T34 Driver Hatch Thickness

[rexford]

Measurements of the T34 driver hatch on M42 and M43 versions resulted in a 75mm thickness, which would make that area impervious to just about anything the Germans could hit it with except the 128mm and 88L71 at close range. But hits around the edges of the hatch would suffer a resistance loss due to edge effects.

Readings also indicate that some German Pak gunners were instructed to aim at the top of the hatch where the pins were, in the hope that the latches could be broken and the hatch would fall off. This suggests that effective hits against the turret front and mantlet were more difficult to obtain.

A German instruction for 7.62cm Pak gunners against the vulnerable locations of enemy tanks estimates a 100m penetration range against the T34A (Model 41) glacis hull front at 30 degrees side angle, and 500m against the driver plate at 30 degrees offset.

The greater penetration range against the driver hatch suggests about 11% less thickness than the glacis, or a 40mm thick driver hatch.

Since the Germans did not appear to modify their calculations for cast armor, the above would suggest that early T34 had considerably less armor on the driver hatch.

It is also worth noting that the German calculations did not take into account the high hardness nature of T34 armor, which would lower the resistance of a 45mm plate by about 26% when it was hit by 75mm or 76.2mm rounds.

And the Germans did not consider the variable thickness of T34 armor, which varied from 42mm to 55mm during measurements of actual plates and could be responsible to the variable penetration ranges that are reported for the 75L43 and 75L46 guns.

[Holman]

OMG a pin latch grog!

[MikeyD]

These profiles of T34s show the drivers hatches pretty much equalling the thickness of the glacis, up until the late T34-85 (though this may be due to sloppy drawing?).

T-34 cut-away drawings

The initial production M1940 definitely shows the driver's hatch the same thickness as the hull. The German gun's greater ability to penetrate the initial productionm hatch may principally be due to the big cast periscope mounts at the top of the hatch, and perhaps the limited area of the hatch being less able to dissipate the kinetic energy applied.

[thewood]

Are those drawings to scale? How can you read the hatch thickness from these drawings. I used to be a draftsman and I am having a hard time getting a thickness reading out of these.

[MikeyD]

I'm looking at relative thickness. A 75mm hatch would be about a third thicker than the 45mm hull front, which it is in the T34-85. The M1940 has a hatch exactly the same width as the hull. About them being to scale, they're pretty much the factory drawings, i believe. Some sources may be pretty iffy, but these are generally pretty accurate.

[rexford]

Jeff Duquette shared some pictures of a T34 M42 from Aberdeen with measurements of the glacis. Using his glacis measurement and scaling off a photo which showed the glacis and driver hatch thickness, the hatch was about 75mm thick.

We have some other info that suggests that the T34 M42 and M43 glacis was 75mm thick, including German penetration drawings for 88L56 which do not allow penetrations of the driver hatch.

[rexford]

The T34 driver hatches that bulge upwards above the glacis throughout their entire area appear to be 75mm thick, while the earlier driver hatch with a rectangular border and slight indentation from the edges is probably on the order of 40mm or so.