Ergonomics of the ST-I

The ST-I tank had some fairly interesting innovations regarding the rate and accuracy of fire, especially on the move. Let's see if the ergonomics of the tank supported this objective.

The Soviet ergonomic standards guide requires a standing loader to have 1750-1800 mm of standing space. The height allotted by the ST-I is only 1680 mm, but 1750 mm standing room is a pipe dream: out of all WWII era tanks listed in the guide, only the Churchill comes close with 1700 mm. 1680 mm is superior to all other vehicles in the table. The breech axis is a little high, at 1130 mm, but the gun does not have a horizontally sliding breech like the manual suggests it should for a height of 950-1000 mm or more.

The data for the gunner's seat is not given, but the proportions of the loader's position allow us to overlay the ideal gunner position over the drawing.

Looks like an almost perfect match, with the sight being a tad too high. Unlike his loader friend, the gunner would have found this tank comfortable to use.

Via Yuri Pasholok.

ST-II

"The heavy ST-I tank is a powerful combat vehicle, equipped with a rapid-firing high caliber gun and sufficient armour. This design is an improvement to the previous tank, mostly in the areas of increased accuracy and rate of fire, and has the following novel features:

1. Installation of two guns of identical (medium or high) caliber, and two machineguns (or low caliber cannons). These four guns give the tank unprecedented firepower, increasing its combat value.
2. Two guns provide very high rates of fire when serviced by two loaders, using a special rapid-fire ammo rack (shells and propellant are loaded pointing in the direction of the guns in the turret bustle).
3. The tank can strike a moving target immediately, due to the ability to fire a second shell immediately as the first one lands near the target. This allows for faster ranging in.
4. If one gun is out of action (misfire, semi-automatic mechanism fault, failure to extract, breakdown, loader error, etc), the second gun continues firing, and the tank remains in action.
5. The coefficient of armour, engine power, and weight compared to the gun doubles. Accuracy when firing at moving targets or on the move increases, as aiming is done by one person with the ability to follow up a shot almost instantly. 

The tank surpasses two tanks of identical firepower, as it would not be possible to attain such a high rate of fire and accuracy. All other mechanisms of the ST-II are equivalent to the ST-I.

Engineer Ganin
Engineer Chasovnikov
June 11th, 1945"
CAMD RF 38-11350-396

ST-I

"Existing domestic and foreign heavy tanks have a series of drawbacks in the design of their fighting compartments, suspensions, etc, which lower their combat value. The main drawbacks are as follows:

1. Gun and fighting compartment:
1. Insufficient rate of fire at low or medium calibers.
2. Lack of gun or turret stabilization, making firing on the move difficult.
3. The capacity of ammunition racks is small.
4. Existing large caliber guns fit into turrets with difficulty.
5. Increasing the muzzle velocity of a shell with the same shell mass and gun size is impossible.
6. The position of the commander in relation to the loader in modern tanks has drawbacks. The gun's oscillations, recoil, case extraction, and the loader's work all annoy the commander and distract him from observing the battlefield. Forward vision is limited.
7. The turret gun mount is complicated and brings little benefit.
8. Even if an AA machinegun is present, it is impossible to simultaneously fire upon enemies on land and in air.
9. The issue of effective ventilation is not fully solved, which is important with powerful, rapidly firing guns.
10. Many tanks lack a foot-operated smooth electric or hydraulic traverse mechanism,
2. Hull and suspension:
1. It would be difficult to seal the turret and gun port for underwater driving on heavy tanks.
2. Underwater driving equipment is complicated and unreliable in case of emergency.
3. The road wheel diameter and track position is not optimal on some heavy tanks.

This heavy tank design resolves the aforementioned drawbacks, and has the following novel features:

1. The large or medium gun mount and two coaxial machineguns (or low caliber autocannons).
2. Crew placement:
1. Driver: front hull
2. Commander and gunner: front of the turret
3. Loaders: rear of the turret
   This position of the commander provides superior visibility and a calmer workspace.
3. The turret bustle contains a rapid fire ammo rack. This design works for one piece and two piece rounds (a tandem design with springs). This allows the removal of extra motions from the loading process, drastically increasing the rate of fire.
4. An oscillating spring-loaded centering roller is mounted on the gun guard rail, reducing the loading effort and increasing the rate of fire.
5. In order to boost the muzzle velocity of the shell without changing the propellant or the gun dimensions, a special muzzle attachment is used.
6. In order to stabilize the gun in the vertical plane, which improves gun accuracy on the move, a special elevation mechanism is used. 
7. In order to stabilize the turret, which improves gun accuracy on the move, a special turret rotation mechanism is used.
8. In order to protect the tank from aircraft, one loader has a semi-armoured AA machinegun (low caliber autocannon) mounted above him, with a stock, improving accuracy. When the loader is firing on airborne targets, the commander can continue observing the battlefield, the second loader can continue to load the gun, and the gunner can continue firing on ground targets. A prototype of the design proposed by the author has been built.
9. In order to conveniently rotate the turret, a lever is used, allowing the gunner to use the electric/hydraulic turret traverse mechanism with a hand or a foot.
10. The electric traverse mechanism is of the Ward-Leonardo or Ampledin type. The commander also has access to the traverse controls, allowing him to turn the turret when marking targets.
11. The gun mount method is optimal using a box-like frame, in which the gun carrier is installed. The frame is welded to the turret. This eases gun installation, preventing jamming, etc.
12. A breech-loading mortar can be used to conceal the tank with smoke or shoot fragmentation mines at infantry. The commander can fire signal flares through the mortar barrel.
13. There are three hatches: one above the commander cupola and one for each loader. This ensures that the crew can exit the tank quickly, and that the commander can continue working when the AA machinegun is being used.
14. A stabilized commander's cupola (that remains on target when the turret is turned) can be used.
15. Sights:
1. Gun: monocular refracting sight with adjustable magnification and field of view.
2. AA gun: collimating sight, and an iron sight, used mostly to calibrate the collimating sight.
16. In order to clear the fighting compartment of gases, the shell catcher railing is hollow with holes, which suck in the gases using a fan.
17. An intake fan is located above the gun.
18. Air-consuming components in the turret can be fed from the engine compartment.
19. The commander has a rotating chair with a footrest.
20. The loaders' seats are removable.
21. Most of the ammunition is located in the turret, in the rapid fire ready rack.
22. The gun port assembly is reliable and technologically simple, allows for watertight sealing, safe from gases and bullets. 
23. In order to provide watertightness of the turret ring, inflatable hoses are present.
24. In order to provide the ability to drive underwater, a flexible floating hose is available for the engine air intake, or a rigid removable pipe. The exhaust can be fed directly into the water, or into the air through another pipe. When the exhaust feeds into the water, a one-way valve is desirable.
25. When the tank is underwater, the air pressure inside increases to prevent accidental leaks.
26. A hatch in the turret bustle allows removal of the gun.
27. Large diameter road wheels with the tracks resting directly on top of them are used, resulting in a more reliable suspension and higher performance.

Engineer Ganin

Engineer Chasovnikov"

CAMD RF 38-11350-395