Landships II

Here's what I have, from Hunnicutt's Firepower (referring to tests on the Mk VIII) and an image of the FCM 2C cupola downloaded years ago, origin unknown. Hunnicutt is pretty self-explanatory.

One thing to note is that the various online comments I've found all say that the cupola consisted of two contra-rotating concentric cylinders furnished with narrow vertical slits. While this may have been the case for the French Char 2C (though I have no evidence one way or the other), the diagram in Hunnicutt shows that this was certainly not the case for the experimental Mk VIII. An internal stationary cylinder with large vision ports apparently filled with thick glass is surrounded by an external rotating cylinder with narrow vertical slits. Only one cylinder rotates. Frankly, this seems far more likely to have been the case for the French device too, as having both cylinders rotating would have been absurdly complex (and hazardous for the observer, unless there was a third internal - stationary - cylinder patterned after the American one).

Thank you - I knew someone on the forum would know.

I have plans for a Landships II article on the FCM 1A, can't waste a perfectly good video.

I'd guess FCM probably shipped a complete cupola to the Americans - there was a lot of technology sharing between the Allies at the end of

WW1 and, it seems, into the 1920s.

Regards,

Charlie 

Hah, I've got that issue and had forgotten the mention of the stroboscopic cupola!For whatever reason, the Americans must have changed the design (perhaps to reduce its complexity).

The factory photos and drawings of the Char 2C show the outer metal cylinder with view slits mounted on top of an internal cupola frame with thick armored glass.

Not necessarily - Guy François was writing about the FCM 1A and he may well have been describing the cupola fitted to that tank. He did not say that the same design was fitted to the

FCM 2C - just that stroboscopic cupolas were fitted to the 2C. It seems to me that the statements of Guy François and Steve Zaloga are not incompatible but the text of the article should

be modified to reflect this.

Nice to know that the forum is being looked at by real experts.

Regards,

Charlie

Here's a couple of images to show how the vision device on the Char 2C worked.

Charlie:

I've contacted you off-board about using the pics.

Here's another thought about the photo of the Char 2C cupola. The spacing on the slits on the outside and inside of the cylinder appear to be different. Maybe the outer cupola assembly actually consists of two layers, a fixed cylinder and the other a rotating cylinder. The separate inner frame has armored glass to protect against any spalling.

I took a quick look at the booklet on the Char 2C by the Saumur museum and noticed that there is a write-up on the operation of the Stroboscope. My technical French is getting rusty, but here's a quick translation. I don't think it settles the issue of the construction of the device, but maybe it contains useful details:

The Stroboscope

The combat experience of the first tanks, and especially the FT 17, highlighted the danger posed by vision slits in the hull or turret armor to the face and especially the eyes of the crew members not only from direct hits but mostly from fragments detached from the inner face by nearby hits. The first precaution against this danger was to give the crew a protected face mask formed of loose chain mail that allowed observation while still attached to the helmet. The Char 2C incorporated initial protection afforded by the design itself . The cylindrical cupola is perforated with large openings. It is topped by a circular cap provided itself with narrow vertical slits and which rotates on an axis more than about 300 revs / minute with an electric motor at the top of the turret . The principle of retinal retention is such that the crew sees the landscape in a continuous manner as through a slit or an episcope, while being protected by the turret and fairing. Only an unlucky blow, always possible, can reach the crew. The stainless steel cylinder, 30 mm thick, was perforated by 45 vertical slits 2 mm wide (over 2.5 mm they would permit the passage of steel armor piercing rounds) that could rotate around its axis. A second cupola fitted in the interior had 7 large rectangular windows of triplex glasses. This cupola was fixed relative to the first. When the outer cupola rotates at a sufficient rate, 250 to 300 revolutions/minute, the interval of time between the conjunction of two consecutive slots to the observer is less than a 1/10th of a second, so that the view of the external object appears to the eyes of the observer to be continuous (in fact the human eye retains that impression for a duration of 1/10th of a second). So that the observer has depth perception, it must offer binocular vision, that is to say, his eyes must each receive a view of the external objects . Therefore the vertical slots are arranged in a particular way in 9 groups of 5 slots. The structure under the two cupolas has three horizontal slots for a fixed observation. A screw controlled by a handle located in the turret allows during the approach march before reaching the enemy, to raise the assembly for ventilation of the turret to improve and to facilitate direct observation .