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Australia's Australian Cruiser 1⁵, Australian Cruiser Mk I⁶, AC1⁶, Sentinel⁶

Australian Cruiser AC1⁶:

Royal Armored Corps Tank Museum

Australian Cruiser AC1:

Australian Cruiser:

Australian Cruiser AC3:

Design

With Japan becoming a threat in the Pacific and England occupied by Germany, the Australian Ministry of Munitions started to consider building their own tanks in early June 1940.⁶

This was to be a major undertaking by the Australians as they had never even built their own automobiles.⁶

A. Chamberlain, was an engineer that was sent to the United States to study tank production.⁶ He was joined by Colonel W. D. Watson, who was an advisor from England.⁶ They both studied the M3 Medium.⁶

In November the Australian General Staff developed the requirements for a tank.⁶ It was to have a 2-pdr (40 mm) gun and two 7.7 mm (0.303") machine guns.^5,6 The tank was also required to go 30 mph and have at least 50 mm of armor.⁶ It was to use as many of the same components as the American M3 Light Tank.⁵ The engine was to be three Cadillac automobile engines joined together.⁵ Cast armor was also a requirement.⁵

It had rubber-block suspension with horizontal volute bogies similar to the French Hotchkiss.

The hull MG had a armored sleeve.

Fighting Compartments

In the front the driver sat on the right side with the hull gunner on the left.⁶ Between them sat the gearbox and the Vickers .303 machine gun that was water cooled.⁶

The middle compartment contained the turret, which contained the commander on the left, the loader / radio operator on the right, and the gunner in front of the commander.⁶

The rear compartment contained the frame which held the three Cadillac 75 engines.⁶ The fuel and radiator was also located in the rear compartment.⁶

Hull

As firms producing rolled armored plates were committed, it was decided to try to make the hull from a solid cast.⁶ Other experiments involved trying to make strong enough armor from metals available in Australia.⁶

Engine

Early hopes to use the Guiberson diesel engine were dashed and the Cadillac automobile engine was selected.⁶ Three engines were combined.⁶

Australia had hoped to make a copy of the M3 Medium's gearbox, but industry in Australia just didn't have the tooling to make them properly.⁶ Chamberlain returned in May 1941 from the United States proposing the design of what would become the AC 2.⁶ The AC 2 would use imported transmissions that were used in heavy trucks.⁶ However, with events in the Pacific rapidly changing, the AC 2 program was cancelled in September 1941 by the Minister for the Army.⁶

With design changes it became possible for the manufacture of the gearbox, for the AC 1, in Australia.⁶

Radio

The radio was a Wireless Set No. 19 Mk 2.⁶

Prototype

A wooden prototype was built in early 1941 and in October the first hull had been cast.⁶ The first three pilot models were completed in January 1942, only 22 months after the original General Staff specifications.⁶

AC 3

The AC 1 was originally designed to be capable of carrying the 6 pdr, but supplies were unavailable due to the British Army needing them in North Africa.⁶ It was decided to install an Australian produced 25 pdr.⁶ The AC 3 was first test fired at Williamstown, Victoria, on June 29, 1942.⁶

Production

The estimated 2,000 would be needed and first ones to be ready by July 1941 and 70 per month being produced.

The Chullona Tank Assembly Shops in New South Wales would produce the tanks. Production started in August 1942 with a total of 66 being built. A new factory was built, but with America able to supply enough tanks for Australia's use production ceased and the tank was used for training.⁶

AC1: 66^3,6
- Production: August 1942 - ?³

Variants

AC 1⁶:
AC 2⁶: Was another design that was dropped after truck components became unavailable from US.⁶
AC 3⁶: Had 25 pdr howitzer mounted in turret.⁶ This had a larger turret ring and turret. The hull MG was removed. The 3 engines were given a single crankcase. Prototypes appeared in early 1943. Never went into production.
AC 4⁶: Was to have the 17 pdr gun in turret.⁶ However, none were available and two 25 pdr guns were installed in the turret to simulate the recoil of the 17 pdr.⁶ A prototype was built in mid-1943. One of the prototypes had a torsion bar suspension.

Usage

Used only for training.

		Australian Cruiser Mk I⁶, AC 1⁶	AC 3⁶	AC 4⁶
Crew	5¹	Commander, driver, hull gunner, gunner, loader^2,6 5^2,3,4,5,6	Commander, driver, gunner, loader^2,6 4⁶, 5²
Physical Characteristics
Weight	62,720 lb, 62,732 lb 28 tons¹ 28,489 kg¹	62,720 lb^2,3,4,5 28 tons⁶ 28,450 kg^4,5	62,720 lb²	31 tons⁶
Length w/gun	20' 9"¹ 6.4 m¹	20' 9"^2,3,4,5,6 6.325 m^4,5	20' 9"²
Length w/o gun
Height	9' 1", 8' 5"¹ 2.59 m¹	8' 4.75"^4,5,6, 8' 5"^2,3 2.56 m^4,5	8' 5"²
Width	8' 2", 8' 5", 9' 1"¹ 2.8 m¹	9' 1"^2,3,4,5,6 2.768 m^4,5	9' 1"²
Width over tracks
Ground clearance	1' 3"
Ground contact length
Ground pressure		13.4 psi⁶
Turret ring diameter		54"⁶	64"⁶	70"⁶
Armament
Main	40 mm (2 pdr)¹	2 pdr. OQF² 2 pdr.^3,4,6	25 pdr.^2,4,5,6 25 pdr. howitzer³	17 pdr.^3,4,5,6
Secondary
MG	2: 7.62 mm MG¹	2: Vickers .303 cal MG²,6 2: Vickers MG³ 2: 7.7 mm MG⁴	Vickers .303 cal MG²
MG - coaxial	7.7 mm	Vickers .303 MG⁶	Vickers .303 cal MG⁶	Vickers .303 cal MG⁶
MG - hull	7.7 mm	Vickers .303 MG⁶
Side arms
Quantity
Main	130	130^2,6
Secondary
MG	4,250	4,250^2,6
Side arms
Armor Thickness (mm)	65¹	25², 65², 25 - 26³, 25-65⁵	25 - 65⁴ 25², 65²
Hull Front, Upper		65⁶
Hull Front, Lower
Hull Sides, Upper		45⁶
Hull Sides, Lower
Hull Rear		45⁶
Hull Top		25⁶
Hull Bottom
Turret Front		65⁶
Turret Sides		65⁶
Turret Rear		65⁶
Turret Top		25⁶
Engine (Make / Model)	3: Cadillac¹	3: Cadillac^2,3,4,5 3: Cadillac 75⁶	3: Cadillac² 3: Perrier-Cadillac 41-75⁶	4: Gipsy Major⁶
Bore / stroke
Cooling		Water⁶
Cylinders	8¹ x 3¹	V-8^2,3,6	V-8²
Capacity
Net HP	117¹ x 3¹	117 each^2,3 330^4,5, 350@3,050 rpm⁶	397²
Power to weight ratio		12:1 hp/ton⁶
Compression ratio
Transmission (Type)
Steering
Steering ratio
Starter
Electrical system		Lights: 6 volt⁶ Radio: 12 volt⁶ Turret traverse: 40 volt⁶
Ignition
Fuel (Type)	Gasoline¹	Gasoline^2,4,5	Gasoline²
Octane
Quantity		140 gallons internal⁶ 44 gallon jettisonable tank⁶
Road consumption
Cross country consumption
Performance
Traverse		360°^2,6 , 18°/second⁶	360°²
Max speed	20 mph, 30 mph¹ 48 kph¹	20 mph³, 30 mph^2,4,5,6 48.2 kph^4,5	30 mph²
Cross country speed		20 mph²	20 mph²
Road radius	200 miles, 198 miles¹ 319 km¹	200 miles^2,4,5,6 322 km^4,5	229 miles²
Cross country radius
Turning radius
Elevation limits
Fording depth	3' 11.5"	4'²	4'²
Trench crossing	8'	8'^4,5,6, 9' 6"² 2.438 m^4,5	9' 6"²
Vertical obstacle		2'²	4'²
Climbing ability
Suspension (Type)	Volute Scissors	Horizontal volute spring⁶
Wheels each side	6x2	3x2 sets⁶
Return rollers each side	3	3⁶
Tracks (Type)		Rubber⁶ Steel⁶
Length
Width	16.5"	16.5"^2,6	16.5"²
Diameter
Number of links		Rubber: 86⁶ Steel: 129⁶
Pitch		Rubber: 6"⁶ Steel: 4"⁶
Tire tread
Track centers/tread		7' 6.5"^2,6	7' 6.5"²

Sources:

The Encyclopedia of Tanks and Armored Fighting Vehicles - The Comprehensive Guide to Over 900 Armored Fighting Vehicles From 1915 to the Present Day, General Editor: Christopher F. Foss, 2002
British and American Tanks of World War Two, The Complete Illustrated History of British, American, and Commonwealth Tanks 1933-1945, Peter Chamberlain and Chris Ellis, 1969
Tanks of the World, 1915-1945, Peter Chamberlain, Chris Ellis, 1972
The Encyclopedia of Weapons of World War II, Chris Bishop, 1998
Tanks - Over 250 of the World's Tanks and Armored Fighting Vehicles, Chris Chant, 2004
Profile AFV Weapons 31 Australian Sentinel and Matildas, Major James Bingham, 1971