aeroplanes and dirigibles of war-第25章

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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　height　to　allow　head…room　to　the　gun　crew

when　standing　at　the　gun。　　All　four　wheels　are　of　the　disk　type

and　fashioned　from　heavy　sheet　steel。　　The　motor　develops　40…50

horse…power　and；　in　one　type；　in　order　to　mitigate　the　risk　of

breakdown　or　disablement；　all　four　wheels　are　driven。　　The　gun；　a

small　quick…firer；　is　mounted　on　a　pedestalin　a　projecting

conning…tower。　　The　mounting　is　placed　behind　the　driver's　seat；

and　is　trained　and　operated　from　the　tonneau。　　The　maximum

elevation　is　75　degrees；　and　like　the　gun　carriage　bearing　the

tube　guide　it　can　be　moved　through　a　complete　circle；　being　free

to　rotate　in　the　fixed　pivot　jack　to　enable　this　end　to　be

attained。



The　foregoing　may　be　said　to　represent　the　most　powerful　types　of

mobile　anti…aircraft　weapons　used　by　the　Austro…German　forces

to…day。　　Arms　of　similar　design；　roughly　speaking；　have　also　been

introduced　into　the　French　and　Russian　services。　　In　addition

many　semi…armoured　weapons　of　this　character　are　in　operation；

some　specially　built　for　the　work；　while　others　have　been

improvised。　　In　the　semi…armoured　motor…car　the　carriage　follows

the　usual　lines；　it　has　an　open　top；　the　armouring　comprising　the

body　of　the　tonneau　and　the　diskwheels；　which　are　made　of　light

bullet…proof　steel。　　Here　again　the　prevailing　practice　is　to

mount　the　gun　as　nearly　above　the　rear　axle　as　possible；　and

to　work　it　from　the　tonneau。　　The　maximum　elevation　is　also　75

degrees；　with　training　throughout　the　entire　circle。



Another　type　comprises　a　very　light　machine　gun　of　rifle　calibre；

and　this　is　intended　for　attachment　to　an　ordinary　motor　car。　

There　is　a　pedestal　mounting　which　can　be　set　within　the　tonneau；

while　the　weapon　is　pivoted　in　an　outrigger；　the　latter　being

free　to　rotate　in　its　pivot　jack。　　This　arrangement　enables　the

arm　to　cover　a　wide　range；while　it　also　admits　of　training

through　an　extensive　angle　of　elevation。



The　Allied　forces　improvised　travelling　anti…aircraft　offences

by　mounting　the　latest　types　of　Vickers；　Hotchkiss；　and　other

machine　guns　in　armoured　motor　cars。　　Some　of　these　have　the

domed　turret　form；　with　the　gun　projecting　through　the　roof；

while　others　are　protected　against　hostile　attack　from　the　side

only；　the　carriage　being　panelled　with　bullet…proof　steel

sheeting。　　While　such　weapons　are　useful；　inasmuch　as　they　can

maintain　a　hot　fire　ranging　up　to　750　shots　per　minute；　they　are

not　to　be　compared　with　the　〃Archibalds；〃　which　are　able　to　throw

heavy　shrapnel　and　incendiary　shells；　and　have　a　vertical　range

of　about　6；000　to　8；000　feet。



The　improvised　motor…gun　has　not　proved　a　complete　success；

except　in　those　instances　when　the　hostile　aircraft　has　ventured

to　approach　somewhat　closely　to　the　ground。　　The　more　formidable

weapons　cannot　be　mounted　upon　ordinary　vehicles；　inasmuch　as　the

increase　in　weight；　which　is　appreciable；　impairs　the　efficiency

of　the　vehicle；　and　at　the　same　time　enhances　the　possibility　of

breakdown　at　a　critical　moment。　　For　such　arms　a　special　and

substantial　chassis　is　imperative；　while　the　motive　power　and

gearing　must　be　adapted　to　the　circumstances。



Motor…mounted　anti…aircraft　weapons；　however；　have　not　proved　an

unqualified　success。　　The　fact　that　the　vehicles　are　condemned　to

the　high　roads；　or　at　least　to　comparatively　smooth　and　level

ground；　constitutes　a　severe　handicap。　　Again；　when　travelling　at

high　speed；　and　this　is　essential　when　pursuing　a　fast　aeroplane；

the　accurate　laying　of　the　weapon　is　extremely　difficult；　owing

to　the　oscillation　of　the　vehicle　itself；　especially　if　the　road

surface　is　in　a　bad　condition。　　The　sighting　arrangements　are　of

a　wonderfully　complete　character；　as　described　elsewhere；　but　the

irregular　rolling　movement　arising　from　high　speed　is　a

nullifying　quantity。　　It　is　tolerably　easy　for　the　aircraft；

especially　an　aeroplane；　to　evade　successful　pursuit；　either　by

rising　to　an　elevation　beyond　the　range　of　the　gun；　or　by

carrying　out　baffling　evolutions　such　as　irregular　undulating

flight；　wheeling；　and　climbing。　　According　to　the　reports　of　the

British　and　French　airmen　the　〃Archibald〃　has　failed　to　establish

the　glowing　reputation　which　was　anticipated；　for　the　simple

reason　that；　unless　it　has　a　clear　straight　road　and　can　maintain

its　high　speed；　it　can　easily　be　out…distanced　by　the　fleet　human

bird。



The　motor…car　suffers　from　another　serious　disability。　　It　cannot

manoeuvre　with　sufficient　celerity。　　For　instance；　if　it　is

necessary　to　turn　round　in　a　narrow　lane；　valuable　time　is　lost

in　the　process；　and　this　the　airman　turns　to　account。　　In　hilly

country　it　is　at　a　still　greater　disadvantage；　the　inclines；

gradients；　and　sinuosities　of　the　roads　restricting　its

effectiveness　very　pronouncedly。　　It　must　also　be　remembered

that；　relatively　speaking；　the　〃Archibald〃　offers　a　better　target