Sentinel ACIV

[robunos]

...AC Mk 2 was a design study only for a very different tank...

Does anyone have any more on this design......?

cheers,
Robin.

 

[Rickshaw]

...AC Mk 2 was a design study only for a very different tank...

Does anyone have any more on this design......?

cheers,
Robin.

A.T.Ross describes AC II as having been a much lighter armoured vehicle than AC I, based around IIRC the use of commercial truck mechanical components for the drive train and armed with a 2 Pdr. He believed it would have been a much more useful and more easily built vehicle than what became the Sentinel. However, he also notes the difficulties where other such vehicles attempted to use such drive trains in their design.

 

[Rickshaw]

True but as Australia was operating invariably on second if not more often third-hand information about technical matters in the North African desert, it would have been worse. We were at the end of the intelligence food-chain, with reports arriving months, often years after they had been digested in London or Washington. Nor, unfortunately was our military bureaucracy noted for its speedy or necessarily wise decision making.

That is unsubstantiated and incorrect. Australian technical intelligence of the battlefield was supplied via the Australian Army’s independent command chain. Far from being behind the times Australia was as well informed of tank developments which is why the Sentinel was redesigned and updated at a rate faster than the British tank program.

Total numbers would still have been small. Our demand for tanks was small as we did not have a disproportionate number of armoured units and formations which required them. Therefore, unit cost would have been higher than a comparable vehicle imported from the US or even the UK, even taking into account transport costs.

Small as in several thousand if full rate production had gone ahead in 1942-45 (planed rate of 70 per month)? Small by Soviet, American or British standards but not uneconomic which was your initial point. Gross cost may have been higher thanks to Australia having to pay for establishment of the production facilities - a cost not passed on via Allied production - but unit cost to build would be comparable. This is another unsubstantiated non argument.

It is noted in several works that a great deal of technical intelligence came from London to Australia, from the Middle East or Europe. Be it on enemy aircraft, armoured vehicles or ships. The AIF HQ in the Middle-East liased closely with their counterparts in the British HQ but those counterparts often produced only initial reports based upon their examination of captured equipment, whereas the War Office produced its own reports which were more wide ranging. I don't have references to hand but I am sure I've read that in several technical books that "information received" was often months, sometimes years after the event.

You're forgetting that until 1941, the entrance to the Red Sea was contested by Italy. All it needed was for Germany to reinforce Ethiopia with Luftwaffe units and the Red Sea would have been closed.

Ahh so then how did the North African forces get their logistics from the UK? It certainly didn’t come via the Mediterranean or over land via the Sudan.

Well, to reach Sudan, they'd have to transit the entrance to the Red Sea anyway. How did they do it? By running the gauntlet. Not that it was that much of a gauntlet I admit. Air cover was provided from Aden by the RAF. Even so, the Italians had several ships and submarines based in the Horn of Africa, as well as many aircraft.

It all came up the Red Sea, after having gone around the Cape, past Italy’s rapidly collapsing East African Front. Another non-issue, non-logical to if you’d bothered to think about it rather than leap at any factoid that may appear to batter my opinions.

A "rapidly collapsing East African front" that I would point out lasted until November 1941 (with the Allied campaign therein lasting from June 1940 to November 1941). Didn't appear to all that rapid, really, although the final stages I admit, were pretty quick. So, effectively we had a window of less than a month between the collapse of the Italians in the Horn of Africa to when the war with the Japanese began, when supplies were unlikely to be molested (except of course by the occasional German raider) in the Indian Ocean.

I would contend that was a poor choice of vehicle for that terrain, not necessarily that the Stuart was a bad tank for use against the Japanese. It would have been ideal for use on the continent, if the Japanese had ever attempted to attack or invade. Small, light, fast, well armed, reliable, it would have been a good vehicle considering the loading difficulties that narrow gauge railways in Queensland and central Australia had with heavier loads.

More non issues. There are no loading issues associated with Queensland railways. Narrow gauge or Cape gauge isn’t toy trains they carry the same loads as other trains. Just that the rails are closer together so they can turn sharper corners and cost less to install.

Wheel loading on trains and rail bed construction though, is. Narrow gauge trains have much lower loading limits for that very reason. The very reason why narrow gauge was adopted in Australia - cheapness - ensured that they could not carry as much load as either standard or broad gauge. Such factors must be considered when undertaking such study. The end result would be that twice as many flat trucks would be required, per unit load as only one medium tank could be carried as against two lighter tanks.

But they did not have many of either. AT defence was not given much emphasis by the Japanese. If, as you suggest they were "punishing to Allied medium tanks" they would have been "punishing to Allied lighter tanks" as well, so it would have made no difference, now would it?

Actually it doesn’t work that way. Light tanks would – and did – suffer *more* punishment from Japanese anti tank defence because they have less armour. Another non issue, based on the semantics of the adjective I used!

BUT as I pointed out, AT defence was a lower priority with the Japanese because they had not encountered large numbers of armoured vehicles in their wars in Asia. Even when they had, as at Khalkhyn Gol, no higher priority was placed on it. This meant that tanks were less likely to meet an AT gun or an Artillery piece which had been re-rolled to AT duties. As these could be easily outflanked and overrun in the broad, open spaces of Australia than they could in the narrow confines of the Tropical Rainforests of the Pacific Islands, light tanks would IMO have been sufficient, if used in large numbers to attack and defeat Japanese forces - exactly as the Russians had done at Khalkhyn Gol.

The Japanese were not supermen. They were in many ways even more fallible than most in their belief in their racial and moral superiority, which led them to be more rigid in their adherence to their set piece tactics.

Why build them before? The allocation of resources would have slowed the build up of the small ships and aero industries. By the time full production had started - mid-late 1942, the "stabilisation" would have just been around the corner.

Because there was no supply of tanks available from the UK for the Australian armoured units! How many times do we have to cover this same material just because you don’t get it? Australian armoured units can’t be equipped with aircraft or small ships. The air force and navy didn’t seem to have a problem before 1942 with their plane and ship supply. The RAAF was actually saying no to RAF suggestions of transferring US contracts. The Navy was building the AMS in numbers faster than they could crew. Of course in hindsight it would have been better for these two services to be building fighters and torpedo boats in Australia in 1940-41 but they didn’t want to because they didn’t think they had the need. You should be thankful the Army established new tank production capability that could later be used to sustain the large allied landing craft fleet because otherwise such capability wouldn’t have existed.

Tanks did come from the UK and in numbers. Not directly from the UK but from British stocks in the Middle-East as the older Matilda and M3 Lee/Grants as they were replaced by newer vehicles. M3 mediums also came directly from the USA. The M3 was a potent vehicle compared to the Japanese tanks and performed more than adequately when deployed against the Japanese in Burma.

As for the establishment of the tank lines - you are partially correct. However, as you yourself note, their value came not when they produced tanks but rather small craft. Small craft which were the lynchpin of the advance through the islands.

Read them all. None of them pay particular attention to the economic issues. I recommend to you A.T. Ross, Armed &​ ready : the industrial development &​ defence of Australia, 1900-1945, Turton &​ Armstrong. Wahroonga, 1995. Moreover, A.T. Ross discusses at length the issues surrounding the Sentinel and its troublesome gestation and its intended usefulness.

As the old adage goes, "amateurs study strategy, professionals study logistics" and by extension economics.

Ross’s arguments about the Sentinel are loaded by hindsight. I actually worked with the man during the time he wrote this book so it’s hardly new to me. I quoted those sources to make fun of your ridiculous claims about how the invasion threat was just some political issue not something to be taken seriously. That you changed the context is no surprise.

That is your opinion. I beg to differ. I note that you did not mention it, despite it having an extensive discussion of the very vehicle we are talking about. Perhaps you merely disagreed with his conclusions? I don't.

As to the surety or otherwise of a Japanese invasion, by late 1942 it was obvious the tide was turning and Japan was overstretched. By then, nearly all Australia's combat forces had returned (bar one Division) from the Middle East. They were battle-hardened, well trained and moderately well equipped for the very sort of battle an invasion would result in, one of manoeuvre in open countryside. Something the Japanese had been shown to be rather badly trained and equipped for at Khalkhin Gol. After the end of 1942, the Japanese were essentially on the defensive in the Pacific. It was the invasion scare of 1943 and the Defensive Strategy controversy which left many Australians with the mistaken belief as to what Japan's intentions were.

LOL. So you’re claiming that the improved security situation in late 1942/43 should have determined defence equipment decisions made in late 1941, early 1942?

The decisions in late 1941, early 1942 should have been made in light of the knowledge that Australia was not going to be "unprotected" and that the war in the Western Desert was looking more firmly to be moving towards the defeat of the Axis. There are no sureties, I agree but what was required was calm consideration, not panicky decisions to build a tank which was not going to be required for the situation likely to be facing Australia in either the near for far future.

In early 1943 decisions were made to stop the Australian counter invasion preparations. To assume that a year previous the Government and Army leadership should have been aware things would be much better in a year or so is ridiculous. But why stop at Australia? Surely by this rational Churchill was just blowing smoke when he declared that they would fight them on the beaches? How much wasted resources were put into counter invasion defences in the UK in 1940? In Rickshaw/Kadija world that was all wasted effort…

The threat of invasion had receded by late 1942. Bureacracy sometimes has an inertia all its own.

 

[Abraham Gubler]

It is noted in several works that a great deal of technical intelligence came from London to Australia, from the Middle East or Europe. Be it on enemy aircraft, armoured vehicles or ships. The AIF HQ in the Middle-East liased closely with their counterparts in the British HQ but those counterparts often produced only initial reports based upon their examination of captured equipment, whereas the War Office produced its own reports which were more wide ranging. I don't have references to hand but I am sure I've read that in several technical books that "information received" was often months, sometimes years after the event.

Of course most technical intel came from London they were involved in a lot more of the war than Australia! It’s also common for a lot of it to be late in reaching the required reader but that’s the nature of the beast not an exclusive Australian problem. But it’s a total non-issue to claim that marques of Sentinel would be behind the times because it was built in Australia and Australian’s didn’t know what was going on. They did and they updated the requirements for Sentinel accordingly on a similar if not better timetable than the British.

Well, to reach Sudan, they'd have to transit the entrance to the Red Sea anyway. How did they do it? By running the gauntlet. Not that it was that much of a gauntlet I admit. Air cover was provided from Aden by the RAF. Even so, the Italians had several ships and submarines based in the Horn of Africa, as well as many aircraft.

Why do you keep pushing this dead horse? The issue was lines of communication to North Africa from Australia were better than lines of communication to North Africa from Great Britain going around the Cape of Good Hope. Both lines have to pass up the Red Sea. Whatever is going on there effects both. You brought up the East African campaign as some deal breaker in my line of reasoning that Australia offered better supply lines. It didn’t so just give up already and allow the thread to move along.

Wheel loading on trains and rail bed construction though, is.

Which is why narrow gauge rails and beds in Australia and South Africa is built to standard gauge standards. The cheapness came in not having to make wider corners and all the required cuttings and the like. You quite clearly don’t know enough about railways to be making informed comment and are just making false arguments for an issue that didn’t exist. Breaks in gauge of course were (and are) a major impediment to Australian rail transport but loading weight is a non issue.

BUT as I pointed out, AT defence was a lower priority with the Japanese because they had not encountered large numbers of armoured vehicles in their wars in Asia. Even when they had, as at Khalkhyn Gol, no higher priority was placed on it. This meant that tanks were less likely to meet an AT gun or an Artillery piece which had been re-rolled to AT duties. As these could be easily outflanked and overrun in the broad, open spaces of Australia than they could in the narrow confines of the Tropical Rainforests of the Pacific Islands, light tanks would IMO have been sufficient, if used in large numbers to attack and defeat Japanese forces - exactly as the Russians had done at Khalkhyn Gol.

So your argument is light tanks were adequate for continental defence. But my point was entirely about the Pacific Islands Campaign. Your context jumping is legendary.

Tanks did come from the UK and in numbers. Not directly from the UK but from British stocks in the Middle-East as the older Matilda and M3 Lee/Grants as they were replaced by newer vehicles. M3 mediums also came directly from the USA. The M3 was a potent vehicle compared to the Japanese tanks and performed more than adequately when deployed against the Japanese in Burma.

These tanks didn’t exist in 1940 and were not available for Australia in 1941. This was when the decision to go ahead with the Australian Cruiser program was launched. At that time the British had said no tanks are available. Lend-lease, American entry into the way, rapid modernisation (and obsolescence of tank fleets), high risk of an invasion of Australia and two bloody years all changed this situation. Which was the context again of this point – why was the program launched in the first place.

I note that you did not mention it, despite it having an extensive discussion of the very vehicle we are talking about. Perhaps you merely disagreed with his conclusions? I don't.

Do you know what the word “context” means? I didn’t list that book because it was not about the issue under discussion. Which was your ridiculous claims that the threat of invasion to Australia in 1942 was a non-issue. Ross’s book is about Australian defence industry policy from 1900 to 1945! And it does spend quite some time talking about the great efforts put into place to counter the risk of invasion in 1942. But is not a strategic appreciation of the Pacific War in the Australian Theatre at this time or any other.

The threat of invasion had receded by late 1942. Bureacracy sometimes has an inertia all its own.

Well they still had the combat power to launch a full scale invasion of Darwin or Perth or somewhere in between by Japanese risk appetites. Of course with the full benefit of hindsight knowing their precarious state – strategic intelligence that only became fully apparent after the war – such an attack would have consumed the last of their offensive resources which they wanted to keep in reserve.

But I’m glad you’ve seen the light and reassessed your invasion threat assessment from “domestic political campaign” to something more realistic. I wonder how long the rest of your opinions will take to catch up to reality.

 

[robunos]

...AC Mk 2 was a design study only for a very different tank...

Does anyone have any more on this design......?

cheers,
Robin.

A.T.Ross describes AC II as having been a much lighter armoured vehicle than AC I, based around IIRC the use of commercial truck mechanical components for the drive train and armed with a 2 Pdr. He believed it would have been a much more useful and more easily built vehicle than what became the Sentinel. However, he also notes the difficulties where other such vehicles attempted to use such drive trains in their design.

Thanks for that...
After I posted here I found this site :-

http://www.mheaust.com.au/Aust/Research/Sentinel/sentinelmk.htm

that has some information about the AC II, as well as the other AC variants.

cheers,
Robin.

 

[Basilisk]

The 25 pdr armed AC3.

An idea of what the AC4 would look like.

The Gipsy Major based tank engine.

 

[Abraham Gubler]

Great pictures Basilisk, thanks for posting them. Especially the quad Gipsy Major engine. Very shiny and chrome.

Not only was the ACIII (and IV) one of the best tanks of WWII (never built) it was also what the Australian Army needed. When the Govt. cancelled the production order they did so because they assumed, and were assured, they could get Sherman tanks via Lend Lease to replace the Matilda tanks for the campaigns of 19s 44, 45 and 46. But the priority for the Shermans was for Europe and with D-Day the demand for new tanks in Europe was too high to allow even a few hundred to be sent to Australia. So the Australian Army went without new tanks and had to keep using the Matilda up to the end of the war and scrabble to try and get a handful of (paid for in Sterling) Churchills from the UK. New production ACIIIs and IVs would hugely improved the combat power of the Australian units in those final campaigns and should have saved some of the lives lost in finishing off the Japanese.

 

[Basilisk]

Great pictures Basilisk, thanks for posting them. Especially the quad Gipsy Major engine. Very shiny and chrome.

...

You're welcome. I'd read about the Quad Gipsy engine in D. P. Mellor's account in The Role of Industry but had never seen much else about it. It was a bit surprising to see pictures of it, a little like finding a photo of some mythical beast. And it certainly looks very professional compared to its predecessors. The accompanying text doesn't say too much about it, 510hp at 2500rpm, best fuel economy 340hp at 2000rpm, and that it was developed in 1942 to guard against loss of supply of Cadillac engines, presumably because the US was now using them in the M3/M5 and M24 light tanks, which is slightly amusing as Cadillac apparently didn't think the Cloverleaf power pack for the Australian Cruiser could actually be made to work.

The Cloverleaf-Cadillac for the Sentinel. Well the whole power pack really, including radiators, fuel tanks, and the engine subframe ready to go into the back of the tank.

The er "bare" Perrier-Cadillac for the Thunderbolt and AC4.


Michael

 

[SleeperService2]

Here's a very bad scan (not my fault) of a blue print of the planned AC3 production tank. Has quite different turret shape to the AC1.

That's a very interesting drawing I've not seen before are there other views and can copies be obtained? I'm looking to build a Sentinel I, III & IV as soon as I can collect the information.

The torsion bar suspension looks remarkably like that trialled on the Sherman right down to the rear idler mounting arrangement

 

[Foo Fighter]

My problems with the Sentinel are based around the usability of the vehicle as a crewman. I have seen a few video items, notably from WOT (yes poo poo that if you like) demonstrating the interior layout which would have resulted in reduced crew efficiency, possibly to the point of vulnerability, much like the T34-76 with its two man turret and paucity of radio's and a reliance on flags for communication between troop/platoon vehicles. It is far easier to produce a reasonable vehicle, harder to make that vehicle work in combat situations. How can you logically have a gunner in an afv sitting sideways on to the gunsight and his legs liable to crush injuries from the gun?

https://www.youtube.com/watch?v=-P1PZtZCup8



https://www.youtube.com/watch?v=XUqBMC5-HPI

 

[Abraham Gubler]

My problems with the Sentinel are based around the usability of the vehicle as a crewman. I have seen a few video items, notably from WOT (yes poo poo that if you like) demonstrating the interior layout which would have resulted in reduced crew efficiency, possibly to the point of vulnerability, much like the T34-76 with its two man turret and paucity of radio's and a reliance on flags for communication between troop/platoon vehicles. It is far easier to produce a reasonable vehicle, harder to make that vehicle work in combat situations. How can you logically have a gunner in an afv sitting sideways on to the gunsight and his legs liable to crush injuries from the gun?

Well I could only watch it up to the point where he admitted he wasn't an electrician but was still upset he couldn't understand the manual's chapter on the electrical traverse system. This guy seems to be the embodiment of the 'I know nothing, but I'll still complain' attitude that is pervasive in this 'hipster’ centric world. Just because you have an IQ one or two standard deviations above the norm doesn’t mean you can just use your intuition to work out everything from a knowledge poor base. You just make things worse!

For starters one needs to place the AC1 in context of 1940. Sure the rotating commander’s cupola only has two periscopes but considering the alternative was the “sun roof” on the Cruiser tanks of the time that isn’t so bad. Yes the turret is cramped but so was every other tank of that time. Try sitting in the turret of an ASLAV-25, you don’t exactly have much room to trim your beard and man bun. But unlike others like the T-34 it provides the crew with a rotating basket and electrical traverse to enable them to fight the tank in response to changing circumstances. So there is a stores box in the way of the gunner’s forward view port, move the box! Having a wide angle forward view for the gunner is fundamental to target acquisition. Tanks that provided the gunner with such forward vision in addition to the gun sight are far more lethal than those that just provide the later. And it did have a freaking radio so what’s the deal with the signal flags comment?

The ACI had a range of faults like the electrical turret traverse would only work when the tank was level to the horizon. But it had things that in 1940-42 would be much missed in other tanks that had to be used in combat. Like horizontal volute spring suspension (HVSS of M4A3E8 “East Eight” fame), under armour access to the engine bay and three power units for degraded operations and pretty importantly for a tank decent armour (resistant to the enemy’s basic anti-tank weapon). All of which would mean it could get into action instead of being left on the side of the road and survive being targeted. Something that couldn’t be said for the Crusiers, Covenanters, Crusaders and Stuarts being used by the Allies at this time.

 

[Basilisk]

Well I could only watch it up to the point where he admitted he wasn't an electrician but was still upset he couldn't understand the manual's chapter on the electrical traverse system. This guy seems to be the embodiment of the 'I know nothing, but I'll still complain' attitude that is pervasive in this 'hipster’ centric world. Just because you have an IQ one or two standard deviations above the norm doesn’t mean you can just use your intuition to work out everything from a knowledge poor base. You just make things worse!

The odd part is that the manual isn't that hard to understand, I'm not an electrician either so there are a few features which I can only make an educated guess at why they were done in a particular way, but I understand the basics of it. There are two motors only, one drives the turret around, the other is there purely to provide high frequency switching to the first, the balance of off and on time being controlled by the position of a set of contact plates. That is it is an electro-mechanical pulse width modulation system. You'll find something very similar in almost any variable speed power tool today only now it's done with electronics.

I agree with you, there are so very many things wrong it those videos they are of limited usefulness. The bit he points to as the power traverse, is a secondary means of control meant to be used for fine control when tracking a moving target. The primary means is the manual traverse crank which can also be used to operate the power traverse system. You can even see the cover that shields the chain drive linking the crank to the traverse controller in the video. This is why the traverse controller is located where it is, not to torment the gunner when using the wheel but so he doesn’t have to use the wheel because his left hand can stay on the crank.

I did get a chuckle when he said the external fuel tank isn't connected to the internal tank, when even as he says this you can see what appears to be the perished remains of a rubber hose going through the engine cover to connect to the internal fuel tank.

The ACI had a range of faults like the electrical turret traverse would only work when the tank was level to the horizon.

Not completely true, during testing the tank's traverse didn't work very well beyond about 16 degrees however it was also apparent that there was something wrong with that particular tank. They got a second tank and it worked just fine at an angle of 30 degrees. The problem with the first one I believe was traced back to spacers installed to raise the turret ring something like 1/16 or 1/8 of an inch, the spacers had been made to fit around the studs not by having a hole punched in them but by having a slot cut instead, this had allowed the the spacers to move a little bit and star rubbing on the moving parts. This additional resistance along with the fact that the Sentinel turret is back heavy to begin with tripped the current limiting relay to stop the circuit burning out.

 

[Foo Fighter]

As a tank gunner myself, out of the army but I still know how things work, or not. Powered traverse is not the fine adjustment tool, manual control is much finer. Also, you need to see the interior to see just how bad the vehicle would be to operate. That thing would be a liability in ANY action involving opposing tank formations. As a qualified tank crewman and commander I have the insight to state this from knowledge rather than not liking the beginning of a video tour of a vehicle (tank).

 

[Basilisk]

Powered traverse is not the fine adjustment tool, manual control is much finer.

I never said it was, I said what was pointed to in the video was intended for finer control of the the input of the powered traverse system when using the powered traverse to track a moving target. The description of its purpose and operation is quite precise. The video is simply wrong on this matter (and many others beside) and no amount of experience you may have had on other vehicles changes that.

If the Chieftain chooses to ride side saddle in the gunner's seat, in spite of all the problems this causes, then that is his business. That a 2M tall Irish tanker doesn’t fit very well into the Sentinel gunner's position isn't a huge surprise, that he didn't twig that the bellows looking thing on the seat support almost certainly means it is adjustable and can therefore be lowered so he can sit facing near forwards like you are clearly supposed to perhaps is.

 

[Foo Fighter]

Not really but then I sometimes wonder what the point of having this designed was in the first place and a point to Mr Gubler, the signal flags point was about the T34-76 and how with different problems the vehicles were going to be of limited use in action.

 

[Abraham Gubler]

Here's a very bad scan (not my fault) of a blue print of the planned AC3 production tank. Has quite different turret shape to the AC1.

That's a very interesting drawing I've not seen before are there other views and can copies be obtained? I'm looking to build a Sentinel I, III & IV as soon as I can collect the information.

The torsion bar suspension looks remarkably like that trialled on the Sherman right down to the rear idler mounting arrangement

Sorry just noticed this post. If I had more imagery I would post it here for sure. There is no doubt a lot more data on the AC program in the ANAO files in Melbourne. But I'm 1,000 miles away and I'm no Proclaimer.

 

[Abraham Gubler]

I agree with you, there are so very many things wrong it those videos they are of limited usefulness.

I did get a chuckle when he said the external fuel tank isn't connected to the internal tank, when even as he says this you can see what appears to be the perished remains of a rubber hose going through the engine cover to connect to the internal fuel tank.

I can't say I watched all of the vid just the start of part 1 and part 2 up until the electrics comment. I was turned off immediately by the smug rejection of what he labeled as a 'chute' on the turret top that went to a port below the turret. He couldn't understand what it was for based on his intuition so rejected it immediately. The worst of post modern anti expertise. He never asked why would such a useless feature be fitted therefore it must be something else. Just assumed the Australian tank engineers wanted an under armour chute from the outside top of the turret to the outside top of the hull. And were therefore complete idiots deserving of his scorn.

It was pretty clear to me that this chute is most likely an air vent for the turret. Fresh cool air in the bottom and hot fumy air out the top. With, most likely, a hard to see from outside vent in the interior side of the chute. It even has a freakin grill over the top of it. Like every air vent everywhere.

Not completely true, during testing the tank's traverse didn't work very well beyond about 16 degrees however it was also apparent that there was something wrong with that particular tank. They got a second tank and it worked just fine at an angle of 30 degrees.

Hoisted by own petard. Here I am complaining about someone elses ignorant compaints and I do the same from some half remembered factoid. My apologies.

 

[Abraham Gubler]

As a tank gunner myself, out of the army but I still know how things work, or not. Powered traverse is not the fine adjustment tool, manual control is much finer. Also, you need to see the interior to see just how bad the vehicle would be to operate. That thing would be a liability in ANY action involving opposing tank formations. As a qualified tank crewman and commander I have the insight to state this from knowledge rather than not liking the beginning of a video tour of a vehicle (tank).

Of course you must be out of Army if you were a tank gunner circa 1940. You must be well into your 90s by now so congratulations on your ling life and thankyou for your service, assuming you fought on the Allied side in WWII.

If by chance your military service was of a more recent vintage then I suggest it has no relevance here. Tank design has come a long way since 1940 and with it the all important human machine interface.

The ACI was an improvement in HMI over it's contemporaries. Have a look inside the turrets of the Crusader (has no commander's hatch), the Valentine (has no commander) and the Comet (1945 and still no room for the gunner to dance a jig) before judging this beast. And as soon as product improvement was available the AC program increased the turret ring in the ACIII and then again for the ACIV allowing for much improved HMI as well as bigger guns. No such luck for the Cromwell and Churchill.

 

[Foo Fighter]

I understand your opinions and thought vis a vis my experience. I did not serve in WWII, however, my experience in armoured vehicles of various types allows me to better understand their use and usability above that of someone who has no experience. The gunners seat back for example, is what suggests the gunner sat sideways, as did the commander and these points reduce efficiency of the crew. I am not stating that the other vehicles you mention are good either, I am well aware that there were many tanks and self propelled guns etc that were totally useless let alone not fit for purpose. For example, the Chieftain tank was fitted with a BL L60 powerpack which was a nightmare. The fanbelts were very well made and with little effort. tore out the fans from the housings and ripped open the radiators. Lots of 29 gallon yellow smokescreens told the bratwurst sellers exactly where lots of our crews could be found. Do you think the east Germans/Russians would have any trouble finding us too? Solution? Drill holes in the fanbelts so the fanbelts simply break up and, you guessed it, made holes in the radiators. Sharp joined up thinking there. For those who like the ac sentinel I merely say this, my opinions are exactly that and nothing more just think on what has been said and think about whether YOU would like to go into action in one of those before you shoot down the opinions of others.

 

[Basilisk]

The gunners seat back for example, is what suggests the gunner sat sideways...

But the Sentinel's gunner's seat doesn't have a back.

 

[Foo Fighter]

I thought I saw one in the video but I know some people in the Bovington tank museum so I'll get back to you on that. Still not a good tank in any event.

 

[Rickshaw]

I understand your opinions and thought vis a vis my experience. I did not serve in WWII, however, my experience in armoured vehicles of various types allows me to better understand their use and usability above that of someone who has no experience. The gunners seat back for example, is what suggests the gunner sat sideways, as did the commander and these points reduce efficiency of the crew. I am not stating that the other vehicles you mention are good either, I am well aware that there were many tanks and self propelled guns etc that were totally useless let alone not fit for purpose. For example, the Chieftain tank was fitted with a BL L60 powerpack which was a nightmare. The fanbelts were very well made and with little effort. tore out the fans from the housings and ripped open the radiators. Lots of 29 gallon yellow smokescreens told the bratwurst sellers exactly where lots of our crews could be found. Do you think the east Germans/Russians would have any trouble finding us too? Solution? Drill holes in the fanbelts so the fanbelts simply break up and, you guessed it, made holes in the radiators. Sharp joined up thinking there. For those who like the ac sentinel I merely say this, my opinions are exactly that and nothing more just think on what has been said and think about whether YOU would like to go into action in one of those before you shoot down the opinions of others.

I think you have some valid points but I am not sure about your criticisms of either the L60 or the Sentinel. Everything should not be viewed through a lens of hindsight. It should be looked at what was known at the time. The L60 had it's problems early on, without a doubt but then so do all new designs. Could it have been made better? Without a doubt but there was a learning process and by the end of the Chieftain, the L60 was considered a reliable and useful tank engine.

Same for the Sentinel. The Sentinel I was as the narrator points out, the first tank ever produced Downunder. They had few others to compare it to and so it had it's problems. That he was also looking at an early example which was over 60 years old, also meant that all he had to work things out were the manuals it was supplied with, rather than the institutional knowledge that was available at the time. I don't doubt they got quite a few things wrong and did them very differently to an M1 Abram MBT of today. However, the Sentinel far from being a "bad" tank was actually in many ways quite admirable, as Chieftain himself points out. It was the first cast hull tank, it was well armoured, and at least initially, adequately armed. Its powerpack while complex worked and moved the vehicle. Its crew was obviously meant to be smaller men than Chieftains 2 metre frame. That their controls and seating was awkward was unfortunate but then, ergonomics hadn't been invented yet. That the Sentinel contributed directly to the Sherman Firefly's mounting of a 17 Pdr gun shouldn't be overlooked, nor that the Sentinel was uparmed twice, going from 2 Pdr to 25 Pdr to 17 Pdr in it's life shouldn't be without consideration either IMO.

 

[Abraham Gubler]

The gunners seat back for example, is what suggests the gunner sat sideways, as did the commander and these points reduce efficiency of the crew. I am not stating that the other vehicles you mention are good either, I am well aware that there were many tanks and self propelled guns etc that were totally useless let alone not fit for purpose.

This is a good point to make and such an arrangement would be foolish but I don’t think you can make that conculsion based on the evidence of how the seats are attached to the turret basket. By the way there are some artillery pieces with a right angle sighting system for the gunner but this is clearly not the way the ACI is laid out.

What determines the orientation of the crew is their controls and sighting axis. The ACI like contemporary Cruiser and Infantry tanks armed with a 2 Pounder gun have axial gunsights parallel to the bore of the weapon. The control panel (if you can call it that) is also located perpendicular to the weapon’s bore. As can be seen in the pictures I uploaded above the gunner’s position is wedged in between the turret ring and the gun mounting creating a small triangular space. But the gunner has to orientate their body (or at least their upper body) parallel to the gun’s bore. At worst they may have to angle their hips inwards towards the centre axis of the turret but their torso, arms and head are all going to be aligned parallel to this axis. Kind of like how we used to be taught to shoot a rifle with the hips angled away from the line of fire. That is until modern body armour made it far safer to have the striking face perpendicular to incoming fire rather than reducing the width of your body as a target and having incoming fire strike your kidneys and then pass on energy through their entire side to side distance of your torso.

For example, the Chieftain tank was fitted with a BL L60 powerpack which was a nightmare. The fanbelts were very well made and with little effort. tore out the fans from the housings and ripped open the radiators. Lots of 29 gallon yellow smokescreens told the bratwurst sellers exactly where lots of our crews could be found. Do you think the east Germans/Russians would have any trouble finding us too? Solution? Drill holes in the fanbelts so the fanbelts simply break up and, you guessed it, made holes in the radiators. Sharp joined up thinking there.

If it is any consolation the T-64 also used the same engine configuration. Two stroke opposed pistons are inherently smoky (even when the radiators haven’t been destroyed by a fleeing fan). Sleeve valve engines on both sides of WWIII would surround both the Chieftain and the T-64 with clouds of white smoke.

 

[Basilisk]

It was pretty clear to me that this chute is most likely an air vent for the turret. Fresh cool air in the bottom and hot fumy air out the top. With, most likely, a hard to see from outside vent in the interior side of the chute. It even has a freakin grill over the top of it. Like every air vent everywhere.

You are right, it is just a vent. Puckapunyal let me crawl around inside theirs to my hearts content. Purely guesswork on my part but the turret rood slopes down away from the commander's cupola so there is nothing to obstruct his view. So presumably a mushroom type vent would be in the way so something internal had to be done. There is a requirement that the tank be protected from burning material, I think it said thermite, hence no air vents in the top of the hull of tank anywhere. To divert anything that enters through the vents or falls into the vent in the roof of the turret there is a sort of three sided tray baffle plate that connects the top and bottom vents but it is not welded to the sides so air can be drawn into the turret by the draft created by the radiator fan when the engine is running. The air vents in the rear corners of the turret also have additional baffle plates welded in to stop bullets and fragments from getting into the turret.

Hoisted by own petard. Here I am complaining about someone elses ignorant compaints and I do the same from some half remembered factoid. My apologies.

Not your fault mate, it is in a few books, presumably copied from the first, and has become 'fact'. The trouble is that it is kind of correct in that in testing the traverse system didn't work past a certain angle, it is probably misleading though.

 

[Basilisk]

I thought I saw one in the video but I know some people in the Bovington tank museum so I'll get back to you on that. Still not a good tank in any event.

Here. AC1 gunner's station. No back.

 

[Foo Fighter]

I concede that, while the gunners seat is slewed it is nowhere near 90 degrees. When I talk about assessing the value of a tank it is from a usability/tactical awareness angle. The early T34 (The 76) having a two man turret had an unacceptable work rate for the commander/gunner. I have seen interviews of crewmen of these vehicles and in particular at Kursk, the orders were not to be picky about tactics but to ram the German tanks.

The quality of armour is of secondary importance if your enemy can very simply flank you and destroy you from that flank at closer ranger. Micheal Wittman was probably killed by a standard 75mm armed Sherman, from the flank and at what was probably under 100 yards rather than the Firefly armed Sherman which would have had to fire at about 2,000 yards, somewhat about its effective range. When the first T34 and KV 1 tanks ran amok in the German lines they were destroyed by the same flanking moves or by the 88mm Flak. If the Sentinel had been flanked it had little in the way of vision to react quickly enough and yes, I concede that it is by no means the only vehicle to suffer this problem. The point of usability also, while paid little heed at the time, also effects whether you live or die when in contact with even inferior opposition.

As a point of note I would suggest the first really good tank we Brits produced was the Centurion and even then it was burdened with a rather pointless 20mm Polsten gun, increasing the work load of the loader for no good return. The military and political high ups were so pathetic that even when they had several in the region of contact, they chose NOT to deploy them.

 

[Abraham Gubler]

The quality of armour is of secondary importance if your enemy can very simply flank you and destroy you from that flank at closer ranger.

Absolutely. An American statistical analysis of WWII and Korean tank battles showed that the side that detected the enemy first won the subsequent engagement 90% of the time. Irrespective of what kind of tank they were using or how many they had. Such situational awareness superiority is more important than other ‘traditional’ tactical factors (armour, firepower, mobility). And clearly demonstrated by the German armoured force in WWII until everyone else caught on. Despite having tanks that were often inferior in traditional quality metrics (armour, firepower, mobility) and numbers they won battle after battle because they had tanks with far better communications, target acquisition, etc and were trained to leverage these advantage.

 

[Abraham Gubler]

You are right, it is just a vent.

Thanks now I can brag about that for ages...

 

[Rickshaw]

The military and political high ups were so pathetic that even when they had several in the region of contact, they chose NOT to deploy them.

Really? And I've always understood the first Centurion Mk.Is which reached NW Europe did so just after the end of hostilities...

 

[Rickshaw]

As a point of note I would suggest the first really good tank we Brits produced was the Centurion and even then it was burdened with a rather pointless 20mm Polsten gun, increasing the work load of the loader for no good return.

So, the Churchill was of no value? Interesting. It was considered the best of the British tanks in 1944-45 by most who understood it's value...

 

[Foo Fighter]

Have you read what I have written? Like the early T-34, the first Churchill was not exactly great being too slow and without a gun worthy of the name. I have read memoirs of tankers who crewed Churchill tanks and they dreaded tank on tank engagements. Churchill was borne out of the WWI theory of tank design namely slow plodding infantry tanks and faster cruisers. Can you honestly say that Churchill was fit to be pitted against later MK IV or especially the MK V?

 

[Rickshaw]

As I said, before it was deleted. the Churchill in it's later marks was virtually invulnerable to 88mm fire - the only active Allied tank in 1944-45 that was. It was reliable and it had the best gearbox available to any AFV in WWII - being able to climb slopes other AFVs would baulk at as was shown in Tunisia and Italy. What it lacked at least initially was a good HE capable gun. That was fixed by initially taking 75mm guns from Shermans which had been knocked out and then through the Britishs' own 75mm gun (based on the 6 Pdr, rebored). The Churchill was of course, an Infantry Tank and was never intended to take on enemy Panzers. It performed admirably in the advance across NW Europe, into Germany. It was also perhaps the most adaptable and adapted AFV the Western Allies had, forming the core of the specialist 79 Armoured Division.

 

[Jemiba]

Let me try to sum up: The Churchill, designed to the British ideas of an "Infantry tank", was good for this task,
but had drawbacks, at least in its early marks, in tank-vs-tank confrontations.

And now, may I remind you, that the title of this thread is "Sentinel ACIV" ?

 

[Abraham Gubler]

Sorry for the long absence in posting but I’ve been very busy with un-secret projects made of real steel and the like of late. I’m currently on holiday in Melbourne until next week when I return to defence projects (real world). So being in this town and one of these guys/gals (member of secretprojects.co.uk) I had to visit the National Archive while here and look up their files on the Australian Cruiser Tank program’s AC1, AC2, AC3 and AC4 (no reference to anything called a Whatsinel).

The results were great and I thought to share a samplerer for you all in the ASAP. More to come as well as CA-15 and CA-23 for the zoom zooms.

 

[GTX]

The results were great and I thought to share a samplerer for you all in the ASAP. More to come as well as CA-15 and CA-23 for the zoom zooms.

Looking forward to more mate.

 

[Abraham Gubler]

Here a handful of AC1 pictures from the archive. The caption (actually a hand typed, half sized, tissue paper sheet inserted before the photo) of the AC1 bogged in the dried up river bed assures the reader that the tank was able to recover from this position under its own power.

In my previous post hawkeyes may have noticed the photo of nine cast hulls of Australian Cruiser Tanks stacked three up? Eight of these are AC3 hulls with a single AC1 in mid right. These hulls have been cast, heat treated and machined were needed and are ready for transport to the production line. 200 AC3s were ordered and there is an extensive folio in the National Archives of all the purchase orders that went out for all the sub-components. Then attached to each one is a 1943 dated stop work order.

 

[Basilisk]

That's quite neat, I haven't seen some of these before. Thanks for sharing.

In my previous post hawkeyes may have noticed the photo of nine cast hulls of Australian Cruiser Tanks stacked three up? Eight of these are AC3 hulls with a single AC1 in mid right.

Looks like 8 AC3 hulls, 2 AC1 Hulls, at least 1 and probably 3 AC3 axle housings, and right at the bottom of the photo what looks to me like the top of an AC1 turret.

 

[Abraham Gubler]

The photos are from a great ‘book’ called “The Production of Armoured Fighting Vehicles in Australia” put together by the AFVs Directorate in early 1943 as a record of what they had done to date with the AC Tank program. It’s a huge leather bound thing held together by three bolts full of photo plates and information about the design and production of the tanks.

 

[Abraham Gubler]

Some more imagery.

 

[Basilisk]

The photos are from a great ‘book’ called “The Production of Armoured Fighting Vehicles in Australia” put together by the AFVs Directorate in early 1943 as a record of what they had done to date with the AC Tank program. It’s a huge leather bound thing held together by three bolts full of photo plates and information about the design and production of the tanks.

Ah, that makes sense, David Fletcher wrote an article in Classic Military Vehicles I think that used that book as a source, so I guess a copy went along with the Sentinel that went to Bovington.