Chinese Eye Chieftain

Forum for discussion relating to the Chietain MBT
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John Clarke
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Re: Chinese Eye Chieftain

Post by John Clarke » Thu Nov 28, 2019 8:53 pm

Stephen, Your certainly not disappointing the Chieftain Clan, out standing workmanship :mrgreen:
If Armortek do a re-run, that front and rear plate mod might be a good upgrade.
I had thought of machining the front plate a little to achieve a little more angle myself, but could only see about 2 degrees either side, loosing a lot of armor material in the process.
This is Armortek, not tek so I'll bow out and stay on the original plan.
Keep the great mods coming. and we may all be able to learn something.
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Stephen White
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Re: Chinese Eye Chieftain

Post by Stephen White » Wed Dec 11, 2019 8:38 pm

This one is fighting me every step of the way so far but today we had a meaningful discussion, I hit it with a rubber mallet and now we've at last made a bit of progress. It's not the kit's fault, we just started out on the wrong foot with some less than perfect aluminium brazing. You ought to love all your children without fear or favour but this one is challenging. It''s partly about the complexity of shapes, which is the price of the ballistic excellence of the armour design.

The bow of the toe plate and glacis has finally come clean and given me what I was after. I had several goes with the UV glue as filler to build up the V line, which runs at an angle to the original Armortek shape. It's finally there:

IMG_8794.jpg
IMG_8793.jpg

Turning to the bottom edge of the side plates, first stage was to mill off the overhang. Given that it took three passes on my mill to run the full length, I decided not to muck around with trying to set up the correct angle but simply milled at right angles and achieved the correct angle with a power file and rasp. I then milled the rebate which simulates the weld joint between the side and bottom plates. This is what I started with:

IMG_8798.jpg

and final shaping:

IMG_8801.jpg

To represent this:

IMG_8236.jpg

Lastly for today, the outer sides of the toe plate need the chamfer to be represented:

IMG_8426.jpg
IMG_8792.jpg

Now repeat.

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John Clarke
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Re: Chinese Eye Chieftain

Post by John Clarke » Wed Dec 11, 2019 9:16 pm

Excellent eye for detail Stephen 8)
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Re: Chinese Eye Chieftain

Post by Stephen White » Sat Dec 14, 2019 4:45 pm

One of the more obscure but effective modifications made to British tanks involved the spacing of the roadwheels. The typical British suspension arrangement of six roadwheels per side on three suspension stations was common to Centurion, Chieftain and both Challenger 1 and 2. It's not immediately obvious though, that there is a larger gap between the front and centre stations compared with the centre and rear. This was to facilitate the practice of "half-tracking" or shortening the track to run from the sprocket around the centre and rear stations only, ie roadwheels 3-6. This practice was the response learned from the British experience of mine damage in WW2. Comet crews in particular used this in the latter stages of the campaign in Europe, where nuisance mining of routes was commonplace. The mine usually caused damage to the idler and possibly the front suspension units which immobilised the vehicle unless the track could be shortened to exclude the damaged units. By half-tracking, the mobility could be restored sufficiently to get the tank to a place of repair. To make the process easier, on the post-War tanks, the gap between the front and centre stations was increased.

This was of course not an option open to the Wehrmacht with the overlapped roadwheels of the Tigers and Panther, another reason for my comment on another post that those tanks are over-hyped and not all they're cracked up to be by modern pundits and fans. It's inexplicable to me also why neither Leo 2 or Abrams M1 make use of this feature, whereas the Russian T-80 does.

On Chieftain, the dimension between the mid-points of the front and centre suspension units is 78.812 inches, whereas that between the centre and rear is 74.688 inches. This differential is faithfully replicated on the Armortek Chieftain and was one of the features we picked up when the original was measured up. It's a good example of the attention to detail in the Armortek models, where it matters.


This is the Centurion layout:

now_we_fix_it[1].jpg
now_we_fix_it[1].jpg (53.76 KiB) Viewed 834 times

The Chieftain design:

FV471116 GA of Suspension.jpg

and a half-tracked Chieftain.

79198021_10216170363316519_5330985606195445760_n.jpg
79198021_10216170363316519_5330985606195445760_n.jpg (46.88 KiB) Viewed 834 times

It wasn't a very commonplace practice in the British Army of the Rhine. I probably only witnessed it once or twice in my time on Chieftain and Challenger. The reasons are now lost on me but maybe others with experience may recall typical circumstances in which it was used. Anyway, a long-winded explanation for something which might otherwise be a puzzle.

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Re: Chinese Eye Chieftain

Post by Steve Stuart » Sat Dec 14, 2019 5:47 pm

The Professor of Engineering would probably not approve of this asymetry, but the practical engineer would say that is a very neat fix! Thank you for that piece of insight, that gap has has always niggled me, but I now know the reason, and it makes sense.
Steve

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Re: Chinese Eye Chieftain

Post by John Clarke » Sun Dec 15, 2019 2:21 pm

I knew about "half-tracking" and capabilities, but always thought the placement of the of the front bogies was more to do with compensating for the weight distribution of the frontal armor and stability of a forward pointing main gun. :oops:


Either way, it still looks cool. 8)
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Re: Chinese Eye Chieftain

Post by Stephen White » Sun Dec 15, 2019 3:29 pm

John, the centre of gravity of a turreted tank changes with turret traverse. The spacing of the road wheels overall is driven by the length of track in contact with the ground, which is critical to ride and turning performance. The C of G isn’t material here. The increased gap between the centre and front stations was born out of bitter experience of trying to half-track under fire. The extra four inches makes it considerably easier to manipulate the shortened track between the road wheels.

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Re: Chinese Eye Chieftain

Post by John Clarke » Sun Dec 15, 2019 11:25 pm

I'm probably getting mixed up with the prototypes, P1 etc.
download (1).jpg
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jagdchieftain_002.jpg
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Re: Chinese Eye Chieftain

Post by Adrian Harris » Mon Dec 16, 2019 1:25 pm

T-34 has a larger gap between the second and third road wheels but, given the forward position of the turret and hence the likely CoG, I would have thought it would fall over like a Reliant Robin if you tried to half-track it like that. T-54/55 has the gap between the first and second road wheels, which seems much more usable.

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Re: Chinese Eye Chieftain

Post by Alan.Crawford.uk » Tue Dec 24, 2019 1:45 am

Hi Stephen,

You mentioned "half-tracking" earlier.
I was unable to find an example for the Chieftain, but I found this illustration in 'WarMachines #06 - M1-M1IP-M1A1 Abrams MBT'

PS, I haven't started my Chieftain #41 yet.
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M1 Abrams - Short-Track Mode 3.png
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M1 Abrams - Short-Track Mode 2.png
M1 Abrams - Short-Track Mode 2.png (375.38 KiB) Viewed 512 times
M1 Abrams - Short-Track Mode 1.png
M1 Abrams - Short-Track Mode 1.png (401.37 KiB) Viewed 512 times

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Re: Chinese Eye Chieftain

Post by Stephen White » Tue Dec 24, 2019 8:20 am

Alan, that’s it. It’s one of those skills which tend to be lost in peacetime but which I learnt with the Australians, who’d needed it frequently in Vietnam. Happy Christmas all. Stephen

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Re: Chinese Eye Chieftain

Post by Mark Heaps » Tue Dec 24, 2019 2:49 pm

Challenger 1 and 2 did not have 3 suspension stations like Chieftain. The six roadwheels either side each had independant hydrogas suspension units.
In my 22 years looking after the tanks and other armoured vehicles, half-tracking was an emergency get-you-home repair and not a get-you-back-in-to-battle repair. The tensioner idler had been lost, the tracks were loose with no way to tighten them, and the vehicle had to be driven extremely carefully to avoid throwing a track, until it could get back to a location where a proper repair could be done.
I only saw it done a few times and that was because we had the next recovery tasking come through on the radio. We could not drag the tank back ourselves so it was quickly half-tracked and sent limping back under its own power.

Mark

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Re: Chinese Eye Chieftain

Post by Mark Heaps » Wed Dec 25, 2019 1:37 pm

Oh and I once experienced a CVR(T) being half-tracked the wrong way. ie around the idler and road wheels as the drive sprockets had shattered on that side. That took some skilfull driving and ground appreciation from the driver with only the track on one side being driven. Whether he made it back the whole way under his own steam, I cannot say, but when we had to leave him, he was heading in the right direction.
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