Author Topic: Churchill Tank  (Read 88663 times)

Offline Rickshaw

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Re: Churchill Tank
« Reply #50 on: December 02, 2013, 09:16:12 AM »
Which then meant that even the brand new Comet could not fit a full sized 17 pdr, it had to use the somewhat derated 77mm gun because the 64" turret ring could not take the recoil like the Sherman could. All because of a continuing lack of vision by the British tank design authorities. They never, right up to the Centurion, could see past the end of the exact tank they were working on. It was bloody criminal, to be sure.

It is always easier to condemn than to understand.  This is one reason why I like Fletcher's books over most of the others which have been written about British tank development in WWII.    I also suppose it all depends on whom you refer to as "the authorities".   The Centurion was the first tank that the Ordnance Department had full authority over and obviously they had been listening and absorbing what they had been told 'cause didn't they come up with a cracker!   Before that, first the Tank design board and then industry actually had first and second say and the Army only last on how tanks should be designed.  It makes one rather suspect that if the Army had, had sole control from the start they might have gotten something better sooner.

The 77mm gun was actually a completely different gun to the 17Pdr, you realise and not "derated" at all?   It actually had it's roots in a private venture Vickers 75mm design, dating back to about 1941-2 IIRC.  It went through several evolutions before finally being adopted as the 77mm.

One of the interesting things to emerge from the use of the Churchill's use in NW Europe was that despite it's supposed handicaps of a lack of speed and poor suspension in the final month of WWII, Churchill units in the final drive into Northern Germany actually advanced further and faster than their medium or even cruiser equipped counterparts.   While they might not have been speedsters, what they could do was keep on fighting and advancing when they encountered opposition whereas the other tanks had to stop and try and outflank rather than go in, head on.

The key to their mobility was always their superior gearbox, which was carried over into the Centurion design.    Funnily enough, the gearbox in both the Churchill and the Tiger had common roots, in British heavy vehicle designs.   Yet the Tiger's version was actually less manoeuvrable.
« Last Edit: December 02, 2013, 09:20:29 AM by Rickshaw »

Offline tankmodeler

  • Wisely picking parts of the real universe 2 ignore
Re: Churchill Tank
« Reply #51 on: December 02, 2013, 09:27:53 AM »

It is always easier to condemn than to understand.  This is one reason why I like Fletcher's books over most of the others which have been written about British tank development in WWII.
Me, too. The Great Tank Scandel is a ringing indictment of the Tank Board and British industry. As you say, only when the Army got the say in their own vehicles did something really useful actually arise, the Centurion.

Quote
It makes one rather suspect that if the Army had, had sole control from the start they might have gotten something better sooner.
I suspect so, even if it was something that the Government and industry didn't want to build for them.

Quote
The 77mm gun was actually a completely different gun to the 17Pdr, you realise and not "derated" at all?

Indeed, however, with a lower amount of propellant in the case, it's performance was marginally less than that of the 17 pdr, hence my term derated, but yes, your clarification was good for those who didn't know the history of the 77mm. It has long been a hoary old story that the 77mm was nothing but a 17 pdr cut down with a smaller amount of propellant.

Paul

Offline Rickshaw

  • "Of course, I could be talking out of my hat"
Re: Churchill Tank
« Reply #52 on: December 02, 2013, 10:05:06 AM »
Ah huh but not looking for a Black Prince, looking for minimal change to the chassis but must have the Meteor and its 600bhp

Black Prince was what was required to get a Meteor into a Churchill chassis.   However, Black Prince was underpowered, even with a Meteor, unreliable and basically a dead end.  This is made very clear from the trials report that Fletcher reprints in the back of "Mr. Churchill's Tank" (well worth reading if you want the the history of Churchill tank development). 

What you want is a standard, Mk.VIII Churchill armed with a 25 pdr gun.  That is IMHO quite doable with relative minor modifications to the turret shape and it's internals (ammunition stowage, etc).   You'd end up with a marginally better HE round but at the expense of AT capability.   You'd need a new gun essentially with only the tube and breech being retained from the field gun.  It would need a new recoil system and a new mounting and associated sights, etc.  All possible but if you want it available for use in mid-1944, you'd more than likely have to start about 18 months earlier, at the latest, to develop the mounting and the fixed case ammunition.

It would not be much use against Germany heavy Panzers IMO.


Offline Volkodav

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Re: Churchill Tank
« Reply #53 on: December 02, 2013, 10:23:51 AM »
The Black Prince used the same Bedford flat 12 as the Churchill, the Meteor was considered during the design phase but never fitted or planned to be fitted to the Black Prince.
 

Offline tankmodeler

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Re: Churchill Tank
« Reply #54 on: December 02, 2013, 10:57:50 AM »
What you want is a standard, Mk.VIII Churchill armed with a 25 pdr gun.
And if you are going that way, why go away from the Churchill VIII, which was a Churchill VII (with slightly modified turret) with the standard Brit 95mm howitzer in the turret, and was used for close support? The extra range of the 25 pdr couldn't really be used in the Churchill turret and the 95mm had an even better HE round than the 25 pdr.

Paul

Offline dy031101

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Re: Churchill Tank
« Reply #55 on: December 02, 2013, 11:53:48 AM »
And if you are going that way, why go away from the Churchill VIII, which was a Churchill VII (with slightly modified turret) with the standard Brit 95mm howitzer in the turret, and was used for close support? The extra range of the 25 pdr couldn't really be used in the Churchill turret and the 95mm had an even better HE round than the 25 pdr.

The 25-pounder wasn't the best anti-tank gun with the Allies, but it was decent enough if you want a bigger punch against armours than the short 75mm while still having good HE.

Or give the 95mm some kind of HEAT ammo.
Forget about his bow and arrows- why wait until that sparrow has done his deed when I can just bury him right now 'cause I'm sick and tired of hearing why he wants to have his way with the cock robin!?

Offline Volkodav

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Re: Churchill Tank
« Reply #56 on: December 02, 2013, 12:35:23 PM »
I always found it interesting that the main criticism on the 95mm was its lack of accuracy, range and velocity; all things that could potentially be fixed by a longer barrel, yet the barrel always appears to have been fitted with a counterweight.  You would think that a longer barrels would be the ideal fix

Offline PR19_Kit

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Re: Churchill Tank
« Reply #57 on: December 02, 2013, 01:52:44 PM »
I know naff all about tanks, but I DO know about 25 pdrs. (I was a BSM in the CCF and we had a 25 pdr for our troop back in the late 50s and early 60s.)

As you mention above you'd need fixed case ammo to use in a tank turret, using the rounds and the bag charges would have been far too chaotic in the close confines of a turret I'm sure. But would you have to use different sets of rounds with different charges or would you dispense with the variable charge capability in tank use? And if so which charge would you use? Presumably Chaarge 3 Super as it gave the greatest velocity?
Regards
Kit

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Offline Volkodav

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Re: Churchill Tank
« Reply #58 on: December 02, 2013, 05:12:08 PM »
Ah huh! Found it!
http://www.mheaust.com.au/Aust/Research/Sentinel/sentinelmk.htm

"The 25 pounder was mounted in the turret with a coaxial 0.303 Vickers water cooled machine gun. The AC3 was of similar dimensions to the AC1 and used the same 137cm (54 inch) turret ring, this in particular meant that the AC3 turret was somewhat cramped particularly for the loader who had to be careful to keep out of the recoil path of the gun. To swing the larger turret the 40 volt electrical traverse motor of the AC1 was replaced by a 110 volt motor. Stowage was provided for 120 rounds of ammunition, 60 High Explosive/Smoke shells and 60 of the shorter 9kg (20 lb) Armour Piercing shot, and 2500 rounds for the coaxial Vickers, stored in 250 round boxes. As the 25 pounder used 2 part ammunition 120 cartridges were to be carried consisting of charge 3 and charge Super. Despite the two part ammunition and the cramped turret the rate of fire showed that the tank was far from unusable, in tests with the commander assisting the loader by ramming the projectile the crew were able to fire 8 rounds in 73 seconds. The tank mounting of the 25 pounder proved to be excellent, unlike the towed version multiple rounds could be fired without having to relay the gun on the target."

Looks like I was right and wrong, I will blame approaching old age

Offline PR19_Kit

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Re: Churchill Tank
« Reply #59 on: December 02, 2013, 06:32:54 PM »
Very interesting.

So they did use 2 part ammo, I'm surprised but one advantage would have been there was no shell casing to get rid of, at least for short periods. They'd have to clean out the breech after 10-15 rounds I'd have thought because the charge bags left some residue behind, even if not that much. And Charge 3 and Charge Super makes sense if you're targeting other armour most of the time.

I bet their ears hurt after a few rounds of Super!  :o We took our gun to Larkhill after I'd found its barrel was still certified and I'd spent WEEKS persuading our CO and our parent company at the Oxford Uni OTC, and fired off maybe half a dozen rounds. I got to fire the 2nd one (they fired the first one via a lanyard!) and chose an APDS shot, shooting against a Comet target with Charge Super. It was LOUD, but I did hit it!  :)
Regards
Kit

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Offline Volkodav

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Re: Churchill Tank
« Reply #60 on: December 02, 2013, 06:55:57 PM »
What did the APDS do to the Comet?

Offline tankmodeler

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Re: Churchill Tank
« Reply #61 on: December 02, 2013, 08:22:13 PM »
There was an APDS round for the 25 pdr????

Offline PR19_Kit

  • Likes to brag about how long his...wings are.
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Re: Churchill Tank
« Reply #62 on: December 02, 2013, 09:06:41 PM »
Made a damn great hole in the side.  :)

I think that's what it's called, the one with four curved bits that fit round a centre core, and then they fly off when the round comes out of the barrel. There were thin wire spring things that held them in place while you loaded it and they had VERY sharp ends if you weren't careful.

Could it have been a post-war development, as they provided the ammunition for our shoot from Larkhill.
Regards
Kit

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Offline tankmodeler

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Re: Churchill Tank
« Reply #63 on: December 03, 2013, 09:02:28 AM »
I think that's what it's called, the one with four curved bits that fit round a centre core, and then they fly off when the round comes out of the barrel.

Well, that's APDS, for sure.
 
Quote
Could it have been a post-war development, as they provided the ammunition for our shoot from Larkhill.
It might have beeen an experimental round as I've taken a look through several books and I see no reference to any production APDS rounds for the 25 pdr either during or after the war. Certainly, after 1945 there would be no realistic expectations of using the 25 pdr in the AT role and the muzzle velocity of the 25 pdr, even on super charge wasn't really that great to make the use of a complicated APDS round make a lot of sense.

Paul

Offline PR19_Kit

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Re: Churchill Tank
« Reply #64 on: December 03, 2013, 04:24:47 PM »
Perhaps the Larkhill guys reckoned our gun was expendible if it all went wrong? Which means I would have been expendible too as I was No 3 on the gun!  :( :o

Mind you, an APDS round didn't have any explosive aboard so there wasn't much to go wrong. Is there a site anywhere that says what sort of ammo was normally used in a 25 pdr?
Regards
Kit

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Offline Rickshaw

  • "Of course, I could be talking out of my hat"
Re: Churchill Tank
« Reply #65 on: December 03, 2013, 05:32:01 PM »
I think you'll find they carried 120 rounds - 120 shells and 120 cases. The 25 Pdr fired with a shell case to provide obturation. It didn't rely on purely bagged charges. Each round was in a "semi-fixed" form, with the shell placed in its top. Each case came with sufficient charge bags for Charge 2 pre-loaded. The loader would remove the shell ram that up the bore and either remove or add bags to give the correct combination before ramming the case into the breech.

This image appears to be giving some difficulty when trying to insert it to the post so I'll just provide the URL.  It shows several 25 Pdr rounds displayed.

http://upload.wikimedia.org/wikipedia/commons/c/c0/QF_25_pounder_Ammunition-001.jpg

This mean you'd have spare charge bags rattling around in the turret with the possibility of split bags with spilt powder. Which is generally not a good idea.

I'm not aware of an APDS round for the 25 Pdr, only an AP round (not sure if its AP, APC or APCBC, I suspect the latter).

If tanks were to mount 25 Pdrs in large numbers, I can see a fixed round being developed, with AP with permanent supercharge bags in the shell case. You might see some bright spark developing an APDS round for the 25 Pdr. but as has been noted, it wouldn't have been of much value (and may have caused problems with the muzzle brake which was developed to cope with Super Charge rounds).
« Last Edit: December 03, 2013, 05:36:48 PM by Rickshaw »

Offline Volkodav

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Re: Churchill Tank
« Reply #66 on: December 03, 2013, 06:12:23 PM »
Would a tank mounted 25pdr have needed a muzzle break even with super charge? The ACIII was said to be a good gun platform with the gun not needing to be relayed between shots, I imagine the significantly heavier Churchill would have been even better.

Offline Rickshaw

  • "Of course, I could be talking out of my hat"
Re: Churchill Tank
« Reply #67 on: December 03, 2013, 08:09:27 PM »
Muzzle brakes are used to relieve recoil stresses on the mounting by directing gases to the rear of the gun.  Those ports on the sides are actually angled rearwards.  Without a muzzle brake you have to either beef up the mount, provide a longer recoil travel or simply wear the fact that the mounting will have a shorter life.   

Now, you don't want to increase the recoil travel - the turret is already very cramped.  If you beef up the mount, that again consumes internal turret space.   So you need to alleviate the recoil, either by mounting more or larger recuperators.  The British tended to mount more, rather than larger ones.  If you ever get to Puckapunyal and the RAC museum, you'll see a sectioned Centurion turret used as a crew trainer.  What is surprising is how short the recoil travel is on the 20 Pdr.  There are four, short but prominent recuperators to absorb all that recoil, two above and two below.

So, yes, you could get rid of the muzzle brake if you wanted to but as in anything there are trade offs.  APDS can be fired from guns with muzzle brakes, the 17 Pdr had one.  It's just that there is a known problem with the petals of the sabot fouling muzzle brakes.   So, perhaps a single baffle one instead of the double baffle?

The Germans were BTW by war's end experimenting with fixed guns - letting the armoured vehicle's mass and suspension absorb the recoil, however that was out of desperation to speed up manufacturing time by simplifying the vehicle and saving materials, particularly oil but were only starting to think about actually putting them in Panzerjaeger vehicles when the war ended.  After the war no one except the Soviets really paid much attention to it as an idea and even they abandoned it after a few experiments.

Offline tankmodeler

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Re: Churchill Tank
« Reply #68 on: December 03, 2013, 08:24:34 PM »
only an AP round (not sure if its AP, APC or APCBC, I suspect the latter).
No, the only production AP round was a simple shot design, the black one in your photo. No cap or balistic cap round was ever fielded.

Which is why I find the concept of an APDS round difficult to fathom.

In a tank mounting, I would expect all of the ammo to be of one charge so there would be no spare charge bags in the turret. The mounting really can't elevate enough to change the range significantly even with higher chargers, so why bother. If using the gun as artillery (as was done with alomst all tanks at one time or another) you could mount the tank on a berm to get the elevation you wanted and then suppply with normal 25 pdr variable charge rounds.

Paul

Offline PR19_Kit

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Re: Churchill Tank
« Reply #69 on: December 04, 2013, 05:41:56 AM »
How odd, I don't recall the brass charge casings either.

We had dummy charges in our limber of course, NO chance they'd let a bunch of schoolkids loose with real live cordite! IIRC they were just cotton, or sort of burlap bags, with the 'charge' inside and they had different numbers on them determining which charge they were, 1, 2, 3 or Super. I think Charge 3 was larger than the other ones as well and the Super was a small bag added after a Charge 3 was loaded.

Would that black AP round have bits that fell off after it was fired, something like a wad used with a muzzle loaded rifle?

I'm still in touch with the No.1 on our gun (he was best man at my first wedding  :)) and I'll ask him what he can remember of the live firing trials we did at Larkhill.
Regards
Kit

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Offline Rickshaw

  • "Of course, I could be talking out of my hat"
Re: Churchill Tank
« Reply #70 on: December 04, 2013, 07:50:26 AM »
You sure it was a 25 Pdr, Kit and not a 18 Pdr?  ;D

The bags would have been cotton.  You should have been using brass cases 'cause otherwise there wouldn't have been sufficient obturation (sealing) from the sliding breech block alone.  Nor was the 25 Pdr equipped IIRC with an exploder tube (a mini-breech on the side where an over-sized shotgun like small brass case was inserted.  This is what was actually "fired" when it was used on larger guns.  It in turn exploded the main charge, in the main breech).

25 Pounder
has some good scenes, particularly about 1:28 of the loading sequence on the 25 Pdr.  You see the breech being opened, the shell being rammed, then the case being inserted and the breech closed and the round fired.


Offline PR19_Kit

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Re: Churchill Tank
« Reply #71 on: December 06, 2013, 02:33:02 AM »
What a terrific vid, brought back loads of memories. :)

The guns in the vid were exactly like the one I served on, even down to the dial sight poking up above the blast shield for indirect firing. I see what you mean about the brass charge casings, but that wasn't like the propellant bags we had, at least not at school. They may have used them when we took the gun to Larkhill but they wouldn't let us load the gun there, presumably as they were using live rounds.

I got in touch with my old No. 1 but he was no good at all as he said all he could remember was painting the darn ting time after time! :)

I suspect they had different procedures for Cadet Forces just BECAUSE we were Cadets and we were issued with 'drill rounds' and stuff for our exercises, but for our Larkhill shoot we may have caught them on the hop as the 25 pdr wasn't in general service with the Army by then. In fact the BSM at Larkhill said we may have got the only 25 pdr with current barrel certificate at that time. I think it was Easter 1961 when we took it to Larkhill BTW.
Regards
Kit

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Offline Volkodav

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Re: Churchill Tank
« Reply #72 on: December 09, 2013, 06:45:52 PM »
Just had a thought for a completely off the wall Wiff for the Churchill.  The original concept that led to the Churchill was to have had sponson mounted guns so why not have a multi gun infantry support tank with a 17pdr on one side and a 25pdr on the other and a twin 20mm AA turret.  The sponson guns would fire forward only and be aimed by turning the whole vehicle but would be able to be elevated and depressed with loading being done from within the hull.

Offline Rickshaw

  • "Of course, I could be talking out of my hat"
Re: Churchill Tank
« Reply #73 on: December 10, 2013, 09:07:23 AM »
Just had a thought for a completely off the wall Wiff for the Churchill.  The original concept that led to the Churchill was to have had sponson mounted guns so why not have a multi gun infantry support tank with a 17pdr on one side and a 25pdr on the other and a twin 20mm AA turret.  The sponson guns would fire forward only and be aimed by turning the whole vehicle but would be able to be elevated and depressed with loading being done from within the hull.

Unnecessarily complicated.  Sponson gun positions are an induced weakness in the hull armour, which is why navies abandoned their use.  They complicate manufacture and they also increase the height of the vehicle to larger than a sitting position (to allow the gunner to aim the gun).   Also, because of their low position, and the narrowness of most European roads/lanes they wouldn't be able to be brought to bear.  You need a low vehicle but not one that is too low.  Different weapon calibres in the one vehicle introduce all sorts of problems with ammunition stowage and fighting the vehicle.  You also need a really good gearbox to give you the finesse required to aim a gun in azimuth.   As the experience with the M3 Medium showed, hull mounted guns also limit what sort of firing position you can take up.

Offline ChernayaAkula

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Re: Churchill Tank
« Reply #74 on: December 10, 2013, 09:43:19 AM »
Good points, but who said whiffs had to be practical?  :icon_beer:
Cheers,
Moritz

"The appropriate response to reality is to go insane!"