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Sentinel ACIV
- Thread starter Abraham Gubler
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ninjrk said:
Basilisk
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ninjrk said:
From memory, if you have a look somewhere around half way through that is a couple of drawings of an AC4 hull. It only has a 64" turret ring so must be an early draft before the design was enlarged to 70".
I've never figured out why certain files get digitised before others that one was scanned something like 18 months ago, they don't seem to be going by age, or by series, or anything else obvious. Tangentially related to this thread since the AC4 could also carry a 25 pounder, these are from a couple of months back, the first experiment towards a 25 pdr tank gun, tested June 1942:
Barcode: 33033164
Barcode: 33033162
The rest are AC1 but you can find them under series MP891/30.
I confess I'm a little surprised that there was no mention of trying to fit the QEF 75mm main gun in the Sentinel instead of the 25 pdr. I'd assume its because the 25 pdr was in production in Australia and ammunition was plentiful?
Basilisk
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Pretty much. The intent was to only to use imported components where there was no local alternative. Sometimes you see comments online suggesting the Vickers was a bit old fashioned or too bulky, and they should have used the BESA, well neither the BESA nor its ammunition were being made in Australia. I think there is a fairly short list somewhere of foreign components required for the tanks, the major ones were the engines and roller element bearings, and bunch of little things like light bulbs.
Having said that, as designs were drawn up to fit a 6 pdr to the Sentinel, and as I understand it the OQF 75mm is essentially a rebarreled 6 pdr, I don't imagine it would have been out of the realm of possibility to make a 75mm Sentinel.
Having said that, as designs were drawn up to fit a 6 pdr to the Sentinel, and as I understand it the OQF 75mm is essentially a rebarreled 6 pdr, I don't imagine it would have been out of the realm of possibility to make a 75mm Sentinel.
And I think the engines, although technically made overseas, were chosen as there was a large stock in country ( I do not know where it was, or who owned it ) and presented no or very little issue with supply.
Basilisk
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rdmr said:
No, the Cadillac V8s came direct from the US. As they weren't anybody's first choice as a tank engine, the Americans and even the manufacturer didn't think a multiple engine power plant would work, there was no competing demand and they could be had in almost any quantity desired. Until the US started putting multiple Cadillac V8s into their tanks.
There was I believe a stock of Ford V8s in Australia, they were used in the LP Carriers. A triple Ford V8 using those was one of the fall backs if the Cadillacs couldn't be had.
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Good point dear Basilisk,
The contemporary Canadian Ram tank was originally fitted with 2-pounder guns ... because that was all that was available.
Ram Mark II got 6-pounder guns.
Post WW2, the Dutch Army re-gunned a batch of abandoned Ram tanks with British QF 75mm guns. QF 75 mm fired the same ammo as American 75 mm tank guns (eg. Sherman) but had outside dimensions similar to the old British 6-pounder.
As for the experimental 25-pounder gun fitted to a Sentinel ... it made more sense for busting Japanese bunkers. British 25-pounders also killed a few Panzers.
Basilisk
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For the suspension, I have no idea of exactly who. The Australians were aware of the Hotckiss tanks and were after drawings of them if possible as it was a quick and easy way to get the job done. The actual suspension used on the AC1 later types was a modified version of what was drawn up for the AC2. It sometimes is credited to Perrier, the french engineer working for the tank project, but he was a high performance aircraft engine specialist who would have no reason to know anything about tank suspension.
The transmission was based on the M3 medium system, though not the same. It was made about as simple as it could be and still work, straight cut gear teeth, no synchronisers, and the gear ratios were altered to work with the Cadillac engine's power band. But overall the design is that of the US Medium tank.
The transmission was based on the M3 medium system, though not the same. It was made about as simple as it could be and still work, straight cut gear teeth, no synchronisers, and the gear ratios were altered to work with the Cadillac engine's power band. But overall the design is that of the US Medium tank.
This book for those interested: https://www.trackpadpublishing.com/product-page/fire-the-25-pounder-in-australian-service
It is a really good reference work. Good coverage of the Sexton as well.This book for those interested: https://www.trackpadpublishing.com/product-page/fire-the-25-pounder-in-australian-service
Basilisk
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Good book, but I think a few of the numbers/descriptions in that section perhaps haven't survived metrication or translation that well? The 2596mm barrel length for example. The standard 25pdr gun barrel is about 2.5m, an additional 2 feet would take it to 3ish metres which looks about right for what's in the photos. Or put another way a 3.45" L34 barrel should be 2979mm long, once again 3ish metres. So the 2595mm length is too short for the full barrel length, could be meant to be length of rifling maybe?
The velocity increase is kind of correct but a little misleading in context, the 138m/s increase I believe is comparing the 25lb HE shell fired with super charge from the standard artillery piece (518m/s) to the 20lb AP shot from the L34 fired with supplemented super charge, which isn't entirely fair or perhaps even that useful. The AP shot for the regular length 25pdr tank gun does about 1900f/s or 580m/s, so at 656m/s the AP shot out of the L34 is "only" doing an extra 77m/s, and I would expect probably not worth the trouble of using three piece ammunition.
Still a good book, I'd have no problem recommending it, just not perfect. Well that's what I think, I mean I could be wrong, wouldn't be the first time.
You meant Yeramba, not Sexton, right?
How much on the Yeramba in it?
I did indeed.
Stranger_NN
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As far as I know, these are two 25-pounder howitzers, mimicking the enormous recoil of a 17-pounder cannon.
Basilisk
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The Australian War Memorial site has a video, News From Home No. 46 - Iron Cavalry - Australian Made, a short news reel item on the Australian cruiser tanks. A little bit jingoistic as is to be expected at the time but it does go through much of the production process and show the completed Sentinels being driven around.
Basilisk
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I've been tossing up weather to buy a copy, and what you've shown here doesn't exactly fill me with confidence. But then, in my view, Jason has made some questionable statements before about the tanks so it's no great surprise. The first shot has the hull number as "BK AK 60", which means he mistranscribed the axle housing information, which should be BK AH 60, as the hull number. Twice, probably three times maybe in one photo as I'm guessing it's another "K" that's just off the side of the picture. That tank has hull 31 I believe, not 60. And the second shot has one of Abraham's photos taken from this very thread, rather than the original in the archives even though Abraham stated exactly where it came from so you could go look it up yourself if you wanted to, unless Jason didn't want to pay the Archive for the publication fee himself or something. Still he could at least have credited Abraham properly.
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Thuggernaut
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I've always found it a bit interesting that they stuck with the Vickers water-cooled machine gun all the way to the end of the project. Was there a reason the Browning wasn't considered suitable? Or was it simply because the Browning was in high demand for many of the Australian aircraft then in production?
Also is there a separate thread for the Australian light tank project of the same period, which (IIRC) used the Universal carrier as a basis?
Also is there a separate thread for the Australian light tank project of the same period, which (IIRC) used the Universal carrier as a basis?
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I don't think the .303 Browning saw much ground use, especially not in tanks. I can't say I know the reason for this however. It might have been a bit too lightly built for ground use but surely a heavier version could have been developed just as there were light (aircraft) and heavy (ground) versions of the .30-06 Browning machine gun.
Britain’s Royal Armoured Corps decided to move from the Vickers .303” to the BESA 7.92mm at the start of the war as the MG for use in British tanks.
The AC1 Sentinel that started the line for the Royal Australian Armoured Corps drew on both British and US tank design. But for Australia switching to the new gun would have added logistical headaches for small volumes. So sticking with a tried and tested weapon would have made sense as the Vickers was also in use as an infantry support weapon.
The AC1 Sentinel that started the line for the Royal Australian Armoured Corps drew on both British and US tank design. But for Australia switching to the new gun would have added logistical headaches for small volumes. So sticking with a tried and tested weapon would have made sense as the Vickers was also in use as an infantry support weapon.
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Honestly, I wonder how much of a liability using the "light" versus the "heavy" versions of the Browning would be for a tank though. If I recall correctly, the main problems with the improvised "Stinger" Brownings (made from scavenged aircraft guns) when used by ground troops was that the rate of fire was excessive, and the aircraft version had more openings that allowed dirt to get in. Neither of these issues would be as problematic when using the gun as a tank's coaxial weapon.
Of course, there might have been other differences introduced in the .303 versions of the Browning (I'm not an expert on British machine guns, obviously) that would preclude this use, and the Vickers still had a much greater capability for sustained fire. The tradeoff is that the Sentinel's armor castings had to be designed to fit around a much bulkier weapon.
Of course, there might have been other differences introduced in the .303 versions of the Browning (I'm not an expert on British machine guns, obviously) that would preclude this use, and the Vickers still had a much greater capability for sustained fire. The tradeoff is that the Sentinel's armor castings had to be designed to fit around a much bulkier weapon.
Basilisk
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It was what the Army wanted.
The specification was for one or two .303 MGs. There would have been a small number of worn out and obsolete/obsolescent Hotchkiss and Lewis guns in Australia, which obviously not have been acceptable, it's why they ended up with the VDC. From new production locally there was the Bren but that was needed by the infantry, and the Vickers which was a known reliable gun used in many previous Australian armoured vehicles including the Vickers tanks, the Medium MkII and the Light MkVI. There was no real need to change it, and any other gun would likely need to be imported like the .303 Brownings which I think came from the UK (BSA?), which would go against the principle of a secure domestic weapon supply.
The logistics of a different calibre probably don't really come into it, as what happened was just about the worst case imaginable, .303 and 30cal and 7.92mm and all of the various pistol cartridges all in use in different guns at the same time.
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Australia basically manufactured .303in, .38 and 9mm calibre military small arms. Brownings used .30cal rounds, which Australia did not manufacture and could only be really supplied by the USA. It would be easily interrupted in wartime. So the Australian army only specified guns which were manufacture in Australia. This was why the Owen Gun was manufactured in 9mm, the .45in version was deemed to be too expensive to manufacture so it never left the test bench. Australia never adopted the Besa gun in 7.92mm calibre, unlike the British Army.
Basilisk
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Are you about to advance the claim that Australia re-armed all the Matildas with a co-ax other than the BESA? And the Centurions prior to the Mk 5 upgrade?
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I was referring to the .303 version of the Browning, as used in British and Australian aircraft that were being assembled locally at the time the Sentinel was being developed (the Beaufort, Boomerang and later marks of the Wirraway used the .303 Browning, for example.)
But my original question has been answered, I think; the .303 Browning had to be imported from Britain (unless someone has a source on Australian production of it), and so the Vickers was used because it was in production locally, and that was considered of greater importance.
The .303 Browning, presumably imported from the UK, was used in the Boomerang fighter, but that would have been a bit later than design decisions were made about the AC1 I guess. The Vickers Mk.V, the air-cooled version of the Vickers was used in the Wirraway, I believe. I wonder if they could have asked Lithgow to come up with a heavy-barreled version of that?
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Australia did not use many Centurions before the Mk.5. Those were all armed with .303in Browning MMGs. The Matilda was rearmed with .303in Browning MMGs as well, rather than the Besa. The point wasn't so much the weapon, the point was the ammunition used. If it was imported, it was more expensive than one which used a native produced round.
Basilisk
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OK, so you are making that claim then.
Ian Skennerton's 100 years of Australian Service Machineguns says the Besa was used in British supplied AFVs in both flex and fixed versions and the only changes were the modification or removal of the accelerator to prevent the use of the higher ROF.
The Matildas would have come from the UK with Besas, and that's what is seen in wartime photos (not the best quality but still recognisably Besas):
From the AWM, Accession Number 062753: SX23158 CORPORAL D. P. MCCUSPIE (1) AND VX59410 SERGEANT H. DODD (2) ARMOURERS OF THE 1ST TANK BATTALION GROUP WORKSHOPS, AUSTRALIAN ELECTRICAL AND MECHANICAL ENGINEERS, OVERHAULING 7.92MM BESA MARK 2 MACHINE GUNS OF A MATILDA TANK.
Ammunition expenditure reports are full of:
View: https://i.imgur.com/u5S6KeC.jpg
Logistics planning:
View: https://i.imgur.com/HsCcvOE.jpg
Seems very odd to plan to bring along 4 tons of ammunition that has no use other than in a Besa. Unless the Matildas still had Besas, then it makes perfect sense.
The Churchills once again a British tank, the standard tank MG will be the Besa. Likewise the first 60 Centurions were Mk3s, which have Besa coaxial guns.
There is an abundance of material evidence of Australian use of the 7.92mm Besa from WWII until the late 1950s. What is your evidence that all of it is wrong?
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I bow to your superior knowledge, except the Centurion Mk.3s intended for Australia were initially sent by Britain to Korea, rather than Australia because of the Korean War. The first Mk.3s arrived in 1952. The Australian Centurions were equipped with 20 pounder guns and the 7.92 Besa mg's which were replaced with .30 cal. Browning mg's.
Basilisk
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Yes the particular tanks Australia was going to get were diverted, but has little bearing on the tanks Australia did get later. The first 60, ARNs 169000 through to 169059 were delivered as Mk 3s. As the Lancer's article says the tanks were Mk 3 if they had a Besa, and they were Mk 5 if they co-ax was replaced by the Browning, and so the abridged quote you used in to link to the article reads in full:"The Australian Centurions were Mk. 3's and these were equipped with 20 pounder guns and the 7.92 Besa mg's were replaced with .30 cal. Browning mg's" (emphasis mine). The Mk 5 upgrade came later, I can't find an exact date but probably around or shortly after the remaining WWII Besa-armed tanks were retired, 1956ish. Mike Cecil's article on 169041 getting nuked has it getting the Mk 5 upgrade finished in 1960, although given that that tank didn't have a turret on it since 1954 I suspect that late a date doesn't mean too much. So best guess is the Besa left Australian service maybe sometime between about maybe 1956 and 1958.
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