During the autumn-winter 1941-42. German campaign in the USSR revealed the weakness of many wheeled and half-tracked vehicles in service with the Wehrmacht. Cars skidded in the mud and got stuck in deep snow, and their high-speed engines would not start well in the cold and would break down when driving through the mud. In these conditions, it was necessary to have a compact transport vehicle with a fully tracked propulsion unit and a less capricious motor. Such a tractor was especially needed for transporting anti-tank guns in winter and in slush.
The most interesting thing is that at this moment, unexpectedly for the Germans, Soviet tracked artillery tractors such as "Stalinets" S-65, STZ-5 NATI and "Komsomolets" showed themselves well, which at first were ignored by representatives of the Armaments Directorate of the Ground Forces, since they did not differ in high-speed indicators and were not suitable for "lightning war". But already in winter, tractors of the "Russian type" more and more showed their advantages in cross-country ability in the absence of good roads.
RSO prototype after testing.
After the end of the battle for Moscow, it became clear to the command of the Wehrmacht that the German army was in dire need of cheap and easy-to-maintain tracked tractors with all-terrain vehicles. The "Tank Commission" of the Reich Ministry of Armaments and Ammunition, chaired by Professor F. Porsche, completed the draft design of such a tractor together with the engineers of the Steyr-Dainler-Puch concern, and the project was completed without the participation of specialists from the Armaments Directorate of the Ground Forces … It is difficult to say how the planned litigation between these departments could have ended if Hitler had not suddenly spoken out in defense of the concept of a "Russian type" tracked tractor with a high ground clearance for use in Russian snow conditions. According to some researchers, it was Hitler who gave the new tractor the nickname "Raupen-schlepper Ost" (abbreviated - RSO), which in translation meant something like "tractor heading to the East". All major parts of the new tractor have been borrowed from the well-established Steyr 1500/02 truck. The heart of the tractor was an 8-cylinder V-shaped gasoline engine with a volume of 3.5 liters. and a maximum power of up to 85 hp, the suspension of a simple design seemed to be conceived for production only in wartime conditions.
Copy of RSO factory drawings.
RSO on the Steyr assembly line.
The road wheels were supposed to be made by stamping from sheet steel and did not have rubber tires. Caterpillar tracks with a width of 340 mm (type Kgs 66/340/120) also did not have rubber pads (as in "half-track" tracks) and could even be made of unalloyed steel. The decoration of the cockpit was distinguished by Spartan severity. All this undoubtedly reduced the speed characteristics of the tractor, but made it cheap in mass production and maintenance. But the main thing is that the tractor had a very high ground clearance, which had the best effect on its cross-country ability in mud and snow.
In December 1941, Steyr received an order for a pilot batch of 50 RSO tractors. Already in the spring of 1942, the tractor underwent minor alterations aimed at somewhat simplifying the release. But, despite the improvements made, the volume of production of tractors was largely constrained by the fact that the tractors were manufactured on the same assembly lines as the truck that the Wehrmacht needed very much. In addition, some of the shortcomings of a high-speed gasoline engine when operating on a tractor were found out.
RSOs of various types captured in battles. Eastern Front 1944
RSO tows a 105mm howitzer. 1943 g.
In the summer of 1942, the Kloeckner-Humboldt-Deutz company, connected to series production, offered its version of this tractor, in which there was a successful four-cylinder diesel engine (KHD F4L 514), which turned out to be more suitable for work in harsh operating conditions. In the fall of 1942, a decision was made to further increase the volume of production of tracked tractors, which by January 1943 should have amounted to 2,000 vehicles. For this, the design underwent another wave of simplifications that found a place in the RSO / 02 products (and in 1943 and RSO / 03). The main external difference of this modification was a simplified ersatz-cabin made of wood and sheet steel. However, the plan for 2,000 vehicles by the end of the year could not be fulfilled and in total 1,452 tractors were produced by January 1943.
In the spring and summer of 1943, the issue of using the RSO chassis as a carrier of all kinds of weapons systems, mainly anti-tank and anti-aircraft weapons, was considered. But it turned out to be not so easy due to the small size of the chassis itself and its cargo platform. In August 1943, a tank destroyer entered trials, carrying a 75-mm anti-tank gun RaK 40 on a cargo platform. At the same time, in order to accommodate a long barrel of a cannon, a covered cockpit had to be abandoned in the vehicle, although its remaining lower part was protected by anti-fragmentation armor.
Despite the mass of "childhood illnesses", this self-propelled gun, being shown to Hitler, made a very favorable impression on him, since in theory it combined high power of the shot, good maneuverability and cheapness. Immediately followed by an order for the manufacture of 50 vehicles for military trials and an order for the preparation in 1944 of the serial production of 400 such self-propelled guns per month.
Tests of 75-mm Cancer 40/4 based on RSO. August 1943
Tests of 75-mm Cancer 40/4 based on RSO. August 1943
Back in the fall of 1943, the troops began to install an open 20-mm FlaK 38 anti-aircraft gun in the body of an unarmored tractor. True, in the anti-aircraft version this tractor turned out to be unsuccessful, since its center of gravity was located quite high and the experience was not widely disseminated. In total, 12 (according to other sources - 20) vehicles that took part in the battles of the final period of World War II were converted in this way.
In January 1944, the 75-mm cannon Rak 40/4 was tested at the RSO and the following production schedule was approved March - 50, April - 100, May - 150, June - 200, July - 400. But most likely this plan was fulfilled was not, since 75-mm anti-tank guns were required, among other things, for organizing the mass production of the Hetzer light tank destroyer, which had significantly greater combat capabilities and a relatively low price.
Comparative tests RSO / 3 for the infantry and mountain units of the Wehrmacht.
Two variants of floating tractors under test.
Broken during the battles at the Kursk Bulge RSO with a trailer in the form of a 75-mm anti-tank vehicle RaK 40.
In 1943-44. a reduced version of the RSO for mountain parts was produced and tested, and work was also underway to create a floating version of the tractor, which was built in several prototypes, which were tested in various conditions, but did not go into the series.
But the most interesting thing is that after actually ending its life on the fronts of the Second World War, RSO, like the mythical bird Phoenix, was reborn … in the national economy of the USSR. The history of this revival is no less interesting than that of Nazi Germany. Back in 1943, captured RSOs were studied by representatives of the artillery command and received very high marks. The following advantages of the tractor were especially noted:
- unpretentiousness;
- high cross-country ability;
- the presence of successful widening snowmobile plates;
- ease of maintenance;
- not critical to the type of fuel (gasoline of the highest and low grades).
Layout of the TDT-40 skidder. Onega plant, 1958
One of the first KT-12 skidders manufactured at LKZ. 1947
By order of the OGK NKTP artillery department under the leadership of V. Bera, he carried out a preliminary design of a similar product with a traction force of about 3.5 tons for the ZIS-5M engine (75-77 hp), for use in divisional and corps artillery. However, this product was late, since a tractor with similar characteristics was already mass-produced in the USSR.
It was the Yaroslavl Ya-12 / Ya-13 and therefore the order for a replica RSO for the needs of the artillery command was canceled in 1944.
However, in 1946, they returned to the tractor, when specialists from the Leningrad Forestry Academy arrived in Leningrad under the leadership of B. Kashpersky in Leningrad for the design of a special tractor for skidding forests, which was urgently needed to restore the destroyed industry and build housing.
The analysis of the available chassis for the tractor showed that the RSO chassis, which has a large ground clearance and a simple design, is most suitable for skidding forests, and from the design bureau they requested a draft design of an artillery tractor developed in 1944 from the design bureau to OGK NKTP.
Soon, work on the tractor was transferred to J. Kotin, who returned from Chelyabinsk as chief designer of the Leningrad Kirov plant. The head of the work on it in the design bureau was N. Kurin, who was appointed head of the "tractor bureau" of the OGK LKZ. In 1947, the tractor was registered in the plan of experimental work of KB LKZ under the index KT-12 and on March 5, 1947, the Ministry of Transport Engineering (formerly NKTP) issued an order to complete experimental work on KT-12 and release the tractor for testing in the third quarter of the current of the year.
Tractor TDT-55M "Onezhets" in operation. Moscow region 1994
In the summer of 1947, the task for the tractor was corrected. In particular, it ordered to equip all "KT tractors" with gas generating units of the ZIS-21 type. This was very important, since it was difficult to supply the cutting areas with gasoline or diesel fuel at that time, and wooden blocks were not in short supply here. After a long debate, it was decided to supplement the tractor with a winch to facilitate the collection of the cut logs into a package.
In November 1947, the first five experimental KT-12s with the power plant of the ZIS-21 gas-generating vehicle, with a capacity of 45 hp. at 2300 rpm, were ready and after the parade on November 7, entered the Volosovsky timber industry enterprise of the Leningrad region. But what was good at the front did not immediately find its place in peaceful life. Almost a year passed before the modified KT-12 passed all the tests and was found suitable for operation as a tractor for skidding and timber hauling.
On January 1, 1949, at the Kirov plant, the serial production of tractors of the KT-12 type began, and in 1950, the design bureau also developed its version with a 50 hp diesel engine, but at that time it did not go into series due to the shortage of such diesel engines.
At the beginning of 1951, the production of the KT-12 skidder was transferred to the Minsk Tractor Plant, where it was produced for four years with a gas generator and one year with a diesel engine.
In 1956, the skidder was transferred to the recreated Onega Tractor Plant in Petrozavodsk, where it went into production under the TDT-40 index.
And still in the forests in the vastness of Russia, from its western borders to the Far East, you can find a slightly unusual appearance of the TDT-55M "Onezhets" skidder, which retained many features of an unprepossessing RSO, which was supposed to conquer (and in its own way conquered) the entire Soviet Union until the very last day of its existence. More precisely, the forests of the Soviet Union. However, he conquered with his diligence and reliability in our conditions.
| Type of | RSO / 01 | RSO / 03 |
| Manufacturer | Steyr-Dalmler-Pucri AG | Kloekner-Humboldt-Dcutz AG |
| Release | 1942-1944 | 1944-1945 |
| Engine | Sleyr 1500A | KHD F4L514 |
| Type of | 8-cyl. carb | 4-cyl, diesel |
| Volume of cylinders | 3517 | 5322 |
| Turnovers | 2500 / 300С | 2250 |
| Power, h.p. | 70/85 | 70 |
| Ignition order | 1-3-6-2-7-8-4-5 | 1-3-4-2 |
| Compression ratio | 15, 75:1 | 13, 1:1 |
| Travel speed, mate km / h | 17, 2 | 18.3 |
| Code reserve, km (highway / revenge) | 250/150 | ? |
| Dimensions | 4425 * 1090x2530 | 4425x1990x2530 |
| Clearance | 550 | 550 |
| Track width, mm | 340 340 | |
| Extenders, mm | 660 | - |
| Curb weight, kg | 5200 | 5500 |
| Carrying capacity, kg | 1500 | 1500 |
| Trailer weight, kg | 2000 2000 | |
| Boarding bridge in the cockpit | 2 | 2 |
| Fuel consumption | approx. 90 l / 100 km | 4-9 p / us |
| Fuel volume, l | 180 | 140 |
| Overcoming obstacles | ||
| Slope | 30° | 30° |
| Brod, mm | 670 | 850 |
| Moat. mm | 1700 | 1700 |
