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Australia's Australian Cruiser 1, Australian Cruiser Mk I, AC1, Sentinel

Photos

Australian Cruiser AC1:
United States' Australian Cruiser AC1
Royal Armored Corps Tank Museum

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.

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

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

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

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

The centered hull machine gun had a large armored sleeve.

Fighting Compartments

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

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.

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

Hull

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

Engine

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

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. Chamberlain returned in May 1941 from the United States proposing the design of what would become the AC 2. The AC 2 would use imported transmissions that were used in heavy trucks. However, with events in the Pacific rapidly changing, the AC 2 program was cancelled in September 1941 by the Minister for the Army.

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

Radio

The radio was a Wireless Set No. 19 Mk 2.

Prototype

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

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. It was decided to install an Australian produced 25 pdr. The AC 3 was first test fired at Williamstown, Victoria, on June 29, 1942.

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.

  • AC1: >60, 66
    • Production: 1942 - ?, August 1942 - ?, ? - July 1943

Variants

  • AC 1:
  • AC 2: Was another design that was dropped after truck components became unavailable from US. Became available in January 1942.
  • AC 3: Had 25 pdr howitzer mounted in turret. 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 4: Was to have the 17 pdr gun in turret. However, none were available and two 25 pdr guns were installed in the turret to simulate the recoil of the 17 pdr. A prototype was built in mid-1943. One of the prototypes had a torsion bar suspension.

Usage

Used only for training.

Specifications

   
Crew 5
Physical Characteristics  
Weight 62,720 lb, 62,732 lb
28 tons
28,489 kg
Length 20' 9"
6.4 m
Height 9' 1", 8' 5"
2.59 m
Width 8' 2", 8' 5", 9' 1"
2.8 m
Width over tracks  
Ground clearance 1' 3"
Ground contact length  
Ground pressure  
Turret ring diameter  
Armament  
Main 40 mm (2 pdr)
Secondary  
MG 2: 7.62 mm MG
MG - coaxial 7.7 mm
MG - hull 7.7 mm
Side arms  
Quantity  
Main 130
Secondary  
MG 4,250
Side arms  
Armor Thickness (mm) 65
Hull Front, Upper  
Hull Front, Lower  
Hull Sides, Upper  
Hull Sides, Lower  
Hull Rear  
Hull Top  
Hull Bottom  
Turret Front  
Turret Sides  
Turret Rear  
Turret Top  
Engine (Make / Model) 3: Cadillac
Bore / stroke  
Cooling  
Cylinders 8 x 3
Capacity  
Net HP 117 x 3
Power to weight ratio  
Compression ratio  
Transmission (Type)  
Steering  
Steering ratio  
Starter  
Electrical system  
Ignition  
Fuel (Type) Gasoline
Octane  
Quantity  
Road consumption  
Cross country consumption  
Performance  
Traverse  
Speed - Road 20 mph, 30 mph
48 kph
Speed - Cross Country  
Range - Road 200 miles, 198 miles
319 km
Range - Cross Country  
Turning radius  
Elevation limits  
Fording depth 3' 11.5"
Trench crossing 8'
Vertical obstacle  
Climbing ability  
Suspension (Type) Volute Scissors
Wheels each side 6x2
Return rollers each side 3
Tracks (Type)  
Length  
Width 16.5"
Diameter  
Number of links  
Pitch  
Tire tread  
Track centers/tread  
  Australian Cruiser Mk I, AC 1
Crew Commander, driver, hull gunner, gunner, loader
5
Physical Characteristics  
Weight 62,720 lb
28 tons
28,450 kg, 28,489 kg
Length 20' 9"
6.32 m, 6.325 m
Height 8' 4.75", 8' 5"
2.56 m, 2.57 m
Width 9' 1"
2.768 m, 2.77 m
Width over tracks  
Ground clearance  
Ground contact length  
Ground pressure 13.4 psi
Turret ring diameter 54"
Armament  
Main 1: 2 pdr. OQF
1: 2 pdr / 40 mm
Secondary  
MG 2: Vickers .303 cal MG
2: Vickers MG
1: 7.62 mm MG
2: 7.7 mm MG
MG - coaxial Vickers .303 MG
MG - hull Vickers .303 MG
Side arms  
Quantity  
Main 130
Secondary  
MG 4,250
Side arms  
Armor Thickness (mm) 25, 65, 25 - 26, 25 - 65
Hull Front, Upper 65
Hull Front, Lower  
Hull Sides, Upper 45
Hull Sides, Lower  
Hull Rear 45
Hull Top 25
Hull Bottom  
Turret Front 65
Turret Sides 65
Turret Rear 65
Turret Top 25
Engine (Make / Model) 3: Cadillac
3: Cadillac 75
Bore / stroke  
Cooling Water
Cylinders V-8
Capacity  
Net HP 117 each
330, 350@3,050 rpm
Power to weight ratio 12:1 hp/ton
Compression ratio  
Transmission (Type)  
Steering  
Steering ratio  
Starter  
Electrical system Lights: 6 volt
Radio: 12 volt
Turret traverse: 40 volt
Ignition  
Fuel (Type) Gasoline
Octane  
Quantity 140 gallons internal
44 gallon jettisonable tank
Road consumption  
Cross country consumption  
Performance  
Traverse 360° , 18°/second
Speed - Road 20 mph, 30 mph
48.2 kph, 48.3 kph
Speed - Cross Country 20 mph
Range - Road 198 miles, 200 miles
319 km, 322 km
Range - Cross Country  
Turning radius  
Elevation limits  
Fording depth 4'
Trench crossing 8', 9' 6"
2.438 m
Vertical obstacle 2'
Climbing ability  
Suspension (Type) Horizontal volute spring
Wheels each side 3x2 sets
Return rollers each side 3
Tracks (Type) Rubber
Steel
Length  
Width 16.5"
Diameter  
Number of links Rubber: 86
Steel: 129
Pitch Rubber: 6"
Steel: 4"
Tire tread  
Track centers/tread 7' 6.5"
  AC 3
Crew Commander, driver, gunner, loader
4, 5
Physical Characteristics  
Weight 62,720 lb
Length 20' 9"
Height 8' 5"
Width 9' 1"
Width over tracks  
Ground clearance  
Ground contact length  
Ground pressure  
Turret ring diameter 64"
Armament  
Main 25 pdr.
25 pdr. howitzer
Secondary  
MG Vickers .303 cal MG
MG - coaxial Vickers .303 cal MG
Side arms  
Quantity  
Main  
Secondary  
MG  
Side arms  
Armor Thickness (mm) 25 - 65
25, 65
Hull Front, Upper  
Hull Front, Lower  
Hull Sides, Upper  
Hull Sides, Lower  
Hull Rear  
Hull Top  
Hull Bottom  
Turret Front  
Turret Sides  
Turret Rear  
Turret Top  
Engine (Make / Model) 3: Cadillac
3: Perrier-Cadillac 41-75
Bore / stroke  
Cooling  
Cylinders V-8
Capacity  
Net HP 397
Power to weight ratio  
Compression ratio  
Transmission (Type)  
Steering  
Steering ratio  
Starter  
Electrical system  
Ignition  
Fuel (Type) Gasoline
Octane  
Quantity  
Road consumption  
Cross country consumption  
Performance  
Traverse 360°
Speed - Road 30 mph
Speed - Cross Country 20 mph
Range - Road 229 miles
Range - Cross Country  
Turning radius  
Elevation limits  
Fording depth 4'
Trench crossing 9' 6"
Vertical obstacle 4'
Climbing ability  
Suspension (Type)  
Wheels each side  
Return rollers each side  
Tracks (Type)  
Length  
Width 16.5"
Diameter  
Number of links  
Pitch  
Tire tread  
Track centers/tread 7' 6.5"
  AC 4
Crew  
Physical Characteristics  
Weight 31 tons
Length  
Height  
Width  
Width over tracks  
Ground clearance  
Ground contact length  
Ground pressure  
Turret ring diameter 70"
Armament  
Main 17 pdr.
Secondary  
MG  
MG - coaxial Vickers .303 cal MG
Side arms  
Quantity  
Main  
Secondary  
MG  
Side arms  
Armor Thickness (mm)  
Hull Front, Upper  
Hull Front, Lower  
Hull Sides, Upper  
Hull Sides, Lower  
Hull Rear  
Hull Top  
Hull Bottom  
Turret Front  
Turret Sides  
Turret Rear  
Turret Top  
Engine (Make / Model) 4: Gipsy Major
Bore / stroke  
Cooling  
Cylinders  
Capacity  
Net HP  
Power to weight ratio  
Compression ratio  
Transmission (Type)  
Steering  
Steering ratio  
Starter  
Electrical system  
Ignition  
Fuel (Type)  
Octane  
Quantity  
Road consumption  
Cross country consumption  
Performance  
Traverse  
Speed - Road  
Speed - Cross Country  
Range - Road  
Range - Cross Country  
Turning radius  
Elevation limits  
Fording depth  
Trench crossing  
Vertical obstacle  
Climbing ability  
Suspension (Type)  
Wheels each side  
Return rollers each side  
Tracks (Type)  
Length  
Width  
Diameter  
Number of links  
Pitch  
Tire tread  
Track centers/tread  

Sources:

  1. 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
  2. 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
  3. Tanks of the World, 1915-1945, Peter Chamberlain, Chris Ellis, 1972
  4. The Encyclopedia of Weapons of World War II, Chris Bishop, 1998
  5. Tanks - Over 250 of the World's Tanks and Armored Fighting Vehicles, Chris Chant, 2004
  6. Profile AFV Weapons #31 Australian Sentinel and Matildas, Major James Bingham, 1971
  7. World War I and II Tanks, George Forty, 2012
20th Century American Military History Crucial Site