Alternative History Armoured Fighting Vehicles Part 3

The Panther and Tiger II(P) both suffered from weakened mantlets because of armour rolling. The Sentinel was unique because of the size of it's castings but did not suffer from weakened armour.
 
Castings usually aren't as strong as rolled plates, but (once you have the technical knowhow to make them big enough[1]) remove pr massively reduce the need for forming, cutting and welding all of which can reduce overall strength, create local weakpoints and take time [2].
[1] see Somua S35 for a good example of a decent cast tank that suffered from a one man turret. While political preference for the smallest possible crews played an important part, French casting technology though world class was about at its limit. Even if a two man turret was wanted, it may have been a step too far in the 1930s, and 1940 was too late. There was at least one French medium with a 2man turret but I'll have to check if it was cast.
[2] Big castings need carefully controlled cooling to avoid distortion, cracking and metallurgical problems like excessive brittleness or low hardness. It can take days to do properly, but the actual labour hours overall can be less than welding forming etc even if the total number of hours elapsed is the same.
Matilda II was both cast, thicker and larger than APX-1, so the limit wasn't really reached.
 
You do realise that rolling armour into a curved shape weakens the armour? Which is why it has largely been abandoned in building tanks...
Acually I do not. I just go with the good old "mhhh, looks good." aproach.

But interesting, when did the curved shape design get abandoned?
 
Matilda II was both cast, thicker and larger than APX-1, so the limit wasn't really reached.
Good point. But not that you can't have bigger casting, but that the combination of metallurgical knowledge of the day and available mould making and cooling experience and expertise, plus having time and capacity to experiment and then to change production. It's unlikely that different manufacturers would share development with competitors, especially in different countries.
Add in that your customer wants one man turrets, and you have a long wait before you get money back on developments.
 
The Panther and Tiger II(P) both suffered from weakened mantlets because of armour rolling. The Sentinel was unique because of the size of it's castings but did not suffer from weakened armour.
As I said, the Panther's mantlet was cast into it's final shape, not forged. I know of no instance of the Germans using curved armor forgings for the frontal armor of a production tank. Because the Indien-Panzer specifically had a dome-shaped turret design that could only be cast, I see no reason to expect the mantlet to be forged instead. Curved castings in general are materially indistinguishable from flat castings, which is why casting is usually used to make curved armor pieces. Because they preferred welded construction, the Germans only used casting for relatively small armor components in their tanks, but that included the Panther mantlet, Tiger I mantlet, and Tiger II mantlet.
 
French casting technology though world class was about at its limit. Even if a two man turret was wanted, it may have been a step too far in the 1930s, and 1940 was too late
Large German casting, 1890 Brandenburg class
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1652631519014.jpeg
Weissenberg, in Turkish service
and on land, here at Liege before WWI
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Technology was there. Application of it was not done. For tanks early in the War, the largest single cast was this
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the M3A1 cast upper hull, which was soon surpassed by the T1 Heavy.
The M3 Turret above, that Ring Diameter similar to the later British Cromwell, with a three man turret
 
Castings usually aren't as strong as rolled plates, but (once you have the technical knowhow to make them big enough[1]) remove pr massively reduce the need for forming, cutting and welding all of which can reduce overall strength, create local weakpoints and take time [2].
[1] see Somua S35 for a good example of a decent cast tank that suffered from a one man turret. While political preference for the smallest possible crews played an important part, French casting technology though world class was about at its limit. Even if a two man turret was wanted, it may have been a step too far in the 1930s, and 1940 was too late. There was at least one French medium with a 2man turret but I'll have to check if it was cast.
[2] Big castings need carefully controlled cooling to avoid distortion, cracking and metallurgical problems like excessive brittleness or low hardness. It can take days to do properly, but the actual labour hours overall can be less than welding forming etc even if the total number of hours elapsed is the same.
Actually, smaller casting is way harder than larger casting. As you start getting into the problem of miniaturization, ie precision and Cooling time.
 
Basically in the 1950s for most combatants...
Of course our good old friends, the Russians, were still using cast homogeneous steel armour to produce the turrets of their comedy T-72 for… well, forever. To be fair, they have added various bits and pieces over the years to try and improve things, ERA, rubber sheets and what now looks like bed frames. Bless!
 
Actually, smaller casting is way harder than larger casting. As you start getting into the problem of miniaturization, ie precision and Cooling time.
True. Small castings are very tricky. I saw some very impressive titanium 3D printed items a few years back which might provide an alternative.
I suspect the big fortress turrets etc were relatively easy shapes to cast because they are fairly symmetrical, so not so much risk of warping, but also the kind of thing you can cast very thick to get sufficient strength without fancy alloying elements.
US casting technology as used on the Lee was very good, but the Somua S35 was mid 30s technology - hence the body cast in a few pieces and assembled using gudgeon pins [1].
[1] worth responding just to use the word gudgeon.
 
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Let your dreams go wild.
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The saddest thing about low recoil 105 NATO and 120 is that the French 105mm F2 cannon became pretty much obsolete overnight. Understandable for a 1971 weapon I guess, but France really took too long to get the AMX-10RC turret in service.

Also in hindsight I kinda feel that what really killed AGS/MPGS was the program being stopped and restarted so many times. The US should just have stuck to the early 80s proposals in the interim to have the actual capability, and select a successor later.
 

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Acually I do not. I just go with the good old "mhhh, looks good." aproach.

But interesting, when did the curved shape design get abandoned?
Basically in the 1950s for most combatants...
Of course our good old friends, the Russians, were still using cast homogeneous steel armour to produce the turrets of their comedy T-72 for… well, forever. To be fair, they have added various bits and pieces over the years to try and improve things, ERA, rubber sheets and what now looks like bed frames. Bless!
Usually when composite armor layers were adopted, so in the 1960's to the 1970's for most nations. The Soviets were limited by budget so they couldn't really abandon them until after the Cold War ended, but a summary of this switch to welded turrets for the USSR and Russia is found here.

I also made a separate post about the history of cast tank turret armor. A lot of the technology likely came from cast steam locomotive beds, which is why most of the cast tank turrets have been produced in locomotive foundries.

Large German casting, 1890 Brandenburg class
Those I think were riveted, based on the more modern photos. But you can see a surviving example of the cast fortress turret at Fort Copacabana, with a cast twin 12" gun turret (it's probably one of the largest single-piece cast turrets made).

True. Small castings are very tricky. I saw some very impressive titanium 3D printed items a few years back which might provide an alternative.
I suspect the big fortress turrets etc were relatively easy shapes to cast because they are fairly symmetrical, so not so much risk of warping, but also the kind of thing you can cast very thick to get sufficient strength without fancy alloying elements.
US casting technology as used on the Lee was very good, but the Somua S35 was mid 30s technology - hence the body cast in a few pieces and assembled using gudgeon pins [1].
[1] worth responding just to use the word gudgeon.
Actually the largest Gruson turrets (the twin 40 cm gun turrets) were cast in multiple pie-shaped sections and assembled together, so those were asymmetrical. More specifically the turret sections had this form:
Armorprofile.png

Source (Page 120)
And looked like this:
Armorsideview.jpg

Source (Page 38)
That slot in the side is for a key that connects 2 armor plates, avoiding the weakness and danger of rivets when struck, and the shape meant that any impact would only push the wedges tighter together. Welding would be stronger, but anything with a thickness measured in meters is... probably a pain in the ass to weld.
 
Does anyone know from the top of their head the Sherman tank variant that would be best placed to stop T - 34 / 85s?

Would a Sherman Easy Eight with their 76 mm gun be able to do so or would they need different ammunition? Just reading a book on the Korean war atm.
 
Does anyone know from the top of their head the Sherman tank variant that would be best placed to stop T - 34 / 85s?

Would a Sherman Easy Eight with their 76 mm gun be able to do so or would they need different ammunition? Just reading a book on the Korean war atm.
You might find this of interest:
and this:
 
You might find this of interest:
and this:
Thanks heaps :).
 
AJE that's a really good page. The tank hull being quenched is very impressive and I like clever features like the fortress turret segments that seal better when hit.
It's easy to forget that until electric welding replaced gas welding, welding was rightly considered an unreliable option. Hence curiosities like rivetted steel and lockbar steel pipes being used into the 1930s.
Add in that bad welding creates weak points and that welding thick sections often means post-welding heat treatment. Now rivetted and bolted armour makes a lot more sense, and the ability to cast thick sections and complex structures looks like a much better option.
 
Could similar vehicles be fielded by UK USSR USA as ATGM armed modern tank destroyers, maybe lower silhouette, portable light and decent speed
 
Could similar vehicles be fielded by UK USSR USA as ATGM armed modern tank destroyers, maybe lower silhouette, portable light and decent speed
We talked a little about this a couple of months ago I think.

- Claymore drew a really good drawing of a Ferret Scout Car modified into a tankette and anti tank missiles for the British.

- The USSR in otl had the BMD-1, which could be dropped via parachute with the crew already in the vehicle.

- The US is currently designing the Ripsaw, originally meant as a "drone tank", but has a manned variant that makes it a tankette.
 
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