A13 Cruiser, Covenanter, Crusader tank construction

Discussion in 'Weapons, Technology & Equipment' started by Topfmine, Dec 20, 2019.

  1. Topfmine

    Topfmine Active Member

    Not being able to find a lot in the archives at Bovington on tank construction of these models especially the A13 Cruiser, it seems that the plate assembly to form the hull and turret was most probably a riveted construction studying the photos and line drawings, I assume that some form of frame work was used to rivet the armour plates to, just like the WW1 MkIV or French Renault FT tank. I noticed on the bottom of the Covenanter that the floor plan is made up of 6 large plates, all riveted in place, i assume to a type of frame work, made from flat strips, angle or T section.
     
  2. Don Juan

    Don Juan Well-Known Member

    The general construction of these models is a layer of D1 Steel (IT 110) riveted to a frame, with another layer of armour (IT 70, 80 or 100) bolted on to the D1 Steel. When you look at a photo of e.g. a Crusader, the knobbly bits are bolt heads and not rivets. The one exception is that the under layer of D1 steel on the Crusader and Covenanter is put together by welding, but the outer armour is still bolted on.
     
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  3. Robert-w

    Robert-w Banned

    It was found in WW1 that an AP round striking a rivet head could convert the rivet into a red hot missile.I presume that is why the outer armour was either welded or bolted in later designs
     
  4. Topfmine

    Topfmine Active Member

    Ahh, so thats how they done it. Thanks for your help.
     
  5. Don Juan

    Don Juan Well-Known Member

    Sorry, I need to amend my above post thus:

    The general construction of these models is a layer of D1 Steel (IT 110) riveted to a frame, with another layer of armour (IT 70, 80 or 100) bolted on to the D1 Steel. When you look at a photo of e.g. a Crusader, the knobbly bits are bolt heads and not rivets. The one exception is that the under layer of D1 steel on the Crusader and Covenanter turrets, which is put together by welding, but the outer armour is still bolted on.
     
  6. Chris C

    Chris C Canadian researcher

    Were bolts used because, I gather there was a relative shortage of trained welders, so the choice was "rivets or bolts"?

    Also, are these two different sized knobs on the Archer at Bovington both likely to be bolts? I also note some holes near the bottom where apparently some bolts have been removed or lost over the years. If I'm interpreting it correctly, there is a bit of a recess for the head of the bolt.

    edited PS - would any rivets used have round heads?

    Circled.jpg
     
    Last edited: Dec 23, 2019
  7. Dave55

    Dave55 Atlanta, USA

    I am not being flippant but I thought all rivets had round heads.
     
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  8. Chris C

    Chris C Canadian researcher

    Well, I don't think anyone has ever accused me of an overabundance of common sense.
     
  9. Don Juan

    Don Juan Well-Known Member

    The whole riveting/welding saga is a bit involved, in that a shortage of welders is one of the excuses that the tank manufacturing firms used to continue using riveting, but the advocates of welding argued that this shouldn't have been an issue because training welders was a fairly quick and easy process. A more substantial argument was that welding took up more floor space than riveting, so that any production time saved by switching to welding was negated by a reduction in though put. Then there were arguments about just how big an improvement welding constituted, with the view being expressed by some that there was only a weight saving of about 5%, so was there really any point in switching?

    So there were a lot of niggling arguments, most of the manufacturers didn't really want to switch, and nobody important at the Ministry of Supply was prepared to make the big call of ordering a universal switch over.
     
  10. idler

    idler GeneralList

    To what extent was it an issue with the unions?
     
  11. Don Juan

    Don Juan Well-Known Member

    I've not seen any documentation to suggest the unions had any influence on this, but then I haven't been looking for it! Generally, the influence of the unions on tank production appears to have been minimal from what I have seen, but it's possible that if I looked into one of the Ministry of Labour files I might get quite a different viewpoint.

    That said, the few strikes that I have seen documented tended to be wildcat rather than union organised. There was also the general principle that Stalin wanted British war production to be as efficient as possible, so the CPGB were going round British factories aggressively suppressing any Trotskyist or anarchist trouble making.
     
  12. Robert-w

    Robert-w Banned

    Only after mid 1941
     
  13. Dave55

    Dave55 Atlanta, USA

    Weren't there some work stoppages or slow downs by union stevedores at the docks? Did they create any raw material shortages for tank production?
     
  14. Chris C

    Chris C Canadian researcher

    Funny thing about 5% is that while 5% less weight might not have made a huge difference in tank performance, I'd have thought it a worthwhile savings in materials.
     
  15. Robert-w

    Robert-w Banned

    Possibly but there are many factors for example did it use more or less energy? If you are using oxy acetylene welding torches what does it cost, if arc welding how much coal is burnt to produce the electricity? Is this more or less than the energy a riveting process uses? Which is quicker? What are the implications for quality control? How easy is it to inspect welds? What is the likely rejection/reworking rate? - and so on.
     
  16. Don Juan

    Don Juan Well-Known Member

    The big thing is that this 5% weight saving could all go into an increase in the frontal armour by 10 to 25mm, so it could be very significant. There are other advantages to welding, such as better resistance to HE, easier to waterproof for wading etc., but these weren't necessarily visible to the tank manufacturers. What happened in real life is that the manufacturers themselves started to become enthusiastic about welding, starting with BRC&W. The first big manufacturer that embraced welding was Vauxhalls, who were quickly followed by Leylands.
     

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