In 1943, a T-34 and a KV-1 (the #11302 mentioned earlier) were sent to the Aberdeen proving grounds in the United States to undergo testing, and see what technical solutions from these tanks can be of use to the Americans, and what can be done to improve their designs. While the report from these tests is not widely available, another document is: a translation of the summary of the tests obtained by a GRU agent at Aberdeen. This text, especially when taken out of context, provides a very scathing, and generally incorrect view of T-34 and KV tanks. Here are a collection of documents elaborating on this information.
"Comments on the evaluation of T-34 and KV tanks by workers of the Aberdeen proving grounds in the USA, representatives of companies, officers, and commission members.
I. Tank condition
According to information received from the Americans, the T-34, after traveling 343 km, was disabled by the breakdown of the V-2 diesel engine. The Americans are of the opinion that this was caused by a poor air filter on the diesel engine.
The T-34 sent to America had an air filter of the "Pomon" type. This filter was installed on T-34 and BT tanks. If properly cleaned and supplied with oil (in exceptionally dusty environments, this must be done once every 2-3 hours), the Pomon filter guarantees normal engine operation with 79.6% air purity at air dustiness of 1 gram per cubic meter. The filter at Aberdeen was not cleaned [Note: the filter was also not oiled. The Americans wonder why the filter is called "oily" by the Soviets in their impressions], which led to uncharacteristic engine wear.
Starting with 1942, all T-34 tanks have an improved Cyclone filter, which provides 99.4% air purity at air dustiness of 1 gram per cubic meter. This filter also needs cleaning and oiling every 3-4 hours.
IS tanks in development will have an improved air filter, providing 100% air purity at air dustiness of 3 grams per cubic meter, and can operate without cleaning for 8 hours. This filter is designated "Multicyclone".
The Americans insist that the T-34 and KV tanks' plates are hardened shallowly, and most of the armour is soft steel. They suggest that we change the hardening technology, which will increase the armour's resistance to impacts. This opinion has no basis in reality, and was likely caused by poor analysis of the armour.
The armour of the sent T-34 tank consisted of 8S steel. All T-34s are armoured this way. This steel is hardened to high hardness (2.8-3.15 mm on the Brinell scale). The KV tank's armour was medium hardness (3.35-3.6 mm on the Brinell scale).
The Americans take the same approach as us, hardening armour of medium thickness to high hardness and armour over 40 mm thick to medium hardness. Our armour provides greater resistance to impact compared to American armour.
German heavy tanks have armour of medium hardness.
Currently, we are in the process of producing high hardness armour for IS tanks.
Perhaps, when commenting on the tanks' armour, the Americans meant that heavy tanks should have armour of high hardness.
The Americans found that the tank takes on water when crossing rivers, and the hatches leak during rain. The hulls of our tanks are sufficiently watertight to cross rivers. However, the top hatches are insufficiently watertight.
The Americans consider the crampedness of our turrets a weakness. The T-34 we sent had a welded turret. New cast turrets are roomier than old welded turrets. New IS and T-43 tanks have larger turrets, due to the enlarged turret ring. The electric turret rotation mechanisms are indeed insufficiently reliable. A hydraulic turret rotation mechanism is currently in development, similar to American ones. This mechanism is very reliable and comfortable to use.
It is necessary to admit that the muzzle velocity of our medium tank gun F-34 is insufficient, and is lower than that of the American 3" gun. However, the muzzle velocity of the American 75 mm gun on the M3 Medium and M4A2 tanks is also insufficient.
During testing at Aberdeen, tracks of the T-34 tore. The track pins, instead of being guided by the guide, get caught on it and bend. This could potentially be caused by an insufficiently wide guide, or defects of the track metal. On currently produced T-34s, tracks are of much higher quality, the guide has been lengthened, and there are additional guides on the sides of the hull.
The Americans do not like our spring suspension, based on their work with Christie tanks. [Note: the impressions of the suspension are from Christie tanks only, since the T-34 only traveled a very limited distance under the Americans' supervision. The suspension of the T-34 was different from the suspension of Christie or BT tanks]. We consider the reliability of the T-34's suspension adequate, but the T-43 is being developed with a torsion bar suspension.
The T-34 tank has a 15 hp ST-700 electric starter. The KV has two 6 hp starters, 12 hp in total. Currently, both the KV and T-34 are built with a ST-700 starter.
A high power tank starter was first developed here. The Americans have much weaker starters. For some reason, they evaluate our starters as weak.
The ST-700 starter has a series of defects, making its reliability unsatisfactory to us. The IS tank is being developed with an electro-inertial starter of higher reliability.
The KV and T-34 transmissions were a result of continued development of the Christie transmission. This transmission is currently obsolete.
The Americans have a poor opinion of the KV and T-34 gearboxes. They assumed that we copied their A-23 gearbox that was built 15-20 years ago by an American company. This same company built gearboxes for Christie tanks in 1929-1930.
The T-34 and KV gearboxes use a cross-bar and a bevel gear and pinion, transmitting the rotation from the motor. Perhaps the blueprints for our gearbox are similar to the A-23 ones.
Currently, a superior gearbox is used on the KV with 8 speeds (the one sent to the Americans had 5). T-34s built by the Kirov and #174 factories use a new 5-speed gearbox (the one sent to the Americans had 4). Quality of the gears in the gearbox is significantly increased.
X. Friction clutch
The Americans consider friction clutches obsolete. Apparently, even American tank companies no longer use them. They suggest that we replace them with double differentials, like they have on their tanks.
We also consider friction clutches obsolete. IS tanks are being developed with a planet gear, which makes the tank more maneuverable and reliable. All further transmission related work is aimed at transmissions of the planet gear type. This transmission is superior to the American one, which consists of a gearbox of the tractor-automobile type and a double differential.
Additionally, American tractors still use friction clutches. For example, these can be found on American Alice-Chalmers, Caterpillar, and International tanks currently being supplied to the USSR.
As for friction clutches on the KV and T-34, they work reliably, provided they are taken care of.
XI. Overall impressions.
The Americans remark that the tank is produced crudely, absent-mindedly, and with undeveloped technology of certain parts and devices. Significant progress has been made in upgrading the quality of produced tanks. However, mechanisms of American tanks are superior to domestic ones in cosmetic finish and performance.
Overall, Americans comment that their tanks are superior in maneuverability, firepower, speed, ease of use and maintenance, and reliability of construction. While American tanks are simpler to use, but ours have superior combat performance. The combination of armour, armament, and maneuverability is significantly more optimal than the Americans', which is proven by combat application."
CAMD RF 38-11355-1712
Since the above commentary makes it seem like the Americans hated everything about the T-34 and KV, here are the good parts they found:
"The shape of the tanks is loved by all, without exception. The T-34 is especially favoured. Consensus is that the T-34's shape is the best of all vehicles known in America.
Ammunition rack placement is very well liked.
The F-34 gun is very good. It is simple, reliable, and easy to service.
Consensus: the gun sights are the best in the world. Incomparable to any currently known worldwide or currently developed in America.
The Americans love the idea of steel tracks.
The suspension on the KV is excellent.
The diesel engine is light and excellent. The idea of using diesel engines has previously come up, but the Navy uses all diesel motors produced in the USA, and therefore the Army lacks the ability to use diesel tanks.
Both of our tanks can deal with sloping terrain better than any American tank.
Small size of radio stations and their placement inside the tank is good.
...overall tank construction is well though out...
Additionally, from the "Minutes of the meeting on the question of the evaluation of T-34 and KV tanks by Americans", CAMD RF 38-11355-360
"Major-General Ogurtsov speaks:
"The Americans provide incorrect data for muzzle velocity of the guns...they claim that their gun has Vo of 5700 ft/sec, or 1730 m/sec, which seems very unlikely, even given all of its advantages.""
You may notice that the T-43 is mentioned a number of times in this report. Development of the T-43 was cancelled, but many solutions from the project were used on other tanks, such as the T-34-85 and T-44.
By the way, if you ever do come across a full report, give me a shout. I'm very interested in reading it. You'll know it when you see it, it's 650 pages.