flying machines-第13章

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weight　215　pounds。



Gnome7　and　14　cylinders；　revolving　type；　air…cooled；

50　and　100　horse　power；　weight　150　and　300　pounds。



Darracq2　to　14　cylinders；　water　cooled；　30　to　200

horse　power；　weight　of　smallest　100　pounds。



Wright4…cylinder；　water…cooled；　25　horse　power；

weight　200　pounds。



Antoinette8　and　16…cylinder；　water…cooled；　50　and　100

horse　power；　weight　250　and　500　pounds。



E。　N。　V。8…cylinder；　water…cooled；　from　30　to　80

horse　power；　according　to　bore　of　cylinder；　weight　150

to　400　pounds。



Curtiss8…cylinder；　water…cooled；　60　horse　power；

weight　300　pounds。



Average　Weight　Per　Horse　Power。



It　will　be　noticed　that　the　Gnome　motor　is　unusually

light；　being　about　three　pounds　to　the　horse　power

produced；　as　opposed　to　an　average　of　4　1/2　pounds　per

horse　power　in　other　makes。　This　result　is　secured　by

the　elimination　of　the　fly…wheel；　the　engine　itself　revolving；

thus　obtaining　the　same　effect　that　would　be　produced

by　a　fly…wheel。　The　Farcot　is　even　lighter；　being

considerably　less　than　three　pounds　per　horse　power；

which　is　the　nearest　approach　to　the　long…sought　engine

equipment　that　will　make　possible　a　complete　flying

machine　the　total　weight　of　which　will　not　exceed　one

pound　per　square　foot　of　area。



How　Lightness　Is　Secured。



Thus　far　foreign　manufacturers　are　ahead　of　Americans

in　the　production　of　light…weight　aerial　motors；　as

is　evidenced　by　the　Gnome　and　Farcot　engines；　both　of

which　are　of　French　make。　Extreme　lightness　is　made

possible　by　the　use　of　fine；　specially　prepared　steel　for

the　cylinders；　thus　permitting　them　to　be　much　thinner

than　if　ordinary　forms　of　steel　were　used。　Another　big

saving　in　weight　is　made　by　substituting　what　are

known　as　〃auto　lubricating〃　alloys　for　bearings。　These

alloys　are　made　of　a　combination　of　aluminum　and　magnesium。



Still　further　gains　are　made　in　the　use　of　alloy　steel

tubing　instead　of　solid　rods；　and　also　by　the　paring　away

of　material　wherever　it　can　be　done　without　sacrificing

strength。　This　plan；　with　the　exclusive　use　of　the　best

grades　of　steel；　regardless　of　cost；　makes　possible　a

marked　reduction　in　weight。



Multiplicity　of　Cylinders。



Strange　as　it　may　seem；　multiplicity　of　cylinders　does

not　always　add　proportionate　weight。　Because　a　4…

cylinder　motor　weighs　say　100　pounds；　it　does　not　necessarily

follow　that　an　8…cylinder　equipment　will　weigh

200　pounds。　The　reason　of　this　will　be　plain　when　it

is　understood　that　many　of　the　parts　essential　to　a　4…

cylinder　motor　will　fill　the　requirements　of　an　8…cylinder

motor　without　enlargement　or　addition。



Neither　does　multiplying　the　cylinders　always　increase

the　horsepower　proportionately。　If　a　4…cylinder

motor　is　rated　at　25　horsepower　it　is　not　safe　to　take

it　for　granted　that　double　the　number　of　cylinders　will

give　50　horsepower。　Generally　speaking；　eight　cylinders；

the　bore；　stroke　and　speed　being　the　same；　will　give

double　the　power　that　can　be　obtained　from　four；　but

this　does　not　always　hold　good。　Just　why　this　exception

should　occur　is　not　explainable　by　any　accepted　rule。



Horse　Power　and　Speed。



Speed　is　an　important　requisite　in　a　flying…machine

motor；　as　the　velocity　of　the　aeroplane　is　a　vital　factor

in　flotation。　At　first　thought；　the　propeller　and　similar

adjuncts　being　equal；　the　inexperienced　mind　would

naturally　argue　that　a　50…horsepower　engine　should

produce　just　double　the　speed　of　one　of　25…horsepower。

That　this　is　a　fallacy　is　shown　by　actual　performances。

The　Wrights；　using　a　25…horsepower　motor；　have　made

44　miles　an　hour；　while　Bleriot；　with　a　50…horsepower

motor；　has　a　record　of　a　short…distance　flight　at　the　rate

of　52　miles　an　hour。　The　fact　is　that；　so　far　as　speed

is　concerned；　much　depends　upon　the　velocity　of　the

wind；　the　size　and　shape　of　the　aeroplane　itself；　and　the

size；　shape　and　gearing　of　the　propeller。　The　stronger

the　wind　is　blowing　the　easier　it　will　be　for　the　aeroplane

to　ascend；　but　at　the　same　time　the　more　difficult

it　will　be　to　make　headway　against　the　wind　in　a　horizontal

direction。　With　a　strong　head　wind；　and　proper

engine　force；　your　machine　will　progress　to　a　certain

extent；　but　it　will　be　at　an　angle。　If　the　aviator　desired

to　keep　on　going　upward　this　would　be　all　right；　but

there　is　a　limit　to　the　altitude　which　it　is　desirable　to

reachfrom　100　to　500　feet　for　expertsand　after　that

it　becomes　a　question　of　going　straight　ahead。



Great　Waste　of　Power。



One　thing　is　certaineven　in　the　most　efficient　of

modern　aerial　motors　there　is　a　great　loss　of　power　between

the　two　points　of　production　and　effect。　The

Wright　outfit；　which　is　admittedly　one　of　the　most　effective

in　use；　takes　one　horsepower　of　force　for　the　raising

and　propulsion　of　each　50　pounds　of　weight。　This；

for　a　25…horsepower　engine；　would　give　a　maximum　lifting

capacity　of　1250　pounds。　It　is　doubtful　if　any　of　the

higher　rated　motors　have　greater　efficiency。　As　an　8…

cylinder　motor　requires　more　fuel　to　operate　than　a　4…

cylinder；　it　naturally　follows　that　it　is　more　expensive

to　run　than　the　smaller　motor；　and　a　normal　increase　in

capacity；　taking　actual　performances　as　a　criterion；　is

lacking。　In　other　words；　what　is　the　sense　of　using　an

8…cylinder　motor　when　one　of　4　cylinders　is　sufficient？



What　the　Propeller　Does。



Much　of　the　efficiency　of　the　motor　is　due　to　the　form

and　gearing　of　the　propeller。　Here　again；　as　in　other

vital　parts　of　flying…machine　mechanism；　we　have　a　wide

divergence　of　opinion　as　to　the　best　form。　A　fish　makes

progress　through　the　water　by　using　its　fins　and　tail；

a　bird　makes　its　way　through　the　air　in　a　similar　manner

by　the　use　of　its　wings　and　tail。　In　both　instances　the

motive　power　comes　from　the　body　of　the　fish　or　bird。



In　place　of　fins　or　wings　the　flying　machine　is　equipped

with　a　propeller；　the　action　of　which　is　furnished　by　the

engine。　Fins　and　wings　have　been　tried；　but　they　don't

work。



While　operating　on　the　same　general　principle；　aerial

propellers　are　much　larger　than　those　used　on　boats。

This　is　because　the　boat　propeller　has　a　denser；　more

substantial　medium　to　work　in　（water）；　and　consequently

can　get　a　better　〃hold；〃　and　produce　more　propulsive

force　than　one　of　the　same　size　revolving　in　the　air。

This　necessitates　the　aerial　propellers　being　much　larger

than　those　employed　for　marine　purposes。　Up　to　this

point　all　aviators　agree；　but　as　to　the　best　form　most　of

them　differ。



Kinds　of　Propellers　Used。



One　of　the　most　simple　is　that　used　by　Curtiss。　It

consists　of　two　pear…shaped　blades　of　laminated　wood；

each　blade　being　5　inches　wide　at　its　extreme　point；

tapering　slightly　to　the　shaft　connection。　These　blades

are　joined　at　the　engine　shaft；　in　a　direct　line。　The　propeller

has　a　pitch　of　5　feet；　and　weighs；　complete；　less

than　10　pounds。　The　length　from　end　to　end　of　the　two

blades　is　6　1/2　feet。



Wright　uses　two　wooden　propellers；　in　the　rear　of　his

biplane；　revolving　in　opposite　directions。　Each　propeller

is　two…bladed。



Bleriot　also　uses　a　two…blade　wooden　propeller；　but

it　is　placed　in　front　of　his　machine。　The　blades　are　each

about　3　1/2　feet　long　and　have　an　acute　〃twist。〃



Santos…Dumont　uses　a　two…blade　wooden　propeller；

strikingly　similar　to　the　Bleriot。



On　the　Antoinette　monoplane；　with　which　good　records

have　been　made；　the　propeller　consists　of　two　spoon…

shaped　pieces　of　metal；　joined　at　the　engine　shaft　in

front；　and　with　the　concave　surfaces　facing　the　machine。



The　propeller　on　the　Voisin　biplane　is　also　of　metal；

consisting　of　two　aluminum　blades　connected　by　a　forged

steel　arm。



Maximum　thrust；　or　stressexercise　of　the　greatest

air…displacing　forceis　the　object　sought。　This；　according

to　experts；　is　best　obtained　with　a　large　propeller

diameter　and　reasonably　low　speed。　The　diameter　is　the