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The Machine Gun Carrier was a light tracked vehicle designed to carry the Vickers machine gun to the battlefield, and which became the basis of the more famous Bren Gun Carrier and Universal Carrier.
Vickers-Armstrong D50
The D50 had two key innovations. The first was its steering system. The Carden-Loyd tankettes used a clutch and brake steering system, which could sometimes trigger ‘reverse steering’, where the vehicle would steer in the opposite direction to that intended when going downhill. This would happen when the clutch was used to disengage a track, but the brakes not applied, leaving that track with no engine brakes. As a result instead of slowing down, that track could speed up.
The D50 used two types of steering, both controlled from the same steering wheel. The front road wheels were carried on a single axle that could move sideways in either direction. When the steering wheel was turned gently the axle would move, and both tracks would warp in that direction, becoming slightly curved and forcing the vehicle into a gentle turn. If the wheel was turned further then the brake on that side would be engaged and the vehicle would turn more quickly.
The second innovation was the use of Horstmann slow-motion suspension. The first version of this, used on the Light Tank Mk I and other Vickers vehicles, had two bogies on each side, each carrying two wheels. The wheels were carried on bell cranks. The horizontal arms of the cranks faced towards each other and were connected on a hinge. The vertical arms were connected by a horizontal spring. If one wheel was forced up the spring would be compressed against the other wheel, pushing it down. This was soon changed so that only one wheel in each bogie was on a bell crank. The spring was connected diagonally from the top of the vertical arm of the bell crank on that wheel to a point close to the centre of the other wheel. The D50 used one and a half bogies on each side, with the front two road wheels carried on a full bogie. The bell crank was on the middle wheel. The rear wheel was connected to a curved arm with the spring at the same angle.
This suspension system gave the D50 a much better ride that the Carden Loyd tankettes. It also gave it good cross country performance. Versions of the Horstmann suspension system were used on British tanks into the 1950s, with the Chieftain the last to use it.
The rest of the vehicle was fairly straightforward. The crew of two sat in a rectangular shaped two man compartment at the front, with the driver on the left (as on the Carden-Loyd vehicles) and the gunner on the right. The Ford V-8 engine was located in the centre of the rear compartment. There was a gap between the engine and the tracks, and seating was provided on top of the track guards, facing in towards the engine.
Vickers-Armstrongs built the D50 in 1934. In 1935 it went to the Mechanisation Experimental Establishment at Farnborough for tests. It was tried out as a light artillery tractor and as a carrier for the Vickers machine gun. The artillery tractor became the Dragon, Light, Mk III, while the Vickers carrier became the basis of the Carrier, Machine Gun No.1 Mark I.
Carrier, Machine Gun No.1 Mark I
After the trials of D50 the War Office placed a contract for a second prototype, the Experimental Armoured Machine Gun Carrier. This had the same engine, transmission and suspension as the D50. The two crew were swapped over, with the driver now on the right and gunner on the left. Four folding backrests were added on the track guards, allowing it to carry six men. Space was provided for six rifles. This vehicle reached Farnborough in December 1935 and after its initial trials was used as an experimental vehicle.
In April 1936 an order was placed for thirteen more of the same vehicle, this time designated as the Carrier, Machine Gun, No.1 Mark I. This time the four seats were removed, but shielded compartment was added on the back-left, behind the driver, for a third crewman. It would appear that the plan had been to fire the Vickers gun mounted on the vehicle, but this type was never used in combat. Instead seven of the thirteen were modified to serve as prototypes for later designs, and the rest used for training.
One of the No.1s was turned into the prototype of an Armoured General Scout Vehicle. This was given a much larger gunner’s compartment, which now carried a Bren gun in the front and a Boys anti-tank rifle on a sliding rail around the top, as well as a radio.
Carrier, Machine Gun No.2 Mark I
The Carrier, Machine Gun No.2 Mark I was the first version to enter mass production, and the first to visually look like the later Bren and Universal carriers. This was because the gunner’s compartment on the left was extended forward by added a three sided bay to the front of the fighting compartment, with a slot for the Vickers gun in the front. This made it much easier for the gunner to use the machine gun, and was retained for the majority of later carriers. The non-symmetrical front layout is one of the key visual features of the Bren and Universal Carrier families.
The Machine Gun Carrier No.2 was produced by Vickers-Armstrongs, Thornycroft, Morris-Motors and Aveling Barford. Around 1,000 were delivered in 1937-38 before production switched to the Bren Gun Carrier. Many of the existing Machine Gun Carriers were also converted into Bren Gun Carriers, a fairly simple process that mainly involved altering the slot for the gun. Not all of them were converted as later photographs exist showing Machine Gun Carriers being used on training exercises.