the mastery of the air(操纵空气)-第15章
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Green engine。 In 1910 he succeeded in winning both the duration and
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cross…country Michelin competitions； and in 1911 he again accomplished
similar feats。 In this year he also finished fourth in the all…round…Britain
race。 This was a most meritorious performance when it is remembered that
his Cathedral weighed nearly a ton and ahalf； and that the 60…horse…power
Green was practically 〃untouched〃； to use an engineering expression；
during the whole of the 1010…mile flight。
The following year saw Cody winning another Michelin prize for a
cross…country competition。 Here he made a flight of over 200 miles； and
his high opinion of the engine may be best described in the letter he wrote
to the company； saying： 〃If you kept the engine supplied from without
with petrol and oil； what was within would carry you through〃。
But the pinnacle of Mr。 Green's fame as an inventor was reached in
1913； when Mr。 Harry Hawker made his memorable waterplane flight
from Cowes to Lough Shinny； an account of which appears in a later
chapter。 His machine was fitted with a 100…horse…power Green； and with it
he flew 1043 miles of the 1540…miles course。
Though the complete course was not covered； neither Mr。 Sopwith
who built the machine and bore the expenses of the flightnor Mr。
Hawker attached any blame to the engine。 At a dinner of the Aero Club；
given in 1914； Mr。 Sopwith was most enthusiastic in discussing the merits
of the 〃Green〃； and after Harry Hawker had recovered from the effects of
his fall in Lough Shinny he remarked in reference to the engine： 〃It is the
best I have ever met。 I do not know any other that would have done
anything like the work。〃
At the same time that this race was being held the French had a
competition from Paris to Deauville； a distance of about 160 miles。 When
compared with the time and distance covered by Mr。 Hawker； the results
achieved by the French pilots； flying machines fitted with French engines；
were quite insignificant； thus proving how the British industry had caught
up； and even passed； its closest rivals。
In 1913 Mr。 Grahame White； with one of the 100…horse…power
〃Greens〃 succeeded in winning the duration Michelin with a flight of over
300 miles； carrying a mechanic and pilot； 85 gallons of petrol； and 12
gallons of lubricating oil。 Compulsory landings were made every 63 miles；
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and the engine was stopped。 In spite of these trying conditions； the engine
ran； from start to finish； nearly nine hours without the slightest trouble。
Sufficient has been said to prove conclusively that the thought and
labour expended in the perfecting of the Green engine have not been
fruitless。
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CHAPTER XXIV The Wright Biplane （Camber of
Planes）
Now that the internal…combustion engine had arrived； the Wrights at
once commenced the construction of an aeroplane which could be driven
by mechanical power。 Hitherto； as we have seen； they had made numerous
tests with motorless gliders； but though these tests gave them much
valuable information concerning the best methods of keeping their craft on
an even keel while in the air； they could never hope to make much
progress in practical flight until they adopted motor power which would
propel the machine through the air。
We may assume that the two brothers had closely studied the engines
patented by Daimler and Levassor； and； being of a mechanical turn of
mind themselves； they were able to build their own motor； with which
they could make experiments in power…driven flight。
Before we study the gradual progress of these experiments it would be
well to describe the Wright biplane。 The illustration facing p。 96 shows a
typical biplane； and though there are certain modifications in most modern
machines； the principles upon which it was built apply to all aeroplanes。
The two main supporting planes； A； B； are made of canvas stretched
tightly across a light frame； and are slightly curved； or arched； from front
to back。 This curve is technically known as the CAMBER； and upon the
camber depend the strength and speed of the machine。
If you turn back to Chapter XVII you will see that the plane is
modelled after the wing of a bird。 It has been found that the lifting power
of a plane gradually dwindles from the front edge or ENTERING EDGE；
as it is calledbackwards。 For this reason it is necessary to equip a
machine with a very long； narrow plane； rather than with a comparatively
broad but short plane。
Perhaps a little example will make this clear。 Suppose we had two
machines； one of which was fitted with planes 144 feet long and 1 foot
wide； and the other with planes 12 feet square。 In the former the entering
edge of the plane would be twelve times as great as in the latter； and the
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lifting power would necessarily be much greater。 Thus； though both
machines have planes of the same area； each plane having a surface of 144
square feet； yet there is a great difference in the 〃lift〃 of the two。
But it is not to be concluded that the back portion of a plane is
altogether wasted。 Numerous experiments have taught aeroplane
constructors that if the plane were slightly curved from front to back the
rear portion of the plane also exercised a 〃lift〃； thus； instead of the air
being simply cut by the entering edge of the plane； it is driven against the
arched back of the plane； and helps to lift the machine into the air； and
support it when in flight。
There is also a secondary lifting impulse derived from this simple
curve。 We have seen that the air which has been cut by the front edge of
the plane pushes up from below； and is arrested by the top of the arch； but
the downward dip of the rear portion of the plane is of service in actually
DRAWING THE AIR FROM ABOVE。 The rapid air stream which has
been cut by the entering edge passes above the top of the curve； and
〃sucks up〃； as it were； so that the whole wing is pulled upwards。 Thus
there are two lifting impulses： one pushing up from below； the other
sucking up from above。
It naturally follows that when the camber is very pronounced the
machine will fly much slower； but will bear a greater weight than a
machine equipped with planes having little or no camber。 On high…speed
machines； which are used chiefly for racing purposes； the planes have very
little camber。 This was particularly noticeable in the monoplane piloted by
Mr。 Hamel in the Aerial Derby of 1913： the wings of this machine seemed
to be quite flat； and it was chiefly because of this that the pilot was able to
maintain such marvellous speed。
The scientific study of the wing lift of planes has proceeded so far that
the actual 〃lift〃 can now be measured； providing the speed of the machine
is known； together with the superficial area of the planes。 The designer can
calculate what weight each square foot of the planes will support in the air。
Thus some machines have a 〃lift〃 of 9 or 10 pounds to each square foot of
wing surface； while others are reduced to 3 or 4 pounds per square foot。
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CHAPTER XXV The Wright Biplane （Cont。）
The under part of the frame of the Wright biplane； technically known
as the CHASSIS； resembled a pair of long 〃runner〃 skates； similar to those
used in the Fens for skating races。 Upon those runners the machine moved
along the ground when starting to fly。 In more modern machines the
chassis is equipped with two or more small rubber…tyred wheels on which
the machine runs along the ground before rising into the air； and on which
it alights when a descent is made。
You will notice that the pilot's seat is fixed on the lower plane； and
almost in the centre of it； while close by the engine is mounted。 Alongside
the engine is a radiator which cools the water that has passed round the
cylinder of the engine in order to prevent them from becoming overheated。
Above the lower plane is a similar plane arranged parallel to it； and the
two are connected by light upright posts of hickory wood known as
STRUTS。 Such an aeroplane as this； which is equipped with two main
planes； known as a BIPLANE。 Other types of air…craft are the
MONOPLANE； possessing one main plane； and the TRIPLANE；
consisting of three planes。 No practical machine has been built with more
than three main planes； indeed； the triplane is now almost obsolete。
The Wrights fitted their machine with two long…bladed wooden screws；
or propellers； which by means of chains and sprocket…wheels； very like
those of a bicycle； were driven by the engine； whose speed was about
1200 revolutions a minute。 The first motor engine used by these clever
pioneers had four cylinders； and developed about 20 horsepower。
Nowadays engines are produced which develop more than five times that
power。
In later machines one propeller is generally thought to be sufficient； in
fact many constructors believe that there is danger in a two…propeller
machine； for if one propeller got broken； the other propeller； working at
full speed； would probably overturn
