Perth Amboy evening news., 1904-04-27
SPEED " MOiOR LNcINEs.
Some That DIVE Propeller Screws of
Fast Atlantic liners Exceed
TTo Niles 4 Minute.

Two Niles 4 Minute.
1t requires some study to ascertain
The precise speed required in an clsino
that drives the fast auto5oat5 that
pillow through the water at the rate Of
% or 20 miles aa hour, aul Having as
certained the figures enc is almost in
tlined to digbelicye theE. although it
IS said they cannot lie. TO attain tho
peel nai:ed, says an authority, the
propeller wheel revolycs from eco TO
l,250 times in a minute. When tho
number of revolutions r. stated enc
carely comprehends wat It means.
In a boat of high power the propeller
will be 20 inches i'll diameter. Thil
means that its periphery is a little over
six feet.
If this screw revolvcs at tho rate Of
1850 times a minute the outer edge
Of the blades of the propeller Is cut
ting through the water at the rate OF
just one and a third miles a minute.
These propellers are not fiat. II
they were they would have no pur-
chase on the water and the boat would
not move an inch. To give them q
grip on the water each blale is twisted
slightly, like a spiral, and this twist
increases the stretch of the blade be-
'ond its circumference by about IA,
so hat what marine engineers call
tho belicoid path of the propeller
would be very nearly two miles in q
minute.
This remarkable speed is produced
by a motor that is only % inches wide,
40 inches long and Al inches high. It
develops a horse power of about 65.
The propellers which drive the fast
Atlantic liners are about 48 feet in cir
conference. The tip of the blade will
cover about q mile and a fifth each
minute when revolving at full speed.
The cruiser Minneapolis, which Is
of the fastest in the navy, has pro-
pellers As feet in circumference. They
make 1872 revolutions a minute, SO that
the tip of the blade when driven at full
speed is travelling at the rate of G,33G
feet each minute, and the helicold
path, or the distance covered by the
spiral twist of the blade, is $50 feet
a minute, or more than a mile and a
half.
The Minneapolis and the ocean
liners are driven by steam, but in tho
fast autoboats gasoline is the motive
power.
It can be understood to what a
nicely the mechanism in a gasoline en-
CINE is adjusted when 1t Is stated that
to make 1000 revolutions q minute
means that in a four cycle engine
there are 500 sprays of gasoline forced
into the cylinder, 500 times the cleo
trio battery makes a spafk and 500
times the escape valve is opened to let
the gas out.
II there arc four cylinders at work
on the same shaft, and many of the fast
boats have four cylinders, then each
operation is repeated four times. Some
motors nave eight cylinders and n
is now being built that will have II
cylinders. 1t is figured that a motor
uses a pint of gasoline per each horses
power and houd. An 8 horsepower
llNlOI Will uEO q SuiiOA OA 6N
oline an hour and will cost about
1G or II cents an hour to run
A "a horsepower motor will take
three gallons an hour, which will
make the cost about so cents an hour.
There is a motor boat being built
that Is to have a SEQ horsepower
motor. This motor will consume
about go gallons of gasoline an hour,
and if run for ten hours a day will
cost more than $50 a day.
Inc G111 $3.50
One day early In March a schoolhouse
in Brooklyn took fire. Through halls
filled with smoke 1000 pupils passed out
in order under the discipline which they
had learned from frequent fire drills.
In three minutes all were in a place Of
safety. Children are benefited by fire.
drills in two ways. Even IL they never
encounter the danger of fire, they have
at least been subjected to valuable train
Ing; and If when they grow up they are
ever In a fire like that in the Iroquois
theater at Chicago, they win find them
selves in a majority with others who
have been to the public schools. Then
1t is not too much to hope that the early
training will show itself in such disci-
pline and steadiness as will diminish,
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