Wallowa chieftain. [volume] (Joseph, Union County, Or.) 1884-1909, 1902-02-06
TOY OCEAN.
Method of Measuring Water Resists,
on Vessels of War.

Method Of Mea~uring Water Resista,,
on Vessels of War.
4 quarter of century ago an p
glish naval constructor, DR.. Wnb,
Froude, performed series of exps
mruts with scale models designed
prpdetcrmine the resistance of sb,E
about to be built for the navy. n
made small models of the vessels Ia
constructed. giving great care to h
preservation Of the scFe; and ths
models he then towed through the v
Ter under varying conditions, by NEE.
guism extremely sensitive TO variatn
in the pull The tension in each cs
WAS carefully recorded, and concluso
drawn rs TO the lines most favoranl
for speed. To verify his results BdI
iSh man-of-war was tOwed by anotbs
vessel. and the actual pull on the TOW
rope was carefully measured and CON
pared with the results of eXperimeDl
made with small model. The tv
sets of answers were so nearly alike N
TO leave no doubt of the practicablltI
of actual experiments with reduce
scale models.
| At the Washington navy-yard mold
basin for experiments of this kind bad
been constructed, mt cost of one hu,
dred thousand dollars.
! Within building designed to protecj
/ 1t from all disturbing conditions of I'D
atmosphere is Il tank of pure. fresl
water. three hundred ana seventy led
long and fOrty-three feet wide, with
uniform depth of fourteen feet. SpaDI
ming this narrow sheet of water Is /
movable bridge, set upon steel raid
which run parallel tOithe length of tAa
basin. Heavily built, and fastened and
braced so rigidly TO avoid all unnece,
sary vibration. this bridge is provide
with n powerful motor, which can driyI
ii along the rails, if need be. at the rat
of twenty knots an hour.
The model of the proposed ship CD
from soft pine, conforming as nearI
as possible to Il uniform twenty.fOd
length, and ballasted with the utmOs
care is firmly fastened to an arm whid
projects from below the center of III
bridge or towing carriage, as it is callei
ON the carriage are placed all the del
cate dynamometrical mechanism
which record the pull of the mod
as it gldes through the water beneat
the span of the bridge. This multiplls
by the proper ratio must establish a.
curately the power that will be II
quired to overcome the resistance .
the finished vessel.
Thanks to an almost fiawless electr
cal adjustment the bridge moves fC
ward with an even motion. without
trace of the rattle and jounce of an ele
triC car.
Besides the motormen, there are tv
persons on the carriage during an e.
pertinent. They watch the pens of Il
recording cylinder of the dynamOmete
These pens by means of electricit
register the actual distance traverse
together with the varying pull of tt
model as the speed changes.
When all is ready for an experimel
mt the clang Of a gong the bridge star
from the south toward the north end
the tank while bpnpath II tbe tWent
foot warship glides evenly through Il
filtered water. As the run nears
end and the spectator wonders how Il
great bridge with its precious freig
of Instruments is going to escape col
sion with the wall ahead. two gre
hydraulic brakes operate automatical
and bring the mass to q gentle ST
without jar or quiver.