aeroplanes and dirigibles of war-第30节

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But　even　under　these　circumstances　the　climatic　conditions　must

be　extremely　favourable。　　If　the　elements　are　unpropitious　the

airship　must　venture　nearer　to　its　objective。　　These　data　were

not　difficult　to　collect；　inasmuch　as　they　were　more　or　less

available　from　the　results　of　military　observations　with　captive

balloons；　the　conditions　being　somewhat　similar。　　With　the

ordinary　captive　balloon　it　has　been　found　that；　in　clear

weather；　a　radius　of　about　3　3/4　miles　at　the　maximum　elevation

constitutes　its　range　of　reliable　utility。



With　the　aeroplane；　however；　the　conditions　are　very　dissimilar。　

In　the　first　place　the　machine　owing　to　its　diminutive　size　as

compared　with　the　airship；　offers　a　small　and　inconspicuous

target。　　Then　there　is　its　high　independent　speed；　which　is　far

beyond　that　of　the　airship。　　Furthermore　its　mobility　is　greater。　

It　can　wheel；　turn　sharply　to　the　right　or　to　the　left；　and

pursue　an　irregular　undulating　flight　in　the　horizontal　plane；

which　renders　it　well　nigh　impossible　for　a　gunner　to　pick　it　up。　

The　machine　moves　at　a　higher　relative　speed　than　that　at　which

the　gun　can　be　trained。　　It　is　the　rapid　and　devious　variation

which　so　baffles　the　gunner；　who　unless　he　be　highly　skilled　and

patient；　is　apt　to　commence　to　fire　wildly　after　striving　for　a

few　moments；　and　in　vain；　to　pick　up　the　range；　he　trusts　to　luck

or　depends　upon　blind…shooting；　which　invariably　results　in　a

waste　of　ammunition。



A　gun；　to　be　of　tangible　destructive　efficiency　when　directed

against　aircraft；　especially　those　depending　upon　the　gas…bag　for

equilibrium；　must　be　of　special　design。　　It　must　be　capable　of

firing　at　an　angle　only　a　few　degrees　less　than　the　absolute

vertical；　and　in　order　to　follow　the　rapid　and　involved　movements

of　its　objective；　must　be　so　mobile　that　it　can　be　trained

through　a　complete　circle　at　any　angle　of　inclination　less　than

its　maximum。　　At　the　same　time；　if　the　weapon　is　being　used　in

field　operations　it　must　be　mounted　upon　a　carriage　of　adequate

mobility　to　enable　it　to　follow　the　airship；　and　thereby　keep

pace　with　the　latter；　so　that　the　aerial　craft　may　be　sorely

harassed　if　not　actually　hit。　　The　automobile　is　the　obvious

vehicle　for　this　duty；　and　it　has　accordingly　been　extensively

used　in　this　service。



The　automobile　and　the　gun　mounted　thereon　follow　widely

different　lines。　　Some　vehicles　are　designed　especially　for　this

duty；　while　others　are　improvisations；　and　be　it　noted；　in

passing；　that　many　of　the　latter　have　proved　more　serviceable

than　the　former。　　Still；　the　first…named　is　to　be　preferred；

inasmuch　as　necessarily　it　is　designed　to　meet　the　all…round

requirements　imposed；　and　consequently　is　better　able　to　stand　up

to　the　intended　work；　whereas　the　extemporised　vehicle　is　only

serviceable　under　favourable　conditions。



The　Krupp　Company　has　evolved　many　designs　of　anti…aircraft

motor…driven　guns〃Archibalds〃　the　British　airmen　term　them　with

emphatic　levity。　　They　are　sturdily…built　vehicles　fitted　with

heavy　motors；　developing　from　40　to　50　horse…power；　with　the

chassis　not　widely　dissimilar　from　that　adopted　for　motor…omnibus

traffic。　　Consequently；　they　are　not　necessarily　condemned　to　the

high…roads；　but　within　certain　limits　are　able　to　travel　across

country；　i。e。；　upon　fields　or　other　level　expanses；　where　the

soil　is　not　unduly　soft。



But　the　very　character　of　the　problem　rendered　the　evolution　of

the　vehicle　a　somewhat　perplexing　matter。　　There　were　many

factors　which　had　to　be　taken　into　consideration；　and　it　was

possible　to　meet　the　imposed　requirements　only　within　certain

limits。　　In　the　first　place；　the　weight　of　the　gun　itself　had　to

be　kept　down。　　It　was　obviously　useless　to　overload　the　chassis。　

Again；　the　weight　of　the　projectile　and　its　velocity　had　to　be

borne　in　mind。　　A　high　velocity　was　imperative。　　Accordingly；　an

initial　velocity　varying　from　2；200　to　2；700　feet　per　second；

according　to　the　calibre　of　the　gun；　was　determined。



Moreover；　as　mobility　was　an　indispensable　condition；　the　gun　had

to　be　so　mounted　that　it　could　be　fired　from　the　motor…car　even

if　the　latter　were　travelling　at　high　speed。　　This　requirement

entailed　another　difficulty。　　The　gun　had　to　be　mounted　in　such　a

manner　as　to　enable　the　gunner　to　train　it　easily　and　readily

through　the　complete　circle　and　through　its　complete　range　of

vertical　inclination。　　As　the　result　of　prolonged　experiments　it

was　ascertained　that　the　most　suitable　arrangement　was　a　pedestal

mounting；　either　within　a　turret　or　upon　an　open　deck。　　To　meet

the　weight　of　the　gun；　as　well　as　the　strains　and　stresses

incidental　to　firing；　the　chassis　was　strengthened；　especially　

over　the　rear　axle　near　which　the　mounting　is　placed。



The　heaviest　gun　of　this　type　is　the　10。5　centimetre　（4　1/4…inch）

quick…firer；　throwing　a　shell　weighing　nearly　forty　pounds；　with

an　initial　velocity　of　2；333　feet　per　second。　　This　〃Archibald〃

is　totally　unprotected。　　The　gun　is　mounted　centrally　upon　the

carriage　over　the　rear　axle；　and　occupies　the　centre　of　the　deck

between　the　driver's　seat　and　that　of　the　gun　crew　behind。　　The

whole　of　the　deck　is　clear；　thereby　offering　no　obstruction　to

the　gunner　in　training　the　weapon；　while　the　space　may　be　widened

by　dropping　down　the　wings　of　the　vehicle。　　At　the　rear　is　a　seat

to　accommodate　the　gun　crew；　beneath　which　the　ammunition　is

stowed。　　When　travelling　and　out　of　action；　the　gun　lies

horizontally；　the　muzzle　pointing　from　the　rear　of　the　car。



To　reduce　the　strains　arising　from　firing；　the　arm　is　fitted　with

what　is　known　as　the　〃differential　recoil。〃　　Above　the　breach　is

an　air　recuperator　and　a　piston；　while　there　is　no　hydraulic

brake　such　as　is　generally　used。　　The　compressor　is　kept　under

compression　while　the　car　is　travelling　with　the　gun　out　of

action；　so　that　the　arm　is　available　for　instant　firing。　　This　is

a　departure　from　the　general　practice　in　connection　with　such

weapons。　　When　the　gun　is　loaded　the　bolt　which　holds　the

compressor　back　is　withdrawn；　either　by　the　hand　for　manual

firing；　or　by　the　action　of　the　automatic　closing　of　the

breech　when　the　arm　is　being　used　as　a　quick…firer。　　In　firing

the　gun　is　thrown　forward　under　the　pressure　of　the　released　air

which　occurs　at　the　moment　of　discharge。　　The　energy　of　the

recoil　brings　the　gun　back　and　at　the　same　time　recharges　the

compressed　air　reservoir。



The　gun　is　so　mounted　upon　its　pedestal　as　to　enable　a　maximum

vertical　inclination　of　75　degrees　to　be　obtained。　　The　mounting

system　also　enables　the　weapon　to　be　trained　in　any　desired

direction　up　to　the　foregoing　maximum　elevation　throughout　a

complete　circle；　and　it　can　be　handled　with　ease　and　celerity。　　A

smaller　〃Archibald〃　is　the　7。5　centimetre　（3…inch　gun）　throwing　a

14。3　pound　shell　at　an　initial　velocity　of　about　2；170　feet　per

second。



The　turret　anti…aircraft　gun　carried　upon　a　motor…car　differs

from　the　foregoing　very　considerably。　　This　is　a　protected　arm。　

The　gun　of　7。1　centimetresapproximately　2。75　inchesis　mounted

in　the　same　manner　upon　the　car…deck　and　over　the　driving　axle；

but　is　enclosed　within　a　sheet　steel　turret；　which　is　proof

against　rifle　and　machine…gun　fire。　　This　turret　resembles　the

conning…tower　of　a　battleship；　and　is　sufficiently　spacious　to

house　the　whole　of　the　gun　crew；　the　internal　diameter　being

about　seven　feet。　　Access　to　the　turret　is　obtained　through　a

rear　door。　　This　gun　has　a　maximum　elevation　of　about　75　degrees；

while　its　operation　and　mechanism　are　similar　to　those　of　the

unprotected　weapon。



The　vehicle　itself　is　practically　identical　with　the　armoured

motor…car；　which　has　played　such　an　important　part　during　the

present　campaign；　the　driver　being　protected　by　a　bullet…proof

steel　screen　similar　in　design　to　the　ordinary　glass　wind…screen

fitted　to　touring　automobiles。　　This　is　carried　sufficiently　high

to　offer　complete　protection　to　his　head　when　seated　at　the

wheel；　while　through　a　small　orifice　in　this　shield　he　is　able　to

obtain　a　clear　view　of　the　road。　　The　engine　and　its　vital　parts

are　also　adequately　protected。　　The　ammunition　is　carried　in　a

cupboard…like　recess　forming　part　of　the　driver's　seat；　encased

in　bullet…proof　steel　sheeting　with　flap…doors。　　This　device

enables　the　shells　to　be　withdrawn　readily　from　the　side　of　the

car　and　passed　to　the　crew　within　the　turret。　　The　caisson　is　of

sufficient　dimensions　to　receive　69　shells。



The　Ehrhardt　airship　fighting　ordnance　is　similarly　adapted　to

motor…car　operations；　one　type　being　especially　powerful。　　The

whole　of　the　vehicle　is　encased　in　armour…plating　impervious　to

rifle　and　machine…gun　fire。　　The　driver　is　provided　with　a　small

orifice　through　which　he　is　able　to　obtain　a　clear　uninterrupted

view　of　the　road　ahead；　while　the　armouring　over　the　tonneau　is

carried　to　a　sufficient　hei