The sun., 1894-05-13

4 the alternating motion Of the wings will In
yolve such dimensions that the weight Of tn,
apparatus and man will amount TO at leas
| three-fourths Of the whole thus leaving buI
one fourth Of the total weight applicable Il
the motor and its adjuncts. including the tue
| and supplies for the tourney.
! Concerning aerial screws there IL no lack oi
sxperine entail data Nndsr. Wenham. and
| Freningss each obtained . sustaining effect
| Of ~ pounds per horse power; Dahlstrom and
Iohman secured 3T.U and 55 pounds per horss
power; whils Rsnsrd got from II to ~ pounds
| thrust BY screws rotating at various speeds.
and Moy recorded 40 pounds per horse power
sustained from . wind wheel with vanes OF
variable pitch. These performances. however.
included certain amount OF ascension, which
absorbed part Of the power so that NJ. .Chanute
feels safe in assuming that In mere horizontal
flight some As pounds per horse power can be
sustained with screws. As the strains, more
over. In a rotating apparatus will be less de-
s'=uctive than those Involving reversals OF mo-
tion. Il seems probable that screws may be
constructed with less weight OF materials
than Tapping wings Of the same sustaining
power. The author estimates that an appara-
tus can be framed to sustain the weight
OF one man with rotating screws, in which
only about two-thirds OF the weight shall be
absorbed by the framing screws. car. and
man. thus leaving one-third OF the whole
weight for the motor and its adjuncts.
There are also many experimental data con-
cerninR aeroplanea lrot Dangley sustained
amhximun OF 2D pounds per horse power
with planes at an angle OF Incidence OF =. ana
NJ Maxim sustained 133 pounds per horse
power at an inclination OF In IL. Neither OF
these performances took into account the head
resistance due to the framing and car which
4. LI.t l.. 80. ahl
. complete model Tatin sustained ITO pounds
and Hargrave 30 pounds per horse power In
horizontal flight. Our author concludes that
100 pounds per horse power can be sustained
in horizontal flight with an aeroplane. As the
latter consists Of fixed surfaces receiving no
strains save the sustaining pressure OF the
air. Dir. Chanute believes that this kind OF ap-
paratus can be constructed OF sufncient size TO
sustain one man so that about one half of the
whole weight ahall be devoted to the motor
and its adiuncta 1t would seem to follow that
aeroplanes are the best forms to experiment
with, inasmuch as they admit OF larger pro-
portion OF the whole weight being arpropria-
ted to the motor. In the judgment Of our au-
thor this comparison OF the three kinds
OF apparatus also indicates tho posi-
bility OF success In artificial flight with
motors Weighing 10 or Is pounds
per horse power. provided that the remaining
problems can be also solved: but We are eau
toned not to overlook the fact that m ore power
will be required In rising from the ground than
in horizontal flight and that the actual pro-
portion Of the total weight available for tho
motor. although in this book couservatlvely
estimated from the best data attainable. 10
still matter to bo determined By experiment.
II is to be observed that the common basis
here selected for comparison 10 that size Of
apparatus which would be sufficient to sup
port tho weight OF one man. This 10 the small
est that can be adopted. and theoretically It is
the most favorable. for lhasmuch as the weight
-, =, a. si,..io,a TIL. Oh. .,,t.I,I,u
surface will only increase MS the square Of
these same dimen sions. It is obvious that the
proportion OF the total weight sustained which
can be spared for the motor will not be con-
slant, but that the larger the apparatus tho
smaller proportion OF the total weight will be
available for the engin o and it's adjuncts Fly
ing machines. therefore. should preferably be
designed a. small as 10 practicable. and ex-