Obviously there was a limit to the amount of armour that could be on the tank, due to weight and cost considerations amongst other things. Unlike many other tanks of the era, the t-34's front hull armour was not thicker than the sides or rear of the tank. Why did the designers not move some of this armour to the front of the tank where it was presumably most likely to be hit in combat? Why did they consider a uniform armour thickness to be optimal?
Edit: I am asking about why the Soviet engineers who designed the t-34 decided to have a uniform thickness to the hull, rather than placing more armour frontally and less to the side and rear. I am not asking about the concept of sloped armour, which is redundant given the t-34's armour was sloped at the front, side, and rear of the hull.
Tanks actually aren't more likely to be hit from the front, as combat during the Second World War showed. They are actually more likely to be hit from the side, more specifically on the hull (near center of mass), as it is difficult, in combat conditions, to pick out and then hit specific parts of the tank when the gunsight is at maximum magnification (say, in this case, since the opponent is a T-34, the Panther's TZF 12 or TZF 12a, which had a field of view of 14 degrees at 5x).
The T-34 was developed from earlier experimental models, the A-20 and A-32, which themselves reflected lessons learned in limited fighting with the Japanese in Manchuria in 1938 and 1939 and were meant to replace the BT and T-26 tanks. The designers of these vehicles chose to distribute the armor thickness, both actual and effective, more evenly over the tank than other tank designs; the T-34 initially proved difficult to kill when it was first encountered by German troops in 1941, but this shortcoming was quickly overcome. The sloping of the T-34's armor unfortunately made it cramped inside (limiting the number of opportunities for escape), and reduced the size of turret ring that could be fitted to the vehicle. The fuel tanks were spread out along the lower sides of the hull, instead of being in one central location such as the back of the tank behind a protective firewall (which was taken up entirely by the engine and transmission), and ammunition was stowed right next to them on the floor and up the sides of the hull.
Similar medium tanks to the T-34, such as the 1942-vintage Sherman (50.8 vs 38.1 vs 38.1 mm) or the 1936-vintage Panzer IV (50 vs 30 vs 30 mm), were different than the T-34 in that, to begin with, they had a disparity in absolute armor thickness of the sides and rear of their upper hull when compared to the front. The T-34 had a uniform armor thickness of 45 mm all around, which was sloped from 45 to 60 degrees from the vertical. The sides of the Sherman and Panzer IV were more vulnerable than the front due to other design choices;
The Sherman's glacis was sloped, giving it an effective thickness of about 90 mm, while the sides stayed constant at 38.1 mm, and were always vertical
The glacis of the Panzer IV was increased in thickness from 50 to 80 mm, while the sides stayed constant at 30 mm; the hull armor of the Panzer IV was always vertical
Gun or projectile development nearly always outpaced the ability of any amount of armor sloped at angle to protect a tank, and the "equal armor" scheme of the T-34 fell out of favor almost immediately after World War II. Gunfire caused a cumulative total of about half of U.S. and Commonwealth tank casualties in Europe, Italy, North Africa, and the Pacific. This is a sampling of some of them, as the full table which covers a significant proportion of all losses in all theaters to all causes is too large to type out;
| Belligerent and Location | Total Number of Hits | Turret # | Turret % | Hull # | Hull % | Suspension # | Suspension % |
|---|---|---|---|---|---|---|---|
| US: ETO-FIRST ARMY | 784 | 247 | 31.5 | 408 | 52.0 | 129. | 16.5 |
| ETO-THIRD, SEVENTH, NINTH ARMIES | 284 | 88 | 31.0 | 145 | 51.0 | 51 | 18.0 |
| ITALY | 23 | 7 | 30.4 | 9 | 39.1 | 7 | 30.4 |
| US: Total | 1,091 | 342 | 31.4 | 562 | 51.5 | 187 | 17.1 |
| UK: ETO | 320 | 104 | 32.5 | 166 | 51.9 | 50 | 15.6 |
| ITALY | 24 | 10 | 41.7 | 12 | 50.0 | 2 | 8.3 |
| AFRICA | 31 | 15 | 48.4 | 4 | 12.9 | 12 | 38.7 |
| UK: Total | 375 | 129 | 34.4 | 182 | 48.5 | 64 | 17.1 |
| ETO: US + UK | 1,388 | 439 | 31.6 | 719 | 51.8 | 230 | 16.6 |
| ETO + ITALY + AFRICA: US + UK | 1,466 | 471 | 31.1 | 744 | 50.8 | 251 | 17.1 |
65 hits examined on "recovered" and "unrecovered" Canadian tanks in Normandy;
| Hit Location | Front | Sides | Rear | Total |
|---|---|---|---|---|
| Hull | 7 (10.8%) | 24 (36.9%) | 6 (9.2%) | 37 (56.9%) |
| Turret | 12 (18.5%) | 12 (18.5%) | 4 (6.2%) | 28 (43%) |
| Total | 19 (29.2%) | 36 (55.4%) | 10 (15.4%) | 65 |
Sources:
Coox, Alvin D., L. Van Loan Naisawald. Technical Memorandum ORO-T-117 Survey of Allied Tank Casualties in World War II. Baltimore: Johns Hopkins University Operations Research Office, 1954.
Copp, Terry, ed. Montgomery’s Scientists: Operational Research in Northwest Europe, The Work of No.2 ORS With 21 Army Group June 1944 to July 1945. Waterloo: The Laurier Center For Military Strategic and Disarmament Studies, 2000.