aeroplanes-第20节

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being　in　range　of　a　circle　with　degrees

indicated　thereon；　and　the　base　attached　to　the

frame　of　the　machine；　can　always　be　observed；

and　the　conditions　noted　at　the　time　the　changes

take　place。



PENDULUM　STABILIZER。In　many　respects　the

use　of　a　pendulum　has　advantages　over　the　gyroscope。

The　latter　requires　power　to　keep　it　in

motion。　The　pendulum　is　always　in　condition

for　service。　While　it　may　be　more　difficult　to

adjust　the　pendulum；　so　that　it　does　not　affect

the　planes　by　too　rapid　a　swing；　or　an　oscillation

which　is　beyond　the　true　angle　desired；　still；　these

are　matters　which；　in　time；　will　make　the　pendulum

a　strong　factor　in　lateral　stability。



_Fig。　67。　Simple　Pendulum　Stabilizer。_



It　is　an　exceedingly　simple　matter　to　attach　the

lead　wires　from　an　aileron　to　the　pendulum。　In

Fig。　67　one　plan　is　illustrated。　The　pendulum

A　swings　from　the　frame　B　of　the　machine；　the

ailerons　a　being　in　this　case　also　shown　at　right

angles　to　their　true　positions。



The　other；　Fig。　68；　assumes　that　the　machine　is

exactly　horizontal；　and　as　the　pendulum　is　in　a

vertical　position；　the　forward　edges　of　both　ailerons

are　elevated；　but　when　the　pendulum　swings

both　ailerons　will　be　swung　with　their　forward

margins　up　or　down　in　unison；　and　thus　the　proper

angles　are　made　to　right　the　machine。



STEERING　AND　CONTROLLING　WHEEL。For　the

purpose　of　concentrating　the　control　in　a　single

wheel；　which　has　not　alone　a　turning　motion；　but

is　also　mounted　in　such　a　manner　that　it　will　oscillate

to　and　fro；　is　very　desirable；　and　is　adapted

for　any　kind　of　machine。



_Fig。　68。　Pendulum　Stabilizers。_



Fig。　69　shows　such　a　structure；　in　which　A

represents　the　frame　of　the　machine；　and　B　a

segment　for　the　stem　of　the　wheel；　the　segment

being　made　of　two　parts；　so　as　to　form　a　guideway

for　the　stem　a　to　travel　between；　and　the　segment

is　placed　so　that　the　stem　will　travel　in　a

fore　and　aft　direction。



The　lower　end　of　the　stem　is　mounted　in　a

socket；　at　D；　so　that　while　it　may　be　turned；　it

will　also　permit　this　oscillating　motion。　Near　its

lower　end　is　a　cross　bar　E　from　which　the　wires

run　to　the　vertical　control　plane；　and　also　to　the

ailerons；　if　the　machine　is　equipped　with　them；　or

to　the　warping　ends　of　the　planes。



_Fig。　69。　Steering　and　Control　Wheel。_



Above　the　cross　arms　is　a　loose　collar　F　to

which　the　fore　and　aft　cords　are　attached　that　go

to　the　elevators；　or　horizontal　planes。　The　upper

end　of　the　stem　has　a　wheel　G；　which　may　also　be

equipped　with　the　throttle　and　spark　levers。



AUTOMATIC　STABILIZING　WINGS。Unquestionably；

the　best　stabilizer　is　one　which　will　act　on

its　own　initiative。　The　difficulty　with　automatic

devices　is；　that　they　act　too　late；　as　a　general

thing；　to　be　effective。　The　device　represented　in

Fig。　70　is　very　simple；　and　in　practice　is　found　to

be　most　efficient。



In　this　Fig。　70　A　and　B　represent　the　upper

and　the　lower　planes；　respectively。　Near　the　end

vertical　standards　a；　D；　are　narrow　wings　E　E；

F　F；　hinged　on　a　fore　and　aft　line　close　below

each　of　the　planes；　the　wings　being　at　such　distances

from　the　standards　C　D　that　when　they

swing　outwardly　they　will　touch　the　standards；

and　when　in　that　position　will　be　at　an　angle　of

about　35　degrees　from　the　planes　A　B。



_Fig。　70。　Automatic　Stabilizing　Wings。_



_Fig。　71。　Action　of　Stabilizing　Wings。_



Inwardly　they　are　permitted　to　swing　up　and

lie　parallel　with　the　planes；　as　shown　in　Fig。　71

where　the　planes　are　at　an　angle。　In　turning；　all

machines　skid；that　is　they　travel　obliquely

across　the　field；　and　this　is　also　true　when　the

ship　is　sailing　at　right　angles　to　the　course　of　the

wind。



This　will　be　made　clear　by　reference　to　Fig。

72；　in　which　the　dart　A　represents　the　direction

of　the　movement　of　the　aeroplane；　and　B　the

direction　of　the　wind；　the　vertical　rudder　a　being

almost　at　right　angles　to　the　course　of　the　wind。



_Fig。　72。　Into　the　Wind　at　an　Angle。_



In　turning　a　circle　the　same　thing　takes　place

as　shown　in　Fig。　73；　with　the　tail　at　a　different

angle；　so　as　to　give　a　turning　movement　to　the

plane。　It　will　be　seen　that　in　the　circling　movement

the　tendency　of　the　aeroplane　is　to　fly　out

at　a　tangent；　shown　by　the　line　D；　so　that　the

planes　of　the　machine　are　not　radially…disposed

with　reference　to　the　center　of　the　circle；　the　line

E　showing　the　true　radial　line。



Referring　now　to　Fig。　71；　it　will　be　seen　that

this　skidding　motion　of　the　machine　swings　the

wings　E　F　inwardly；　so　that　they　offer　no　resistance

to　the　oblique　movement；　but　the　wings　E

E；　at　the　other　end　of　the　planes　are　swung　outwardly；

to　provide　an　angle；　which　tends　to　raise

up　the　inner　end　of　the　planes；　and　thereby　seek

to　keep　the　planes　horizontal。



_Fig。　73。　Turning　a　Circle。_



BAROMETERS。These　instruments　are　used　for

registering　heights。　A　barometer　is　a　device　for

measuring　the　weight　or　pressure　of　the　air。

The　air　is　supposed　to　extend　to　a　height　of　40

miles　from　the　surface　of　the　sea。　A　column　of

air　one　inch　square；　and　forty　miles　high；　weighs

the　same　as　a　column　of　mercury　one　inch　square

and　30　inches　high。



Such　a　column　of　air；　or　of　mercury；　weighs

14　3/4　pounds。　If　the　air　column　should　be

weighed　at　the　top　of　the　mountain；　that　part

above　would　weigh　less　than　if　measured　at　the

sea　level；　hence；　as　we　ascend　or　descend　the　pressure

becomes　less　or　more；　dependent　on　the　altitude。



Mercury　is　also　used　to　indicate　temperature；

but　this　is　brought　about　by　the　expansive　quality

of　the　mercury；　and　not　by　its　weight。



_Fig。　74。　Aneroid　Barometer。_



ANEROID　BAROMETER。The　term　Aneroid　barometer

is　frequently　used　in　connection　with　air…

ship　experiments。　The　word　aneroid　means　not

wet；　or　not　a　fluid；　like　mercury；　so　that；　while

aneroid　barometers　are　being　made　which　do　use

mercury；　they　are　generally　made　without。



One　such　form　is　illustrated　in　Fig。　74；　which

represents　a　cylindrical　shell　A；　which　has　at　each

end　a　head　of　concentrically　formed　corrugations。

These　heads　are　securely　fixed　to　the　ends　of　the

shell　A。　Within；　one　of　the　disk　heads　has　a

short　stem　C；　which　is　attached　to　the　short　end

of　a　lever　D；　this　lever　being　pivoted　at　E。　The

outer　end　of　this　lever　is　hinged　to　the　short　end

of　another　lever　F；　and　so　by　compounding　the

levers；　it　will　be　seen　that　a　very　slight　movement

of　the　head　B　will　cause　a　considerable　movement

in　the　long　end　of　the　lever　F。



This　end　of　the　lever　F　connects　with　one　limb

of　a　bell…crank　lever　G；　and　its　other　limb　has　a

toothed　rack　connection　with　a　gear　H；　which

turns　the　shaft　to　which　the　pointer　I　is　attached。



Air　is　withdrawn　from　the　interior　of　the　shell；

so　that　any　change　in　the　pressure；　or　weight　of

the　atmosphere；　is　at　once　felt　by　the　disk　heads；

and　the　finger　turns　to　indicate　the　amount　of

pressure。



HYDROPLANES。Hydro　means　water；　hence　the

term　hydroplane　has　been　given　to　machines

which　have　suitable　pontoons　or　boats；　so　they

may　alight　or　initiate　flight　from　water。



There　is　no　particular　form　which　has　been

adopted　to　attach　to　aeroplanes；　the　object　generally

being　to　so　make　them　that　they　will　sustain

the　greatest　amount　of　weight　with　the　least

submergence；　and　also　offer　the　least　resistance

while　the　motor　is　drawing　the　machine　along　the

surface　of　the　water；　preparatory　to　launching　it。



SUSTAINING　WEIGHT　OF　PONTOONS。A　pontoon

having　within　nothing　but　air；　is　merely　a　measuring

device　which　determines　the　difference　between

the　weight　of　water　and　the　amount　placed

on　the　pontoon。　Water　weighs　62　1/2　pounds　per

cubic　foot。　Ordinary　wood；　an　average　of　32

pounds；　and　steel　500　pounds。



It　is；　therefore；　an　easy　matter　to　determine

how　much　of　solid　matter　will　be　sustained　by　a

pontoon　of　a　given　size；　or　what　the　dimensions

of　a　pontoon　should　be　to　hold　up　an　aeroplane

which　weighs；　with　the　pilot；　say；　1100　pounds。



As　we　must　calculate　for　a　sufficient　excess　to

prevent　the　pontoons　from　being　too　much　immersed；

and　also　allow　a　sufficient　difference　in

weight　so　that　they　will　keep　on　the　surface　when

the　aeroplane　strikes　the　surface　in　alighting；　we

will　take　the　figure　of　1500　pounds　to　make　the

calculations　from。



If　this　figure　is　divided　by　62　1/2　we　shall　find

the　cubical　contents　of　the　pontoons；　not　considering；

of　course；　the　weight　of　the　material　of　which

they　are　composed。　This　calculation　shows　that

we　must　have　24　cubic　feet　in　the　pontoons。



As　there　should　be　two　main　pontoons；　and　a

smaller　one　for　the　rear；　each　of　the　main　ones

might　have　ten　cubic　feet；　and　the　smaller　one

four　cubic　feet。



SHAPES　OF　THE　PONTOONS。We　are　now　ready

to　design　the　shapes。　Fig。　75　shows　three　general

types；　A　being