The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1898-03-29

TESTING A MODEL WAR VESS
yachts and other vessels of a more COM
mercial nature.
EXPERIMENTS ON PROPELLERS.
/ The trolley structure to be used on
| this tank will enable its operators to
make some very valuable experiments
upon the shape and the action of screw
! propellers. There seems to be dearth
| of information in the line of propeller
performance. Several private firms
! have made experiments concerning the
| shape and size of propellers, but the
data obtained has not been sufficiently
specialized sto result in any radical i'm
provement over heretofore existing
styles. Professor Durand and his as
sistants in Cornell college have been
carrying on a series of experiments
with propellers on Cayuga lake. They
rugged up a steam launch with a false
bow, which was designed to carry a
small propeller. down in the water
ahead of the boat. AS the boat steamed
forward the little propeller ahead of it
was forced to revolve. AS it was con-
nected with delicate measuring instru-
ments, the character of its performance
could be determined accurately by
those. on board the boat Attached to
this small propeller was a belt-rope,
"
known as a tachometer, which meas
ured its revolutions. A clock with a
seconds break indicated the speed of
the apparatus forward through the wa
ter. The apparatus was tried over a
course 1000 feet long. The course was
divided into ten parts of 100 feet each.
Various kinds of propellers were tried
some having long and narrow bla les,
some having short and thick blades
some with four blades, and others with
three. These experiments are still be-
ing carried on, and the general results,
when plotted, will be very valuable to
marine engineers.
WORKING THE TROLLEY TRUCK.
But, after all, these efforts are in a
measure crude, because the medium
which carried the propellers through
the water wasItself somewhat infiu-
enced by the resistance of the water
and also by the resistance of the pro-
peiler in front. But the trolley truck,
proceeding along the newly made tank.
Will not be influenced in the least by
the performance of the apparatus be-
meath 1t. Furthermore, some expert
ments will now be possible which were
not possible with the boat For in
stance, there is always certain
amount of interaction between a ship
and her propeller, and the resistance
of this combination is quite different
from the simple resistance that is gen.
Grated by the forward motion of the
boat through the water. This interac-
ton will be studied by means of pro-
pellers inserted in the water just be-
hind the model, but unconnected di-
rectly Herewith. For determining the
resistance of a model boat and her
propeller there will be a special trolley
truck capable of carrying forward the
model and provided with means for
running the propeller steadily at any
speed. This truck will also be pro-
vided with means for measuring the
thrust developed by the propeller as
Wen as the power required to run in. |
These facts Will be recorded on a drum. |
so that a record may be made of the
performance of the propeller as well as I
the resistance of the ship. The models q
are usually tried at various speeds and /
at various depths of immersion, which I
IS varied by adding or subtracting bal !
last. They are also tired at two or /
more sets OF trims. or sidewise inclin- I
atoms, such as would naturally be as !
sumed by vessel when pitching and
rolling through heavy waves.
1t is the desire Of the Cornell pro-
fessors to make experiments which viii [
De more in the line of pure science than
IN the line of commercial science. The ,
ldea is to establish a set of general
rules or laws which can be used by
constructors whose efforts are entirely
commercial. Their idea is to point out
exactly what kind of propeller will do,
what every shape of boat will do under
varying conditions, how much mower
would be needed to propel certain boats
at certain speeds and the limitations
which would govern these perform
ances. These facts are to be ascer-
tanned merely for the benefit of science.
then II the various governments or
{ u n gf+g- Iae-f,-
OF them and so construct very fast
vessels or vessels using minimum
amounts of power with maximum
lreighting capacity, they may do So.
The remarks of Professor Durand ON
inns subject explain the condition of
marine engineering problems. He saws:
ENGINEERING PROBLEMS.
Our idea is that marine engineering.
IKE All other branches of engineering.
must have scientific basis. There has
oeen IN this country very little work in
ms llne Of d scientific character; that I
s. disasscciated with the solution Of a I 4;
,omercial problem. For instance. in the {
iesign Of a proposed ship, there is. IN
ielIylng II all, q fundamental field of ,
Problems in which the conditions relate
lot TO one problem, but to the whole !
leld- My work has not been devoted TO
he design of any one propeller or to
-'-f N'iAlAiitiN ldl A]ibbltiAi. Bul 10 dSCGl- =
ain certains facts and then furnish :
hem 20 the profession at large, and to !
cave it to the practical engineer to cx-
'rcise his own judgment from expe- :
fence in the use of such data as to put
ing it into application. He is the one
aho must judge how far this matter is [,
applicable to his particular use. But !
n order To treat any of these problems
nteliigently. he must have Il certain \
lumber of facts. We have supplied ia |
small way some facts in propeller de- |
igns, to which ! have been devoting
he last year. The propeller of the pres :
mt time is designed in very large mea- 5
ure upon mathematical and accidental :
and the result is in large mea- $
urc tkat it is not as it ought to be-
BUT we don't know how to be sure to !
'btain the highest efficiency. This =
whole line of work is for the purpose of / I
hitting down the margin of uncertain c
y. There are also large numbers of b
ther problems which are rising regard
ng the conditions in the phenomena of f.
ngineering parts-in torpedo boats, :
asst yachts, etc. New conditions We're =
ound to exist when the screw propeller 5
vas coupled up with the turbine in u
england. Other problems are to be