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INTRODUCTION

The Stuart was the first type of American tank, in any numbers, to see active service in WWII. The basic design went through many improvements and whilst for much of their active service they were outgunned and outclassed they continued in use throughout the war seeing service on all fronts. The purpose of this article is to describe the differences between the various models of Stuart, where possible with reference to preserved vehicles.

Research for this article has at times been quite confusing issues with reference sources proving to be either contradictory or ambiguous. Whilst the results of out efforts may not be definitive we hope that they are not ambiguous. If you the reader has difficulty in understanding anything or thinks we’ve got it wrong then please contact us. One of the true benefits of this medium is that it is dynamic and this feature will continually be subject to enhancements, additions and corrections as new information comes to light.

 

VEHICLE DESIGNATION

Official American designations for M3 Light Tank series give three separate vehicle specifications, the M3, M3A1 and M3A3. However throughout the production period of the M3 there were a considerable number of significant design improvements including new turrets, armament, vision devices as well as changes in construction methods. The British method of classification is slightly more useful, distinguishing between the diesel and gasoline versions and also creating a separate designation to cover the final versions of M3. Neither British nor American designations fully cover all the various models produced and so a commonly applied approach has been to split the production in to stages such as early, mid and late production. Unfortunately this can (and has) lead to even more confusion as different authors seemingly interpret these terms differently.

For the purpose of this feature we have split the M3 series into four class of vehicle: M3, M3 Hybrid, M3A1 and M3A3. For each class of vehicles we have attempted to define in detail a number basic production 'types'. Obviously changes rarely happen all at once so there is scope for 'blurring' at the edges when one 'type' evolves into another. For each class we give a brief overview of it’s basic characteristics and then provide a table of our production types. Official American and British designations are shown in the second column of this table. The last table column gives some sample serial numbers of vehicles of the specified type.

 

M3 Stuart

The M3 Light Tank first entered production in March 1941 and was a direct development of the M2A4 light tank. The M3 had stepped front hull with a machine gun mounted in each sponson in addition to a hull machine gun. These sponson machine guns had a fixed aim and were fired via a control cable. Trials showed that they were more actually more effective than the manually aimed bow machine gun (so long as you wanted to shoot in the direction you were facing). The turret mounted a 37mm main gun with a coxial machine gun and had a prominent cuploa. A particular feature of the suspension was the arrangement of the rear mounted idler wheel which, unlike most tracked AFVs, was mounted on a trailing arm to increase the length of track in contact with the ground thereby reducing the overall ground pressure. The tank carried a crew of four, the loader, the gunner, the driver and a co-driver who operated the hull machine gun. You will notice that I have not mentioned a vehicle commander. This is an area of potential confusion as some references refer to commander-loaders (U.S. Ordnance Dept Catalog) others to commander-gunners. Given the positioning of the cupola on the left of the turret it would seem most likely that the gunner was best positioned to perform the role that we now regard as that of vehicle commander. Being stationed on the left he obviously had the best access to the cupola and was also in an ideal position to convey directional commands to the driver by taps on the shoulder (vehicle intercoms came later). Unfortunately the loader had no access to any vision devices other than the pistol ports. This wouldn’t have been a great handicap except for the fact that the turret traverse wheel was mounted on his side of the turret. The gunner would therefore have to shout commands to the loader to attain an initial aim before using the limited amount of traverse of the gun within it's mount to fine lay the gun. This situation was obviously less than ideal and it became a preferred practice to aim the tank at the target rather than rotate the turret. The turret had no basket and so the gunner and loader had to walk round with the turret as it turned. This was harder than it sounds for the fighting compartment was bisected by a high large drive shaft tunnel from the Engine behind to the transmission in front which must have made turret rotation difficult.

The M3 first saw active service with the British in North Africa. The types initially supplied were mostly of the type 2 configuration but there were a few of type 1. Despite concern about the vehicles size and the internal layout the British were very enthusiastic with the performance of this tank, especially with regard to its reliability which was a particular weakness of the early war British tanks. The tankies of the Western Desert gave them the nickname 'honey', a measure of the high regard in which they were held. For desert warfare a considerable number of modifications were made including the fitting of sand-skirts, the addition of external stowage boxes, and the addition of external fuel tanks. There was very little stowage space internally and so the British removed the sponson machine guns which together with their ammunition had taken up most of the available sponson space. Officially classified a Light Tank, the Stuart had comparable armour protection to the Cruiser tanks of the day and its 37mm main armament was only slightly inferior to the 2-pdr armament found on the contemporary British tanks. As a result the Stuart often found itself being used as a Cruiser and this change of role lead to some operational changes to the turret crew. British Cruisers typically had a three man turret crew, the commander being tasked with identifying targets often operating with his head out of the turret to gain a better view. In the M3 a sling seat was installed under the cupola for the commander, the turret traverse wheel was moved to the gunner's side giving him sole control of traverse and elevation with the loader on the right hand side. The gunner or loader would double as co-driver/hull machine gunner leaving that position prior to entering combat. It is doubtful this change of positions could have been easily achieved within the close confines of the M3 on the battlefield itself.

Production of the M3 ran from March 1941 until January 1943 with 5811 vehicles being produced, 1784 of which were supplied to Britain.

Type 1
M3
Stuart I
Early production M3:-
Riveted hull, vision slots in front hull doors, sponson machine guns, gasoline engine.
 
Turret type D37812
Riveted octagonal sided with an hexagonal riveted cupola fitted with vision slots. Manual traverse gearbox mounted right front. 37mm Gun M5 in Combination Mount M22 (with limited gun traverse, with fine lay done with shoulder bracket) Telescope sighting. No basket. Pistol ports in turret sides with armor flaps.
 
Standardised July 1940, enters production March 1941. 100 made.
1
Type 2
M3
Stuart I
Early production M3:-
Hull same as type 1
 
Turret type D38976
Same as Type D37812 except most armour plates are welded, front turret plate bolted on, riveted cupola.
 
Enters production April 1941
 
151
279
721
1366
Type 3
M3 (Diesel)
Stuart II
Early production M3:-
Same as type 2 except for engine (which has longer air inlet hoses that are externally visible). Enters production from June 1941.
 
Type 4
M3
Stuart I
Mid production M3:-
Same as type 2 with grouser storage boxes at rear, and new protectoscope vision slot covers.
Turret type D39273
"Horseshoe" turret, with riveted ellipsoid shaped cupola. Internals same as turret type 1. Pistol ports fitted with new protectoscope covers. The first 160 produced lacked vision slots in the cupolas. Front armor plate bolted on.
Produced from October 1941
From December 1941 a lifting hook is added on both sides between the front and rear bogies.
1946
2188
2346
Type 5
M3 (Diesel)
Stuart II
Mid Production M3:-
Same as type 4 except for the engine (which has longer air inlet hoses that are externally visible).
 

 

M3A1 & M3 Hybrids

We now come to the M3A1 and the M3 Hybrids. Chronologically the Hybrids (late production M3s) were the first to reach production but they were a direct result of the M3A1 development which and already been standardised and entered production a short time later.

M3A1

British combat reports on the M3 initially criticised the lack of a turret backet and the resulting dificulites experienced by the gunner and commander 'walking' round with the turret when it was traversed. A new turret design was initiated to incorporate a turret basket together with other new design improvements. To facilitate easier escape from the vehicle separate hatches for gunner and loader incorporated. The cupola was removed and replaced by a rotating periscope for the loader who now with the best all round vision doubled up as commander. With the addition of a turret basket came also hydraulic traverse the control of which was now on the gunners side (with manual crank at the rear). A new gyro-stabilised combination mount M23 was fitted which provided solenoid firing. The gun could traverse in it's mount but this was locked as the hydraulic turret traverse gave sufficient control for the gunner to fine lay the gun. The gunner was given a periscopic sight linked to the main armament in addition to the coaxial telescopic sight. Despite these new features the new turret had a number of drawbacks. Due to the height of the drive shaft which passed through the fighting compartment, the basket itself had to be quite shallow with the consequence that the turret crew had to operated form a seated position. Because of the minimal clearance under the basket the hydraulic pump, oil reservoir, electric motor, and rotary electrical junction all had to be mounted on the basket floor making the crew positions even more cramped. When the gun was elevated it was difficult for the gunner to achieve a position where he could actually see through the telescopic sight so the periscopic sight was heavily favoured. Clearly the shallow basket, lack of cupola and sighting arrangements made the M3A1 unsuitable for adoption of the three man turret organisation as employed by the British in M3s. However, at this stage of the war the Stuart no longer possessed the attributes to be employed as a cruiser whilst for it's intended role of a reconnaissance vehicle, where enemy engagement was not the objective, a two man turret was adequate. The gyro-stabiliser provided a mechanism where the aim of the gun could be held on a fixed point with regard to elevation compensating for the movements of the vehicle. The system did work but was often disabled due to inadequate training of the turret crew. When crossing rough terrain the stabilisation would obviously continually be adjusting the gun elevation making the loader’s job particularly difficult. As the stabilisation provided was only for the vertical axis the poor gunner had to provide correction for any rolling of the vehicle and so firing on the move was still a difficult proposition.

Vehicles fitted with this turret (turret 4) became standardised as M3A1 and production of the M3A1 ran from May 1942 to January 1943 with some 4621 vehicles being produced, 1594 of which were supplied to Britain

Type 10
M3A1
Stuart III
Early production M3A1:-
Same as type 4 with auxiliary generator, and blanking plates where sponson machine guns were eliminated. Some fitted with jettisonable fuel tanks.
 
Turret type D58133
Externally similar to type 3 except without cupola and with the pistol ports moved higher up the turret wall. New persicope added for the commander and a persicopic sight for the gunner which is protected two projecting semicircular guards. Internal changes are significant with the addition of a turret basket, hydraulic power traverse, gun stabilization, Turret traverse gearbox is located at turret rear, and hydraulic pump and motor on turret floor. Gun is 37mm Gun M6 in Combination Mount M23. Front armour plate welded on.
 
Enters production May 1942
 
Type 11 M3A1(Diesel) Stuart IV
Early production M3A1:-
Same as type 10 except for engine.
 
Type 12
M3A1
Stuart III
Late production M3A1
Same as type 10 but with welded hull.
 
Type 13 M3A1 (Diesel) Stuart IV
Late production M3A1
Same as type 12 except for engine.
5260

 

M3 Hybrids

Clearly it was felt that the new style turret being developed for the M3A1 incorporated some desirable features and as a result a similar turret was introduced into the M3 production line but without the turret basket. The resulting vehicles, technically late production M3s, became widely known as hybrids or flat-tops. Initially not all the components were available and consequently the early hybrids did not have either gunner's or loader's periscopes, the apertures for which were plated over. Given the lack of a cupola this meant that the turret crew now had no vision devices except the telescopic sight and the pistol ports which had been moved higher up the turret wall to suit the seated crew of the M3A1 so probably were not at an ideal height. Because without the turret basket there was no hydraulic traverse a hand wheel was installed on the loaders side as per the standard M3 configuration. Because turret traverse was now manual it was necessary to provide a version of the M23 mount which allowed some traverse within the mount. This was achieved by means of a traversing knob rather than the shoulder brace of the earlier M22 mount. Some hybrids were supplied to New Zealand with the wrong mount. I assume that the hybrids were produced as a by-product of the change over to produce M3A1s. Certainly it cannot be regarded as an improvement over the mid production M3s save for the provision of an extra hatch for the loader. In due course more M3A1 components became available and hybrids may have been produced with periscopes however I cannot see how the fixed traverse periscopic sight could have been linked to a gun with independent traverse.

Several authors indicate that gyro-stabilisation of the 37mm gun was applied to late production M3s. If this is the case (and I’m still seeking evidence) then it would probably be safe to assume that it was the same equipment developed for the M3A1 which may well have been in production at this time and in any case had been long since standardised. Given that the Hybrids had the same M23 mount as the M3A1 it would seem reasonable that If there is evidence stabilised M3s then the Hybrids will be the place to look for it. Unfortunately I have yet to see a photograph or drawing that shows how such a mechanism was fitted in a tank without a turret basket. The equipment necessary to drive the hydraulics (electric motor, hydraulic pump, reservoir etc.) is quite bulky and it seems unlikely that it could have been mounted on the turret ring which in any case would require some form of rotary junction to provide the necessary power. Perhaps the hydraulics were mounted on the fighting compartment floor and connection to the gun mount was via flexible hoses but this doesn’t sound particularly viable either.

The Hybrids cannot be considered a success being universally derided by all who received them and generally employed as training vehicles. Despite this they continued in production for a short while in parallel with the M3A1 being mostly sent overseas. New Zealand certainly appears to have received some late production Hybrids with all welded hulls. (see Jeff Ploughmans "The Stuart Hybrid in New Zealand")

Type 6
M3
Stuart Hybrid
Late production M3:-
 
Hull
Same as type 4.
 
Turret type D58101
Essentially type D58133 without the turret basket, hydraulic traverse and stabilisation. No periscopes - apertures plated over. Hand traverse wheel mounted at right cheek of turret. Combination Mount M23 but with limited gun traverse in the mount and manual firing mechanisms for the 37mm and coaxial mg.
 
Enters production February 1942
3722
Type 7
M3 (Diesel)
Stuart Hybrid (Diesel)
Late production M3:-
Same as type 6 except for the engine
 
Type 8
M3
Stuart Hybrid
Final production M3:-
 
Hull
Same as type 6 but with welded hull.
 
Turret
Same as for type 6 put possibly with power traverse and stabilisation. Periscopes may also have been fitted.
 
Produced until August 1942
4927
Type 9
M3 (Diesel)
Stuart Hybrid
Final production M3:-
Same as type 8 except for engine.
.

 

M3A3

The M3A3 (Stuart V) came into being as a result of a request to upgrade the M3A1 to incorporate some of the design features of the M5 Light Tank which was already in development/production. The M3A3 was produced almost exclusively for Lend-Lease and saw service with the British and Commonwealth Armies in Italy and NW Europe as well as with the Chinese. The upgrade can be charactersied as follows:

The stepped front of the M3A1 was replaced with a sloping glacis with roof hatches for the driver and co-driver. This arrangement provided more internal space for the driver and co-driver. The driver and co-driver now had roof hatches which made escape from the vehicle much easier. On the M3A1 the co-driver had no easy means of escape. Each hatch was fitted with an adjustable traversing periscope with direct vision being restricted to two two inch direct holes in the glacis with plugs that could be pushed out or pulled back from within the vehicle. When not in combat the driver and co-driver could raise their seats so that they could look out of the hatches and the steering levers were lengthened so that they were easily reached. When operating with his head out of his hatch the driver could install a detachable windscreen and weather cover that was attached to mounting brackets on the glacis plate. The fire protection system was improved with five fire detectors being located in the engine compartment with a fire-warning signal being visible to the driver and co-driver. The hull was fitted with a electric ventilation system to expel fumes and smoke from the gun when firing. Detachable headlights were used which could be stored internally when in combat. The sponson sides were enlarged and angled providing extra internal stowage space. The larger sponsons allowed for two additional fuel tanks and also for the air cleaners to be afforded greater protection by making them fully enclosed.

The turret was redesigned and enlarged to provide a bustle in which the radio equipment could be installed. The pistol ports removed and the new shape of turret allowed for larger squarer hatches to be introduced for both gunner and commander. The commander’s hatch was fitted with a rotating periscope for an easy view to the rear. The internals of the turret remained pretty much the same as the M3A1 but with the addition of the radio set to the rear. A new gun mount (M44) was introduced in which the telescopic sight was mounted in a higher position to the M23 mount. This overcame the restrictions of the M23 mount with respect to its use at higher elevations. Interestingly the M3A3 technical manual (Nov 1942) describes and illustrates a M23 mount although no telescope (or aperture) are shown. Perhaps some early vehicles were made with this arrangement, If so they should be east to spot by looking at the height of the telescopic sight aperture. The manual predates the initial production so the decision to use the M44 mount may have come at a last minute change perhaps as a result of the M5A1 which entered production around this time and also used the M44 mount. The prototype M3A3 was completed in August 1942 and the new turret design was obviously considered a success as it was quickly introduced to the M5 Light Tank which became the M5A1 and was produced from September 1942.

Despite the many design improvements, by the time the M3A3 was produced it was very much under-gunned and under-armoured for tank combat and so was mostly used in a reconnaissance role. A common practice in British and Canadian service was to remove the turret altogether. Without the weight of the turret the Stuart recce could travel faster and obviously had a much lower profile. Additional mg mounts were often improvised upon these vehicles and sometime a canvas cover.

The M3A3 was manufactured between September 1942 and September 1943 with 3427 vehicles being produced of which 2045 were supplied to Britain.

Type 14
M3A3
Stuart V
Radical hull change with a sloped front and sides. New additional fuel tanks, greater gross weight, new final drive gear ratio.
Turret type 6.
 

 


M3 Light Tank Development Timeline
  1940 1941 1942 1943
J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M
     
M3
Type 1 S    
Type 2    
Type 3    
Type 4    
Type 5    
M3 Hybrid Type 6    
Type 7    
Type8    
Type 9    
M3A1 Type 10   S    
Type 11    
Type 12    
Type 13    
M3A3 Type 14   S