. All other refinements,
such as investigating the influence of weather conditions,
erosion, etc., can give reliable results only when the principal deciding
element-the initial velocity-is also measured. The variations in the
initial velocity, as they occur normally with every kind of ammunition,
cause dispersions in points of impact that are frequently equal in
dimensions to those due to other causes.
At proving grounds the measurement of initial velocities has been
carried on during a number of decades with the Boulenge apparatus,
an implement not yet surpassed in construction, certainty of operation,
and simplicity of service. Theoretically, the applicability of that instrument
is not restricted to any definite firing angle, yet in actual practice
one seldom goes beyond 20 degrees elevation with the higher
initial velocities, in order that the trestles carrying the measuring framework
may not become inconveniently high. In consequence, we are
confined to rather narrow limits when using rough and inexpensive
apparatus.
In order to be able to measure the initial velocity of artillery projectiles
when using greater angles of elevation or to carryon the measurements
in a terrain unadapted to the use of measuring frames (seacoasts,
fortifications, ships}, an attempt has been made during the past
ten years to develop other and principally photographic methods.
Photography of artillery projectiles in flight is, in the daytime,
always dependent, in the first place, upon the pre"..-aiIinglight. While
it is possible to secure pictures of artillery projectiles, even of very
high velocities, on almost any day of the year in southern latitudes,
one is, in northern latitudes, restricted to a few days in midsummer
in which pictures fit for use can be made, because of the condition
of the sky.
This restriction has been obviated in photography by resorting to
small light fuzes (weighing 90 to 100 grams) which burn only about
half a second, calculated from the muzzle of the gun. The ballistic
[~291