Sentinel cruiser tank [Australia]

[copeab]

Sentinel cruiser tank
copyright 2005 by Brandon Cope

In late 1940, the Australians realized that with the war in Europe and the potential threat from Japan, there was a good chance that military shipments to the country could be disrupted. One of the projects that came out of this concern was designing a tank that could be produced locally. Test models were ready by early 1942 and the first production Sentinels appeared in August 1942.

Originally, the tank was to be based on the American M-3 medium (p.W:MP68), but several problems prevented this, one being that the facilities to created rolled steel armor were occupied. This led to one of the more unusual features of the tank in that the hull and turret were each cast in one piece. The tank also used three V8 automobile engines; it could be run on one, two or all three of them. The turret was intentionally made larger than required for the 2-pounder to allow the easy upgrading of the armament.

Only around 65 AC1’s were built and none saw combat. The first 13 tanks didn’t have their armor properly treated and were designated for training only. With sufficient numbers of American and British tanks coming in, all Sentinel designs were terminated in 1943. In an alternate WWII (where, for example Japan won the Battle of Midway), the Sentinel could be built in larger numbers and see combat in the Pacific. While the 2-pounder was obsolete by 1942 against Germany tanks, it would have still been perfectly adequate against the think armor of tanks fielded by Japan. Likewise, the relatively thick Sentinel armor would have given the Japanese a hard time.

The AC1 Sentinel has a crew of five. The commander sits in the turret and operates the AA Bren gun. The gunner fires the cannon and coaxial MG, while the loader also operates the radio. The driver sits in the body with the co-driver, who also operates the hull MG. The turret electrically traverses at 20 degrees per second. The AC1 uses 11 gallons per hour at routine usage.

AC1 (Mk I) Sentinel

Subassemblies: Medium Tank chassis +3, full rotation Small AFV turret [Body:T] +2, full rotation Mini open mount [Tur:T] +0, tracks +3.
Powertrain: 3¥82-kW HP gas engine w/ 246-kW tracked drive train and 156 gallons fuel in standard fuel tank [body]; 12,000-kWs batteries.
Occupancy: 2 CS Body, 1 CS Turret, 2 CS both Cargo: 2.5 Body, 4.4 Turret.

Armor
Body: F 4/250, RL 4/175, B 4/175, T 4/90, U 4/60
Tracks: 4/40
Tur: F 4/250, RL 4/250, B 4/250, T 4/95

Weaponry
40mm Medium TG/2-pounder QF [Tur:F] (130).
Ground LMG/Vickers [Tur:F] (*).
Ground LMG/Vickers [Body:F] (*).
Ground LMG/Bren [OM:F] (900).
* 4,250 rounds total

Equipment
Body: Small radio receiver and transmitter. Turret: 4.5-kW traversing gear. Open Mount: Universal mount.

Statistics
Size: 20’¥9’¥9’ Payload: 1.45 tons Lwt.: 30.25 tons
Volume: 104 Maint.: 39 hours. Price: $25,800

HT: 10.
HP: 1500 Body, 150 Turret, 540 each Track, 30 Open Mount.

gSpeed: 30 gAccel: 2 gDecel: 20 gMR: 0.25 gSR: 6
Ground Pressure is Low. 2/3 Off-Road Speed.

Design Notes
The design purchased 5,000 rounds of LMG ammo and 150 rounds of tank gun ammo. The historical values have been used
instead. The design weight was increased 9.5% to match historical weight and gSpeed was increased from the 29 mph design
speed. Turret armor is Expensive.

The Sentinel could be fitted with a 53 gallon external fuel tank if required.

Variants
The Mark IA upgraded the main gun to a 6-pounder (57mm Medium TG). None were produced.

The Mark IB replaced the 2-pounder with a 25-pounder howitzer (87.6mm Short Howitzer). None produced.

In 1941, work began on the Mark II (AC2), which was similar to the Mark IA, but replaced the three petrol engines with two diesel engines. It was lighter and simpler than the AC1 but was hated by the military. None built and design dropped in September.

The Mark III (AC3) Scorpion was similar to the Mark I, but with a single 298-kW engine. None built.

The Mark III (AC3) Thunderbolt was similar to the Mark IB, with 120 rounds for the 25-pounder and 2,500 rounds for the coaxial Vickers MG. The co-driver and the hull MG were removed. Weight 31.9 tons but, with a 296-kW engine, speed was unchanged. Fuel tankage was increased to 222 gallons. Although turrets and hulls for 81 vehicles had been produced, only one was completely built.

The Mark IV (AC4) would have mounted a larger turret and a 17-pounder gun (75mm Very Long TG) with 50-60 rounds. Only one prototype built.
--
A generous and sadistic GM,
Brandon Cope

http://www.geocities.com/copeab

[flyingwombat]

Interesting vehicle. A "might've been."

Thanks Brandon!

[copeab]

Originally Posted by flyingwombat

Interesting vehicle. A "might've been."

Thanks Brandon!

You're welcome.

One little factoid I stumbled on after posting the tank:

Before mounting the 17-pounder in the turret of the final prototype, they wanted to make sure it could take the recoil. Thus, they wedged two 25-pounders into one turret and fired them simultaneously (by remote, apparently). Two 25-pounders were used as their combined recoil was estimated to be about 20% more than that of a lone 17-pounder.

Brandon