aeroplanes- 第16部分

line　E　would　be　900　pounds；　being　the　composition

of　the　two　forces　pulling　along　the　lines　D；　F。



THE　HORIZONTAL　AND　VERTICAL　PULL。Now　it

must　be　obvious；　that　if　the　incline　takes　half　of

the　weight　while　it　is　being　drawn　forwardly；　in

the　line　of　D；　if　we　had　a　propeller　drawing　along

that　line；　which　has　a　pull　of　450　pounds；　it　would

maintain　the　plane　in　flight；　or；　at　any　rate　hold

it　in　space；　assuming　that　the　air　should　be　moving

past　the　plane。



_Fig。　60。　Horizontal　and　Vertical　pull。_



The　table　of　lift　and　drift　gives　a　fairly　accurate

method　of　determining　this　factor；　and　we　refer　to

the　chapter　on　that　subject　which　will　show　the

manner　of　making　the　calculations。



THE　POWER　MOUNTING。More　time　and　labor

has　been　wasted；　in　airship　experiments；　in　poor

motor　mounting；　than　in　any　other　direction。

This　is　especially　true　where　two　propellers　are

used；　or　where　the　construction　is　such　that　the

propeller　is　mounted　some　distance　from　the　motor。



SECURING　THE　PROPELLER　TO　THE　SHAFT。But

even　where　the　propeller　is　mounted　on　the　engine

shaft；　too　little　care　is　exercised　to　fix　it　securely。

The　vibratory　character　of　the　mounting

makes　this　a　matter　of　first　importance。　If　there

is　a　solid　base　a　poorly　fixed　propeller　will　hold

much　longer；　but　it　is　the　extreme　vibration　that

causes　the　propeller　fastening　to　give　way。



VIBRATIONS。If　experimenters　realized　that　an

insecure；　shaking；　or　weaving　bed　would　cause　a

loss　of　from　ten　to　fifteen　per　cent。　in　the　pull　of

the　propeller；　more　care　and　attention　would　be

given　to　this　part　of　the　structure。



WEAKNESSES　IN　MOUNTING。The　general　weaknesses

to　which　attention　should　be　directed　are；

first；　the　insecure　attachment　of　the　propeller　to

the　shaft；　second；　the　liability　of　the　base　to

weave；　or　permit　of　a　torsional　movement；　third；

improper　bracing　of　the　base　to　the　main　body　of

the　aeroplane。



If　the　power　is　transferred　from　the　cylinder

to　the　engine　shaft　where　it　could　deliver　its　output

without　the　use　of　a　propeller；　it　would　not

be　so　important　to　consider　the　matter　of　vibration；

but　the　propeller；　if　permitted　to　vibrate；

or　dance　about；　absorbs　a　vast　amount　of　energy；

while　at　the　same　time　cutting　down　its　effective

pull。



Aside　from　this　it　is　dangerous　to　permit　the

slightest　displacement　while　the　engine　is　running。

Any　looseness　is　sure　to　grow　worse；　instead

of　better；　and　many　accidents　have　been

registered　by　bolts　which　have　come　loose　from

excessive　vibration。　It　is　well；　therefore；　to　have

each　individual　nut　secured；　or　properly　locked；

which　is　a　matter　easily　done；　and　when　so　secured

there　is　but　little　trouble　in　going　over　the　machine

to　notice　just　how　much　more　the　nut　must

be　taken　up　to　again　make　it　secure。



THE　GASOLINE　TANK。What　horrid　details　have

been　told　of　the　pilots　who　have　been　burned　to

death　with　the　escaping　gasoline　after　an　accident；

before　help　arrived。　There　is　no　excuse　for

such　dangers。　Most　of　such　accidents　were　due

to　the　old　practice　of　making　the　tanks　of　exceedingly

light　or　thin　material；　so　that　the　least

undue　jar　would　tear　a　hole　at　the　fastening

points；　and　thus　permit　the　gasoline　to　escape。



A　thick　copper　tank　is　by　far　the　safest；　as　this

metal　will　not　readily　rupture　by　the　wrench　which

is　likely　in　landing。



WHERE　TO　LOCATE　THE　TANK。There　has　been

considerable　discussion　as　to　the　proper　place　to

locate　the　tank。　Those　who　advocate　its　placement

overhead　argue　that　in　case　of　an　accident

the　aeroplane　is　likely　to　overturn；　and　the　tank

will；　therefore；　be　below　the　pilot。　Those　who

believe　it　should　be　placed　below；　claim　that　in

case　of　overturning　it　is　safer　to　have　the　tank

afire　above　than　below。



DANGER　TO　THE　PILOT。The　great　danger　to　the

pilot；　in　all　cases　of　accidents；　lies　in　the

overturning　of　the　machine。　Many　have　had　accidents

where　the　machine　landed　right　side　up；　even

where　the　fall　was　from　a　great　height；　and　the

only　damage　to　the　aviator　was　bruises。　Few；　if

any；　pilots　have　escaped　where　the　machine　has

overturned。



It　is　far　better；　in　case　the　tank　is　light；　to　have

it　detached　from　its　position；　when　the　ship　strikes

the　earth；　because　in　doing　so；　it　will　not　be　so

likely　to　burn　the　imprisoned　aviator。



In　all　cases　the　tank　should　be　kept　as　far　away

from　the　engine　as　possible。　There　is　no　reason

why　it　cannot　be　placed　toward　the　tail　end　of

the　machine；　a　place　of　safety　for　two　reasons：

First；　it　is　out　of　the　reach　of　any　possible

danger　from　fire；　and；　second；　the　accidents　in　the

past　show　that　the　tail　frame　is　the　least　likely　to

be　injured。



In　looking　over　the　illustrations　taken　from　the

accidents；　notice　how　few　of　the　tails　are　even

disarranged；　and　in　many　of　them；　while　the　entire

fore　body　and　planes　were　crushed　to　atoms；

the　tail　still　remained　as　a　relic；　to　show　its

comparative　freedom　from　the　accident。



In　all　monoplanes　the　tail　really　forms　part　of

the　supporting　surface　of　the　machine；　and　the

adding　of　the　weight　of　the　gasoline　would　be

placing　but　little　additional　duty　on　the　tail；　and

it　could　be　readily　provided　for　by　a　larger　tail

surface；　if　required。



THE　CLOSED…IN　BODY。The　closed…in　body　is　a

vast　improvement；　which　has　had　the　effect　of

giving　greater　security　to　the　pilot；　but　even　this

is　useless　in　case　of　overturning。



STARTING　THE　MACHINE。The　direction　in　which

improvements　have　been　slow　is　in　the　starting

of　the　machine。　The　power　is　usually　so　mounted

that　the　pilot　has　no　control　over　the　starting；

as　he　is　not　in　a　position　to　crank　it。



The　propeller　being　mounted　directly　on　the

shaft；　without　the　intervention　of　a　clutch；　makes

it　necessary；　while　on　the　ground；　for　the　propeller

to　be　started　by　some　one　outside；　while

others　hold　the　machine　until　it　attains　the　proper

speed。



This　could　be　readily　remedied　by　using　a

clutch；　but　in　the　past　this　has　been　regarded　as

one　of　the　weight　luxuries　that　all　have　been　trying

to　avoid。　Self　starters　are　readily　provided；

and　this　with　the　provision　that　the　propeller　can

be　thrown　in　or　out　at　will；　would　be　a　vast　improvement

in　all　machines。



PROPELLERS　WITH　VARYING　PITCH。It　is　growing

more　apparent　each　day；　that　a　new　type　of

propeller　must　be　devised　which　will　enable　the

pilot　to　change　the　pitch；　as　the　speed　increases；

and　to　give　a　greater　pitch；　when　alighting；　so

as　to　make　the　power　output　conform　to　the　conditions。



Such　propellers；　while　they　may　be　dangerous；

and　much　heavier　than　the　rigid　type；　will；　no

doubt；　appear　in　time；　and　the　real　improvement

would　be　in　the　direction　of　having　the　blades

capable　of　automatic　adjustment；　dependent　on

the　wind　pressure；　or　the　turning　speed；　and　thus

not　impose　this　additional　duty　on　the　pilot。







CHAPTER　XI



FLYING　MACHINE　ACCESSORIES





THE　ANEMOMETER。It　requires　an　expert　to

judge　the　force　or　the　speed　of　a　wind；　and　even

they　will　go　astray　in　their　calculations。　It　is

an　easy　matter　to　make　a　little　apparatus　which

will　accurately　indicate　the　speed。　A　device　of

this　kind　is　called　an　Anemometer。



Two　other　instruments　have　grown　out　of　this；

one　to　indicate　the　pressure；　and　the　other　the

direction　of　the　moving　air　current。



THE　ANEMOGRAPH。While　these　instruments　indicate；

they　are　also　made　so　they　will　record　the

speed；　the　pressure　and　the　direction；　and　the　device

for　recording　the　speed　and　pressure　is　called

a　Anemograph。



All　these　instruments　may　be　attached　to　the

same　case；　and　thus　make　a　handy　little　device；

which　will　give　all　the　information　at　a　glance。



THE　ANEMOMETROGRAPH。This　device　for　recording；

as　well　as　indicating　the　speed；　pressure

and　direction；　is　called　an　Anemometrograph；

The　two　important　parts　of　the　combined　

apparatus；　for　the　speed　and　pressure；　are　illustrated；

to　show　the　principle　involved。　While　the　speed

will　give　the　pressure；　it　is　necessary　to　make　a

calculation　to　get　the　result　while　the　machine　does

this　for　you。



_Fig。　61。　Speed　Indicator。_



THE　SPEED　INDICATOR。Four　hemispherical

cups　A　are　mounted　on　four　radiating　arms　B；

which　are　secured　to　a　vertical　stem　C；　and

adapted　to　rotate　in　suitable　bearings　in　a

case；　which；　for　convenience　in　explaining；　is　not

shown。



On　the　lower　end　of　the　stem　C；　is　a　small　bevel

pinion；　which　meshes　with　a　smaller　bevel　pinion

within　the　base。　This　latter　is　on　a　shaft　which

carries　a　small　gear　on　its　other　end；　to　mesh

with　a　larger　gear　on　a　shaft　which　carries　a

pointer　D　that　thus　turns　at　a　greatly　reduced

speed；　so　that　it　can　be　easily　timed。



_Fig。　62。　Air　Pressure　Indicator。_



AIR　PRESSURE　INDICATOR。This　little　apparatus

is　readily　made　of　a　base　A　which　is　provided

with　two　uprights　B；　C；　through　the　upper　ends　of

which　are　holes　to　receive　a　horizontally…disposed

bar　D。　One　end　of　the　bar　is　a　flat　plane

surface　E；　which　is　disposed　at　right　angles　to　the

bar；　and　firmly　fixed　thereto。



The　other　end　of　the　bar　has　a　lateral　pin　to

serve　as　a　pivot　for　the　end　of　a　link　F；　its　other

end　being　hinged　to　the　upper　end　of　a　lever　G；

which　is　pivoted　to　the　post　C；　a　short　distance

below　the　hinged　attachment　of　the　link　F；　so

that　the　long　end　of　the　pointer　which　is　constituted

by　the　lever　G　is　below　its　pivot；　and　has；

therefore；　a　long　range　of　movement。



A　spring　I　between　the　upper　end　of　the　pointer

G　and　the　other　post　B；　serves　to　hold　the　pointer

at　a　zero　position。　A　graduated　scale　plate　J；

within　range　of　the　pointer　will　show　at　a　glance

the　pressure　in　pounds　of　the　moving　wind；　and

for　this　purpose　it　would　be　convenient　to　make

the　plane　E　exactly　one　foot　square。