43997639 S Tank From Www Jgokey Com

8/3/2019 43997639 S Tank From Www Jgokey Com

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R . M . Ogorkiewicz


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A F Y I l e o p o n s P r o f i l e sEdited by DUNCAN CROWCheck list of published titles:. ; ; : : . ' : - - - ; < ~1 Churchlll-c-Brf tish Infantry Tank Mk. IV'by B. T . White

2 PanzerKampfwagen III. by Walter Spielberger3 Tanks Marks I to Vby Chris Ellis and Peter Chamberlain4 Light Tanks M1-M5 (Stuart/Honey)by Chris Ellis and Peter Chamberlain5 Light Tanks Marks I-VIby Major-General N W . Duncan6 Valentine-Infantry Tank Mark IIIby B. T . White7 Medium Tanks Marks A to Dby Chris Ellis and Peter Chamberlain8 Crusader-Cruiser Mark VI (includesCruisers Marks I-VI)by Major J. K . W . Bingham, Royal Tank Regt.9 Early (British) Armoured Carsby Major-General N. W . Duncan10 PanzerKampfwagen V Pantherby Chris Ellis and Peter Chamberlain11 M3 Medium (Lee/Grant)by Peter Chamberlain and Chris Ellis12 Mediums Marks I-IIIby Major-General N W . Duncan13 Ram and Sextonby Peter Chamberlain and Chris Ellis14 Carriersby Peter Chamberlain and Duncan Crow15 PanzerKampfwagen I and IIby Major-General N W . Duncan

16 Landing Vehicles Trackedby Colonel Robert J. leks, USAR Retd.

17 Russian KV and ISby Major Michael Norman, Royal Tank Regt .18 Chieftain and Leopard (Development)by Major Michael Norman19 Chieftain and Leopard (Description)by Major Michael Norman20 Churchill and Sherman Specialsby Peter Chamberlain and Chris Ellis21 Armoured Cars-Guy, Daimler,Humber, A.E.C.

by B. T. White22 PanzerKampfwagen 38(t) and 35(t)by John Milsom23 Soviet Mediums T44, T54, T55 and T62by Major Michael Norman24 The M48/M60 Seriesof Main Battle Tanksby Colonel Robert J. leks. USAR Retd.25 Cromwell and Cometby Major James Bingham26 Hellcat, Long Tom, and Priest

PLUS Complete Check Listof All U.S. World War II S.P.sby Colonel Robert J. leks, USAR Retd.27 Saladin Armoured Carby Major Michael Norman28 Swedish S-Tankby R. M. Ogorkiewicz

Paris J-17 price 25p each from your local book or 1II0del shop. Pari J8 011wards price 35p each.Retail prices in USA J-J7SI25. J801lIVardsS/50.

If you have any difficulty in obtaining Profiles from your local book or model shop please write direct to:

Mail Order/Subscription Department,PROFILE PUBLiCATIONS Ltd, Coburg House, Sheet Street, Windsor, Berks. SL41EB


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Original production version of SI,." 103, or S-tank type A, without flotation gear.

s- TankB y R . M . OgorkiewiczTank design has tended to follow a well-establishedpattern. In consequence, battle tanks resemble each

other to a large extent. But there are exceptions to this,the most notable being the controversial SwedishS-tank which differs in many important respects fromall other tanks.The most obvious feature of the S-tank is its lack of a

turret. This alone makes it unconventional but does not,in itself, represent anything new. In fact, the very firsttanks were turretless and so have been many others.What makes the S-tank different and an advance on allthe earlier turretless vehicles is that the mounting of itsgun is fixed in relation to the hull. As a result, it possessesseveral important advantages over other, more con-ventional, turreted as well as turretless vehicles.Because it has no turret, the S-tank is considerablylower than conventional, turreted tanks, which makes it

a more difficult target to hit. Moreover, its fixed gunmounting has eliminated the need for the space requiredwithin the armour envelope of turreted and even more ofturretless vehicles by the movement of the breech end ofthe gun. The fixed gun mounting has also made itpossible to install a relatively simple automatic loadingmechanism, since it eliminates angular movementbetween the gun and the ammunition magazine. This,in turn, made it possible to dispense with the humanloader and thus save a considerable amount of spacewithin the vehicle, making the S-tank even more com-pact and consequently also lighter.These and other advantages of the S-tank imply,however, that its gun can only be elevated or depressed

by altering the pitch of the hull and traversed only byturning the whole vehicle. In other words, its gun canonly be aimed by moving the whole vehicle. Tills hadnot been done before and it was only after several yearsof development that this method was successfullyestablished. '

ORIGINS OF THE DESIGNIdeas which led to the S-tank originated with SvenBerge, the head of the tank design section of the Vehicle

Division of the Swedish Army Ordnance. They aroseout of his studies of tanks which had been produced bythe early fifties and especially of the French AMX-13.At the time the Swedish Army actually consideredpurchasing this light tank from France although in theend it bought the more powerful Centurions fromBritain. Nevertheless, some features of the AMX-13attracted Berge, as they did other tank designers. Inparticular, he recognised the advantages of AMX-J3'snovel oscillating or trunnion-mounted turret. Tillsallowed the gun to be mounted closer than ever to theturret roof, so that the tank needed to expose itself lesswhen firing, and simplified fire control equipment andthe installation of an automatic loading mechanism,because the gun did not move in relation to the opticalinstruments and the ammunition magazine. All theseadvantages accrued from the fact that the gun of theAMX-J3 was fixed in the upper part of its two-pieceoscillating turret and was elevated or depressed with it.However, the oscillating turret also had its disadvantages


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Lvkv 42, all experimentol qil-mm. self-propelled anti-aircraft gUll with an adjustable suspension bui lt by Bofors ill 1954.

and this led Berge to propose an alternative way ofexploiting its good features in the form of a turretlessvehicle with a fixed gun mounting.The origin of the ideas which led to the S-tank isparticularly interesting because in retrospect it appearsas a logical development of the earlier assault guns andother turretless vehicles. In fact, historically and fromother points of view it is at least as much a developmentof turreted tanks, with the turret mounted directly on atracked suspension.PRELIMINARY INVESTIGATIONSBerge put forward his original proposal in August

1956. At the time some of the concepts embodied in ithad already been partly proved and this had, in fact,contributed to the formulation of the proposal. Inparticular, AB Bofors, the Swedish company world-famous for its guns, developed between 1949 and 1954an experimental self-propelled 40-111111.anti-aircraftgun with an adjustable hydro-mechanical suspensionwhich showed the feasibility of elevating or depressinga gun by altering the pitch of the hull in which it wasmounted. The feasibility of traversing the gun byturning a vehicle was less clear. That the gun could beswung rapidly using a vehicle's clutch-and-brake steeringsystem was shown several years earlier when the SwedishArmy tested a German assault gun, the SturmgeschutzIII, as well as several other foreign vehicles acquired forevaluation purposes after the Second World War. Butwhether the gun could also be traversed sufficientlysmoothly and accurately remained to be proved: theSturmgeschutz and all but one other vehicle with hull-mounted guns could move them to a limited extent inrelation to the hull for fine traverse.The one exception was the French Char B of thethirties. This battle tank had a hull-mounted 75-mm.gun which was elevated independently of the hull butwhich was traversed by turning the vehicle by means of adouble-differential steering mechanism with a hydro-static steering drive. The steering system was derived

from the SRB experimental tank designed in 1921 underthe direction of E. Brillie, of the Schneider company,who had designed the first French tank. It provided apositive, infinitely variable degree of control over thespeed of the tracks which made it superior for manyyears to other steering systems. However, in spite of theexcellent steering system, the method of aiming the75-mm. gun of the Char B by turning the whole tankdid not prove entirely satisfactory after the tank was putinto service in 1936 and was eventually abandoned.Thus on the final Char Bl ter version, of which only fivewere built before the French Army was defeated in1940, the gun was no longer fixed in traverse but couldbe moved, independently of the hull, over an arc of 10degrees.The experience of the French Army with the Char B

did not discourage Berge nor did it prevent his proposalfrom being accepted for further study by the SwedishArmy Ordnance. However, it clearly indicated the needto reexamine the problem of gun laying by turning avehicle very carefully. This was first explored in thewinter of 1957~58 at the Swedish Armoured Centreat Skovde using an IKY 103, a light turretless 105-mm.assault gun built by AB Landsverk and Bofors, fitted witha "crowbar" steering system.In essence, the "crowbar" system consisted of a leveron either side of the vehicle, one end of each lever beingpivoted on the hull and the other having a foot whichcould be made to rest on the track and move it when thelever was rotated about the pivot by a hydraulic rammounted on a frame attached to the front of the vehicle.The "crowbar" system fitted to the IKY 103 provided asimple method of precise control over small trackmovement and proved that a gun could be aimedwith sufficient accuracy by turning a vehicle with anappropriate steering system.The results obtained with tho IKY 103 were verifiedin 1959 using the chassis of a U.S. M4 Sherman mediumtank. In this case the levers of the "crowbar" systemwere located between the tracks and the hull and the


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IKV 103 assault gUll with Oil experimental, external "crowbar" steering system.

hydraulic rams were inside the hull superstructure, overthe tracks, which made it all look much tidier. However,the main reason for building the second test rig was tocheck that there were no unforeseen scale effects betweenthe 9-ton IKV 103 and the proposed tank which like theSherman chassis was expected to weigh about 30 tons.The Sherman chassis was also fitted with a 150-nlln.gun without recoil gear to explore the effects of rigidlymounting guns, which was originally proposed inGermany towards the end of the Second World War.The rigid mounting proved acceptable but it was notpursued further.COMPONENT DEVELOPMENTIn the meantime, on the strength of the results ob-tained with the IKV 103 and paper studies, Bofors were

awarded a contract in mid-1958 to develop the proposedSherman medium tank chassis with an internal r'crowbar" steering system.

turretless tank with a fixed gun mounting. This was toembody such novel features as an adjustable hydro-pneumatic suspension, a new steering system and anautomatic loading mechanism.Bofors had by then only designed two armoured

vehicles and neither got beyond the prototype stage.One was the Lvkv 42, the 13.5-ton 40-mm. self-propelledanti-aircraft gun with an adjustable suspension builtfor the Swedish Army in 1954; the other was a 20-tonturretless 120-mm. assault gun with an automaticloading mechanism which was built by Bofors on theirown initiative in the late forties. However, both vehiclesincorporated original features which foreshadowed thoseof the S-tank and Bofors were well qualified to under-take its development not only because of this but evenmore because of their very considerable experience ofnaval and anti-aircraft gun control systems which was


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Bofors 1 2 0- 11 1 11 1 .e xp er im e nt al a s sa u lt gUll with automatic loading.

highly relevant to a sophisticated fighting vehicle such asthe S-tank.Moreover, Bofors were assisted in the development ofthe S-tank by AB Volvo, Sweden's leading motormanufacturers, who were brought into it in 1959 assubcontractors for the power plant, and by AB Land-sverk, who became subcontractors for much of therunning gear. A little earlier, in May 1959, Boforsreceived an order from the Swedish Army for theconstruction of two prototypes.At about the same time the Swedish Army alsodecided to abandon the development of an earlier,turreted battle tank, the Strv KRV, designed by ABLandsverk who had been Sweden's leading tank pro-ducers since 1930. This was a 45-ton vehicle powered by aspecially developed 850 h.p. V-12 air-cooled sparkignition engine which was to have been fitted with a

large Bofors-designed turret mounting a smooth-boreautomatically-loaded 150-mm. gun. However the turretwas never made and the two KR V tank chassis whichhad been built by 1957 were converted into test rigs forthe S-tank components. In the process the number ofroad wheels was reduced from six per side to fourso that in this respect, as well as in their 30-ton weight,they would resemble the S-tank. The modified chassiswere then fitted with the hydro-pneumatic suspensionintended for the S-tank, which was extensively testedin them during 1960, and a new steering mechanismwith a hydrostatic steering drive. Finally one of themwas also fitted with a high-velocity gun-the 83.4-mm.20-pounder of the contemporary Centurions. Thus,even before the first prototype of'the S-tank was com-pleted, its basic components had been extensivelytested and its general characteristics were being proved.

Sillall-scale 1II0dei of the 45-tol l KRV batt le tank which was to 1101'ebeen fit ted wi th al l autonunically-loaded smooth-bore 150-111111.Ull .


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SUSPENSION AND STEERINGThe final proof of the S-tank concept was provided bythe two prototypes which were completed in 1961 andwhich for the first time incorporated all its essentialfeatures. The hydro-pneumatic suspension which allowedthe pitch of the hull to be changed includes four roadwheels per side, the front and third wheels being mountedon leading arms and the second and fourth on trailingalms. Each arm is connected to a piston in a hydrauliccylinder and this, in turn, is hydraulically connected to asecond, or spring, cylinder where a floating pistonseparates the hydraulic fluid from the springing medium,which is nitrogen. The cylinder assemblies of the twocentre wheels on each side are independent of each otherand the rest of the system. But the front and rear wheelsuspension units are connected diagonally across thevehicle, e.g. the front right unit is connected to the rearleft unit, and each hydraulic interconnection includesa positive displacement pump which can transfer fluidfrom the front to the rear unit, or vice versa. This changesthe pitch of the hull by altering the setting of the roadwheel arms and consequently elevates the gun to amaximum of 12degrees above the horizontal or depressesit 10 degrees below the horizontal.Changes in the attitude of the hull inevitably involvechanges in the length of the track which had to becompensated for. The usual method by mechanical

Prototype of the KRV battle tank wi th a cylindrical weight simulating itsturret.

Chassis of the KRV modified into a test rig for the Sstank's hydro-pneumatic suspension and steering system.

control of the idler position was deemed too cumber-some and s "nother electro-hydraulic servo system wasadded to I ,vc +iagonally interconnected suspensionsystems. 11 alters the height of the hull above theground by 'simultaneously ,adding or subtracting anequal amount of fluid f[Ol~: the front and rear units andthereby compensates for changes in track length.Between each pair of cylinders there is a special valveto damp vehicle motion. 'and there is also a hydraulicinterconnection between the four front and rear unitswhich provides the equivalent of a stable, three-pointsupport for the hull. In addition there are cut-off valveswhich can isolate any of the four units should it getdamaged while hull pitch control is still possible with theother three units. To make it rugged the suspensionsystem has been made to operate at a relatively lowpressure, even though this has made it somewhat lesscompact. The most vulnerable parts of the suspension,namely the road wheels, are the same as those of theCenturions so that they can be replaced more easilyfrom a common stock of spares.The second of the two major problems associatedwith a fixed gun mounting has been solved by a novel

two-stage steering system. In essence, it consists of adouble-differential mechanism with a hydrostatic steer-ing drive and a superimposed clutch-and-brake systemwhich comes into operation when sharp turns are


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Test rig based 011 'he KRV chassis filled with a 8 3 . 4 - 1 1 1 1 1 1 . 20-pol/llder oj 'he Centurion.

required. Thus, the steering system of the S-tankoperates in two stages. In the first instance it behaves as adouble-differential system, so that it is regenerative and(here is no loss of vehicle speed during steering move-ments. At the same time the hydrostatic steering drivemakes the steering infinitely variable and provides thesmooth traverse control necessary for laying the gunaccurately on target. In the second stage of steering,when one of the clutches is disengaged and the associatedbrake is applied, the steering behaves like a gearedsystem with a large step-down. This enables the S-tankto change direction very rapidly-so much so that itcan swing its gun round as quickly, or quicker, than theturret of a conventional tank.The provision of hull pitch control and of a two-stagesteering system has not, for all its inevitable complexity,brought in any complication from the vehicle users'point of view. The S-tank is, in fact, simpler to operate

than other tanks due to the integration of the steeringand gun controls into a single unit which consists of a

Unit oj the Bofors hydro-pneumatic suspension.

box with handle-bars. Rotation of the box about avertical axis steers the vehicle: the first 23 degrees ofrotation control the hydrostatic steering unit whilefurther rotation actuates the clutch-and-brake system.Twisting the handle-bars, on the other hand, alters thepitch of the hull. In addition the control box contains anumber of push buttons for loading and firing the mainand auxiliary armament.Both the driver and the commander of the S-tank areprovided with such a control unit and each also has anaccelerator and a brake pedal, so that either can operatethe tank by himself, the commander being able tooverride the gunner. Normally the driver is also expectedto act as the gunner but if a target is to be engagedquickly the commander, who is likely to acquire it first,can do it by himself. Thus the commander does not haveto go through the usual motions of issuing orders toother crew members who then have to react to thembefore a target can be engaged.The driver/gunner and the commander are located


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Drawing oj the Srtank prototype which shows the original pair oj machine-gun boxes with two 7.62-mm. machine-guns ill each.

Steering and suspension control unit with loading andfiring buttons for the main and auxiliary armament.

------ -- -. _ -


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J-" ". ,

Sstank prototype with the original all-steel track,

Sectioned drawing of the Sstank ill prototype/arm which shows the forward location a/the engines and transmission and the rear location of the ammunitionmagazine.

-,


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Side view of S-Inllk pre-production model without machine-gull boxes.

abreast of each other in the centre of the tank. Behindthe driver and facing rearwards is the third member ofthe S-tank's three-man crew-a radio operator who isalso provided with a simplified set of driving controls sothat he can drive the tank backwards. Its ability to bedriven backwards as easily as forwards is peculiar to theS-tank and gives it a unique advantage in this respectover others. The rearward facing location of the thirdcrewman also means that he can keep a constant watchover the rear sector of the S-tank which gives it anotherunique advantage over other tanks.

ARMAMENT SYSTEMBetween the driver/gunner and the commander is theS-tank's 105-mm. gun. The guu is very similar to the

British L7 105-mm. gun used in several tanks, includingthe final versions of the Centurion, the U.S. M60, theGerman Leopard, the Swiss Pz.61 and the Anglo-IndianVickers Vijayanta, and it can fire the same type ofammunition. This is particularly important to theSwedish Army as it has a considerable number ofCenturions in its armoured units. However, the gun ismade in Sweden by Bofors and is 62 instead of 51calibres long, which gives its APDS projectiles a muzzlevelocity significantly higher than the 1450 m/sec of theshorter barrelled gun. The higher muzzle velocitygives, in turn, greater penetration, the resulting improve-ment being equivalent to penetrating a typical armourplate at 500 metres longer range. At the same time thesector swept by the gun when traversed is smaller thanthat swept by shorter turret-mounted guns because itsbreech is located towards the rear of the tank.Behind the crew compartment, at the rear of the hull,is a 50 round ammunition magazine for the gun with ahydraulically-operated automatic loading mechanism.

The magazine is split into two halves on the centre line ofthe vehicle, one half normally containing APDS and theother HE rounds. The rounds are stowed in ten racksand descend by gravity on to a loading tray from wherethey are transported to the centre of the magazinearea by a hydraulic ram-one to each magazine half.Once a round reaches the centre of the floor anotherram lifts it to the level of the breech and a fourth pushesit home. After the round has been fired the empty case isautomatically ejected through a trap door in the rearhull plate. Since there is no relative movement betweenthe gun mounting and the ammunition magazine thewhole installation is relatively simple and trouble free.The magazine is reloaded from outside through twohatches in the rear hull plate and two men can do itin approximately 10 minutes, which is considerably lessthan the time required to stow more conventionalturreted tanks as well as being less fatiguing.Apart from eliminating the need for a human loader,

saving space and making all rounds immediatelyavailable for firing, the automatic loader of the S-tankhas also increased the rate offire to IS rounds per minute,which is almost twice the rate of fire of tanks withmanually loaded rounds of the same calibre. Its rateof fire is such in fact that the S-tank could fire its lOS-nun.gun in bursts, to increase the probability of destroying aparticularly dangerous target, and the possibility ofdoing this is increased by the automatic lock-out of thesuspension whenever the gun firing button is pressed,which makes it practicable to fire successive roundswithout relaying.In addition to its main armament, the S-tank in theprototype fOIID was to be fitted with four 7.62-mm.machine-guns mounted in pairs in armoured boxes oneach side of the frontal hull plate. All four were to besighted in parallel with the 105-mm. gun and fired by


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S - tank Type B Profile Publications Ltd.


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remote control. The commander's rotating cupola wassimilar to that fitted at about the I',e time to thePbv 301 armoured personnel carrier and like the latterwas to have been fitted with an externally mounted20mm. automatic gun. However, tpe mounting of thelatter was considered too vulnerable for the S-tank and itwas never fitted.

EN91NJ INSTALLATIONAs the rear:1'


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S-tank, lef t, compared with a cOl lve~lt iona/, turreted Centurion tonk .

Sstank pre-production model with the original, domed commander'scupola.

Rear view oj {/II Sstank pre-production model which shows the locationof the radiator louvres.

Pre-production models oj the Sstank. during' t rials: note the absence oj the machine-gun boxes.


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relatively low location of its gun ammunition, which isthe most serious source of fires in tanks whose armourhas been perforated.The S-tank's chances of survival on a battlefield arealso greatly increased by its low silhouette. Its height,measured to the top of the roof, is in fact only 1.9 metrescompared with a height of at least 2.3 or 2.4 metres forturreted tanks. In consequence it presents a much moredifficult target to enemy weapons and its probability ofbeing hit is considerably reduced. For instance, whenfired at in the open at 1000 metres by a typical tank gunwith no sophisticated fire control equipment its pro-bability of being hit is 12 per cent lower than that of thelowest of contemporary turreted battle tanks. Itschances of avoiding being hit are even greater than thisfigure would indicate because the bottom metre, or so,of any tank is usually hidden by the uneveness of theground, which means that the percentage differencebetween the exposed heights of the S-tank and of aturreted tank is considerably greater than "the differencebetween their actual heights. Thus when the bottommetre of both types is ignored the chances of a hit at1000 metres become 34 per cent lower for the S-tank.To put it in yet another way, the probability of theS-tank being hit is only about 60 per cent that of theinevitably higher turreted tanks.

P re-p ro du ctio n v ersio n of the S-tank with a 1 2 .7 - 11 1 1 11 .ranging machine-gun ill (he rig ht hand machine-gun box.

piston engine of the same nominal output because itdid not have to drive cooling fans which consume asignificant fraction of the gross horse power of pistonengines.The Boeing gas turbine was to have been replaced in

time by a more efficient Volvo gas turbine with a heatexchanger but the latter did not materialize. Eventuallyanother, more powerful Boeing model succeeded theoriginal one and more than made up for the powerwhich was earlier expected to come from furtherdevelopment of the K-60 diesel. At different timesvarious other high output diesels were also considered,as they became available, as a possible replacement bythemselves for the diesel-gas turbine combination, butnone was able to provide as much power and fit in theavailable space.

PROBABILITY OF SURVIVALThe location of the engine compartment at the front

of the S-tank complicated access to it. In fact, provisionhad to be made for removing the front glacis plate whichwas split into three parts. Thus, a part of the frontalarmour on either side of the central portion can beunbolted and swung over the centre to provide sufficientaccess for maintenance of the engine under it. But toreplace the diesel the central portion of the plate and thegun barrel also have to be removed.On the other hand, the location of the engines in frontof the crew compartment has increased the protectionagainst attack from the most probable direction. Themain protection over the frontal arc is, of course,provided by the glacis plate which is exceptionally wellsloped due to the S-tank's peculiar configuration andis therefore particularly effective against high-velocityarmour-piercing projectiles. Its effectiveness has beenfurther increased by the addition of a series of horizontalribs, or rectangular bars, which deflect armour-piercingprojectiles and thereby increase protection for lessweight than the addition of conventional, solid armourplate. Ribbed armour was not, however, used on eitherof the prototypes as this would have revealed it pre-maturely.Additional protection has also been gained againstattack by shaped charge projectiles or rockets by placing

the main fuel tanks outside the hull above the tracks.The vulnerability of the S-tank is also reduced by the

PRE-PRODUCTION VEHICLESThe various features of the S-tank were extensivelytested, starting in mid-1961 with one of the two proto-

types. However, even before the manufacture of thefirst prototype was completed, the Swedish Army becameso confident of the soundness of the S-tank conceptthat in mid-1960 it placed an order with Bofors fora pre-production series of ten vehicles. The first of thesewas completed in 1963 and they were subjected tofurther, much more extensive trials.As was to be expected, the pre-production vehiclesincorporated a number of changes called for by the

testing of the prototypes and a number of features whichthe S-tank was intended to have from the beginning butwhich were left off the prototypes. One of the mostobvious changes was the addition at the front of the hullof a stout bracket to support the gun tube, particularly'against bending when it accidentally hit the ground.Following similar developments elsewhere, including


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S-tank coming ashore with its flotation screen erected.

Sstank swimming with the aid of its flotation screen.Pre-production model wi th the bulldozer blade locked ill the working position; like the prototypes this vehicle has 11 0 track return rollers.


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Beginning oj the assembly oj Sstanks at Bofors.

that of the British 105-mm. tank gun, the gun tube wasalso fitted with a fume extractor. This, together with theautomatic ejection of spent cases outside the tank,virtually eliminated all chances of powder fumesentering the crew compartment.Two return rollers were also added on each side tosupport the track which had previously rested on thetops of the road wheels and the track links had rubberpads bonded to them to improve road performance.A less obvious change was the replacement of the righthand pair of 7.62-mm. machine-guns by a l2.7-llll11.ranging machine-gun. The ranging machine-gun tookthe place of the optical range finder which was con-

sidered at first for the S-tank and which was fitted tomost contemporary battle tanks, except in Britainwhere the 12.7-mm. ranging machine-gun was originallydeveloped. However, the armoured boxes for themachine-guns were not fitted to all the pre-productionvehicles and even when they were no weapon wasgenerally fitted in the right-hand box because the idea ofusing a ranging machine-gun was abandoned by 1966.Two other features of the S-tank which materialisedonly during the testing of the pre-production vehiclesalthough they had been planned earlier were a collapsibleflotation screen and a bulldozer blade. The flotationscreen had been developed in Britain during the SecondWorld War but the S-tank was the first battle tankdesigned to carry it permanently, neatly folded in atrough running round the upper part of the hull where itis protected from small arms bullets and shell fragments.The screen is slit at the front, to accomodate the pro-truding gun barrel, and when it is raised the slit is closedby means of clips. Altogether it takes the crew 15minutesto erect the screen which enables the S-tank to float andpaddle itself across inland water obstacles by means of itstracks at up to 5.5 km/hr. The propulsive effect of thetracks is increased by short shrouds fitted over theirfront part and the S-tank can enter or leave water at amore favourable attitude than other vehicles becausethe hull and the screen can be tilted by its adjustablesuspension.The adjustable suspension has also facilitated fitting

the S-tank with a bulldozer blade with which it can digitself in for greater protection. Normally the blade isfolded under the nose of the hull but when required itonly needs to be swung forward and secured by means oftwo pin-ended tie-rods, which is done manually by thecrew in about 5 minutes. Once this is done the verticalposition of the blade and hence the depth of the cut iscontrolled by tilting the tank's hull by means of itssuspension.

PRODUCTION MODELTesting of the pre-production vehicles and improving

of the details of the design continued until 1967. Up tothat time the cost of developing the S-tank, includingthe construction of the two prototypes and ten pre-production vehicles amounted to 120 million Swedishkronor, or 8.4 million at the contemporary rate ofexchange. This meant that the development of the S-tankdid not cost an undue amount and less in fact than that ofseveral other tanks in spite of its novelty and sophistica-tion.In the meantime, the Swedish Army decided to adoptthe S-tank for its armoured units and in July 1964placed with Bofors a production order worth 33 million.The order began to bear fruit three years later whenBofors started to deliver the production model whichthey called S-tank Type A and which the Swedish Armydesignated Strv 103.Externally the production models differed from thepre-production vehicles mainly in having ribbed armour,a new commander's cupola and stowage bins at therear of the hull. However, their most interesting featureis the Jungner OPS-l combination periscope and sight,one of which is provided for the commander andanother for the driver/gunner. It consists of a unitymagnification prismatic periscope with an exceptionallywide, 102 degree field of vision combined with a bino-cular sight whose magnification is six, ten or eighteenfold depending on the position of a small selector lever,and whose oculars are just below the bottom lens of theperiscope. The driver/gunner's instrument is fixed but


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Early production version of Strv 103, or Sstan Type A, without flota t ion equipment.

S-/(I lIk Type B with flo tation equipment,

Rear vie\\ ' of {liZ Sstank Type B with fiotation equipment.


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An Svtank with a mine exploding under one of it s tracks during immunity trials, damage to the running gear could be repaired by the crew ill about 3 hours.

the commander's is gyro-stabilised in elevation andmounted in a powered cupola which is gyro-stabilisedin azimuth. In consequence the commander can observeon the move more easily that the commanders of othertanks and when he has acquired a target he can turn thetank to face it while retaining it in his sight.On top of the commander's cupola is mounted a7.62-mm. machine-gun which the commander can firewithout exposing himself. In addition to the OPS-lperiscope/sight the commander's cupola also mountsfour simple periscopes, instead of the American-typevision blocks of the original cupola, and there is also

one such periscope for the driver and two for the radiooperator, which gives the crew complete, all-roundvision. For the first time on any tank all periscopes arefitted with armoured visors which are operated by rodsfrom within the tank. The visors not only .provideprotection against accidental damage when the peri-scopes are not in use but also can be used to eliminatereflections from the periscope glasses which prematurelygive away the position of the tank at night.The periscope/sight has also been developed to

transmit laser pulses and echoes. Experiments with alaser range-finder for the Sstank started as early as

Contents of a napalm bomb burning around 01 1 Svtank which Dilly required a few minutes' c leaning of optics to be fit for action again.


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1965 and provision for installing it, coupled to thecommander's or driver/gunner's periscope/sight, hasbeen made in the production vehicles.The original, Type A production model was fittedwith the same gas turbine as the. prototypes and pre-production vehicles but the later Type B has been fittedwith the more powerful Boeing 553, produced inBelgium by F.N.-Boeing S.A., which was adopted in

1966. It develops 49 0 b.h.p. and has improved the per-formance of the tank, particularly its acceleration andaverage road speed.

TACTICAL PERFORMANCEDelivery of the production vehicles enabled the S-tank

to be tried on an increasingly large scale by the Swedisharmoured units. The trials, which have been primarily ofa tactical nature, confirmed that the S-tank can carry outall but one of the roles expected of battle tanks and thatit has several advantages over turreted tanks. A similarTwo Sstonks Type B passing through (J Swedish village during winter mlmoeUl'res.

#

conch.tID'9 -was' r,eached in Britain where two S-tankswere evaluated lW '1968. .,The one thing ~~he S-tank can not do is to movein one direction a'mtfl:$its main armament in another,as turreted tanks can.~ other wo.rfl~'it.}:~l11not engage

major targets on the move, unlt?~~Uiey happen to be at ashort range ~traig~t., ah..~a~o'(lt. 'This ha.s given rise tomuch prejudice aga'm_~'nd the View, whtci{I,obstmatelypersists in several quarters, thaIS-tank but only alimited-purpose tank destroyer ,However, all tanks have to' fi~,e accurately,even when their guns are gyro-stabilised in el~_v~tionandazimuth. What really matters, therefore, is the relativespeed with which the S-tank can stop and fire"jtsgun,which depends on the overall reaction time\1!This ismade up of a sequence of events whose duration hasbeen significantly reduced in the S-tank or which havebeen entirely eliminated. In particular, because itscommander and driver/gunner are both provided with aset of integrated driving and gun controls either can


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An Sstank exposed to the shock wave of a simulated nuclear explosion.

stop the tank and fire its weapons by himself. Thus, thetime which inevitably elapses in a conventional tankbetween the commander acquiring a target, issuing anorder and the driver, gunner and loader acting on it hasbeen eliminated. In consequence, the S-tank can reactas quickly, or even quicker, than a conventional tank.There are some occasions, of course, when the abilityof the turreted tank to fire to either flank is an advantage,even though this implies having the relatively morevulnerable sides of the hull face the enemy. But in mostother respects the S-tank has the advantage.For instance, its possession of two engines reduces thechances of it being immobilised. Similarly, because

the commander and driver/gunner are provided withduplicated driving and gun controls the S-tank can stillbe operated when either is incapacitated. In other words,in an emergency the S-tank can be effectively operatedby one man. Under normal conditions the duplicationof controls greatly reduces the strain on the crew. Theconfiguration of the S-tank not only reduces the heightof the target it presents but also facilitates the use ofground cover and, in particular, finding advantageoushull-down firing positions. It has also made it possibleto provide its crew with a high degree of protection, inspite of the fact that at 37 tons the S-tank is one of thelightest members of the current generation of battletanks.The high degree of protection afforded by the S-tankwas brought out particularly clearly during extensiveimmunity trials carried out between 1968 and 1970.During these trials S-tanks successfully survived thefire of high velocity tank guns, infantry anti-tankweapons and aircraft cannon, explosions of anti-tankmines, napalm bombs and even the blast of simulatednuclear explosions.

AcknowledgementsThe writer wishes to thank Mr. S. Berge for his help in retracingthe history oj the S-tank and Captain K. B. Jonell for otherinformation about it. The writer also wishes to thank theSwedish Army Materiel Department and the Bofors Companyfor photographs and for making it possible for him to study theS-tank at different stages oj its development.

Summary of the Leading Characteristics ofStrv 103 (S-tank Type B)

Gun. calibre. 105mm.length 62 calibres

50 roundsmmunitionMachine-guns. f ixed

external .2 x7.52-mm.. 1 x7.62-mm.

Weight. netcombat loaded

Length, with gun and stowage bins.

.37000 kg39000 kg

.9.8 m.. 7.0 mithout gun and bins

Width, overall .3.6 mwithout removable f it tings

Height, to roof over driver .3.4 m .1.9 m

to top of cupolaGround clearance, at centre .

2.1 m .0.5 m .0.4 mt sides

Width of tracks .0.67 m. . 1 .1 :1rack length to centre distance

Ground pressureEngine, diesel, make and model

.0.9 kg/em'.. Rolls-Royce K-60 .240ross horse power

gas turbine. make and modelgross horse power

Maximum road speedRange, on roadsCrew.

.. FN-Boeing 553 .490 .50 km/hr.300-400 km

.3

A.F.V. Series Editor: DUNCAN CROW


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A F V /W e o p o n s P r o l i l e sEdited by DUNCAN CROWStarting with AFVjWEAPONS PROFILE 24 the Publishers intend to step up th .' .. of pld"'~ation. Thisdeparture, taken in order to meet the great demand for coverage of more AI'YS more quickly thau in theprogramme that has been running for the past two years, has necessitated some further re-ar.z :,Incnt in thelist of tit les.29 M4 Medium (Sherman)Perhaps the best-known and certainly the most widelyproduced tank in the history of armoured warfare theSherman was first in action in October 1942, and was still onactive service in the Middle East in 1971. This PROFILEgives a full account of the Sherman and its variants-apartfrom the Specials dealt with in AFV/ Weapons Profiles 20and si:BY PETER CHAMBERL."'IN AND CHRIS ELLIS, authors ofBritish and American Tanks of World War 11etc., and AFVProfiles], 4, 7, 10, I I, I] and AFV/ Weapons Profile 20.30 Armoured Cars-Marmon-Herrington,Alvis-Straussler, Light ReconnaissanceThe South African-built Marmon-Herringtons werefamiliar to all armoured car regiments in the Middle Eastin World War II; although only a handful of Alvis-Strausslers were used these were a significant advance inthe design of wheeled fighting vehicles; the section on LightReconnaissance Cars describes the vehicles that equippedthe Reconnaissance Corps formed in 1941 to providereconnaissance units for infantry divisions: IlY 8. T. WHITE,author of British Tanks and Fightil/g Vehicles 1914-1945,Tanks and other Armoured Fighting Vehicles 1900-191/-J,etc., and AFV Profiles I, 6 and A FV/Weapons Profile 21.31 Australian Cruiser-Sentinel;and Australian MatildasDesigned and built in Australia during World War II theSentinel was a remarkable achievement for a limited engi-neering industry, and in its cast hull, for a tank of this size,it preceded the American M48 by about 10 years; it wasnot the Sentinel, however, that was used in action in theSouth-West Pacific by the Australians but the Matilda, forwhich they developed specialised equipments and tactics:IlY MAJOR JAMES BINGHAM, Royal Tank Regiment, author ofAFV Profile /- J and AFV/ Weapons Profile 25.32 M6 Heavy and M26 (Pershing)This Profile describes the curious history of the U.S. M6Heavy Tank and highlights the fierce controversy thatraged over "giant" tanks-not only in the United States, itmust be added; the M26, named after General Pershing,also started life as a heavy tank, and a few were in action inGermany in 1945. In May 1946 the Pershing's designationwas changed from Heavy Tank M26 to Medium Tank M26,and as such it fought in Korea along with the M46 and M47Mediums (Patton) that were a re-built version of it: IlYCOLONEL ROBERT J. ICKS, author of AFV Profile 16 andA FV/ Weapons Profiles 24, 26, who has a close knowledgeof the tanks' development.

33 German Armoured Cars "-As light tanks became popular in the 1930s the impqrra~of armoured cars declined ... except in Gefmany ""~France; Germany attached great importance to them andthey were the basic vehicles of the Panzer divisions'reconnaissance units in World War II, achieving greatsuccess as this Profile shows: IlY MAJOR-GENERAL N. W.DUNCAN, whose distinguished military career in armour hasincluded service in armoured cars in the Royal Tank Corps,and command of the 30th Armoured Brigade in 791hArmoured Division. General Duncan has been Representa-tive Colonel Commandant of the Royal Tank Regiment,Governor of the Royal Hospital Chelsea, and Curator of theRoyal Armoured Corps Tank Museum. He is the author ofAFV Profiles 5,9, 12, 15.34 ScorpionBritain's new aluminium light tank, weighing eight tons,powered by a conventional Jaguar XK 6-cylinder engine of4,200 c.c., and mounting a 76-mm. gun, is the first all-aluminium armoured vehicle in the world: BY R. M.OGORKIEWICZ, author of AFV/Weapolls Profile 28, who isthe first non-American and only the tenth person in its 85-year history to be made an honorary life member of theU.S. Army Armor Association.35 Wheels, Tracks and TransportersBritish Armoured Recovery VehiclesThe problems of getting tanks to the battle and recoveringthem when they have been disabled are the subject of thisProfile, in which MAJOR-GENERAL DUNCAN (author of AFVProfiles 5,9, 12, 15, and AFV/Weapons Profile 3]) tracesthe development in Britain of machines-some like"skyscrapers on roller skates"-to overcome the trackwear bugbear until the adoption of wheeled transportersproved a better solution, and Peter Chamberlain describesthe armoured recovery vehicles used by British andCommonwealth units in World War II .36 French H35, H39 and S35The Hotchkiss and Somua tanks equipped the brigades decombat of the French mechanised cavalry's divisionslegeres mecaniques, two of which had been formed beforethe outbreak of war in 1939, and there was a denii-brig adeof Hotchkisscs in the divisions cuirassees ; the Hotchkiss wasthe second most numerous type of French tank, while theSomna was considered by many to be one of the finestAFYs of its day: BY MAJOR JAMES BINGHAM, RTR, whofought in France in 1940 when these tanks were in action.37 Russian BT

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24/24

Wiiihip seriesThe most ambitious series so far conceived and produced by P ro fi le P u blic at io ns L im ite d. This new inter-national series will span the era of the modern fighting ship from the launching of the Dreadnought in 1906up to the present day ship-a complex of floating electronics, weaponry and technology. Profile havecreated a team of international experts in naval history backed by a first rate group of researchers andconsultants. This new series will continue to reflect the high standard of the Profile series already published.Presentation will follow the format which has proved so popular with the other series with first rate text,supported by many superb black and white illustrations and, of course, the famous Profile colour centrespread which will show complete side and plan views of each warship and where applicable additionalinformation such as ships badges, camouflage schemes, cross sections and details of ships fittings.T he pu blish ers inten d issuing o ne p art per m onth and the initial progrannne w hich at th is stage is subject to revisionw ill b e a s fo llo ws :1. HMS DreadnoughtThe first all-big-gun ship which heralded the newera that was to last for fifty years: by John Wingate,

D.S.C., W a rs hip s' S erie s E di to r.2. HMS Cossack

Tribal Class Destroyer. The class ofsuper-destroyerswhich were to serve with such distinction in WorldWar II: by Lieutenant David Lyon, R.N.R., ~L\.,National Maritime Museum, Greenwich.

3. USS Hornet (CV 8)Aircraft carrier who, with a life of only 372 days,launched Doolittle's raid on Tokyo before shefinally paid the penalty: by Lieutenant-Com-mander \IV. H. Cracknell, USN, former observer inthe US Navy Air Force.4. Kriegsmarine Admiral Graf SpeePocket Battleship, the first class of all-welded,diesel-powered capital ships, specifically designed

as commerce raiders. The Battle of the River Platesealed her fate: by Kapitan zur See GerhardBidlingmaier, lately Naval Historian of the Federal.German Navy, Navigating Officer of Tirpit ; duringWorld \'Var II.5. HMS Campbeltown (USS Buchanan)One of the 'four-stackers' to be turned over by theUSN to the RN. Her life ended gloriously duringthe Raid on St Nazaire in 1942: by John \lVingate,

D.S.C., W a rs hi ps ' S er ie s E d it or .6. Kriegsmarine Prinz EugenHeavy Cruiser. She took part in some of the mostdramatic actions of World War II: by fregatten-

kapitan a.D. Paul Schmalenbach who was herGunnery Officer and is now a naval historian.7. HM Motor Torpedo Boats:

THE VOSPER 70ft BOATThis class of boat formed the backbone of CoastalForces' Motor Torpedo Boats during World WarII. The development of the boat, the resultanttactics and strategy and the action reports aredescribed by the author, David Cobb, R.O.J.,R.S.M.A., the marine artist, who was himself aCommanding Officer and MTB Con troller.

8. Kriegsmarine U-107The life history of a German World War II sub-marine, described in detail by the world's leadingauthority on U-boat warfare, Dr. Jllrgen Rohwer,Head of Modern Historical Section, Bibliothek Fu rZeitgeschichte, Stuttgart.9. USS Charles AusburneDD 570, Fletcher Class destroyer, of AdmiralArleigh (31-knot) Burke's famous Squadron. Thisfighting destroyer saw operational service from

World War II until the Vietnam War: by Lieu-tenant-Commander \'V. H. Cracknell, USN, authorof War sh ij J P r of il e H o rne t.10. HMS IllustriousAircraft Carrier, 1939-1942. The history of this shipwill appear as two Profiles during the same month:From design stage to her major refit in America.This phase includes her attack on Taranto (thefirst carrier-borne attack in history, to be copied

later by the Japanese at Pearl Harbour) and herterrible punishment suffered oflMalta at the handsof the Luftwaffe: by Lieutenant David Lyon,R.N.R., ~I.A., author of War sh ij J P r of il e C o s sack.

11. HMS IllustriousAircraft Carrier, 1942-1946. Following the USrefit, through the Madagascar landings to her finalrecall after her active service in the Pacific theatreof war: byJ. D. Brown, a former Royal Navalaviator, author of A ir cr af t P ro fi le 224, Supermarine,W alru s a nd S ea gu ll va ria nts and 'Carrier Operationsof World vVarTwo'.12. IJN Kongo

Battleship. This ship, the world's largest warshipof the time, saw continuous action until she wasfinally sunk in April 1945: by a Japanese authoryet to be commissioned.13. HMS Exeter8-inch-gun Cruiser, 1928-1942. Her life includesthe Battle of the River P late against Admiral Gra]Spec (W arship Profile No.4) and the Bailie of theJava Sea: by Robin Tonks, M.A., Assistant Directorof Studies and Head of History Department,Britannia Royal Naval College, Dartmouth.

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