The commonwealth. (Greenwood, Miss.) 1896-1923, 1904-05-14
OF MOTOR ENGINES.
I That Drive Propeller Screws Of
Fast Atlantic Liners Exceed ...
Two Miles a Minute. ay,s bly,

tu lNrequires some study. 70 ascertain
TIE precise speed required in an engine
that3 drives the fast autQboats that
ploM through the water at the rate Of
20 q Is miles an hour, and having as
certained the figures one is almost in
eiinsd to disbelieve them, although it
bis said they cannot lie. TO attain the
speef named, says an authority, the
propeller wheel rsyolyes from 500 to
leg times in a minute When the
nu1bbor Of revolutions Is stated one
rarely c~omprehends what it means.
ira boat Of high power the propeller
Will be % inches In diameter. This
maansthatits neripheFgais saalittle over
six feet.
If Shts screw revolyes at the rate Of
L. 5OPtimes a minute the outer edge
Of tip blades Of the propeller is cut,
ting fhrAushstb sMateFaat the rate Of,
Just ane and a third~mi4es 2 mipute~ a,
Thgse propellers ara nQt 1at. n
they Swere they would have no pur-
chasS on the water al, aid he boat would
not HoyF@, an inch. To- giTe, them Il
grip On the water each blade Is twisted.
slightly 1itea, a SPIRAL ana This twist.
infreHses The, stretch Sof the blade be-
20 md Its sIilrffGpnfeFenGe By. about "a,
So taat Fhat,, marine engineers can
the Ael{GQid path, Of rtbe. propelled
would be very nearly two miles III d
mlnr4e. a. '5''F>|oA 81 ~ '"'
IfAs remarkable, speed is produced
by a mot.os, thataislonly Is inches wide,
40 INCHES ~Ions1aRd, A inches high 1t
develops a horse poweg Of ABOUT g.
The propellers which drive the fast,
AtlaNic lineFs gre about As feet in cir
~c1msreges,. The |. !, tip q the blade will
cover about a mile ana a fifth each
minute when revolving at full speed.v
The cruiser Minneapolis. which is
one of the fastest in the navy, has pro-
pellers AZ feet in circumference. They
make 1872 revolutions a minute, so that
of the blade when driven at full
speed is travelling at the rate of 1886
feet each minute, and the .helicoid
path, or the distance covered by the
twist of the blade. is $50 feet
a minute, or more than a mile and a
haH.
Ehe Minneapolis and the ocean
are driven by steam, but in the
fast autoboats gasoline Is the motve
7
t can be understood to what a
nlcety the mechanism in a gasoline en-
g ne is adjusted when it is stated that
to gmake 1000 revolutions a. infinite
means that in a four cycle engine
here are 500 sprays of gasoline forced
ifp the cylinder, 500 times the cleo
trie battery makes a spark and 500
times the escape valve is opened to let
the gas out.
If there are four cylinders at work
on 1.-THE sam shaft. and many of the fast
bpats have four cylinders, then each
operation is repeated four times. Some
m etors have eight cylinders and one
Il snow being built that will have y
cylinders. 1t is figured that a motor
uses a pint Of gasoline per each horse
DoEer and houd. An s horsepower
will use a gallon of gas
olile an hour and will cost about
ISL or II cents an hour to run.
\ "a horsepower motor will take
.hree gallons an hour, which will
nake the cost about so cents an hour.
There is a motor boat being built
hat is to have a 500 horsepower
This motor will consume
tbgut 60 gallons Of gasoline an hour,
If run for ten hours a day will
,bs more than $50 a day.