flying machines-第4节

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In　order　to　understand　the　theory　of　the　modern　flying

machine　one　must　also　understand　bird　action　and　wind

action。　In　this　connection　the　following　simple　experiment

will　be　of　interest：



Take　a　circular…shaped　bit　of　cardboard；　like　the　lid　of

a　hat　box；　and　remove　the　bent…over　portion　so　as　to

have　a　perfectly　flat　surface　with　a　clean；　sharp　edge。

Holding　the　cardboard　at　arm's　length；　withdraw　your

hand；　leaving　the　cardboard　without　support。　　What　is

the　result？　　The　cardboard；　being　heavier　than　air；　and

having　nothing　to　sustain　it；　will　fall　to　the　ground。

Pick　it　up　and　throw　it；　with　considerable　force；　against

the　wind　edgewise。　　What　happens？　　Instead　of　falling

to　the　ground；　the　cardboard　sails　along　on　the　wind；

remaining　afloat　so　long　as　it　is　in　motion。　It　seeks

the　ground；　by　gravity；　only　as　the　motion　ceases；　and

then　by　easy　stages；　instead　of　dropping　abruptly　as　in

the　first　instance。



Here　we　have　a　homely；　but　accurate　illustration　of

the　action　of　the　flying　machine。　The　motor　does　for

the　latter　what　the　force　of　your　arm　does　for　the　cardboard

imparts　a　motion　which　keeps　it　afloat。　The

only　real　difference　is　that　the　motion　given　by　the

motor　is　continuous　and　much　more　powerful　than　that

given　by　your　arm。　The　action　of　the　latter　is　limited

and　the　end　of　its　propulsive　force　is　reached　within　a

second　or　two　after　it　is　exerted；　while　the　action　of　the

motor　is　prolonged。



Another　Simple　Illustration。



Another　simple　means　of　illustrating　the　principle　of

flying　machine　operation；　so　far　as　sustentation　and　the

elevation　and　depression　of　the　planes　is　concerned；　is

explained　in　the　accompanying　diagram。



A　is　a　piece　of　cardboard　about　2　by　3　inches　in　size。

B　is　a　piece　of　paper　of　the　same　size　pasted　to　one　edge

of　A。　If　you　bend　the　paper　to　a　curve；　with　convex

side　up　and　blow　across　it　as　shown　in　Figure　C；　the

paper　will　rise　instead　of　being　depressed。　The　dotted

lines　show　that　the　air　is　passing　over　the　top　of　the

curved　paper　and　yet；　no　matter　how　hard　you　may

blow；　the　effect　will　be　to　elevate　the　paper；　despite　the

fact　that　the　air　is　passing　over；　instead　of　under　the

curved　surface。



In　Figure　D　we　have　an　opposite　effect。　Here　the

paper　is　in　a　curve　exactly　the　reverse　of　that　shown　in

Figure　C；　bringing　the　concave　side　up。　Now　if　you

will　again　blow　across　the　surface　of　the　card　the　action

of　the　paper　will　be　downwardit　will　be　impossible　to

make　it　rise。　The　harder　you　blow　the　greater　will　be

the　downward　movement。



Principle　In　General　Use。



This　principle　is　taken　advantage　of　in　the　construction

of　all　successful　flying　machines。　Makers　of　monoplanes

and　biplanes　alike　adhere　to　curved　bodies；　with

the　concave　surface　facing　downward。　Straight　planes

were　tried　for　a　time；　but　found　greatly　lacking　in　the

power　of　sustentation。　By　curving　the　planes；　and　placing

the　concave　surface　downward；　a　sort　of　inverted　bowl

is　formed　in　which　the　air　gathers　and　exerts　a　buoyant

effect。　Just　what　the　ratio　of　the　curve　should　be　is　a

matter　of　contention。　In　some　instances　one　inch　to　the

foot　is　found　to　be　satisfactory；　in　others　this　is　doubled；

and　there　are　a　few　cases　in　which　a　curve　of　as　much　as

3　inches　to　the　foot　has　been　used。



Right　here　it　might　be　well　to　explain　that　the　word

〃plane〃　applied　to　flying　machines　of　modern　construction

is　in　reality　a　misnomer。　Plane　indicates　a　flat；

level　surface。　As　most　successful　flying　machines　have

curved　supporting　surfaces　it　is　clearly　wrong　to　speak

of　〃planes；〃　or　〃aeroplanes。〃　Usage；　however；　has　made

the　terms　convenient　and；　as　they　are　generally　accepted

and　understood　by　the　public；　they　are　used　in　like　manner

in　this　volume。



Getting　Under　Headway。



A　bird；　on　first　rising　from　the　ground；　or　beginning

its　flight　from　a　tree；　will　flap　its　wings　to　get　under

headway。　Here　again　we　have　another　illustration　of

the　manner　in　which　a　flying　machine　gets　under　headway

the　motor　imparts　the　force　necessary　to　put　the

machine　into　the　air；　but　right　here　the　similarity　ceases。

If　the　machine　is　to　be　kept　afloat　the　motor　must　be

kept　moving。　A　flying　machine　will　not　sustain　itself；

it　will　not　remain　suspended　in　the　air　unless　it　is

under　headway。　This　is　because　it　is　heavier　than　air；

and　gravity　draws　it　to　the　ground。



Puzzle　in　Bird　Soaring。



But　a　bird；　which　is　also　heavier　than　air；　will　remain

suspended；　in　a　calm；　will　even　soar　and　move　in　a

circle；　without　apparent　movement　of　its　wings。　This

is　explained　on　the　theory　that　there　are　generally　vertical

columns　of　air　in　circulation　strong　enough　to　sustain

a　bird；　but　much　too　weak　to　exert　any　lifting　power

on　a　flying　machine；　It　is　easy　to　understand　how　a

bird　can　remain　suspended　when　the　wind　is　in　action；

but　its　suspension　in　a　seeming　dead　calm　was　a　puzzle

to　scientists　until　Mr。　Chanute　advanced　the　proposition

of　vertical　columns　of　air。



Modeled　Closely　After　Birds。



So　far　as　possible；　builders　of　flying　machines　have

taken　what　may　be　called　〃the　architecture〃　of　birds　as

a　model。　This　is　readily　noticeable　in　the　form　of

construction。　When　a　bird　is　in　motion　its　wings　（except

when　flapping）　are　extended　in　a　straight　line　at　right

angles　to　its　body。　This　brings　a　sharp；　thin　edge

against　the　air；　offering　the　least　possible　surface　for

resistance；　while　at　the　same　time　a　broad　surface　for

support　is　afforded　by　the　flat；　under　side　of　the　wings。

Identically　the　same　thing　is　done　in　the　construction　of

the　flying　machine。



Note；　for　instance；　the　marked　similarity　in　form　as

shown　in　the　illustration　in　Chapter　II。　Here　A　is　the

bird；　and　B　the　general　outline　of　the　machine。　The

thin　edge　of　the　plane　in　the　latter　is　almost　a　duplicate

of　that　formed　by　the　outstretched　wings　of　the　bird；

while　the　rudder　plane　in　the　rear　serves　the　same　purpose

as　the　bird's　tail。







CHAPTER　IV。



VARIOUS　FORMS　OF　FLYING　MACHINES。



There　are　three　distinct　and　radically　different　forms

of　flying　machines。　These　are：



Aeroplanes；　helicopters　and　ornithopers。



Of　these　the　aeroplane　takes　precedence　and　is　used

almost　exclusively　by　successful　aviators；　the　helicopters

and　ornithopers　having　been　tried　and　found　lacking　in

some　vital　features；　while　at　the　same　time　in　some

respects　the　helicopter　has　advantages　not　found　in　the

aeroplane。



What　the　Helicopter　Is。



The　helicopter　gets　its　name　from　being　fitted　with

vertical　propellers　or　helices　（see　illustration）　by　the

action　of　which　the　machine　is　raised　directly　from　the

ground　into　the　air。　This　does　away　with　the　necessity

for　getting　the　machine　under　a　gliding　headway　before

it　floats；　as　is　the　case　with　the　aeroplane；　and　consequently

the　helicopter　can　be　handled　in　a　much　smaller

space　than　is　required　for　an　aeroplane。　This；　in　many

instances；　is　an　important　advantage；　but　it　is　the　only

one　the　helicopter　possesses；　and　is　more　than　overcome

by　its　drawbacks。　The　most　serious　of　these　is　that　the

helicopter　is　deficient　in　sustaining　capacity；　and　requires

too　much　motive　power。



Form　of　the　Ornithopter。



The　ornithopter　has　hinged　planes　which　work　like

the　wings　of　a　bird。　At　first　thought　this　would　seem

to　be　the　correct　principle；　and　most　of　the　early　experimenters

conducted　their　operations　on　this　line。　It

is　now　generally　understood；　however；　that　the　bird　in

soaring　is　in　reality　an　aeroplane；　its　extended　wings

serving　to　sustain；　as　well　as　propel；　the　body。　At　any

rate　the　ornithoper　has　not　been　successful　in　aviation；

and　has　been　interesting　mainly　as　an　ingenious　toy。

Attempts　to　construct　it　on　a　scale　that　would　permit

of　its　use　by　man　in　actual　aerial　flights　have　been　far

from　encouraging。



Three　Kinds　of　Aeroplanes。



There　are　three　forms　of　aeroplanes；　with　all　of　which

more　or　less　success　has　been　attained。　These　are：



The　monoplane；　a　one…surfaced　plane；　like　that　used

by　Bleriot。



The　biplane；　a　two…surfaced　plane；　now　used　by　the

Wrights；　Curtiss；　Farman；　and　others。



The　triplane；　a　three…surfaced　plane　This　form　is

but　little　used；　its　only　prominent　advocate　at　present

being　Elle　Lavimer；　a　Danish　experimenter；　who　has　not

thus　far　accomplished　much。



Whatever　of　real　success　has　been　accomplished　in

aviation　may　be　credited　to　the　monoplane　and　biplane；

with　the　balance　in　favor　of　the　latter。　The　monoplane

is　the　more　simple　in　construction　and；　where　weight…

sustaining　capacity　is　not　a　prime　requisite；　may

probably　be　found　the　most　convenient。　This　opinion　is

based　on　the　fact　that　the　smaller　the　surface　of　the

plane　the　less　will　be　the　resistance　offered　to　the　air；

and　the　greater　will　be　the　speed　at　which　the　machine

may　be　move