Thunderbolt tank

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Australian Cruiser Tank Mk. 3 "Thunderbolt"
[An AC3 tank.] AC3 tank (AWM 101155).jpg
[An AC3 tank.]
The pilot production AC MkIII tank
Type Cruiser tank
Place of originAustralia
Production history
Manufacturer New South Wales Government Railways Workshops
No. built1
Mass29 long tons (29.5 t) [1]
Length20 feet 9 inches (6.32 m)
Width9 feet 78 inch (2.77 m)
Height8 feet 4 34 inches (2.56 m)
Crew4 (Commander, Gunner, Loader/Operator, Driver)

Armour Hull front 65 millimetres (2.6 in)
sides and rear 45 millimetres (1.8 in)
Turret 65 millimetres (2.6 in) all round
25 pounder tank gun, 120 rounds
one .303 (7.7 mm) Vickers machine gun, 2,500 rounds
397 horsepower (296 kW) [1]
Power/weight13.7 hp/ton
SuspensionHorizontal Volute Spring
200 miles (320 km)
Speed35 miles per hour (56 km/h)

Australian Cruiser III also known as Thunderbolt [2] [3] was a cruiser tank designed and built in Australia in World War II as the successor to the AC1 Sentinel. Like the Sentinel the AC3 featured a one piece cast hull and turret. The AC3 featured a much improved design over the AC1 with better armour protection, a more powerful engine, and most importantly increased firepower.

Cruiser tank British tank concept of the inter-war period

The cruiser tank was a British tank concept of the interwar period for tanks designed to function as modernised armoured and mechanised cavalry. Cruiser tanks were developed after the Royal Armoured Corps were not satisfied with many of the medium tank designs of the 1930s. The cruiser tank concept was conceived by Giffard Le Quesne Martel, who preferred many small light tanks to swarm the enemy, instead of a few expensive medium tanks. There were two main types of cruiser tanks: "light" cruiser tanks and "heavy" cruiser tanks. "Light" cruiser tanks were lightly armoured and relatively fast, while "heavy" cruiser tanks were more heavily armoured and slightly slower than "light" cruiser tanks.

Sentinel tank Australian cruiser tank

The AC1 Sentinel was a cruiser tank designed in Australia in World War II in response to the war in Europe, and to the threat of Japan expanding the war to the Pacific or even a feared Japanese invasion of Australia. It was the first tank to be built with a hull cast as a single piece, and the only tank to be produced in quantity in Australia. The few Sentinels that were built never saw action as Australia's armoured divisions had been equipped by that time with British and American tanks.


The program was terminated in 1943 before any production vehicles were completed.


Even before the AC1 Sentinel began rolling off the assembly line in August 1942 it had been seen that the 2 pounder was becoming less effective as tank armour increased in thickness on new and improved enemy tanks. To address this a 25 pounder (87.6 mm, 3.45 in) gun-howitzer was fitted to a turret on the second prototype Australian cruiser tank hull and successfully test fired on 29 June 1942. [4] With this success decided to use the 25 pounder as a tank gun. The 25 pounder, redesigned as a tank gun, was tested on 10 October 1942, the work on the overhead recoil system would later prove useful for the design of the Short 25 Pounder.

Howitzer Type of artillery piece

A howitzer is a type of artillery piece characterized by a relatively short barrel and the use of comparatively small propellant charges to propel projectiles over relatively high trajectories, with a steep angle of descent.

Ordnance QF 25-pounder Short

The Ordnance QF 25-pounder Short was an Australian variant of the British Ordnance QF 25-pounder field gun/howitzer. The gun was developed by modifying the 25-pounder's design to improve its mobility during jungle warfare. Development began in 1942, and the weapon first entered service with the Australian Army the next year. It was used by several Royal Australian Artillery regiments during fighting in the South West Pacific Area, before being declared obsolete in 1946.

Mounted in a fully traversable turret larger than that of the AC1 but using the same 54 in (1.4 m) turret ring, [5] it was slightly cramped for the turret crew but gave the AC3 both armour-piercing capability as well as an effective high explosive round. The 40 volt electrical turret traverse system of the AC1 was replaced by a more powerful 110 volt system. [6]

The hull machine gun and gunner were removed from the design to make room for stowage of the larger 25 pounder ammunition. Powered by the same three Cadillac V8 engines as the AC1, they were now mounted radially on a common crank case and geared together to form the "Perrier-Cadillac", [Note 1] a single 17.1 L, 24 cylinder engine, very similar in some respects to the later A57 Chrysler multibank used in some variants of the US M3 and M4 tanks. While the AC3 shared the same armour basis as the AC1, the hull profile had been greatly redesigned to improve the ballistic shape.

The programme was authorised to build a total of 200 Thunderbolts. [7] [1] Although only one pilot model AC3 had been completed, large scale production of components had been ordered and 150 AC3 hulls cast. [8] New South Wales Government Railways' production line at Chullora work had started on assembling the first 25 AC3 tanks for trials when the programme was terminated in July 1943. [8]


The Australian War Memorial's AC3 in 2013 Cruiser Tank ACIII Thunderbolt at the Treloar Technology Centre September 2013.jpg
The Australian War Memorial's AC3 in 2013

At the end of World War II all but three Australian Cruiser tanks were disposed of by the Australian government. [9] [10] [Note 2] The 65 tanks that were not required to serve as a physical record in war museums in Australia and the UK were sold off by the Commonwealth Disposals Commission. [9] One of the three saved was the only completed AC3 (serial number 8066) which is now located at the Treloar Resource Centre at the Australian War Memorial in Canberra. [11]

Treloar Resource Centre

The Treloar Resource Centre, also known as the Treloar Centre and Treloar Technology Centre, is the Australian War Memorial's (AWM's) storage and conservation facility. It is located in the industrial suburb of Mitchell, Australian Capital Territory. The AWM describes the Treloar Resource Centre as "the Memorial's conservation facility and store for large objects of military technology, including aircraft, vehicles, boats, missiles and guns".

Australian War Memorial historic national heritage site in Campbell ACT

The Australian War Memorial is Australia's national memorial to the members of its armed forces and supporting organisations who have died or participated in wars involving the Commonwealth of Australia, and some conflicts involving personnel from the Australian colonies prior to Federation. The memorial includes an extensive national military museum. The Australian War Memorial was opened in 1941, and is widely regarded as one of the most significant memorials of its type in the world.

An AC3 mockup was assembled from unused AC3 armour castings and a mix of AC3 and AC1 parts at the Melbourne Tank Museum in 1996–97, this piece was sold to a private collector in 2006. [12]


See also

Tanks of comparable role, performance, and era


  1. Named after the French engineer Robert Perrier who was largely responsible for the design, seeMellor 1958, p. 319.
  2. Some sources state that the Sentinels were used for training after the cancellation of the program, and were not declared obsolete by the Australian Army for this purpose until 1956, see Mellor 1958, p. 308 and Bingham 1972, p. 73. However, Koudstaal 2005 states that the Sentinels were too different to the M3s and Matildas to be used for training and would require modifications and the manufacture of spares if they were to be used as special purpose vehicles. In 1945, three had been selected for preservation in war museums, while the remainder were dismantled.
  1. 1 2 3 "MP730/13, 7 A) Australian Tank Production Report by Colonel G A Green: B) Related Documents". National Archives of Australia.
  2. "MP392/36, 269/12/1713 Tanks: Australian Cruiser, Mark 3 (Experimental).". National Archives of Australia.
  3. Beale 2011, p. 143.
  4. Bingham 1972, p. 69.
  5. "A816, 45/302/184 Australian tank production (File No.2)". National Archives of Australia.
  6. Bingham 1972, p. 73.
  7. Mellor 1958, p. 319.
  8. 1 2 3 "MP508/1, 325/703/3084 G.S. Specifications Cruiser Tank AC3 and AC4". National Archives of Australia.
  9. 1 2 "MT1274/1 325/0118/1". National Archives of Australia. Retrieved 22 June 2014. Australian "Cruiser" tanks: dismantling and disposal of 63 in total 66
  10. "No Demand For Army Tanks". Townsville Daily Bulletin . Townsville, Queensland: National Library of Australia. 2 February 1946. p. 2. Retrieved 21 June 2014.
  11. Koudstaal 2005.
  12. "The Melbourne Tank Museum Sale". Antiques Reporter. 23 June 2006. Retrieved 27 June 2016.

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