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Late M3A1 Stuart III

Our subject vehicles for this section are the Patton Museum's M3A1 (interior photographs by Jon Hornbostle) and a privately owned vehicle (photographed by Geoff Winnington-Ball of Maple Leaf Up)

1999 G. Winnington-Ball
1999 G. Winnington-Ball

As you can see from these two photos the exterior surfaces of the Late M3A1s were devoid of any rivets being of welded construction. Lets now have a look inside these two vehicles ....

1999 J. Hornbostle


a Steering levers
b Transmission oil pressure gauge
c Engine Hour meter
d Stating switch
e Booster switch
f Hand throttle
g Engine oil pressure gauge
h Oil dilution switch
i Compass mounting holes
j Brake adjustment aperture plug
k Transmission
l Throttle pedal
m Clutch pedal
1999 J. Hornbostle


a Steering lever
b Brake adjustment aperture plug
c Transmission
d Tachometer
e Engine oil temperature gauge
f Ammeter
g Light switch
h Volt meter
i Headlight dimmer switch
j Magneto switch
k Priming pump
l Dash light switch
m Speedometer
n Dash lights
o Oil circulation test cock

The driver's controls and instruments are similar for all the M3 variants with the exception of the M3A3 which due to it's sloping glacis has a different layout.

The following images are of the the turret interior. Neither of our two subject vehicles is totally complete but in combination the images give pretty complete coverage.

1999 J. Hornbostle


a Elevating wheel
b Linkage to gunners periscopic sight
c Telescopic sight
d Sight head rest
e 37mm firing solenoid
f Cocking handle
g Counter weight
h Elevating rack
i Gunners seat

The primary sighting device in the M3A1 was the periscopic sight mounted in the turret roof. As we can see from this photograph a direct sight telescopic sight was also fitted but due to the shallow turret basket this was difficult to use at higher elevations and apparently was not particularly favoured. Missing from this vehicle are the recoil guard and the gyro-stabiliser but these items are shown in the photographs below of our other subject vehicle.

1999 G.Winnington-Ball


a Radio Set
b Traverse control handle
c Saftey trigger
d 0.30 MG trigger
e 37mm gun trigger
f Stabilser mounting bracket
g Stabiliser grease nipples
h Commander's perscope
i Gyro-stabiliser control unit
j Stabiliser recoil switch
k Cal .30 MG firing solenoid
l 37mm firing cable
m Traverse lock
n Recoil guard
0 Cocking handle

This photograph shows clearly the gunner's combined traverse control and firing triggers. The various parts of the gyro-stabiliser can also been seen fitted on this vehicle. In trials the gyro-stabilser was shown to be quite effective but its use did require a lot of training and practice. As a consequnece of this the gyro-stabiliser was sometime removed where gunners had not been given the required training experience. Missing is the coaxial cal. 0.30 browning machine gun although parts of it's mount are visible as well as the firing solenoid. In the bottom corner we can see the radio set mounted on the left hand sponson. This was the prefered side for the radio set as the right hand sponson would usually be packed full of 0.30 ammunition boxes as both co-axial and hull machine guns are on the right hand side of the vehicle.

1999 G. Winnington-Ball


a elevating wheel handle
b Hand firing button
c 37mm firing solenoid
d Telescopic sight mount
e Stabiliser control unit
f Right hand sponson
g Comander seat
h Recoil guard
i Manual traverse handle
j Adjustable counter-weight
k Stabilizer hydraulic oil pump
l Traverse electric motor
m Hydraulic oil pot
n Slip ring assembley
0 Transmission casing

Moving back over to the left hand side of the gun we can see a few more significant items of equipment have been revealed. The recoil guard can be seen in full and we can see the slots through which the adjustable counter-weight is mounted. In the centre of the elevating wheel is a 'hand' firing button for the main armament which although clearly visible in our earlier photo can be seen to protrude from the elevating wheel in this one. Missing from this vehicleis the telescopic sight. The white area in the top left hand corner is, I assume, the mount for the gunners periscopic sight. On the turret basket floor we can see the equipment necessary for hydraulic traverse. The four lines going around the right side of the turret are for the stabilizer and go between a small pump on the far side of the motor and the hydraulic cylinder on the right side of the gun. On the near side of the motor (out of shot) is a pump for the tydraulic turret traverse. At the rear of the turret can be seen the manual travers cranking handle which leads us to our next photo.....

1999 J. Hornbostle

Attached to the rear of the turret is the traverse control gearing. On the left is the manual crank, the lever on top is the clutch lever and on the right we can see where the hydraulic power lines would have connected. In this particular turret there is no evidence of the hydraulic motor or pump assemblies shown in the previous photograph. Where this equipment is remains a bit of a mystery as we are not aware of any M3 hybrids or M3A1 tanks that only had manual traverse. In the background we can see the fire-extinguisher line passing through the rear bulkhead into the engine compartment. We can clearly see the sprung seats of the gunner and commander and also see the adjusting lever under the gunner's seat. Note that the back rests for the seats are of a different pattern to those of our other subject vehicle. The shallowness of the turret basket meant that it was impossible for the crew to stand when the turret hatches were closed and the rim which partially surround the basket floor unfortunately meant that there was no means of escape for the co-driver if the turret was traversed. It is fair to say that the cramped nature of the M3A1 turret was not liked and indeed M3A1 Stuarts of the Indian 7th Cavalry had their turret baskets removed.

1999 J. Hornbostle

In this photo we are pretty much sitting in the commander's/loader's seat looking down at the turrt basket floor. Note that on the M3 hybrids and M3A1s the turret cupola was removed with the commander gaining a periscope on the the right hand side of the turret (the cupola on the M3 was on the gunners side). We can see here a 37mm Ammunition bin which has two part hinged lid. One part hinges towards the sponson and is clearly visible, the other hinges up towards the bulkhead. In all 106 rounds of 37mm ammunition were stored in the M3A1, more than half would appear to be in this bin alone. Behind the hinged lid of the ammo box is the SCR 508 radio set. In this vehicle the radio set is positioned on the right hand sponson, which is somewhat unexpected. It would be more usual for the radio set to be positioned on the left and in command tanks the extra set would be placed on the right at the expense of cal. 0.30 ammunition.

1999 J. Hornbostle

This photo is of the same area as the previous one but from a lower position. We can see that in this quadrant of the turret there is no wall to the turret basket allowing easy access to the ammuntion rack and, in this particular case, the radio sets, but only if the turret is not rotated. It is through this area that the co-driver would have to scramble to evacuated the vehicle. The ammunition bin lids have now been dropped back into place to give a clear view of the BC604 transmitter, RC298 interphone and BC603 receiver which make up the SCR 508 set. The positioning of the radio set on the sponson must have been somewhat inconvenient for the commander. The turret basket makes this area not paricularly accesible, especially if the turret is traversed. In the foreground we can see the elevating wheel of the main gun and behind this we can see a turret support roller.

1999 J. Hornbostle

Mounted on the rear firewall is a fixed 10 lb fire-extinguisher which supplies lines into the engine cmpartment. Operation was by a lever on the top of the bottle or from outside the tank by a hand lever on the left rear fender, below the tail light. Unlike the M4 medium tanks, the driver was not able to operate the main extinguisher system however there was a smaller 5 lb portable extinguisher mounted by the drive shaft casing behind the drivers position. As you can see this particular part of the turret basket has high side to it - quite why this was necessary I don't know as it must have hampered access to the stowage bins and left hand sponson.

1999 J. Hornbostle


a Generator
b Duplex pressure and scavenger oil pump
c Magnetos
d Starter
e Starter solenoid switch
f Fuel filter
g Carburetor body
h Fuel pump
i Governer
j Oil temperature thermometer
1999 J. Hornbostle


a Starter
b Starter solenoid switch
c Cylinder heads
d Primer distribution
e Hose to air intake filter

The above two photographs show the engine comparment with Contimemtal W-670-9A gasoiline engine fitted. Production of the M3A1 ran from May 1942 until February 1943. Of the 4621 tanks made during this period all but 211 were fitted with the W-670 gasoline engine, the remainder being equipped with Guiberson T1020 diesels.

Continental W-670-9A Engine Specification

Type Radial, Air Cooled
Cylinders 7
Fuel 80 Octane Gasoline
Bore & Stroke 5.125 in, 4.625 in
Displacement 667 cubic ins
Compreesion 6.1:1
Max. governed speed 2,400 r.p.m.
Gross horse power 262 at 2,400 r.p.m.
Max. gross torque 590 lb-ft at 1,700 r.p.m.
Crankshaft rotation counter clockwise
Length 32 in
Width 53.25 in
Height 42.375 in
Ignition Magneto
Dry weight 1070 lb
Weight installed 1,214 lb

1999 Jon Hornbostle, Geoff Winnington-Ball & Chris Shillito