The Abbeville press and banner. [volume] (Abbeville, S.C.) 1869-1924, 1910-08-17
AEROPLANE ENGINES.
llShtneSs and Economy in Fuel Less
Important Than TruStWorthinesS.


engine and proleller to the glider was
as curious as it was unexpected. The
memorable experiments Of Professo,
Langley on the Potomac River with
gliders of his invention and a small.
steam engine whose weight was some,
thing like twelve pounds a horse pow
er gave rise to the idea that only a
motor of much lighter weight a horse
power was required to transform the
glider into a successful power driven
machine, but now that such a motor
is available through the ~perfecting OF
the internal combustion engine it is
found that extreme lightness though
desirable is not altogether essential
and in fact an engine Of twelve pounds
a horse power, if fitted to n of the
oest types of aeroplane to-day, would
carry it with a pilot into the air.
It has lately been seen that a BIZ
plane can lift three passengers be-
sides the pilot over short distances,
while two may be carried with ease.
Assuming the combined weight of the
three passengers to be 420 pounds,
this is equivalent to an allowance of
more than eight pounds a horse power
ior a fifty horse power engine. in ad-
, 1ition to the actual weight of the en-
CINE, which would be three to four
pounds a'horse power. While there
fore the ultimate achievement of dy-
manic flight was due to the lightness
of the internal combustion engine in
relation to the power developed, sub
, 5equent experiment has demonstrated
how to improve the efficiency of the
sustaining surfaces and to diminish
head resistance to such an extent as
to make extreme lightness in the mo-
tor desirable only on the score of
freight carrying capacity.
The competing claims of freight ca
pacity and of motor trustworthiness,
as insured by duplication of parts
with consequent increase in weight,
will be determined by the objects
sought in the design of the a%eroplane.
Saving of weight in the motor, how
ever, permits the construction of a
more compact and comfortable ma
chine than would be possible if the
sustaining surfaces were designed to
carry considerable dead weight, and
it is toward a compromise in these re-
spects that the design of the motors
Is tending.
The original motor used by the
Wright brothers was comparatively
heavy and crude for the power devel-
oped, but with the large sustaining
surfaces with which the early ma
chimes were fitted this extra weight
was by no means a disadvantage,
! since with a motor constructed on the
lines of an automobile engine it en-
abled them without undue risk to
carry on experiments which resulted
in all round improvement in the ma
chine. The result of experience now
shows that the %aeroplane proper,
methods of stabilizing and control,
and construction generally, are more
highly developed than the motor,
/ which suffers from some palpable de-
fects that must circumscribe the use
fulness of the machine until the in
creasing attention directed to the sub
ject has wrought the improvements
which are desired.
To gain freight carrying capacity
the weight of the motor a horse pow
er must be kept low, but without any
sacrifice in the certainty of its work
ing, and the ideal motor, like the
lone boss shay" of Oliver Wendell
Holmes, should be constructed
throughout with such a regard to the
saving of weight that all parts should
have the same factor of safety for the
stresses that come upon them. Con-
siderable doubt still exists as to the
best size and type Of propeller, and
therefore the efficiency of the propel-
ling mechanism as a whole must re-
main indeterminate; but the lack of
definite rules upon which to design
propellers need not interfere with the
problem of the motor engineer, who
has to provide a constant power at
the propeller shaft with small weight
of motor and adequate strength.
At present the airman is more con-
cerned with trustworthiness of run
ming than with economy in fuel, but
he is content to expend a gallon of
petrol in traversing only twelve miles
if by so doing, he can secure infallibil-
ity in the motor upon which his safe
ty depends. In this respect the de-
sign of aerial motors is unlike that OF
the motor al engine, where economy
forms one of the competing claims OF
the manufacturers.
Leading airmen have expressed the
belief that flight will be impossible
with motors of less horse power in
the future than are fitted to aero
planes to-day, and when the expert
ments at the National Physical Lab
oratory on propellers have been coz
cluded the reasons for this prophetic
utterance may become apparent. The
low thrust a horse power is due to the
ignorance at present existing as to
propeller design. Like the marine
turbine, the aerial engine runs toe
fast for the best propeller speeds. The
Wright brothers overcame this diff
Guilty by the somewhat unmechanical
expedient of chain gearing, n chain
being crossed. A French firm has