aeroplanes and dirigibles of war-第30章

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dispensing　with　the　rotary　converter。　　The　operating　principle　is

the　obtaining　of　a　series　of　unidirectional　impulses　by　a

condenser　discharge；　the　pulsating　currents　following　one　another

at　regular　intervals　at　a　frequency　of　500　impulses　per　second；

which　may　be　augmented　up　to　1；000　impulses　per　second。　　The

complete　weight　of　such　an　apparatus　is　40　pounds；　the　electric

generator；　which　is　no　larger　than　the　motor　used　for　driving　the

ordinary　table　ventilating　fan；　accounts　for　16　pounds　of　this

total。　　Under　test　at　sea；　upon　the　deck　of　a　ship；　a　range　of

250　miles　has　been　obtained。　　The　British　Government　carried　out

a　series　of　experiments　with　this　system；　using　a　small　plant

weighing　about　30　pounds；　with　which　communication　was　maintained

up　to　about　20　miles。



In　the　French　system　the　Reuget　transmitter　is　employed。　　The

apparatus；　including　the　dynamo；　which　is　extremely　small；　weighs

in　all　70　pounds。　　A　small　alternator　of　200　watts　and　100　volts

is　coupled　direct　to　the　aeroplane　motor；　a　new　clutch　coupler

being　employed　for　this　purpose。　　By　means　of　a　small　transformer

the　voltage　is　raised　to　30；000　volts；　at　which　the　condenser　is

charged。　　In　this　instance　the　musical　spark　method　is　employed。



The　whole　of　the　high　tension　wiring　is　placed　within　a　small

space　so　as　not　to　endanger　the　pilot；　while　the　transformer　is

hermetically　sealed　in　a　box　with　paraffin。　　The　aerial　comprises

a　trailing　wire　100　feet　in　length；　which；　however；　can　be

wound　in　upon　its　reel　within　15　seconds。　　This　reeled　antenna；

moreover；　is　fitted　with　a　safety　device　whereby　the　wire　can　be

cut　adrift　in　the　event　of　an　accident　befalling　the　aeroplane

and　necessitating　an　abrupt　descent。　　With　this　apparatus　the

French　authorities　have　been　able　to　maintain　communication　over

a　distance　of　30　miles。



In　maintaining　ethereal　communication　with　aeroplanes；　however；　a

portable　or　mobile　station　upon　the　ground　is　requisite；　and　this

station　must　be　within　the　radius　of　the　aerial　transmitter；　if

messages　are　to　be　received　from　aloft　with　any　degree　of

accuracy　and　reliability。　　Thus　it　will　be　recognised　that　the

land　station　is　as　important　as　the　aeroplane　equipment；　and

demands　similar　consideration。



A　wide　variety　of　systems　have　been　employed　to　meet　these

conditions。　　There　is　the　travelling　automobile　station；　in　which

the　installation　is　mounted　upon　a　motor…car。　　In　this　instance

the　whole　equipment　is　carried　upon　a　single　vehicle；　while　the

antenna　is　stowed　upon　the　roof　and　can　be　raised　or　lowered

within　a　few　seconds。　　If　motor　traction　is　unavailable；　then

animal　haulage　may　be　employed；　but　in　this　instance　the

installation　is　divided　between　two　vehicles；　one　carrying　the

transmitting　and　receiving　apparatus　and　the　generating　plant；

the　other　the　fuel　supplies　and　the　aerial；　together　with　spare

parts。



The　motive　power　is　supplied　by　a　small　air　cooled　petrol　or

gasoline　motor　developing　eight　horse…power；　and　coupled　direct

to　a　2…kilo　watt　alternator。　　At　one　end　of　the　shaft　of　the

latter　the　disk　discharger　is　mounted；　its　function　being　to

break　up　the　train　of　waves　into　groups　of　waves；　so　as　to　impart

a　musical　sound　to　the　note　produced　in　the　receiver。　　A　flexible

cable　transmits　the　electric　current　from　the　generator　to　the

wagon　containing　the　instruments。　　The　aerial　is　built　up　of

masts　carried　in　sections。



The　Germans　employ　a　mobile　apparatus　which　is　very　similar；　but

in　this　instance　the　mast　is　telescopic。　　When　closed　it　occupies

but　little　space。　　By　turning　the　winch　handle　the　mast　is

extended；　and　can　be　carried　to　any　height　up　to　a　maximum　of

about　100　feet。　　The　capacity　of　these　mobile　stations　varies

within　wide　limits；　the　range　of　the　largest　and　most　powerful

installations　being　about　200　miles。　　The　disadvantage　of　these

systems；　however；　is　that　they　are　condemned　to　territories　where

the　ground　at　the　utmost　is　gently　undulating；　and　where　there

are　roads　on　which　four…wheeled　vehicles　can　travel。



For　operation　in　hilly　districts；　where　only　trails　are　to　be

found；　the　Marconi　Company；　has　perfected　what　may　be　described

as　〃pack〃　and　〃knapsack〃　installations　respectively。　　In　the

first　named　the　whole　of　the　installation　is　mounted　upon　the

backs　of　four　horses。　　The　first　carries　the　generator　set；　the

second　the　transmitting　instruments；　the　third　the　receiving

equipment；　and　the　fourth　the　detachable　mast　and　stays。



The　generator　is　carried　upon　the　horse's　saddle；　and　is　fitted

with　a　pair　of　legs　on　each　side。　　On　one　side　of　the　saddle　is

mounted　a　small　highspeed　explosion　motor；　while　on　the　opposite

side；　in　axial　alignment　with　the　motor；　is　a　small　dynamo。　　When

it　is　desired　to　erect　the　installation　the　saddle　carrying　this

set　is　removed　from　the　horse's　back　and　placed　upon　the　ground；

the　legs　acting　as　the　support。　　A　length　of　shaft　is　then

slipped　into　sockets　at　the　inner　ends　of　the　motor　and　dynamo

shafts　respectively；　thus　coupling　them　directly；　while　the

current　is　transmitted　through　a　short　length　of　flexible　cable

to　the　instruments。　　The　mast　itself　is　made　in　lengths　of　about

four　feet；　which　are　slipped　together　in　the　manner　of　the

sections　of　a　fishing　rod；　and　erected；　being　supported　by　means

of　wire　guys。　　In　this　manner　an　antenna　from　40　to　50　feet　in

height　may　be　obtained。



The　feature　of　this　set　is　its　compactness；　the　equal　division　of

the　sections　of　the　installation；　and　the　celerity　with　which　the

station　may　be　set　up　and　dismantled　in　extremely　mountainous

country　such　as　the　Vosges；　where　it　is　even　difficult　for　a

pack…horse　to　climb　to　commanding　or　suitable　positions；　there　is

still　another　set　which　has　been　perfected　by　the　Marconi

Company。　　This　is　the　〃knapsack〃　set；　in　which　the　whole　of　the

installation；　necessarily　light；　small；　and　compact；　is　divided

among　four　men；　and　carried　in　the　manner　of　knapsacks　upon　their

backs。　　Although　necessarily　of　limited　radius；　such　an

installation　is　adequate　for　communication　within　the　restricted

range　of　air…craft。



Greater　difficulties　have　to　be　overcome　in　the　mounting　of　a

wireless　installation　upon　a　dirigible。　　When　the　Zeppelin　was

finally　accepted　by　the　German　Government；　the　military

authorities　emphasised　the　great　part　which　wireless　telegraphy

was　destined　to　play　in　connection　with　such　craft。　　But　have

these　anticipations　been　fulfilled？　　By　no　means；　as　a　little

reflection　will　suffice　to　prove。



In　the　first　place；　a　wireless　outfit　is　about　the　most　dangerous

piece　of　equipment　which　could　be　carried　by　such　a　craft　as　the

Zeppelin　unless　it　is　exceptionally　well　protected。　　As　is　well

known　the　rigidity　of　this　type　of　airship　is　dependent　upon　a

large　and　complicated　network　of　aluminium；　which　constitutes　the

frame。　　Such　a　huge　mass　of　metal　constitutes　an　excellent

collector　of　electricity　from　the　atmosphere；　it　becomes　charged

to　the　maximum　with　electricity。



In　this　manner　a　formidable　contributory　source　of　danger　to　the

airship　is　formed。　　In　fact；　this　was　the　reason　why　〃Z…IV〃

vanished　suddenly　in　smoke　and　flame　upon　falling　foul　of　the

branches　of　trees　during　its　descent。　　At　the　time　the　Zeppelin

was　a　highly　charged　electrical　machine　or　battery　as　it　were；

insulated　by　the　surrounding　air。　　Directly　the　airship　touched

the　trees　a　short　circuit　was　established；　and　the　resultant

spark　sufficed　to　fire　the　gas；　which　is　continuously　exuding

from　the　gas　bags。



After　this　accident　minute　calculations　were　made　and　it　was

ascertained　that　a　potential　difference　of　no　less　than　100；00

volts　existed　between　the　framework　of　the　dirigible　and　the

trees。　　This　tension　sufficed　to　produce　a　spark　4　inches　in

length。　　It　is　not　surprising　that　the　establishment　of　the

electric　equilibrium　by　contact　with　the　trees；　which　produced

such　a　spark　should　fire　the　hydrogen　inflation　charge。　　In　fact

the　heat　generated　was　so　intense　that　the　aluminium　metallic

framework　was　fused。　　The　measurements　which　were　made　proved

that　the　gas　was　consumed　within　15　seconds　and　the　envelope

destroyed　within　20　seconds。



As　a　result　of　this　disaster　endeavours　were　made　to　persuade

Count　Zeppelin　to　abandon　the　use　of　aluminium　for　the　framework

of　his　balloon　but　they　were　fruitless；　a　result　no　doubt　due　to

the　fact　that　the　inventor　of　the　airship　of　this　name　has　but　a

superficial　knowledge　of　the　various　sciences　which　bear　upon

aeronautics；　and　fully　illustrates　the　truth　of　the　old　adage

that　〃a　little　learning　is　a　dangerous　thing。〃　　Count　Zeppelin

continues　to　work　upon　his　original　lines；　but　the　danger　of　his

system　of　construction　was　not　lost　upon　another　German

investigator；　Professor　Schiitte；　who　forthwith　embarked　upon　the

construction　of　another　rigid　system；　similar　to　that　of

Zeppelin；　at　Lanz。　　In　this　vessel　aluminium　was　completely

abandoned　in　favour　of　a　framework　of　ash　and　poplar。



The　fact　that　the　aluminium　constituted　a　dangerous　collector　of

electricity　rendered　the　installation　of　wireless　upon　the

Zeppelin　not　only　perilous　but　difficult。　　Very　serious

disturbances　of　an　electrical　nature　were　set　up；　with　the　result

that　wireless　communication　between　the　travelling　dirigible　and

the　ground　below　was　rendered　extremely　uncertain。　　In　fact；　it

has　never　yet　been　possible　to　communicate　over　distances

exceeding　about　150　miles。　　Apart　from　this　defect；　the　danger　of

operating　the　wireless　is　obvious；　and　it　is　generally　believed

in　technical　circles　that　the　majority　of　the　Zeppelin　disasters

from　fire　have　been　directly　attributable　to　this；　especially

those　disasters　which　have　occurred　when　the　vessel　has　suddenly

exploded　before　coming　into　contact　with　terrestrial

obstructions。



In　the　later　vessels　of　this　type　the　wireless　installation　is

housed　in　a　well　insulated　compartment。　　This　insulation　has　been

carried；　to　an　extreme　degree；　which　indicates　that　at　last　the

authorities　have　recognised　the　serious　menace　that　wireless

offers　to　the　safety　of　the　craft；　with　the　result　that　every

protective　device　to　avoid　disaster　from　this　cause　has　been

freely　adopted。



The　fact　that　it　is　not　possible　to　maintain　cornmunication　over

a　distance　exceeding　some　20　miles　is　a　severe　handicap　to　the

progressive　development　of　wireless　telegraphy　in　this　field。　　It

is　a　totally　inadequate　radius　when　the　operations　of　the　present

war　are　borne　in　mind。　　A　round　journey　of　200；　or　even　more

miles　is　considered　a　mere　jaunt；　it　is　the　long　distance　flight

which　counts；　and　which　contributes　to　the　value　of　an　airman's

observations。　　The　general　impression　is　that　the　fighting　line

or　zone　comprises　merely　two　or　three　successive　stretches　of

trenches　and　other　defences；　rep