Sentinel ACIV

[Abraham Gubler]

British tanks had the following turret ring diameters:
Cromwell - 60 in (1524 mm)
Comet - 64 in (1626 mm)
Challenger - 70 in (1778 mm)
Sherman* - 69 in (1753 mm)

And the Australian Sentinel ACIV tank with 17 pounder had a turret ring of 70” (1,778mm).

 

[JohnR]

I have always been intrigued by the Sentinel, an amazing achievement when considering it was a design built from scratch in terms of design and engineering capability. That they achieved a design that could take the 17pdr ahead of the UK is also amazing.

I have often wondered how it would have performed against German tanks?

 

[Petrus]

And the Australian Sentinel ACIV tank with 17 pounder had a turret ring of 70” (1,778mm).

I've read somewhere that when the Challenger was designed it was thought that minimum turret ring diameter allowing to mount the 17-pdr was 66in (1676mm).



Piotr

 

[Abraham Gubler]

I have always been intrigued by the Sentinel, an amazing achievement when considering it was a design built from scratch in terms of design and engineering capability. That they achieved a design that could take the 17pdr ahead of the UK is also amazing.

And in 1943 apart from preparing a 17 pounder armed version the Sentinel tank program was also running torsion bar suspension versions… So in 1944 they could have been producing something not far from the tank state of the art of the 1950s.

The key reason Australia was able to produce in the Sentinel a tank superior to what the British and the Americans were producing at the same time is the clean slate approach. Without the impost of established industry and their factories and established tank experts and their opinions the Sentinel emerged as the best that could be built based on war experience. While there were lots of critical shortages this often lead to some innovative solutions that may have been superior to the state of art. For example instead of a single high power engine clover-leafing together three engines enabling clutching in and out of engines as per power need and resultant lower fuel consumption, wear and tear (COPAP).

Also the start up Australian tank industry wasn’t as bad off in relation to workforce as people tend to believe. There were a few key engineers with lots of experience including a couple sent to the UK to learn tank building and a refugee French suspension expert. Also the rest of the workforce were all experienced train builders working in their workshops.

Back to turret rings. The original Sentinel Mks 1-3 had a 54” (1,370mm) turret ring. They were able to mount and fire the 17 pounder and even a twin 25 pounder used to simulate 17 pounder recoil before they were available. It was able to do so because turret rings are not actually a direct indicator of a turrets ability to mount and fire a gun. The turret ring just gives an indication of turret size if it has vertical walls (like most British and American tanks at the time).

The Sentinel had angled out and angled in walls so the turret volume and maximum diameter was actually larger than indicated by the turret ring. The Mk 4 Sentinel had a larger turret ring to improve this volume further and make it easier to elevate the 17 pounder and move ammunition from the hull to the turret (also to lengthen the tank to increase track surface area to keep ground pressure stable as the weight increased). Also the Sentinel program was producing far superior recoil absorbing mounts at the time. It was actually the Australian gun mount that was used for the Sherman Firefly to fire the 17 pounder.

I have often wondered how it would have performed against German tanks?

The Sentinel Mk 4 had a 17 pounder with 60 rounds of ammunition and 110 volt electrical turret traverse, a maximum speed of 56kph and a gross weight of only 32 tonnes. Glacis armour was only 51mm but highly oblique so presenting an actual thickness of 120mm to the horizontal. Turret walls was sub-standard at only 50-65mm but provided all round, but angled or layered to provide between 71-100mm to the horizontal. 510 Mk 4s were ordered for production (including 110 with interchangeable 25 pounder gun) to follow from 200 Mk 3s with 25 pounder. Only one tank of this full rate production following the initial batch of 65 Mk1s (2 pounder gun) was built.

More data at:

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

 

[JohnR]

Interesting read, thank you.

Regards.

 

[Rickshaw]

One of the developers of the Firefly was inspired by the AC3 "Thunderbolt" (with twin 25 Pdrs), after reading of its ability to withstand the recoil of the two guns fired simultaneously.

Australia's real problem with the Sentinel was that it was completely inappropriate for the needs of the defence of Australia at that time. The Army wanted to fight in Europe, not the Pacific and so decided they needed a tank capable of defeating the best the Germans had produced, rather than one which was needed to defeat the best the Japanese had produced. In the end though, it was economics which saw it off. A clear choice between producing aircraft and small ships or tanks and when it was obvious that tanks were available more cheaply and easier from overseas, the die was cast and the Sentinel was quietly put out to pasture. Its only use in propaganda campaigns and a movie ("Rats of Tobruk" where the only unit actually equipped with them used them to portray German Panzers). As technically superior as they might have been or become, the M3 Grant/Lee was the better vehicle on the grounds of economics.

I heartily recommend A.T. Ross' "Armed and Ready: Australian Defence Preparedness 1900-1945" for an excellent discussion about the problems of the Sentinel programme.

 

[Abraham Gubler]

One of the developers of the Firefly was inspired by the AC3 "Thunderbolt" (with twin 25 Pdrs), after reading of its ability to withstand the recoil of the two guns fired simultaneously.

They weren’t just inspired they obtained examples of the overhead short recoil system which was used as the technology base for the Firefly mounting.

Australia's real problem with the Sentinel was that it was completely inappropriate for the needs of the defence of Australia at that time. The Army wanted to fight in Europe, not the Pacific and so decided they needed a tank capable of defeating the best the Germans had produced, rather than one which was needed to defeat the best the Japanese had produced.

That is totally wrong. The original requirement was to equip an armoured division to fight in North Africa as the British could not meet additional Australian demand for tanks. When the Japanese attacked the Australian armoured divisions (1-3) were re-rolled from training for North Africa for preparing to resist a Japanese invasion of Australia. The plan was to meet them with tanks and destroy them. The requirement for this role was something built in Australia because if the Japanese were invading then it’s unlikely that convoys of American and British equipment would have made it through and the Mk 1 Sentinel was all Australian.

After the victories of 1942 it was clear the Japanese couldn’t invade so the armoured divisions were disbanded and the domestic tank program halted. If Sentinel tank production had continued with the Mk 3 it would have been far better suited for fighting in the Pacific than the Stuart and Matilda tanks the Australian Army used.

In the end though, it was economics which saw it off. A clear choice between producing aircraft and small ships or tanks and when it was obvious that tanks were available more cheaply and easier from overseas, the die was cast and the Sentinel was quietly put out to pasture.

Again more “common knowledge” which is equally wrong as the last statement. Sentinel production couldn’t compete with importing tanks from America. It was never an issue of building aircraft or ships or tanks. But rather domestic production competing with imports. As Australian labour was very short it was redirected from production of tanks and aircraft as these supply sources improved from our allies. n 1943 Australia cancelled production of the domestic Sentinel, the CA-15 fighter and the Woomera bomber. Much of the Sentinel industry capability went into supporting the huge fleets of landing craft that were flooding into the Pacific for use against Japan. Aircraft production continued at a reduced rate on other types but more so to retain industry capacity for post war use.

 

[Rickshaw]

One of the developers of the Firefly was inspired by the AC3 "Thunderbolt" (with twin 25 Pdrs), after reading of its ability to withstand the recoil of the two guns fired simultaneously.

They weren’t just inspired they obtained examples of the overhead short recoil system which was used as the technology base for the Firefly mounting.

They did not request the examples until after they had read about the "Thunderbolt's" ability to absorb the recoil of its twin 25 Pdrs on such a comparatively small turret ring diameter, Abraham. Hence the use of the word "inspired".

Australia's real problem with the Sentinel was that it was completely inappropriate for the needs of the defence of Australia at that time. The Army wanted to fight in Europe, not the Pacific and so decided they needed a tank capable of defeating the best the Germans had produced, rather than one which was needed to defeat the best the Japanese had produced.

That is totally wrong. The original requirement was to equip an armoured division to fight in North Africa as the British could not meet additional Australian demand for tanks. When the Japanese attacked the Australian armoured divisions (1-3) were re-rolled from training for North Africa for preparing to resist a Japanese invasion of Australia. The plan was to meet them with tanks and destroy them. The requirement for this role was something built in Australia because if the Japanese were invading then it’s unlikely that convoys of American and British equipment would have made it through and the Mk 1 Sentinel was all Australian.

After the victories of 1942 it was clear the Japanese couldn’t invade so the armoured divisions were disbanded and the domestic tank program halted. If Sentinel tank production had continued with the Mk 3 it would have been far better suited for fighting in the Pacific than the Stuart and Matilda tanks the Australian Army used.

Again, you miss the point, Abraham. It was inappropriate because there was never any likelihood after December 1941 that any Australian armoured division was going to fight in North Africa. Even if it had, taking yet another completely different type of tank to that theatre in such small numbers would have made it impossible to support the numbers required. Finally, if the tank was intended to defend Australia against the perceived Japanese threat, then it was too heavy and heavily armoured to be easily deployable over the very poor transport system available (rather as the M1 Abrahms are today). It would have been even worse in the SW Pacific. The Mk. 3's only advantage over the Stuart and the Mathilda would have been its armament. The Stuart was not used after the "Battle of the Beachheads" because of its light armour but the 'tilly was an excellent balance of protection, mobility and armament and so was the preferred vehicle in the SW Pacific (even after the M3 and M4 Mediums became available).

Now, you may wish to live in some fantasy land where those factors were ignored but in real life they were the determinants, along with the real killer - the ease and cheapness of imported AFVs in the form of the M3 medium series, which ensured that Sentinel programme was dismantled.

In the end though, it was economics which saw it off. A clear choice between producing aircraft and small ships or tanks and when it was obvious that tanks were available more cheaply and easier from overseas, the die was cast and the Sentinel was quietly put out to pasture.

Again more “common knowledge” which is equally wrong as the last statement. Sentinel production couldn’t compete with importing tanks from America. It was never an issue of building aircraft or ships or tanks. But rather domestic production competing with imports. As Australian labour was very short it was redirected from production of tanks and aircraft as these supply sources improved from our allies. n 1943 Australia cancelled production of the domestic Sentinel, the CA-15 fighter and the Woomera bomber. Much of the Sentinel industry capability went into supporting the huge fleets of landing craft that were flooding into the Pacific for use against Japan. Aircraft production continued at a reduced rate on other types but more so to retain industry capacity for post war use.

Abraham, Australia suffered from a lack of manpower. Indeed, it had over-committed itself to putting men into uniform to the point that units were demobilised in late 1944-early 1945 in order to keep the civilian economy working. I wonder if you actually read what I said. "Light ships", the last time I checked, included landing craft and indeed they made up a large bulk of what our shipyards produced. It was a choice of either the light ships (Destroyers, Corvettes, Landing Craft, etc) and aircraft (Beauforts, Mosquitos, Beaufighters, Boomerangs, Wirraways, etc) or tanks instead of one of the preceding two. The government decided it could import the tanks so discontinued the Sentinel programme. Now Abraham, I named my source. Can you please name your source(s) for these claims?

 

[Abraham Gubler]

Ahh another wonderful ego + ignorance battle for all to behold…

They did not request the examples until after they had read about the "Thunderbolt's" ability to absorb the recoil of its twin 25 Pdrs on such a comparatively small turret ring diameter, Abraham. Hence the use of the word "inspired".

So you agree that they weren’t just inspired they based their solution on the Australian technology. To leave it at just “inspired” would mean that the British heard about this great recoil absorbing system and then went off and did their own thing. Inspiration happens daily, building a new short recoil system enabling a high power gun to be fitted to a turret that previously only held a medium power gun happens very rarely, the difference is considerable. So give credit where credit is due and don’t just leave the role of Australian technology in the Sherman Firefly program as “inspiration” rather than the actual starting point. That is as misleading as not acknowledging the downunder involvement at all.

Again, you miss the point, Abraham. It was inappropriate because there was never any likelihood after December 1941 that any Australian armoured division was going to fight in North Africa. Even if it had, taking yet another completely different type of tank to that theatre in such small numbers would have made it impossible to support the numbers required. Finally, if the tank was intended to defend Australia against the perceived Japanese threat, then it was too heavy and heavily armoured to be easily deployable over the very poor transport system available (rather as the M1 Abrahms are today). It would have been even worse in the SW Pacific. The Mk. 3's only advantage over the Stuart and the Mathilda would have been its armament. The Stuart was not used after the "Battle of the Beachheads" because of its light armour but the 'tilly was an excellent balance of protection, mobility and armament and so was the preferred vehicle in the SW Pacific (even after the M3 and M4 Mediums became available).

Ahh a subscriber to the gross weight theory of tank warfare… clear indication of someone who knows something more than a person on the street but not enough to be credible.

So what you are suggesting is in December 1941 the Sentinel tank program should have been abandoned and a new program started from scratch to build a lighter tank because clearly – as everyone knows – the Japanese only had light armour and anything over some undefined weight limit can’t be used anywhere near the Pacific Ocean? What a total load of crap.

The Sentinel was the best tank to defend Australia against Japanese invasion and it was the best tank to take the Pacific Islands back from Japan. And one doesn’t even need to assess its capability or mobility because it was the only thing domestically available within the timeframe. A tank that weighs 32 tonnes is better than a tank that weighs 0 tonnes.

As to the claim of poor transport systems this pretty much effects anything over a man portable load in the same way. Since the Sentinel only weighed 7 tonnes more than the Matilda (32 vs 25 tonnes) this would have made little difference. In the Australian defence scenario it’s a no argument.

Now, you may wish to live in some fantasy land where those factors were ignored but in real life they were the determinants, along with the real killer - the ease and cheapness of imported AFVs in the form of the M3 medium series, which ensured that Sentinel programme was dismantled.

The Sentinel was more than suitable for the Australian Army mission in the war against Japan. It was far more suitable than any alternative both real and imagined. Of course it couldn’t compete economically with the imports but it was never cancelled because it was considered unsuitable. To try and generate this argument based on a fanciful concept of lead time required to build a tank, a lack of appreciation of the tanks role in defence of Australia warfare (not tank vs tank but tank vs infantry), attribution of awesome insight into the nature of all Japanese tank armour to the Australian Army and a magical belief that a certain gross weight makes a tank immobile; is an insult to the kind of appreciation of military technology that is the norm here at secretprojects.co.uk.

I wonder if you actually read what I said. "Light ships", the last time I checked, included landing craft and indeed they made up a large bulk of what our shipyards produced. It was a choice of either the light ships (Destroyers, Corvettes, Landing Craft, etc) and aircraft (Beauforts, Mosquitos, Beaufighters, Boomerangs, Wirraways, etc) or tanks instead of one of the preceding two. The government decided it could import the tanks so discontinued the Sentinel programme.

No our shipyards did not produce many light ships, destroyers, corvettes, etc after 1943. Nor was the aircraft industry manufacturing those aircraft that you claim. The Beaufort and Boomerang programs were effectively over, Wirraway kept on for make work and Mosquito only starting up with most of it actually been done in the UK.

The workforce wasn’t needed for building ships or aircraft but supporting those that had been built, imported and operated near Australia by our allies. So industry like the Sentinel program converted to providing spare parts, repair and other supporting services to the huge fleets of landing craft and so on. It wasn’t as glamorous as building some of the best tanks or fighters in the world but it won the war which was the important thing.

Now Abraham, I named my source. Can you please name your source(s) for these claims?

I sincerely doubt you’ve actually understood anything in Ross’s “Armed and Ready” by the statements you’ve made above. But please feel free to make various references to other books that don’t support your arguments.

 

[Rickshaw]

Ahh another wonderful ego + ignorance battle for all to behold…

At which point it would be better to leave it there, Abraham. I see little further point in battling with both your ignorance and ego. It is obvious you have only a superficial understanding and no experience of these topics.

 

[Abraham Gubler]

At which point it would be better to leave it there, Abraham. I see little further point in battling with both your ignorance and ego. It is obvious you have only a superficial understanding and no experience of these topics.

Nice to see that even when you’re just typing insults you don’t want to deviate from your steady course of never letting a fact get in the way of a good opinion.

 

[Abraham Gubler]

If Rickshaw’s attempts to rewrite Australian defence history is behind us perhaps we can return to the original question…

The design for Sentinel Mk 4 armed with an interchangeable 17 or 25 pounder had a turret ring of 70” but none of these tanks were actually built.

And the Australian Sentinel ACIV tank with 17 pounder had a turret ring of 70” (1,778mm).

The Australian War Memorial picture I attached in this original Sentinel turret ring post was not of a Mk IV but rather the E1. The E1 was a highly modified Mk 1 Sentinel that was used for trial mounting the 17 pounder. It was the famous tank with the turret with two 25 pounders mounted to simulate 17 pounder recoil (they actually generated 120% of the recoil).

The whole point of this post is the E1 had a 64” (1,624mm) turret ring. So it would be feasible to mount a regular 17 pounder on a Comet tank chassis with a new turret. But loading would be limited to a horizontal or depressed gun elevation.

For fans of the Sentinel here is what the Mk 3 or 4’s new hull front looks like with the removal of the hull gunner.

 

[JohnR]

Thats a big aesthetic improvement over the rather odd looking bow gunners, and I would imagine a considerable balistic improvement.

Regards.

 

[Abraham Gubler]

After another look at “Armed and Ready” Rickshaw is right that Andrew Ross does criticize the Sentinel as being “unsuited” for use against the Japanese. But he counters and qualifies his own argument a few times and his reasoning is very unsound (having spent quite a few years a decade or so ago serving on some committees with Dr Ross I don’t find this a surprise at all! Great guy but).

He points out that the original staff requirement for an Australian built tank in ‘40 was for something around 10 tons with minimal armour and able to counter Japanese light tanks. This was changed quite quickly to a medium tank able to fight German tanks after the Blitzkrieg in France. While Ross criticizes this decision it is heavily informed by hindsight. In 1940 Australia was at war with Germany and while the Japanese were considered a major threat all the planning to fight them was done so in the context of the Singapore and Bataan fortresses. The idea that the Japanese could defeat and advance past the UK and USA forces into SE Asia and the SW Pacific was considered ludicrous before they did it. In this context the land fight against Japan was seen as fighting them off from fixed positions and the need for a light anti-Japanese tank is a poor second to the medium anti-German tank.

Ross’s main criticism of the Sentinel program is that after the Japanese attack the Army kept asking for improved weapons (17 Pounders) to fight the Germans when 2 Pounders were adequate for defeating Japanese tanks. While this argument is on more solid ground it doesn’t take into account that the Australian Government made a commitment to retain a division in the European theatre until the end of the war and said division would require tanks (just like the equivalent NZ division). It was only after the loss of an Australian division in Singapore and Java thanks to poor British command that the European division was recalled to Australia and the policy changed (even then it stayed until after El Alemein).

Ross agrees that the Sentinel Mk 3 with 25 pounder was the best suited tank to fighting the Pacific campaign against the Japanese. He still remains critical of its medium size but this thick armour would be crucial for its survivability and didn’t appear to be a production bottleneck for the Sentinel. The cast armour by Bradford Kendall Ltd (still casting steel today) was one of the success stories of the program and enabled rapid design evolution compared to jigged welding or bolting production.

Japanese anti-tank tactics may not have used big guns but were sufficient to require medium tanks and clear light tanks from the battlefield. Because of the close terrain their 20mm anti-tank gun was extremely lethal against light tanks and their heavy use of mines and suicide command detonated explosives required strong protection. The Sentinel with its thick castings of softer but tougher steel alloy made it very resistant to spalling from blast effects.

As to the difficulties of moving a 30 ton tank into the SW Pacific battlefield they aren’t much more difficult than moving a 10 ton tank. Once on the ground the difference is minimal (thanks to equal ground pressure) and with no such thing as local bridging this is not an obstacle. A US Army study in the mid 1960s found that 50% of South VietNam was accessible to main battle tanks (50 tons). Which is amazing considering a quarter of South VietNam is the Mekong river delta impassible to any weight bearing vehicle and another third is the central highlands a thickly forested mountain range.

PS Perhaps a moderator should split a lot of this off to a separate Sentinel thread?

 

[Abraham Gubler]

Thats a big aesthetic improvement over the rather odd looking bow gunners, and I would imagine a considerable balistic improvement.

Its a very well shapped tank. The strange looking bow gunner ball in the Sentinel Mk 1 was influenced by the use of Vickers .303 MG. Since Australia didn't have BESA or 7.92mm production they had to use the Vickers with the barrel shroud.

Here are pictures of the side and rear of the Mk 3. The turret ring is actually in a depressed section surrounded by bulwarks so any shot can't hit it directly.

 

[JohnR]

I am intrigued by the picture of the rear of the tank, it appears to have a solid plate over the engine compartment. Is this original or has it been added later, if it is original how was the engine cooled as there does not appear to be an air intakes?

 

[Abraham Gubler]

I am intrigued by the picture of the rear of the tank, it appears to have a solid plate over the engine compartment. Is this original or has it been added later, if it is original how was the engine cooled as there does not appear to be an air intakes?

That was the design through the various marks of the Sentinel. The air vents for cooling are located under armour lips mounted along the side of the tank between the hull wall and the storage boxes. I've defaced these pictures of a scratch built model of a Mk 1 by Michael Koudstaal to point out the intakes and exhausts. On the Mk 3/4 Sentinel the intake level with the turret were covered by an armoured housing that also protected the sides of the turret ring.

 

[JohnR]

Interesting, thank you.

 

[Abraham Gubler]

The Australian Cruiser (AC, aka Sentinel though this name only applied to the AC Mk 1) tank had a unique power plant approach using multiple low power car engines to provide high power output in the absence of a single high power unit. While leading to complex transmission solutions this provided the advantage of redundancy and efficient low power running. All versions of the AC had multiple engines but with very different arrangements.

The AC1 Sentinel had three Cadillac 75 V8 engines (the famous car engine built in Australia by GM Holden) mounted in a cloverleaf with one on the centreline aft and two port and starboard amidships with shafts from each engine running forward to a transverse transfer box mounted under the turret basket (see picture AC1.png). The combined power of the engines was then shafted forward to the transmission via a single, centreline shaft with an output of 330 hp. Interestingly in the engine bay the three engines, radiators, fans and fuel tanks were all mounted on a common subframe and could be lifted in and out of the engine bay together.

The next variant the AC Mk 3 Thunderbolt (AC Mk 2 was a design study only for a very different tank) armed with the 25 Pounder (88mm) medium velocity gun kept the three engines but in a totally different arrangement. The three Cadillac 75 engines were mounted radially on a single triangular steel case (AC3_1.png) where they shared a common crankcase and integral transfer box. This radial mount was designed by French tank designer Mr Perrier who had been in Japan on loan from the French Government in 1940 before making his way to Australia. When fitted with the three engines the single unit was known as the Perrier-Cadillac 41-75 (AC3_2.png, aft view, note the alternator on the top engine). Also added to the frame was the fans and radiators enabling a very compact single unit without the need for the bulky under turret transfer case and subsequent power loss (AC3_3.png, forward view, note the single transmission shaft attachment below the fans). A single shaft ran under the turret floor forward to the transmission on the AC3 (AC3_4.png) with an output of just under 400 hp.

The AC Mk 4 armed with the 17 Pounder (76mm) high velocity gun was to have kept the Perrier-Cadillac 41-75 in at least the initial versions. A new engine was under development combining four Gipsy Major I4 engines (built in Australia by GM Holden for the de Havilland Australia Tiger Moth production line). This arrangement would have the potential for around 500 hp output using a very simple and reliable base engine without the need for a radiator and water cooling.

 

[PMN1]

The AC1 Sentinel had three Cadillac 75 V8 engines (the famous car engine built in Australia by GM Holden) mounted in a cloverleaf with one on the centreline aft and two port and starboard amidships with shafts from each engine running forward to a transverse transfer box mounted under the turret basket (see picture AC1.png). The combined power of the engines was then shafted forward to the transmission via a single, centreline shaft with an output of 330 hp. Interestingly in the engine bay the three engines, radiators, fans and fuel tanks were all mounted on a common subframe and could be lifted in and out of the engine bay together.

The next variant the AC Mk 3 Thunderbolt (AC Mk 2 was a design study only for a very different tank) armed with the 25 Pounder (88mm) medium velocity gun kept the three engines but in a totally different arrangement. The three Cadillac 75 engines were mounted radially on a single triangular steel case (AC3_1.png) where they shared a common crankcase and integral transfer box. This radial mount was designed by French tank designer Mr Perrier who had been in Japan on loan from the French Government in 1940 before making his way to Australia. When fitted with the three engines the single unit was known as the Perrier-Cadillac 41-75 (AC3_2.png, aft view, note the alternator on the top engine). Also added to the frame was the fans and radiators enabling a very compact single unit without the need for the bulky under turret transfer case and subsequent power loss (AC3_3.png, forward view, note the single transmission shaft attachment below the fans). A single shaft ran under the turret floor forward to the transmission on the AC3 (AC3_4.png) with an output of just under 400 hp.

The AC Mk 4 armed with the 17 Pounder (76mm) high velocity gun was to have kept the Perrier-Cadillac 41-75 in at least the initial versions. A new engine was under development combining four Gipsy Major I4 engines (built in Australia by GM Holden for the de Havilland Australia Tiger Moth production line). This arrangement would have the potential for around 500 hp output using a very simple and reliable base engine without the need for a radiator and water cooling.

What were the weights and dimensions of these three multiple power units (particularly the Gipsy Major option) compared to the Liberty engine and the Bedford Twin 6?

 

[Abraham Gubler]

What were the weights and dimensions of these three multiple power units (particularly the Gipsy Major option) compared to the Liberty engine and the Bedford Twin 6?

There is no widely published data as to the gross weight of the Perrier-Cadillac three engine unit or the proposed quad Gipsy Major. This information is no doubt archived in the Australian Cruiser files but no one has looked it up and published it. The initial cloverleaf Cadillac arrangement was never considered a single unit as it was three separate engines and only mounted on a common tray for ease of removal. However the Cadillac 75 and Gipsy Major were very common engines and I’m sure their dry weights are easy enough to find. Also the weight for the steel case for the Perrier-Cadillac mounting frame could be deduced by calculating its dimensions if someone was really keen.

 

[Pioneer]

Yes it's a great pity that Australia never had the sense or tenacity to put the Sentinel series into serious production!
It's unfortunate that it is one of our traits as a nation - as a people, that we have continuously given into the negativity of our own capabilities and capacity to develop indigenous weapons/weapons systems.
With the exception of only but a hand full of weapons, Australia has always looked at the easy option (and political pressure) to buy surplus weapons or 'weapons of compatibility with our allies'
We'd sooner give up home-grown expertise and the cultivation of home-grown R&D and manufacturing to line the pockets of foreign corporations.

P.S. I apologize for my rant in advance !!

I recall reading the irony that Australia was able to build the Sentinel, before it built its first cars!

There can be no argument that the indecisiveness of the Australian Army in the way of deciding on the Sentinel's gun type/size - hence turret size ............ contributed greatly and detrimentally to the Sentinel tank design being placed into serious production and combat operations

The Sentinel's metal casting was only possible at the time, due to the skill and knowledge of the railways industry, who had developed this skill in manufacturing cast iron boilers for steam trains!

Sadley at the end of the Second World War "much of the Australian army's WWII equipment [armoured vehicles] had been sold off in vast quantities............ Despite the immediate post war plans the Australian Army had to soldier on with vehicles long since obsolete in their country or origin" [Matilda infantry tanks, Grant medium tanks and M3A1 White scout cars.](source: 50 Years of the Royal Australian Armoured Corps)

Even sadder (well I dare say pathetically), by the outbreak of the Korean War, the most modern of tanks that Australia fielded was the Churchill tank, which they dared not deploy [through a combination of well known obsolescence and server lack of spare parts and serviceability]. Pathetically, the Australian Army would not receive a new and modern combat efficient tank in the form of the excellent Centurion Mk.3's. I can not but help wonder how had the resolution of both Australian politician's and Army top brass been such as to have the foresight and intelligence to seriously consider the need of its army (and potential of its manufacturing potential), that if they had of seriously supported this indigenous tank design, the Australian Army could have been far more combat self efficient, not just in its own defence, but also in its sensible requirement to provide tank / direct fire support to its own troops in Korea, instead of having to risk/rely on allies armour!
but during the Korean War, if they had of opted for the Sentinel to go into production and active service! I wonder how it would have gone against the T-34?

Early this year, I was privileged to be able to climb in to and over the Sentinel at the Armoured museum at Pukapunyal. I was greatly impressed with its thickness of armour and reasonably low silhouette, when compared to other tanks at the museum. I'll have to find them pics.........

Regards
Pioneer

 

[Rickshaw]

A.T.Ross in his book, "Army and Ready" makes it clear that the Sentinel was not suitable nor required when there were more than sufficient overseas vehicles to fulfil the role. It was not intended to defend Australia it was intended to fight the Germans in North Africa, not the Japanese. As Australia's commitment to that theatre was already winding down and there were sufficient vehicles already in theatre or on their way there. We also able to source tanks for our own defence as well, which were cheaper than producing our own. It was an expensive project which would have consumed resources which were better employed elsewhere.

 

[JFC Fuller]

This picture was posted at anther forum and is purported to show a Sentinel hull with the prototype torsion-bar suspension. I have always been very fond of the sentinel design, as pointed out in this thread it proved easy to up-gun and seems to have been very logically designed. If it had been combined with the Meteor engine it could have been an incredible tank for its time.

 

[Abraham Gubler]

If it had been combined with the Meteor engine it could have been an incredible tank for its time.

The Sentinel tank wasn’t held back by its engine in the likely war production versions (Mks 3 and 4) the Perrier-Cadillac three engine unit or the proposed quad Gipsy Major produced adequate power, were easy to manufacture and would have had the advantage (compared to the Meteor) of clutching out 2 (or 3) engines for low power needs. The biggest problem the Sentinel had was the lack of a combat opportunity. If the Japanese had been wise enough not to join WWII then Sentinels probably would have seen combat in North Africa with the 1st Australian Armoured Division. Or if the Japanese had been foolish enough to invade Australia in 1942/43 the Sentinel would have been available to drive them back into the sea.

I find the retrospective arguments that the Sentinel was a waste of effort like in the terrible book “Fallen Sentinel - Australian Tanks in World War II” by Peter Beale particularly disingenuous (or just plain stupid). It was a tank program launched at a time when the Empire desperately needed tanks and there was no guarantee or suggestion that the Americans would continue to supply war material after the exhaustion of British credit (Lend Lease). While Japanese entry into the war naturally ended any chance of Australian ordnance going overseas Sentinel then provided the assurance of a continental defence that would defeat Japanese invasion. While this never happened it was a pretty bloody important assurance to the Australian government.

 

[JFC Fuller]

The Meteor would have provided an additional 20% power over the proposed Gipsy unit and probably a more compact installation; space that could have been used for additional fuel and power that could have been used for additional protection. Certainly in the types as-built form power was not an issue more powerful could have produced a better overall platform.

 

[Abraham Gubler]

The Meteor would have provided an additional 20% power over the proposed Gipsy unit and probably a more compact installation; space that could have been used for additional fuel and power that could have been used for additional protection. Certainly in the types as-built form power was not an issue more powerful could have produced a better overall platform.

The Meteor would require a coolant radiator system where the other motors were all air cooled. If more power was needed the solution was bigger motors on the Perrier frame. Which is why they were proposing the Gipsy Major to replace the Caddilac.

 

[JFC Fuller]

The Meteor would require a coolant radiator system where the other motors were all air cooled. If more power was needed the solution was bigger motors on the Perrier frame. Which is why they were proposing the Gipsy Major to replace the Caddilac.

So the question becomes whether the more compact nature of the Meteor, combined with 20% greater power over and above even the Gipsy configuration would more than offset the need for a liquid over air-cooled system. I suspect it would have. incidentally, the ACIII may well have sacrificed the ability to clutch different engines in an out by effectively turning them into a common unit running through a common crankcase.

 

[royabulgaf]

A few items: IRT the clover leaf engine, Chrysler in the US had a similar project, the Multibank, using five six cylinder auto engines. It powered the M4A6 tank, which was mostly unloaded on lend-lease recipients. The idea of shipping Sentinels to North Africa or wherever the European theater would be presuming Japan stayed neutral, was unworkable. The supply line would be easily several months long, and at that time there simply was not the tonnage to spare. The smart thing to do would be supply Australian armor units in Europe out of British stocks, and supply Commonwealth units in south Asia with Sentinels or whatever.

 

[Rickshaw]

I find the retrospective arguments that the Sentinel was a waste of effort like in the terrible book “Fallen Sentinel - Australian Tanks in World War II” by Peter Beale particularly disingenuous (or just plain stupid). It was a tank program launched at a time when the Empire desperately needed tanks and there was no guarantee or suggestion that the Americans would continue to supply war material after the exhaustion of British credit (Lend Lease). While Japanese entry into the war naturally ended any chance of Australian ordnance going overseas Sentinel then provided the assurance of a continental defence that would defeat Japanese invasion. While this never happened it was a pretty bloody important assurance to the Australian government.

The problem for Sentinel was that it was launched at a time when the only physical enemy were the Germans in North Africa. Because of the rapid evolution of the AFVs in that conflict, it was always, like the other Allied tanks always going to be playing catch-up. While it had the potential to do so, the small numbers which were going to be produced were always going to be uneconomic. Their costs would be disproportionately high and the costs of maintaining them so far from home would also be hight because of the lack of commonality with the other Allied AFVs which would have predominated in that theatre. The UK was never going to adopt it, both because of it's source and because it was cheaper and easier to source already built AFVs, like most other military materiale from either home or the USA. This was obvious even at the time, if the Australian Army had been willing to open its eyes.

Because it was designed to counter the Germans' AFVs it was more difficult to manufacture than one which was designed to counter the real enemy which did eventuate - the Japanese. As their AFVs were light and had little armour, a much lighter vehicle could have been used but because the Army had decided on one designed for North Africa, the result was a vehicle that was expensive, both in material and manpower to produce. In the end, the choice was either tanks or light ships and aircraft. Tanks are excellent for defence of the mainland, less useful in the Islands. As by the time the Sentinel reached production, US AFVs were available in quantity and cheaply, it was obvious what would happen.

Romantics might like to think we should have produced them but much more hard-headed men decided otherwise. With the winding down of the commitment to North Africa and the withdrawal of Australian troops to home defence and then the offensive against the Japanese, the need for Sentinel had all but disappeared. If we had produced them in the numbers desired, the offensive against the Japanese would have been stalled (at least from an Australian perspective) as we would not have had the light ships, nor the aircraft to carry that offensive to the enemy. It might be felt that these arguments are made in hindsight but they were considered at the time, which is of course why the Sentinel failed to be produced in the quantities that some feel they should have.

The same romantics still believe perhaps that it was likely that the Japanese were to invade or even directly attack in force the mainland. While it wasn't known with absolute surety at the time, the succession of invasion scares and defensive strategy arguments which occur had more to do with domestic politics than they did with the reality of both what the Japanese were capable of and what they actually did. The remote threat that the Japanese represented could be countered more cheaply and easily with imported AFVs. As the Lee/Grant and Matilda were obsolescent against the European enemy, they were ideal against the Japanese one.

 

[Abraham Gubler]

The problem for Sentinel was that it was launched at a time when the only physical enemy were the Germans in North Africa. Because of the rapid evolution of the AFVs in that conflict, it was always, like the other Allied tanks always going to be playing catch-up.

So that’s a problem facing every weapon system ever developed, everwhere.

While it had the potential to do so, the small numbers which were going to be produced were always going to be uneconomic.

Sentinel was planned for mass production through two new plants (one built in Sydney, one planned in Melbourne) using mass production items (motors, guns, etc.). Far from being a small production run of uneconomic vehicles.

Their costs would be disproportionately high and the costs of maintaining them so far from home would also be hight because of the lack of commonality with the other Allied AFVs which would have predominated in that theatre. The UK was never going to adopt it, both because of it's source and because it was cheaper and easier to source already built AFVs, like most other military materiale from either home or the USA. This was obvious even at the time, if the Australian Army had been willing to open its eyes.

It wasn’t obvious because there was no guarantee of supply to North Africa from both the UK and certainly the USA. Australia had more resilient lines of communication to North Africa that the Germans couldn’t interdict.

Because it was designed to counter the Germans' AFVs it was more difficult to manufacture than one which was designed to counter the real enemy which did eventuate - the Japanese. As their AFVs were light and had little armour, a much lighter vehicle could have been used but because the Army had decided on one designed for North Africa, the result was a vehicle that was expensive, both in material and manpower to produce.

Yet the Stuart light tank was proven to be inadequate in jungle operations and was replaced by the heavy Matilda. Tanks used against the Japanese in the Pacific Islands campaign very rarely encountered their tanks. But their anti-tank weapons and artillery were punishing to Allied medium tanks. But the tanks were also decisive in winning battles. Saying only light tanks were needed is a very amateurish tank argument.

Romantics might like to think we should have produced them but much more hard-headed men decided otherwise.

No one here is suggesting they should have been built after the stabilisation of war in 1943.

The same romantics still believe perhaps that it was likely that the Japanese were to invade or even directly attack in force the mainland. While it wasn't known with absolute surety at the time, the succession of invasion scares and defensive strategy arguments which occur had more to do with domestic politics than they did with the reality of both what the Japanese were capable of and what they actually did. The remote threat that the Japanese represented could be countered more cheaply and easily with imported AFVs. As the Lee/Grant and Matilda were obsolescent against the European enemy, they were ideal against the Japanese one.

So by your own words you think preparing to counter an invasion that you didn’t know “with absolute surety” was not going to happen is “romantic”? Please whatever you do in life, please stay away from risk assessment! An invasion is the worst thing that could have happened even if there was only a slim chance of it going ahead (and at the time there was strong indication it was very likely) justified the huge effort the Australian nation put into countering it:

Brown, Gary; Anderson, David (1992). "Invasion 1942? Australia and the Japanese Threat". Background Paper Number 6 1992. Department of the Parliamentary Library.
Horner, David (1993). "Defending Australia in 1942". The Pacific War 1942. Canberra: Department of History, Australian Defence Force Academy.
Stanley, Peter (2002). "He’s (not) Coming South": the invasion that wasn’t" (PDF). Conference Papers. Remembering 1942.
Stanley, Peter (2008). Invading Australia. Japan and the Battle for Australia, 1942. Melbourne: Penguin Group (Australia).

I think your claims that others are ‘romantic’ is as misguided as your attempt to pass yourself off as a combat veteran with your new alternate nick (Kadija Man was Rickshaw) while you were banned from posting.

I have several medals to show that indeed I have "humped this stuff downrange" on a two-way rifle range, thank you very much.

Military imposters make me sick. Applying hindsight to make calls against contemporary decision making is not so sickening, just plain dumb.

 

[Abraham Gubler]

So the question becomes whether the more compact nature of the Meteor, combined with 20% greater power over and above even the Gipsy configuration would more than offset the need for a liquid over air-cooled system. I suspect it would have. incidentally, the ACIII may well have sacrificed the ability to clutch different engines in an out by effectively turning them into a common unit running through a common crankcase.

Even in the common frame mounting (Perrier) the engines could be clutched out. But without the full data on weight and so on it’s a hard call to make which would be better. Certainly the Cadillac and Gipsy Major engines were being manufactured in Australia in 1940 while the Merlin (and a potential Meteor) wasn’t until 1944-46. I would suspect however despite multiple motors maintenance in the Perrier arrangements would be much lower than a single Meteor. The Cadillac and Gipsy Major engines were well known as two of the most reliable motors in the world at the time and Meteor plus coolant system was a well-known fitter magnet.

 

[Abraham Gubler]

The idea of shipping Sentinels to North Africa or wherever the European theater would be presuming Japan stayed neutral, was unworkable. The supply line would be easily several months long, and at that time there simply was not the tonnage to spare. The smart thing to do would be supply Australian armor units in Europe out of British stocks, and supply Commonwealth units in south Asia with Sentinels or whatever.

The supply line to Egypt from Australia was actually much shorter and far less risker than from the UK to Egypt in 1940-42 It was 20,000 km from the UK to Egypt around the Cape of Good Hope through the U Boat infested Atlantic. From Australia (Sydney) to Egypt it is only 15,000 km through much safer waters.

 

[Rickshaw]

The problem for Sentinel was that it was launched at a time when the only physical enemy were the Germans in North Africa. Because of the rapid evolution of the AFVs in that conflict, it was always, like the other Allied tanks always going to be playing catch-up.

So that’s a problem facing every weapon system ever developed, everwhere.

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.

While it had the potential to do so, the small numbers which were going to be produced were always going to be uneconomic.

Sentinel was planned for mass production through two new plants (one built in Sydney, one planned in Melbourne) using mass production items (motors, guns, etc.). Far from being a small production run of uneconomic vehicles.

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.

Their costs would be disproportionately high and the costs of maintaining them so far from home would also be hight because of the lack of commonality with the other Allied AFVs which would have predominated in that theatre. The UK was never going to adopt it, both because of it's source and because it was cheaper and easier to source already built AFVs, like most other military materiale from either home or the USA. This was obvious even at the time, if the Australian Army had been willing to open its eyes.

It wasn’t obvious because there was no guarantee of supply to North Africa from both the UK and certainly the USA. Australia had more resilient lines of communication to North Africa that the Germans couldn’t interdict.

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.

Because it was designed to counter the Germans' AFVs it was more difficult to manufacture than one which was designed to counter the real enemy which did eventuate - the Japanese. As their AFVs were light and had little armour, a much lighter vehicle could have been used but because the Army had decided on one designed for North Africa, the result was a vehicle that was expensive, both in material and manpower to produce.

Yet the Stuart light tank was proven to be inadequate in jungle operations and was replaced by the heavy Matilda. Tanks used against the Japanese in the Pacific Islands campaign very rarely encountered their tanks.

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.

But their anti-tank weapons and artillery were punishing to Allied medium tanks. But the tanks were also decisive in winning battles. Saying only light tanks were needed is a very amateurish tank argument.

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?

Romantics might like to think we should have produced them but much more hard-headed men decided otherwise.

No one here is suggesting they should have been built after the stabilisation of war in 1943.

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.

The same romantics still believe perhaps that it was likely that the Japanese were to invade or even directly attack in force the mainland. While it wasn't known with absolute surety at the time, the succession of invasion scares and defensive strategy arguments which occur had more to do with domestic politics than they did with the reality of both what the Japanese were capable of and what they actually did. The remote threat that the Japanese represented could be countered more cheaply and easily with imported AFVs. As the Lee/Grant and Matilda were obsolescent against the European enemy, they were ideal against the Japanese one.

So by your own words you think preparing to counter an invasion that you didn’t know “with absolute surety” was not going to happen is “romantic”? Please whatever you do in life, please stay away from risk assessment! An invasion is the worst thing that could have happened even if there was only a slim chance of it going ahead (and at the time there was strong indication it was very likely) justified the huge effort the Australian nation put into countering it:

Brown, Gary; Anderson, David (1992). "Invasion 1942? Australia and the Japanese Threat". Background Paper Number 6 1992. Department of the Parliamentary Library.
Horner, David (1993). "Defending Australia in 1942". The Pacific War 1942. Canberra: Department of History, Australian Defence Force Academy.
Stanley, Peter (2002). "He’s (not) Coming South": the invasion that wasn’t" (PDF). Conference Papers. Remembering 1942.
Stanley, Peter (2008). Invading Australia. Japan and the Battle for Australia, 1942. Melbourne: Penguin Group (Australia).

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.

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.

There is a very good, short discussion in fact of that in the recent book, Craig Collie and Hajime Marutani, The path of Infinite Sorrow: The Japanese on the Kokoda Track, Allen and Unwin, Sydney, 2012. It is an excellent read in it's own right and places the Japanese aspect of the campaign into perspective very well.

 

[Abraham Gubler]

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.

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. 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.

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.

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!

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.

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.

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? 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…

 

[Pioneer]

A couple of years ago, I took my son and his mate to Puckapunyal Armoured Museum, where I took this photo of them in front of a Sentinel. One thing that stood out to the boys was its cast construction method and the thickness of its armour!

Regards
Pioneer

 

[Abraham Gubler]

A couple of years ago, I took my son and his mate to Puckapunyal Armoured Museum, where took this photo of them in front of a SentinelOne thing that stood out to the boys was its cast construction method and the thickness of its armour! RegardsPioneer

Great photos. The boys look the right size to be 'hull beast' crew.

 

[JFC Fuller]

I would like to see a source about the ACIII engine allowing certain cylinders to clutch out; I have only seen this claim made for the original ACI clover leaf configuration, it easy to see how that would have worked as each engine ran through its own clutch before reaching the transfer case, obviously that is not the case on the ACIII configuration. The base Cadillac and Gipsy motors may have been reliable but generally speaking, combining a collection of smaller motors tends not to enhance reliability- though there are of course very reliable multi-bank engines. The Meteor became a highly successful tank engine and offered 20% + more power than even the proposed Gipsy configuration.

 

[Abraham Gubler]

I would like to see a source about the ACIII engine allowing certain cylinders to clutch out; I have only seen this claim made for the original ACI clover leaf configuration, it easy to see how that would have worked as each engine ran through its own clutch before reaching the transfer case, obviously that is not the case on the ACIII configuration.

Bad use of language on my behalf there were no separate clutches but each engine unit could still be turned on and off separately despite being mounted on a single case.

 

[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.