flying machines-第2节

按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！



one　hundred　and　twenty　square　feet　of　supporting　surface。

The　man　was　placed　horizontally　on　a　base　board

beneath　the　spar。　This　apparatus　when　tried　in　the　wind

was　found　to　be　unmanageable　by　reason　of　the　fluttering

motions　of　the　fabric；　which　was　insufficiently　stiffened

with　crinoline　steel；　but　Mr。　Wenham　pointed　out　that

this　in　no　way　invalidated　the　principle　of　the　apparatus；

which　was　to　obtain　large　supporting　surfaces　without

increasing　unduly　the　leverage　and　consequent　weight

of　spar　required；　by　simply　superposing　the　surfaces。



This　principle　is　entirely　sound　and　it　is　surprising　that

it　is；　to　this　day；　not　realized　by　those　aviators　who　are

hankering　for　monoplanes。



Experiments　by　Stringfellow。



The　next　man　to　test　an　apparatus　with　superposed

surfaces　was　Mr。　Stringfellow；　who；　becoming　much　impressed

with　Mr。　Wenham's　proposal；　produced　a　largish

model　at　the　exhibition　of　the　Aeronautical　Society　in

1868。　It　consisted　of　three　superposed　surfaces　aggregating　28

square　feet　and　a　tail　of　8　square　feet　more。

The　weight　was　under　12　pounds　and　it　was　driven　by　a

central　propeller　actuated　by　a　steam　engine　overestimated

at　one…third　of　a　horsepower。　It　ran　suspended

to　a　wire　on　its　trials　but　failed　of　free　flight；　in

consequence　of　defective　equilibrium。　This　apparatus　has

since　been　rebuilt　and　is　now　in　the　National　Museum

of　the　Smithsonian　Institution　at　Washington。

Linfield's　Unsuccessful　Efforts。



In　1878　Mr。　Linfield　tested　an　apparatus　in　England

consisting　of　a　cigar…shaped　car；　to　which　was　attached

on　each　side　frames　five　feet　square；　containing　each

twenty…five　superposed　planes　of　stretched　and　varnished

linen　eighteen　inches　wide；　and　only　two　inches　apart；

thus　reminding　one　of　a　Spanish　donkey　with　panniers。

The　whole　weighed　two　hundred　and　forty　pounds。　This

was　tested　by　being　mounted　on　a　flat　car　behind　a

locomotive　going　40　miles　an　hour。　When　towed　by　a　line

fifteen　feet　long　the　apparatus　rose　only　a　little　from　the

car　and　exhibited　such　unstable　equilibrium　that　the

experiment　was　not　renewed。　The　lift　was　only　about　one…

third　of　what　it　would　have　been　had　the　planes　been

properly　spaced；　say　their　full　width　apart；　instead　of

one…ninth　as　erroneously　devised。



Renard's　〃Dirigible　Parachute。〃



In　1889　Commandant　Renard；　the　eminent　superintendent

of　the　French　Aeronautical　Department；　exhibited

at　the　Paris　Exposition　of　that　year；　an　apparatus

experimented　with　some　years　before；　which　he　termed

a　〃dirigible　parachute。〃　It　consisted　of　an　oviform　body

to　which　were　pivoted　two　upright　slats　carrying　above

the　body　nine　long　superposed　flat　blades　spaced　about

one…third　of　their　width　apart。　When　this　apparatus

was　properly　set　at　an　angle　to　the　longitudinal　axis　of

the　body　and　dropped　from　a　balloon；　it　travelled　back

against　the　wind　for　a　considerable　distance　before

alighting。　The　course　could　be　varied　by　a　rudder。　No

practical　application　seems　to　have　been　made　of　this

device　by　the　French　War　Department；　but　Mr。　J。　P。

Holland；　the　inventor　of　the　submarine　boat　which　bears

his　name；　proposed　in　1893　an　arrangement　of　pivoted

framework　attached　to　the　body　of　a　flying　machine

which　combines　the　principle　of　Commandant　Renard

with　the　curved　blades　experimented　with　by　Mr。　Phillips；

now　to　be　noticed；　with　the　addition　of　lifting　screws

inserted　among　the　blades。



Phillips　Fails　on　Stability　Problem。



In　1893　Mr。　Horatio　Phillips；　of　England；　after　some

very　interesting　experiments　with　various　wing　sections；

from　which　he　deduced　conclusions　as　to　the　shape　of

maximum　lift；　tested　an　apparatus　resembling　a　Venetian

blind　which　consisted　of　fifty　wooden　slats　of

peculiar　shape；　22　feet　long；　one　and　a　half　inches　wide；

and　two　inches　apart；　set　in　ten　vertical　upright　boards。

All　this　was　carried　upon　a　body　provided　with　three

wheels。　It　weighed　420　pounds　and　was　driven　at　40

miles　an　hour　on　a　wooden　sidewalk　by　a　steam　engine

of　nine　horsepower　which　actuated　a　two…bladed　screw。

The　lift　was　satisfactory；　being　perhaps　70　pounds　per

horsepower；　but　the　equilibrium　was　quite　bad　and　the

experiments　were　discontinued。　They　were　taken　up

again　in　1904　with　a　similar　apparatus　large　enough　to

carry　a　passenger；　but　the　longitudinal　equilibrium　was

found　to　be　defective。　Then　in　1907　a　new　machine　was

tested；　in　which　four　sets　of　frames；　carrying　similar　sets

of　slat　〃sustainers〃　were　inserted；　and　with　this

arrangement　the　longitudinal　stability　was　found　to　be　very

satisfactory。　The　whole　apparatus；　with　the　operator；

weighed　650　pounds。　It　flew　about　200　yards　when

driven　by　a　motor　of　20　to　22　h。p。　at　30　miles　an　hour；

thus　exhibiting　a　lift　of　about　32　pounds　per　h。p。；　while

it　will　be　remembered　that　the　aeroplane　of　Wright

Brothers　exhibits　a　lifting　capacity　of　50　pounds　to

the　h。p。



Hargrave's　Kite　Experiments。



After　experimenting　with　very　many　models　and

building　no　less　than　eighteen　monoplane　flying　model

machines；　actuated　by　rubber；　by　compressed　air　and　by

steam；　Mr。　Lawrence　Hargrave；　of　Sydney；　New　South

Wales；　invented　the　cellular　kite　which　bears　his　name

and　made　it　known　in　a　paper　contributed　to　the　Chicago

Conference　on　Aerial　Navigation　in　1893；　describing

several　varieties。　The　modern　construction　is　well

known；　and　consists　of　two　cells；　each　of　superposed　surfaces

with　vertical　side　fins；　placed　one　behind　the　other

and　connected　by　a　rod　or　frame。　This　flies　with　great

steadiness　without　a　tail。　Mr。　Hargrave's　idea　was　to

use　a　team　of　these　kites；　below　which　he　proposed　to

suspend　a　motor　and　propeller　from　which　a　line　would

be　carried　to　an　anchor　in　the　ground。　Then　by　actuating

the　propeller　the　whole　apparatus　would　move

forward；　pick　up　the　anchor　and　fly　away。　He　said：

〃The　next　step　is　clear　enough；　namely；　that　a　flying

machine　with　acres　of　surface　can　be　safely　got　under

way　or　anchored　and　hauled　to　the　ground　by　means　of

the　string　of　kites。〃



The　first　tentative　experiments　did　not　result　well　and

emphasized　the　necessity　for　a　light　motor；　so　that　Mr。

Hargrave　has　since　been　engaged　in　developing　one；　not

having　convenient　access　to　those　which　have　been　produced

by　the　automobile　designers　and　builders。



Experiments　With　Glider　Model。



And　here　a　curious　reminiscence　may　be　indulged　in。

In　1888　the　present　writer　experimented　with　a　two…cell

gliding　model；　precisely　similar　to　a　Hargrave　kite；　as

will　be　confirmed　by　Mr。　Herring。　It　was　frequently

tested　by　launching　from　the　top　of　a　three…story　house

and　glided　downward　very　steadily　in　all　sorts　of　breezes；

but　the　angle　of　descent　was　much　steeper　than　that　of

birds；　and　the　weight　sustained　per　square　foot　was　less

than　with　single　cells；　in　consequence　of　the　lesser　support

afforded　by　the　rear　cell；　which　operated　upon　air

already　set　in　motion　downward　by　the　front　cell；　so

nothing　more　was　done　with　it；　for　it　never　occurred　to

the　writer　to　try　it　as　a　kite　and　he　thus　missed　the

distinction　which　attaches　to　Hargrave's　name。



Sir　Hiram　Maxim　also　introduced　fore　and　aft　superposed

surfaces　in　his　wondrous　flying　machine　of　1893；

but　he　relied　chiefly　for　the　lift　upon　his　main　large　surface

and　this　necessitated　so　many　guys；　to　prevent　distortion；

as　greatly　to　increase　the　head　resistance　and

this；　together　with　the　unstable　equilibrium；　made　it

evident　that　the　design　of　the　machine　would　have　to

be　changed。



How　Lilienthal　Was　Killed。



In　1895；　Otto　Lilienthal；　the　father　of　modern　aviation；

the　man　to　whose　method　of　experimenting　almost　all

present　successes　are　due；　after　making　something　like

two　thousand　glides　with　monoplanes；　added　a　superposed

surface　to　his　apparatus　and　found　the　control　of

it　much　improved。　The　two　surfaces　were　kept　apart

by　two　struts　or　vertical　posts　with　a　few　guy　wires；　but

the　connecting　joints　were　weak　and　there　was　nothing

like　trussing。　This　eventually　cost　his　most　useful　life。

Two　weeks　before　that　distressing　loss　to　science；　Herr

Wilhelm　Kress；　the　distinguished　and　veteran　aviator

of　Vienna；　witnessed　a　number　of　glides　by　Lilienthal

with　his　double…decked　apparatus。　He　noticed　that　it

was　much　wracked　and　wobbly　and　wrote　to　me　after

the　accident：　〃The　connection　of　the　wings　and　the

steering　arrangement　were　very　bad　and　unreliable。　I

warned　Herr　Lilienthal　very　seriously。　He　promised

me　that　he　would　soon　put　it　in　order；　but　I　fear　that　he

did　not　attend　to　it　immediately。〃



In　point　of　fact；　Lilienthal　had　built　a　new　machine；

upon　a　different　principle；　from　which　he　expected　great

results；　and　intended　to　make　but　very　few　more　flights

with　the　old　apparatus。　He　unwisely　made　one　too

many　and；　like　Pilcher；　was　the　victim　of　a　distorted

apparatus。　Probably　one　of　the　j