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AC1 SENTINEL Historical review - Tier?

AC1 Sentinel Australia

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A_Headless_Chicken #1 Posted 11 July 2013 - 10:38 AM

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AC1 SENTINAL TANK
Australia’s hidden wonder


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Good day chaps
Today’s historical ramble takes us to the far flung corners of the Commonwealth to look at the tanks manufactured by Australia during the early 1940’s, why they were made and the difficulties and challenge’s this commonwealth country had in developing an effective tank. At first glance these machines look archaic and have some suspiciously amusing external features, but they were for their time both innovative and advanced in thinking, with numerous features and concepts that were far ahead of the other allied designs. indeed were it not for the American reluctance to keep things strictly domestic when manufacturing weapon’s it is feasible that the Sentinel rather than the Sherman that was the iconic tank of WW2.

Background
With the Second World War under way, and Japan advancing after its surprise attack against the US, the Australians were savvy enough to know they were under threat of invasion. The Australians had little to defend themselves with, amounting only 4 Vickers Medium Tanks of 1928 vintage, 10 Vickers Light Tanks MKVlA, and 18 locally produced Armoured Cars of three marks, and whilst able to muster a large amount of tough infantry they lacked effective tanks. After having observed the crushing defeat Britain and French took from Germany’s blitzkrieg the Australian’s realised that they would be receiving very little if any help in the way of war materials and that to stay effective in this rapidly changing war they would need to manufacture tanks themselves. The next obstacle Australia had in in in the early years was a lack of experience in this field having no dedicated tank manufacturers, and those capable of producing the correct components to make armoured vehicles were spread out over the territories. As such they sent a single engineer over to the US and another to the UK to learn what they could about making tanks.

From the information they gathered they set out to build a strong, reliable, and more importantly practical machine that was easy to fix and repair in the field, have enough armour with a level of reliability in the hard climate that the Australian’s would be defending. The specifications set down by the General Staff in 1940 was for a cruiser style tank with a top speed of about 35mph a 2pdr AT gun and a Vickers heavy machine gun for close protection, to be crewed by four men and have a armour playing of 50mm thick. The engineers originally wanted to make a vehicle based on the US M3 with a turret, much like the Canadians were doing with the RAM but the lack of equipment to spare equipment capable of rolling the armour coupled with a shortage of engines meant that the vehicle was to be produced from locally sourced parts while keeping a level of interchangeable parts with other allied vehicles where possible. The War office asked for 859 Tanks to be produced, of which 340 were to equip one Armoured Division. The remainder being for Corps Troops and 12 months reserve stock.

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The NSW Government Railways company was chosen to build the tank with the first experimental prototype completed at the Everleigh Loco Works in Sydney, during January 1942. This was quickly followed by two further models Extensive testing of these vehicles was conducted first at the Railway's test track at Villawood NSW, and then at the Army's Mechanisation Experimental Establishment at Monegeetta, Victoria. The main issues were engine cooling, failure of the rubber bonding of the bogie wheel tyres andthe turret got stuck when turning on an angle.
Once rectified the machine they created was superb; the AC1 or the Australian Cruiser Mk with the whole process from scratch to finish taking 22 months.
From the outset they designed their tank to be an Anti-tank weapon, they had seen the way the Brits had split their armour into cruiser and Infantry support roles and considered this a waste of resources proving less than effective in the field, they also duly noted that the current British designers were struggling to up gun their current tanks due to small turret rings and narrow hulls. From these perceived lessons the Australian’s realised that they should build their tanks to be easily upgradable and wield any weapons that may be needed in the future.

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Firepower
The only tank weapon the Australian’s had in ready numbers in 1940 was the 40mm 2pdr gun and although an excellent weapon at the beginning of the war it would soon be obsolete but with Japan’s tanks being the small tankette types it was deemed adequate for the time. The Sentinel hull was therefore built large enough to constantly increase it turret ring diameter thus allowing it to wield the new 17pdr gun with the turret mantle able to take the 17prd breech block though a slide in method when available. While this weapon was scarce in the early days of the war the Aussies were confident it would be available later on and had pre-designed the Sentinel to mount this fearsome weapon along with even larger calibres if needed, something that the other allies had extreme difficulties with. From the 2 pounder they increased the Sentinel on a regular basis whenever weapons became available and various weapons were fitted including 6, 17, 18 and 25 and twin 25 pounder guns as well as 3” and 3.7” AA guns (it was rumoured at some point an 8.8cm L30 was tested by I can find no reliable source)

They did finally manage to install a 17Pdr (although only tested) as Australians wanted to see if it would take the recoil; fitting a pair of 20 pounder (Derp) guns into the turret that when fired together created 20% more recoil than a standard 17pdr. Once again the tank did not let them down and she took the recoil with no outstanding issues, the Sentinel it seemed would readily accept the long Brit AT gun. Ammunition was kept in a circular pattern around the turret basket, with 120 AP and HE rounds for the 2pdr, 120 rounds for the 20pdr and 60 rounds for the 17Pdr The engines powered the turret though a 40volt (110 volt on AC3/4) electric motor at a rather poor (by WOT standards) 20 degrees per second all guns had – 10 depression and + 20 elevation.

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ACIV with 17pdr left AC1 and crew right


Mobility and Suspension
The hull layout was a simple design with Driver to the right and radio/bow gunner to his left (note the bow gunner had to use the gunners periscope to sight targets and was not given his own sights) when building the AC1 they took apart several M3 Lee tanks and simplified the complex transmission system the American designers had installed, they kept the HVS suspension but switched to a better Hotchkiss type when it proved inadequate, drafting plans to move over to HVSS when time allowed. Power wise the Aussies did not have a large enough commercial engine to fit the tank at the time so opted to install three V8 Cadillac gauge car engines in a two by one clover leaf patter later mounted radially to provide the grunt necessary to move the tank.
Maintenance was made accessible (contrary to what the yanks say) by pioneering the pull out engine pack in the rear, this allowed a rapid field change that is still used by some tanks today. Power was adequate despite having 70 less horsepower than the M4 the sentinel was able to reach her top regulated speed of 48kph and unregulated speed of 64kph (40mph) allowing her to move quickly while the Sherman had to build up momentum first before the larger Chrysler A57 Multibank was fitted.

Of interest was that the three engines (two abreast, one behind) were connected via a clutch to a three in one transfer box located directly below the turret, the drive shaft then ran though the main clutch to the gearbox (later updated to crash type but originally they tried to use the M3 synchromesh style) and a Cletrac style differential system like the M4 this uniquely allowed the Sentinel to run on one, two or three engines independent of one another and continue to drive even if one was knocked out, likewise the tank could be started up with just one engine or all three at once. Large radiators and fuel tanks were situated behind the engine rather than to the sides offering less chance of leaks from side hits and the tank held 130 gallons of 70 octane fuels
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AC3E1 with twin 25pdr guns

Armour
Armour was simple but advanced with sloped, well angled shapes and more importantly both the hull and turret were made from a single cast piece which the American manufacturing plants had not yet managed to implement (At the time of design mass rolled armour would not have been possible and a single cast was more effective and stronger than a riveted hull or multi cast that would crack on the seams like the French tanks) –
The hulls were made by Bradford Kendall ltd using a homemade zirconium alloy that had been developed for bullet proof plates some years earlier and could be found on vehicles like the DINGO armoured car, the metal contained no nickel as Australia had none, leading to a softer but tougher plate it was easy to cast and spalled a lot less than western plate and when compared to an imported Sherman was found to be of a marginally superior quality.

as the war progressed the reality was that Sentinel would face German tanks and as such would need to be unarmoured from 65mm to 75mm of cast armour at the same angles; three models were built known as the E-series and put into trials when one considers the Sherman had 76mm of armour at steeper angles these newer sentinel offered a thicker effective belt of armour.
Sentinel was also lighter than the Sherman coming in at 28tons offering more logistical promise than the heavier Sherman, other notable features were seen in the crew safety, which was to have built in provisions for safe ammunition storage; reducing the chance to set alight in the event of being struck; rather innovative as the Sherman’s were still readily burning in 1944, it did suffer from a slight shot trap near the turret but this oversight would have been rectified if the Sentinel had gone into mass production.

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Possibly the AC Christie model left, and the 17pdr right


FATE
Sadly the Sentinels career was cut short, with the US making good headway in the Pacific war and the Allies pushing the Germans on other fronts the program was stopped in favour of lend-lease tanks, The Australians now had large stocks of surplus Matlilda’s and M3’s which although of no use in Europe would prove themselves again in the Jungles fighting now taking place. The Americans had also been pressurising the Australian government to switch to M4 production threatening to pull all lend lease if they did not comply.
Britain had shown far more interest in the Sentinel an had also given the designer’s a few tanks to reverse engineer including a Cromwell and a Crusader, the Aussies were impressed by the Cromwell’s speed and Crusaders suspension but nothing else came from this..

those that had been built were used as training vehicle for a while but being so very different from the Matlilda’s and the M3 it proved more costly to keep them in service only very few were kept before sadly being scrapped or converted after the war, now about 9 survive 1 at Bovington and the rest in various states in Oz, two in a museum and a third shell in private ownership, but tanks do keep turning up in the ozzy outback and its possible there are other survivors out there.

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AC1 constuction

Basic stats AC1
Armour: LFP 65/45mm UFP 65mm@66Deg = (159mm relative Thickness at 0 deg) top 23/25mm sides/rear 45mm. Hull top 23mm
Turret: Frontal 65mm (+/- 40mm mantle?) With 50mm well sloped sides from front
Turret traverse 20 degrees per second
Elevation/depression +20/-10
Crew 5
Weight 28 tons
Speed max 48kph standard/64kph feasible
Height 2.56M Width 2.8M Length 6.35M

some variants
Most variants share the same stats: any that differ I will mark out.
AC1 – Sentinel 40mm main gun
AC1A 57mm main gun
AC1B 87.6mm 20Pdr Derp with HE smoke and AP rounds, ROF recorded at 8RPM
AC2 40mm – It should be noted the original AC2 concept was a lighter version of the AC1 that did not use imported parts, this in turn resulted in a heavier weight which the transmission couldn’t handle, and therefore needed lighter armour- which was not good enough for its roll, the project was then scrapped.
AC2 57mm main gun, 2 x diesel engines
AC3* “Scorpion” 2pdr high velocity gun and single 400 Hp Radial pratt and Whitney engine.
AC3E1 Prototype 2 x 25Pdr gun firing in synchrony 4/8 Rpm
AC3 1 x 25pdr gun, a new "Perrier-Cadillac" style power pack mounted around a common drive shaft with 80 octane fuel for more Hp – redesigned armour with no MG and even more sloping
AC4 1 x 17Pdr AT gun
ACIV Suspension test bed – An unknown vehicle that was tested with 5 large road wheels similar to the Crusader, it was seen to be running on Christie type suspension at high speeds but I have at this time no further records than hear say. This may have ended up being used in a film and then sadly destroyed.

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AC1 testing ground


In WOT
This is one of the hardest tanks to place in a select tier/role; at any point it seems either better or worse than its rivals depending on where it’s placed for example the 17pdr is tier 7 on tanks but this vehicle won’t survive in tier 8-9 games, while the 2pdr is ok for tier 4 but the tank is OP armour wise and a bit speedy for that tier, so I will leave this bit to you. Have a read, look at the versions and stats and see where you would place this or think it would be best suited, bearing in mind that there are other contenders such as Lend lease Sherman’s etc to slot in as well.

Looking at the basics it’s got good armour both on the hull and turret, with the upper hull being 65mm angled at 66 degrees for an effective 159mm on the upper plate, lower plate is thinner and not angled as such, turret is 65mm but the mantle appears to be at least 40mm giving it 105+mm of armour. The turret is well sloped and looks to be bouncy although there is a shot trap.
Mobility is good, and while the official department of boring restrained it at 30mph, it could easily it 40mph when any half competent engineer tinkered with it, however reverse is an appalling 6mph. The 3 x engines makes an interesting choice and as such the Sentinel should have an invisible stat that either causes repairs in this area to be 100% more efficient or just increase the modules toughness dramatically. Rear mounted fuel tanks have their own pros and cons.

Firepower the AC series offers a huge selection of guns, from rapid 2 pounders, up to the 17pdr and even the derpy twin 25pdrs (and why not it’s got as much right to have that as the semi fictional KV1S tank) this offers a great choice of roles from light tank hunter, Heavy tank buster to Very high alpha/low pen derper. Also don’t forget this is one of the only tanks that had a built in safe stowage system so racking should be lower (make the module smaller I guess?)
Conclusion a great tank, with innovative features and good all round stats, it has a few weak areas and some pretty strong ones a real solid contender and a lot more interesting than some.


also there is this


http://archive.org/d...obruk-UsTrailer

^ its a traler for a film "rats of torbuk - the germna panxers in this are Sentinel tanks.. but dammed if i can get links to work, feel free to try below ty


Edited by edfrancis001, 11 July 2013 - 10:56 AM.


anonym_kL7qtn3e52MB #2 Posted 11 July 2013 - 10:47 AM

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Looks like an Australian "Matilda" type tank. Heavy armour, slow etc.

Interesting indeed +1

marcvs #3 Posted 11 July 2013 - 10:53 AM

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Awesome read!

+1 for you good sir

I would put this tank somewhere around tier6, depending on its armament

kwk75l48 #4 Posted 11 July 2013 - 10:59 AM

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just a note you put 20pdr when you ment 25pdr the 20pdr was the centurion gun mounting two of those with 120 rounds would be problematic. :blinky:

DixieBlitz #5 Posted 11 July 2013 - 11:00 AM

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I have always liked the sentinel, handsome tank to look at. Their is one feature which make me giggle, the armoured mounting for the machine gun... it looks like a penis on the front of the hull :harp:

I reckon tier 5 would be about right with the 2 pdr

KekelMyShekel #6 Posted 11 July 2013 - 11:20 AM

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Why does it have a penis sticking out the front?

deveen23 #7 Posted 11 July 2013 - 11:23 AM

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View PostCptTriggerHappy, on 11 July 2013 - 11:20 AM, said:

Why does it have a penis sticking out the front?

Why do we all have it?

lonigus #8 Posted 11 July 2013 - 11:29 AM

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View PostCptTriggerHappy, on 11 July 2013 - 11:20 AM, said:

Why does it have a penis sticking out the front?

Seems like Iam not the only sick person that asap noticed it rofl... :D

KekelMyShekel #9 Posted 11 July 2013 - 11:29 AM

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View Postdeveen23, on 11 July 2013 - 11:23 AM, said:

Why do we all have it?

To please da pusseh.

A_Headless_Chicken #10 Posted 11 July 2013 - 11:36 AM

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It was made to look like a dick so that when it sprayed hot lead all over the Germans they would be demoralized - citation needed

xCaptainObviousx #11 Posted 11 July 2013 - 11:36 AM

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It would fit pretty well at tier 6 I think. It would be a faster, more well armed Churchill 7 with worse side/rear armor.

The 20 deg/sec turret traverse shouldn't be an issue as WG have confirmed that all tanks ingame have buffed turret traverse to fit with the small maps, I'd expect it to have 30-35 deg/sec ingame.

xCaptainObviousx #12 Posted 11 July 2013 - 11:38 AM

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View PostCptTriggerHappy, on 11 July 2013 - 11:20 AM, said:

Why does it have a penis sticking out the front?
From what I understand that is an MG, as Australia is a very hot place they had to make a cooling system for it and then they decided to armor this coolong system... and it ended up being a huge metal dong to wave in Japan's face.

A_Headless_Chicken #13 Posted 11 July 2013 - 11:54 AM

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View PostxCaptainObviousx, on 11 July 2013 - 11:38 AM, said:

From what I understand that is an MG, as Australia is a very hot place they had to make a cooling system for it and then they decided to armor this coolong system... and it ended up being a huge metal dong to wave in Japan's face.

Ty, that makes logical sense ty

RedBear87 #14 Posted 11 July 2013 - 11:55 AM

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Very interesting article, thanks a lot for sharing it, I've been interested in this tank from a while but I couldn't find much more about it than what wikipedia says. Finding the right tier for this tank could be difficult but I would say tier VI, I kinda see it as something like a more armoured but less fast Hellcat.
EDIT: it should be mentioned that in the old leaked icons Sentinel AC1 and AC4 were apparently two different vehicles, of course it doesn't necessarily mean that they'll stay like that.

Edited by RedBear87, 11 July 2013 - 12:21 PM.


A_Headless_Chicken #15 Posted 11 July 2013 - 01:58 PM

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View PostRedBear87, on 11 July 2013 - 11:55 AM, said:

Very interesting article, thanks a lot for sharing it, I've been interested in this tank from a while but I couldn't find much more about it than what wikipedia says. Finding the right tier for this tank could be difficult but I would say tier VI, I kinda see it as something like a more armoured but less fast Hellcat.
EDIT: it should be mentioned that in the old leaked icons Sentinel AC1 and AC4 were apparently two different vehicles, of course it doesn't necessarily mean that they'll stay like that.

yes that would make more sense, maybe a premium and a regular?

sword_of_Damocles #16 Posted 23 July 2013 - 05:21 PM

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Nice "horny" tank!!!
Thanks Eddie!! :blinky:

shaermon #17 Posted 23 July 2013 - 06:01 PM

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View Postlonigus, on 11 July 2013 - 11:29 AM, said:

Seems like Iam not the only sick person that asap noticed it rofl... :D

No you were not. Immediately started skimming the text for the explanation for the... thing.

MkH #18 Posted 23 July 2013 - 07:25 PM

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View PostCptTriggerHappy, on 11 July 2013 - 11:20 AM, said:

Why does it have a penis sticking out the front?

Hehehe... penis.

exauroura #19 Posted 23 July 2013 - 10:54 PM

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Very interesting tank i cant wait for them to add it (maybe as part of the lend lease line).
I can see this tank sitting at tier 5 and the up armored version at tier 6 ( maybe even tier 7 with the 17 pounder and premium mm).


Edit: Forgot to say Props to edFrancis for yet another awesome article, keep up the good work.

Edited by exauroura, 23 July 2013 - 10:58 PM.


speedphlux #20 Posted 24 July 2013 - 05:28 AM

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If that comes as Tier 5-6 Brittish Medium, I'm buying it in an instance ! Looks troll, has to be good  :playing:





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