M70A2 Krueger MBT, Gulf War, 1991

[Jakko]

What are ya going to do with the main gun mate?
Going to upgrade to the M256 120mm ?

Yes, it will have an M256 gun from an old Tamiya M1A1 kit.

Guy there the same gun ..M256 is just the US designation for the Rh-120 L44.

I think there are some manufacturing differences, probably in order to suit US methods and tooling. Chances are they converted most measurements to US customary units, for all I know — they seem to feel a need to do that kind of pointless thing

This was repeated in the famous Vickers 105mm L7 gun.  The British used one version and the Americans another.  The most obvious difference was the fume extractor.  The British version was symmetrical, the American version was not.

They're also different on the inside of the turret: the British L7A1 has a squared-off breech with a horizontally sliding block, the American M68 has an almost cylindrical breech with a vertically sliding block. (The L7A3 fitted to Leopard 1 is like the L7A1 but has the rear part of the top of the breech cut off at an angle, so it won't hit the turret roof at full depression.)

There are, I don't doubt other examples but they are the two that immediately spring to mind.   

Hell, they even managed it with Bailey bridges ... A British invention, designed to Imperial measurements. The Americans start making them too, and because of different engineering practices, you can't build a bridge using parts from both countries — they just won't fit together properly. For this reason, the British kept their Bailey parts painted in SCC 2 (a milk-chocolate brown) even though that had been replaced as the standard colour for Europe in early 1944, while American parts were finished in US olive drab: easy to tell by colour which parts would fit together and which won't.

The Americans weren't the only ones doing this, of course. The UK redesigned the FAL in Imperial measurements for manufacture in the UK, Canada and Australia to produce the L1A1/C1A1, resulting in some parts not being interchangeable with "metric" FALs, and you can use the magazine from one in the other, but not vice versa (I always forget which, though).

Yeah I know it's weird how the USA live with feet and inches but the military have been using metric since just before the Vietnam War.

NATO land forces went metric mainly because they expected to do their fighting in Germany and because the majority of NATO countries were not the USA and UK. American gun calibres (other than small arms) were changed to metric during the Second World War, because most of the USA's artillery could trace its lineage to French guns acquired during the First World War, and of course those were 75 mm, 105 mm, 155 mm, etc. This is why (for example) the M4 medium tank had a 75 mm gun. However, the US at the time also used a bunch of weapons designated in inches, but the decision was taken at some poont to reduce confusion as to which was larger by designating them all in metric. Which means that, for most of the Second World War, it's correct to refer to the 8-inch howitzer M1, but the exact same weapon used in Vietnam was called the 203-mm howitzer M115.

[Wardukw]

Yeah it's easy to sort with the big guns as yep alot of early American guns and howitzers were of French origin but crew served weapons were even thru the Korean conflict still being called by the same thing they had since WW1.
The Brits had the Lee Enfield .303in/7.7mm rifle and machine guns..the US had .30cal everything and everything was called a .30 cal be it a M1 Gerand..M2 Carbine ..1908 Springfield 30.06 ..freaking love that rifle by the way and still regret selling that.
Having many friends in quite a few different militaries around this planet I did get to yap with em ..or shooting the poop..not the right word there   
Tankers was one of my targets for knowledge as im a armour modeller and the best info is from the horses mouth and ya do find out some quite useful crap ..course the tank crews don't change main guns ..armourers do that and I did find out something form your neck of the woods matey..Challenger 2..all the hull measurements are all Imperial and the entire turret is metric..yup the REMEs have to carry two sets of tools just to work on it..
One thing which I would not be surprised about is the way the Germans do contracts and Rheinmetall is quite notorious for this and that's when you sign a contract or license what they say.. you have to do ..you can't even sell a Leo 2 tank without their expressed permission even tho you might own it ...pretty damn sure the Rh-120 would be no different.

[PR19_Kit]

Hell, they even managed it with Bailey bridges ... A British invention, designed to Imperial measurements. The Americans start making them too, and because of different engineering practices, you can't build a bridge using parts from both countries — they just won't fit together properly. For this reason, the British kept their Bailey parts painted in SCC 2 (a milk-chocolate brown) even though that had been replaced as the standard colour for Europe in early 1944, while American parts were finished in US olive drab: easy to tell by colour which parts would fit together and which won't.

As an aside, the very first piece of a Bailey Bridge, the prototype section indeed, is currently part of a car park barrier about a mile from my house. The company who now builds such bridging sections, Mabey & Johnson, have their factory in Lydney, where I live, and they also had one of my employer's test systems too. Needless to say they had a VERY fast service response time! 

Here it is, still being useful.

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[Jakko]

Challenger 2..all the hull measurements are all Imperial and the entire turret is metric..yup the REMEs have to carry two sets of tools just to work on it..

That's also why the M113-series was not overly popular in the Bundeswehr: fitters had to carry a second set of tools specifically for them, because every nut and bolt was in American sizes. Oh, and come to think of it: Centurion Mk. 7 in the Dutch Army. Those used different threads than the Mk. 5, which was the mainstay in the 1960s. Spanners would have fit, of course, but the logistics problem of having to stock two different bolts for everything was part of the reason why all the Mk. 7s delivered spent almost 100% of their time in mobilisation complexes.

One thing which I would not be surprised about is the way the Germans do contracts and Rheinmetall is quite notorious for this and that's when you sign a contract or license what they say.. you have to do ..you can't even sell a Leo 2 tank without their expressed permission even tho you might own it ...pretty damn sure the Rh-120 would be no different.

That is the German government, though, not Rheinmetall. It has two reasons: Germany doesn't want their equipment being sold to a warring party whose ideals run counter to Germany's, and it also gives Germany the option of refusing a country to sell stuff to someone so that Germany can then sell the same stuff to them instead.

As an aside, the very first piece of a Bailey Bridge, the prototype section indeed, is currently part of a car park barrier about a mile from my house.

That is very cool, and nice they put up a plaque to tell people what they're looking at, too.

Continuing with the model, I also replaced the whole hull rear plate:

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I just copied the kit part in plastic card, though with square upper corners to fit the new engine deck. In retrospect, I should have just cut and filed the unnecessary details off the kit plate and added those corners, it would have been about as much work. The rear lights are from a Tamiya Bradley, with the side glued to the hull filed at an angle so the lights are horizontal relative to the ground. The real MBT 70 had very different tail lights (the same kind as used on the M60 and back to before the Second World War) as well as an infantry telephone on the rear, but my reasoning was that the M70A1 would have gotten the more modern lights that were being used from the 1970s on, like on the Bradley and the real-world M1 Abrams.

The lifting eyes are kit parts, the rest is mostly scratchbuilt from plastic card. The round lids on the engine deck were made from very thin plastic card (Tamiya Pla-Paper that I've had for 35 years or so) with a hole punch for two-ring binders, which produces 6 mm discs. Not recommended for thicker card, as it bends the discs into a curve, but the Pla-Paper is easily flattened again.

On the engine deck, I added antislip texture:

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This is acrylic texture gel, sold for artists, with beach sand sprinkled in. River sand or construction sand is too coarse, while beach sand is much finer (at least in my part of the world), and as I live literally a few minutes' walk from the beach, I've got an unlimited supply of the stuff anyway

At the front of the hull sides, I noticed the MBT 70 had a different profile to the KPz 70. This photo illustrates it quite well:

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The drawing is a scan from Hunnicutt's Abrams, enlarged to 1:35 scale. If you look closely, you can see the KPz 70 (model) hull side comes to a sharp point at the front and angles to about the third roadwheel position before becomign horizontal, but the MBT 70's hull angles down much more steeply to above the second roadwheel. Again, at the time I didn't yet realise this was because of differences between early and late prototypes (and the Americans only built early ones while the Germans built both) so I set about correcting the kit.

(The tape is for the antislip coating, which obviously isn't there yet on the model because this photo was taken before the previous one )

First, I removed a few millimetres of width along the hull side, leaving just the bit of mudguard at the front:

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I then trimmed the underside to be equal with the sponson underside, which is moulded as part of the lower hull, and the upper hull overhangs it:

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I could then add a piece of plastic card of the right thickness (1.5 mm) to make up the lost material, but going far enough forward to reach the point where the MBT 70's angle starts:

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Followed by a sloping piece to make that angled section:

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Then it was just a matter of filling the gap with putty and filing and sanding it all smooth:

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[NARSES2]

Master class 

As an aside and going back to gun calibres we Brits continued to use weight as a means of sizing our artillery pieces long after the rest of the world had moved on    Then at some point, WWI ?, started to use weight for some and inches for others 

[Jakko]

Master class 

Thanks

Then at some point, WWI ?, started to use weight for some and inches for others 

It took until after the Second World War for the British Army to fully change over, probably due to NATO standards. You had things like 6- and 25-pounder guns but also 4.5- and 5.5-inch ones. Oh, and for added fun: a 3-inch mortar that was not 76 mm but actually 81 mm (about 3.2 inches) calibre like everyone else's. But, of course, in that respect the pre-war Dutch army had much the same problem: a kanon van 7 Veld ("gun of 7 Field") was a 7.5 cm gun, for example — I would have rounded that to 8 myself, but hey ...

[Old Wombat]

The RN started the transition to inch bores & calibres at around the turn of the 19th-to-20th Centuries with the advent of the pre-dreadnoughts & the dreadnoughts cemented the change - for main guns, anyway, they were still using 6-pounders & 2-pounders (40mm Vickers machine guns, a.k.a. the Pom-Pom gun) & the like to the end of WW2, though.

[NARSES2]

But, of course, in that respect the pre-war Dutch army had much the same problem: a kanon van 7 Veld ("gun of 7 Field") was a 7.5 cm gun, for example — I would have rounded that to 8 myself, but hey ...

Round to the even number is what I was taught 

[Jakko]

What, so 6.9 rounds to 6 but 7.1 rounds to 8? That makes no sense to me whatsoever What I was always taught is that anything ≥ .5 rounds up to the nearest whole number, everything < .5 rounds down instead.

[NARSES2]

What, so 6.9 rounds to 6 but 7.1 rounds to 8? That makes no sense to me whatsoever What I was always taught is that anything ≥ .5 rounds up to the nearest whole number, everything < .5 rounds down instead.

No sorry what I should have said was that you round point .5 to the nearest even all others are as you were taught.  So 2.5 rounds to 2 and 3.5 to 4. 

[Wardukw]

Jakko mate I'm lovin this build..been wanting someone to go bonkers on something like this 

Oh I can imagine the nightmare we'd have in the army if numbers were rounded up ..8in is 203 mm ..7.5in is 190.5mm ..one thing they absolutely can't do without in the military is accuracy with numbers that why everything is in triplicate.
If it's 8in then it's 8in ..in engineering we never round up or down  ...we cut a couple of mill more then fit it from there..always easier to remove than add especially with 30mm plate ..which I was working with a couple of weeks ago.
Shops tho that's a whole different matter..they always go up here even if it's a smeg under .5

[rickshaw]

Interestingly, the Soviets used to round certain calibres one way or the other to differentiate between the weapons that used those rounds, so 105mm rockets became 107mm supposedly,  Apparently, Stalin ordered them to prevent foulups in the logistic system.

[zenrat]

People come up to the counter at work and ask me for "about five stamps" and look at me oddly when I try to sell them six.

[PR19_Kit]

            

[kerick]

Looking forward to more of this! Have you considered paint yet? Sand or NATO camo? It seemed to be luck of the draw wether a vehicle was painted sand or not. Then later replacement parts could be sand or not. It became a real hodge podge of paint colors.