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Gasoline T-34s

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It would not be an exaggeration to say that the V-2-34 diesel engine was the T-34's core feature. This engine gave the T-34 its high mobility. However, not all T-34 tanks had this engine. Quite a large amount of T-34 tanks produced in the most difficult parts of the Great Patriotic War were equipped with M-17T and M-17F gasoline engines. This article will tell the tale of what the M-17 engine was, what the T-34 tanks with them looked like, and what the reason for this replacement was.

BT-7's engine for the T-34

The M-17T V-12 four stroke gasoline tank engine was a derivative of the M-17F aircraft engine adapted for use in tanks. The maximum power of the M-17F (715 hp) was throttled down to 500 hp. Like its aircraft "brother", the M-17T ran on B-70 aircraft gasoline. Before the war, M-17T engines were produced in Rybinsk at factory #26 and installed in BT-7 tanks. The M-17 family also had another member, the M-17L. This engine was used on T-28 and T-35 tanks. It had a higher power (650 hp) and an air starter.

M-17T tank engine.

Since the next generation of tanks (KV-1, T-34, and BT-7M) used the V-2 diesel engine, M-17T and M-17 L engines were removed from production. All specialized tools and equipment necessary for their production were put into long term storage.

The question of equipping tanks with M-17T engines returned with the start of the Great Patriotic War. The decision to install M-17T engines in T-34 tanks was made on July 1st, 1941 with State Committee of Defense (GKO) decree #1ss. This document ordered Krasnoye Sormovo factory #112 to immediately begin production of the T-34 tank. Instead of the V-2-34 diesel, they were permitted to use the M-17T engine. The Molotov GAZ factory in Gorky was tasked with M-17T engine production. The same decree required the People's Commissariat of Medium Machinebuilding (NKSM) to conduct experimental work on adapting the M-17T to work on heavy fuel: diesel or gas oil.

The use of M-17T engines in T-34 tanks was a temporary and necessary evil. The only factory that built V-2 engines was factory #75 in Kharkov. It could not keep up with increased demand in tank production. To solve this problem, the State Committee of Defense signed decree #29ss "On creating backup factories to produce tank diesel engines and on evacuation of tank diesel engine factories" on July 5th, 1941. This decree ordered the evacuation of diesel engine factories deep into the country. Production at new facilities had to be sufficient to satisfy the new KV and T-34 production program. Factory #75 was being evacuated to the Chelyabinsk Tractor Factory, the aircraft diesel plant of the Kirov factory to the UralTurboMash factory in Sverdlovsk, and the diesel plant of the Kharkov Tractor Factory went to STZ in Stalingrad. The decrease in tank engine production as a result of evacuation of the factories that produced them was unavoidable. The shortfall was to be made up with by producing the simpler if less effective M-17T at the GAZ.

First page of the State Committee of Defense decree #1ss.

Recall that the V-2 had a number of advantages over the M-17T:

  • Reduced fuel consumption and therefore greater cruising range.
  • More stable temperature range during operation.
  • Simplicity of service (due to a lack of carburettors or a buggy starter).
  • Reduced fire risk.
The flashpoint of gasoline (the temperature at which enough fumes are produced in order to make an explosive mixture with the air) is -40°С. The flashpoint for diesel is +40°С. The improved fire safety of diesel engines eliminated practically all fires that arose as a result of tank usage.

In addition to that, the use of cheaper and more widely available fuel (either DT type diesel or E type gas oil) had a significant economic benefit. For example, the treasury paid 188 rubles and 50 kopecks for a 100 km long drive of a BT-7 tank on tracks. The same distance driven by a BT-7M tank with a V-2 diesel cost four times less: 42 rubles and 30 kopecks. Such a considerable difference was achieved by using a cheaper fuel and more economic engine.

Adaptation of the M-17T engine to working on heavy fuel was supposed to partially compensate for its drawbacks compared to the V-2. NKSM order #280ss issued on July 2nd 1941 tasked factory #183 with this research. Factory #183 was also tasked with development of documentation for installation of the M-17T engine into the T-34 to pass on to factory #112.

Transplant

Factory #183 got to work immediately and on July 10th informed factory #112 that the blueprints will have to be heavily altered. The installation of the M-17T engine required a new engine bed, engine compartment bulkhead, lubrication and cooling systems, air cleaners, starter, exhaust system, main clutch, controls, electrical equipment, and ammunition racks.

Blueprints for installation of an M-17T engine into a T-34 tank developed at factory #183 in July of 1941.

Factory #183 staged trials of an M-17T engine installed in a T-34 tank in mid-July. The results of summer time driving were not encouraging. The cooling system could not deal with the heat during protracted driving in fourth gear. The oil and water temperature exceeded acceptable parameters. Nevertheless, the blueprints were passed on to factory #112 without approval by the customer (GABTU).

Experimental work to adapt the M-17T for heavy fuel also did not give good results. Trials carried out in August showed that the performance of a T-34 tank with an M-17T engine and a special fuel preparation attachment was unsatisfactory when fuelled with gas oil or tractor kerosene.

Factory #183 was unable to mitigate the drawbacks of the M-17T engine by adapting it to working on heavy fuel. A report written by GABTU specialists indicate that the T-34 tank with the M-17T engine had the following drawbacks compared to the T-34 with a V-2 engine:

  • Cruising range reduced by half.
  • Higher operating temperature.
  • Increased risk of fire.
  • Need for a better trained crew to service the tank. 

As a result, the NKSM and GABTU decided in mid-September of 1941 that the installation of the M-17T engine in the T-34 tank needs work. Due to the evacuation of factory #183 to Nizhniy Tagil, factory #112 was on the hook for these improvements. They were tasked with correcting defects of the cooling system that resulted in overheating of the water and oil in any mode of operation, developing a new 12 V electrical system different from the one proposed by factory #183, developing a compressed air starter together with the GAZ factory, and complete a number of other tasks to ensure the normal operation of the M-17T engine and its transmission in the T-34 tank. Additionally, a list of changes aimed at reducing the fire risk of the M-17T engine was to be developed and submitted to the GABTU and NKTP.

T-34 tank with an M-17T engine on parade on Red Square, November 7th 1941.

Factory #112 partially completed the tasks they were given. The factory was able to quickly set up production of T-34 tanks with M-17T engines. The first such tanks were delivered in October of 1941. Interestingly enough, some of these tanks were delivered to the 128th Independent Tank Battalion and took part in the parade on Red Square held on November 7th 1941.

From sky to earth

One must appreciate the difficult situation that Soviet tank production was in by October of 1941. Factory #75 was evacuated to Chelyabinsk, while STZ and UralTurboMash were only starting to get the hang of diesel engine production. Production of the M-17T engine at the GAZ factory was also not going smoothly. Due to a number of production difficulties and organizational shortfalls, GAZ achieved 20% of quota in August and 14.6% in September. This meant that only 13 complete engines were delivered by this factory.

GKO decree #732ss issued on October 4th 1941 was aimed at dealing with this situation. The decree instructed Chief of the VVS Directorate P.F. Zhigarev and People's Commissar or Aircraft Production A.I. Shakhurin to deliver 900 M-17F aircraft engines for their repair and conversion for installation into T-34 and KV tanks in October-December of 1941 inclusive. The NKTP issued its own order #54 on October 7th, instructing Kirov Factory, STZ, and factory #183 to "immediately begin refurbishment and adaptation of M-17 aircraft engines received from the UVVS to installation into KV and T-34 tanks instead of the V-2". The same decree instructed factory #183 to begin installing M-17T engines into T-34 tanks starting with the first tank produced in Nizhniy Tagil. STZ was instructed to do the same "in such a manner that M-17 engines can be installed in case of an absence of V-2 engines without deviating from the production schedule". 

Some time later, on October 11th 1941, the GAZ was instructed to repair M-17F aircraft engines that had expended their warranty period in aircraft and conversion for installation into T-34 tanks at factory #112.

In practice, only two factories produced T-34 tanks with M-17T engines and refurbished M-17F engines adapted for use in tanks: factory #112 and STZ. Factory #183 was fully supplied with diesel engines. Al T-34 tanks produced by factory #183 in Nizhniy Tagil had V-2-34 engines.

How many T-34 had gasoline engines?

943 T-34 tanks with M-17T and M-17F gasoline engines were produced and delivered from October of 1941 to April of 1942 inclusive. Of those, 632 came from factory #112 and 311 from STZ.

 

1941

1942

October

November

December

January

February

March

April

Factory #112

20

53

83

145

131

150

50

STZ

15

93

109

94 in Q1

-

In this period factory #112 produced T-34 tanks only with M-17T and M-17F engines. STZ produced primarily T-34 tanks with diesel engines and only used the M-17T and M-17F to make up the shortfall. STZ stopped production of T-34 tanks with gasoline engines as soon a supplies of V-2-34 engines became sufficient.

The decision to stop producing T-34 tanks with M-17T and M-17F engines at factory #112 was made by the GKO on March 14th 1942. Production and repairs of M-17 engines at the GAZ ceased. The automotive workshop used for this purpose was refactored out as its own factory and transferred to the NKAP for production of M-105P aircraft diesel engines. NKTP order #268s given on March 15th 1942 instructed the director of factory #112 to "immediately begin preparations for production of T-34 tanks with V-2 diesel engines and transition to production of T-34 tanks with V-2 diesel engines on April 1st of this year". 

Deliveries of V-2-34 engines to factory #112 were supposed to come from the Kirov factory in Chelyabinsk. Factory #112 carried out this order and began to produce T-34 tanks with V-2 engines. The last 50 tanks with gasoline engines produced in March were not completed due a shortage of tracks, and were only accepted by the customer in April.

Drawbacks and mitigations

As mentioned above, T-34 tanks with gasoline engines had a series of drawbacks compared to the tanks with diesel engines. First of all, these were issues with the cooling system. Factory #112 never fully resolved them. T-34 tanks with gasoline engines were fine in the winter due to lower temperatures, but nearly unusable in the summer.

Fire risk was another drawback. Factory #112 mitigated this with a number of changes, including installation of two fire extinguishers (a portable one and a stationary one with nozzles leading to the engine compartment), additional cooling of the engine exhaust collectors, and composition of special instructions including directions for the driver. Nevertheless, the military complained about fires in T-34 tanks equipped with M-17T and M-17F engines mainly due to "flowing of fuel in carburettors". In addition, in cases where the fuel tanks were penetrated by AP or HEAT ammunition, the odds of explosion of the fuel and a fire were much higher in T-34 tanks equipped with gasoline engines than for the tanks with diesel engines.

A destroyed T-34 tank with applique armour and an M-17T gasoline engine.

The military also complained about low reliability of these engines. This was especially true for refurbished M-17F engines (most of these went to STZ vehicles). The most frequent cause of issues with these engines was leaking of oil through various seals in the engine and leaking of water from the cylinder jackets. GABTU military representatives at STZ claimed that "these defects have to do with not entirely satisfactory repairs of M-17F engines and their high wear, since engines arriving at STZ worked a minimum of 500-700 hours in aircraft, some over 1000 hours".

The NKTP gave order #303s on April 8th 1942 to resolve the aforementioned drawbacks and defects and improve the performance of these tanks in summer conditions. This order instructed factory #112 to develop a new cooling system for the M-17T engine to allow for normal function in summer time. Factory #112 and STZ were also ordered to develop instructions to replace gasoline engines in T-34 tanks with V-2-34s. The 1st Department of the NKTP was ordered to "compose and clear with the BTU a schedule to supply GABTU repair bases with V-2 engines including all parts required to replace the M-17 engine and improved cooling systems for tanks where the M-17 will remain by April 18th." 

In conclusion, let us note that despite the drawbacks of the M-17T and M-17F gasoline engines, their use allowed Soviet industry to produce almost a thousand very capable and very sorely needed T-34 tanks which undoubtedly made a considerable contribution to the fight against German invaders in the Great Patriotic War.

Original article by Aleksey Makarov.


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