Welcome to the WWII Forums! Log in or Sign up to interact with the community.

Cast Turrets and hulls...

Discussion in 'The Tanks of World War 2' started by Hoosier phpbb3, May 30, 2007.

  1. Hoosier phpbb3

    Hoosier phpbb3 New Member

    Joined:
    May 11, 2005
    Messages:
    904
    Likes Received:
    1
    Location:
    Bloomington, Indiana USA
    via TanksinWW2
    The United States utilized castings to produce turrets, transmission-covers and hulls on various models of the Sherman.
    The M3A1 Lee medium tank employed a cast upper-hull which was more 'shapely' and better angled and sloped than the riveted hull of the M3... not to mention being a much-safer tank for the crew as as well.

    This tank was built in small numbers--300--from Jan to June 1942, serving mostly as training and test-bed vehicles in the US. (At least one vehicle made a cameo apperance in the opening scenes of the 1943 move "Sahara" starring Humphrey Bogart.)

    Were castings more difficult, costly and time-consuming to produce than welded or bolted componets? Why did the British persist with building riveted turrets, such as Cromwell, and Crusader?

    For example:
    An early use of a cast-turret is present on the British M3 Grant. Was economy a factor in this decision? If so, I'm curious about the T-34... did it not employ a cast-turet fromm it's inception?

    Is a cast turret inherantly stronger than a welded turret such as employed on Tigers, Panthers and MkIVs?
    Thoughts?

    Tim
     
  2. Christian Ankerstjerne

    Christian Ankerstjerne Member

    Joined:
    Jan 20, 2004
    Messages:
    2,801
    Likes Received:
    10
    Location:
    Denmark
    via TanksinWW2
    Cast steel is softer than rolled steel, thus requiring more steel for the same protection.
     
  3. Hoosier phpbb3

    Hoosier phpbb3 New Member

    Joined:
    May 11, 2005
    Messages:
    904
    Likes Received:
    1
    Location:
    Bloomington, Indiana USA
    via TanksinWW2
    Chris:
    Very interesting comment. I'm not a student of metallurgy... but I would have assumed the opposite to be true.
    I thought different base metals are added before the "pour" to improve tensile strength, and other properties of toughness as desired. Is it not possible then to temper a cast piece in fire?
    The United States had the advantages of a robust steel industry already in place. Why would they strive to produce an inferior product?
    What would be the advantages then to casting in the first place if the result would add heavier-weight to the driveline with no improvement in protection?

    Tim
     
  4. markvs

    markvs New Member

    Joined:
    Dec 31, 2006
    Messages:
    41
    Likes Received:
    0
    Location:
    new zealand
    via TanksinWW2
    It is much easier, engineering wise to make flat steel plates, and then use them in any construction.
    That being said, a single piece unit is always stronger than a multi piece unit.
    an assembly is only as strong as its weakest part, generally rivets, in this case.
    In terms of easier to make, then I'm not entirely sure. Castings require a lot of work before machining can occur, but don't need the larger number of holes or whatever to assemble them.
     
  5. JCalhoun

    JCalhoun New Member

    Joined:
    Sep 7, 2004
    Messages:
    1,911
    Likes Received:
    0
    Location:
    Mobile, Alabama- Heart of Dixie
    via TanksinWW2
    On the Shermans, the welded tanks were made by companies who didn't have access to large casting facilities. It was a matter of making mass production easier.
     
  6. Ricky

    Ricky Well-Known Member

    Joined:
    May 10, 2004
    Messages:
    11,974
    Likes Received:
    105
    Location:
    Luton, UK
    via TanksinWW2
    And in British Industry at the time there were only a few companies who were set up for making large castings, and they were generally railway locomotive works, and were typically the locations where Matilda tanks (for example) were produced. We just didn't have enough large-scale casting equipment to mass-produce our standard medium tank with cast turrets or hull.
     
  7. Christian Ankerstjerne

    Christian Ankerstjerne Member

    Joined:
    Jan 20, 2004
    Messages:
    2,801
    Likes Received:
    10
    Location:
    Denmark
    via TanksinWW2
    Hoosier
    I'm by no means an expert myself, but that is what I've read. If you look at the tolerences for cast and rolled steel, rolled steel has the highest tolerences.
     
  8. lynn1212

    lynn1212 New Member

    Joined:
    Apr 14, 2005
    Messages:
    351
    Likes Received:
    1
    Location:
    upstate NY USA
    via TanksinWW2
    cast vs built up

    castings are better if you can make large ones for several reasons. its faster and cheaper to cast one large part that it is to build the part from smaller peices. at the time welding still had problems with distortion and heat stress. rivets or bolts are unable to evenly share impact loading which leads to cascade failures.
     
  9. Ebar

    Ebar New Member

    Joined:
    Apr 27, 2004
    Messages:
    2,006
    Likes Received:
    1
    Location:
    On a space station in geosynchronous orbit above y
    via TanksinWW2
    Re: cast vs built up

    Is it? I'm not an expert on casting or the steel industry in general, but I could see were there would be potenially complications. I would guess the tooling up before you start casting takes longer. Although the steel can be poured in a minute or two how long do you have to leave it to cool? Hours? Days? Your certainly for casting your taking about a dedicated factory, whereas a turret made out of flat steel plates could be made in really any factory.

    Certainly a cast turret and hull should have advantages over a welded or rivited one, but those advantages might not extent to production.

    I maybe completely wrong, just throwing thoughts out there.
     
  10. FNG phpbb3

    FNG phpbb3 New Member

    Joined:
    Feb 22, 2005
    Messages:
    1,359
    Likes Received:
    0
    Location:
    Manchester, UK
    via TanksinWW2
    american tanks were designed to be made by car and heavy machine manufactorers on production lines.

    As such the designs had to be simple enough to implemented with existing lines and equipment rather than supply each factory with custom steel casting facilities and molds

    FNG
     
  11. Boba Nette

    Boba Nette New Member

    Joined:
    Feb 17, 2004
    Messages:
    3,142
    Likes Received:
    0
    Location:
    Chicago
    via TanksinWW2
    A bit of trivia.At the time,the cast hull of the M4 was the largest peice of cast armor ever made.6,281 cast hull M4A1 Shemans were produced.
     
  12. Oli

    Oli New Member

    Joined:
    May 20, 2005
    Messages:
    1,569
    Likes Received:
    0
    Location:
    Scunthorpe, UK
    via TanksinWW2
    Re: cast vs built up

    Manufacturing a casting is easier overall. You need skilled labour to make the master and then you can produce mould after mould from the master and just pour steel into it. Once cooled the casting can be put on a machine to have the requisite faces machined flat and holes drilled where required.
    Whereas welding requires skilled labour to do each separate weld, and armour requires especially skilled welding - just ask how many fully "coded welders" there are (i.e. those qualified to weld all types of metal). And then the welds have to be checked and certified. Then the welded components have to be checked for alignment before maching and drilling can take place.
    It's standard practice in the engineering industry to reduce welding as much as possible. It adds cost and complication.
     
  13. Grieg

    Grieg New Member

    Joined:
    Feb 25, 2005
    Messages:
    2,625
    Likes Received:
    1
    via TanksinWW2
    AFAIK the Germans were the only ones set up to produce very large RHA plates. (rolled homogenous armor). In general RHA is superior to cast steel for armor protection(though the difefrence isn't huge, if the cast steel is produced carefully)). If RHA is riveted it loses some of it's advantages as rivets create weak points. They have a tendency to become shrapnel inside the tank when struck directly. The Germans welded their RHA.
     
  14. Gryle

    Gryle New Member

    Joined:
    Nov 13, 2005
    Messages:
    148
    Likes Received:
    0
    via TanksinWW2
    Cast armour has its own quirks that can cause you some serious problems if you don't have experience with large castings, you can very easily produce some really sub-standard armour. Mind you it isn't terribly hard to mess up rolled armour plate either. For good quality stuff the difference is around 5-10% in favour of RHA. So for around 75mm/3inchish thickness you would only need an additional 5-10mm.

    You can't effectively face harden cast armour, something the Germans were quite fond of putting on their tanks. Casting does allow you to smoothly change thickness and have composite curves, something you can't do with RHA.

    I know one of the limitations on the production if the Australian Cruiser tank was the long time it took to build the mould for the hull, and that some of the early armour castings exhibited temper brittleness and so a series of purpose built heat-treatment ovens was built to anneal and temper the whole hull, the final stage was to drop the hot hull into cold water, I've got a video of that around here somewhere.

    I think it's worth pointing out that once the facilities were setup post war it did seem to be the preferred method for producing many heavy armour components until Chobham/Dorchester, eg turret and bits for the Centurion and Conqueror, hulls and turrets of the Chieftain and Patton series, early Leopard 1 turret, nearly every turret for the Russian T-series.

    Hoosier, the British continued with rivets/bolts because that's what they were familiar with and they weren't sure that welding and the heat stresses that it creates would hold up under fire until they had tested it themselves. I think there were some models of the Cromwell that had welded hulls/turrets.
     
  15. canambridge

    canambridge Member

    Joined:
    Mar 15, 2004
    Messages:
    1,649
    Likes Received:
    7
    via TanksinWW2
    The molds for casting are difficult to produce and expensive as well, requiring time, specialized equipment and extra time. The strength propoerties of cast metals tend to be lower and quality is harder to maintain, especially as cooling times are as much an art as science. The bain of all castings is inclusions, forgien material, and voids, empty areas in the casting. These are difficult to detect or fix once found. It is also more difficult to modify cast sections, they don't generally take well to unplanned drilling so attaching things needs to be planned out ahead of time so you cna add a boss where you want to tap.
     
  16. majorwoody10

    majorwoody10 New Member

    Joined:
    Sep 20, 2005
    Messages:
    1,898
    Likes Received:
    1
    Location:
    ca.usa
    via TanksinWW2
    ive done some small castings in bronze and silver ..i had no idea it could be done with a tank turret ... tho ,when i reflect on the shermans smooth curves it is plain that it is a casting , what else could it be ,pounded into shape with a peening hammer? lol ...silly me...
     
  17. Boba Nette

    Boba Nette New Member

    Joined:
    Feb 17, 2004
    Messages:
    3,142
    Likes Received:
    0
    Location:
    Chicago
    via TanksinWW2
    Not just the turret,but the hull as well.
     
  18. markvs

    markvs New Member

    Joined:
    Dec 31, 2006
    Messages:
    41
    Likes Received:
    0
    Location:
    new zealand
    via TanksinWW2
    I would be very surprised to hear that the cast hulls were tempered (dropped into) cold water as some steels, if treated in that way will crack and thus become unuseable. I guess that would be even worse on such large scale pieces.At work, we used to temper ( quench actually) hot castings in oil,
    As a matter of interest the best oil was WARNING:: :lol: If you are PC. then you wont like this!!
    Whale oil.
    the oil allowed for slower cooling, whuich allowed the metallurgical changes to both take place, and to stress relieve themselves.
     
  19. Gryle

    Gryle New Member

    Joined:
    Nov 13, 2005
    Messages:
    148
    Likes Received:
    0
    via TanksinWW2
    Well the narrator of the film does make a few glaring gaffs, as you might expect from a war time news reel, he does say "sudden immersion in a cold water bath" here is one frame of the film as they pull a hull back out (Not the best quality but what would you expect of a sample of a VHS copy of a print of a 64 year old film), it certainly looks like steam coming off the hull to me, and while it could be another mistake in this case he is backed up by one of the better books I've read on them which says "...exhibiting what was known as temper brittleness. ... the remedy was simple and consisted of quenching the steel in water after in had been tempered."

    So the case of the ACs their armour was, as for other nations I wouldn't have a clue.

    (Edited for speeling :) )
     
  20. CometFan

    CometFan Member

    Joined:
    Apr 22, 2005
    Messages:
    113
    Likes Received:
    3
    via TanksinWW2
    Slightly OT

    It seems the Brits preferred a mix of welding and Casting for the Chieftain tank.
    According to 'Chieftain Main Battle Tank 1965-2003' (New Vanguard) page 7-8 :
    "at first a complex shape of welded plates similar to tht IS-3 was tried but then it was decided to take a step backwards (here follows a brief description of how an IS-2 tank was found in the british sector in Berlin)
    Instead of welded plates, it featured a cast hull front with wll sloped armour and this was copied for FV4201,. Similarly, the turret front of FV4201 was a massive casting, which after a cooling period of at least 12 months, was welded together with the roof and rear turret section of rolled armour plate".

    So high quality cast armour is stronger but more time consuming, expensive and complicated to produce than welding rolled armour plate (which requires highly skilled welders) ?

    Seems to me that the Brits used the best compromise in the Chieftain, but then again : these tanks were not produced in times of war.
     

Share This Page