The morning news. [volume] (Savannah, Ga.) 1887-1900, 1896-05-09
TIMING A CANNON BALLS FLIGHT
A Delicate Electrical Appliance
Called the BOuinnger Chrome

From the Pittsburg Dispatch.
A lot Of powder has been burnt recently
IN the big guns proving grounds. but 20
people who don't know cannon from a
mortar the most Interesting part Of these
tests has been the method by which the in
itial velocity OF the projectues has been
determined. The difficulty Of such calcula-
ton is indicated by the fact that with
modern high power guns the shot is often
expelled al an initial velocity Of 1000 feet
per second which Is at the rate of "a mile in
less than seconds. Accurate knowledge
Of the velocity OF a projectile is Of the
greatest importance 10 the ordnance Off
Ger, who has 10 predict the range Of the
Sn0t and Its penetration, and 10 determine
the accuracy and efhciency Of the gun, OF
the powder, and of the prOjectile itself
Recently fault was found with the pow
der giving an initial velocity OF $50 feet
when its velocity should be $40 feet per
second. This Is a difference Of only 10
must be capable of measuring the time in
terVal TO within a e-thOusandths part of
a second. A difference Of DO or 800 feet in
Neloclly means IN the Dig guns an lnpor-
Tant difference in the powder used In the
tests. A delicate electrical appliance cali
ed the BOulanger chronograph, viii meas
ure this velocity accurately, and record Its
does it:
frames are set up In front of the gun at
a distance Of 80 feet from each other
Wires are stretched back and fourth
acIuss each a these frames. making
a screen through which the prO1ectile
must pass. The wires I'm each of these
screens form a complete electrical cir
cult, which includes also an electric bat
terry ana an electro-magneL When the
gun IS fired the proJectile breaks the wire
IN the first screen, interrupts the circuit,
and at the same time the armature of
IS lt gD1 NDF gVrTn
fraction OF a second the projectle has
covered the distance to the second screen
and interrupted its circuit, releasing an
other armature. The interval OF time be-
tween the drop of these two armatures rep
resents the time taken by the prOjectile
TO travel $50 feet.
The period is so short that # is hardly
conceivable. The chronograph, however,
registers It accurately. Wires run from
each Of these screens TO the laboratory
near them, where are placed the chrome
graphs, batteries. and other apparatus.
The two electromagnetic in circuit with
the screens are embodied in the chrome
graph. The first magnet has an arma-
ture, an iron rod about three feet long,
which is suspended in a vertical position
from its core. When the wires of the
nrst screen are broken this iron rod falls
When the shot ruptures the wire of the
second screen the armature of the second
electro-magnet, which is placed a short
distance before the first Is also reached
II operates as a knife, and striking the
sides OF a falling rod makes a slight
ma n. Inc distance through WnlCh the
rod drops while the shot is passing from
one screen to the other is indicated by the
distance Of the cut from the end Of the
roo. From this the corresponding inter
val or time is easily computed, and this
form the unit for the calculation of the
projectles velocity in feet per second
When it is necessary to obtain very accu-
rate records several chronographs are
used for testing the same shot
The rate Of a projectiles velocity dimin-
ishes rapidly during its fight from the
gun and the calculations of the initial
velocity must be confined to a short por-
ton OF its path Immediately after il leaves
the gun. instantaneous photographs are
obtained Of the projectile as 1t strikes the
target. From such experiments in velocity
the ordnance officer is able to determine
the relative strength of different powders