Drezyna K (1936)

Poland TK and TK-S tank rail guide, c50 built

Historical Context

The use of autonomous armoured draisines (Pancerny Drezyna) was looked for in 1919 and shortly after the independence and battles against the invading Red Army. This started with a joint Czech-Polish project, born from the private-ventured Tatra T-18 model tested and ordered in the 1920s. However the the T-18 proved underpowered and lightly armed in case of a bad encounter. Thus, Colonel Tadeusz Kossakowski of the Engineering Department proposed to the general staff in 1931 to "recycle" the now aging Renault FT from 1919 into an armoured draisine, providing it was given the right chassis.

Design started at the Military Engineers Research Institute which power source came directly from the tank itself. Without engine but just a transmission apparatus, it was simpler to manufacture, maintain, while being cheaper, was armed and armoured as per the carried vehicle, and thus did not required much extra training. The other advantage was that the carried tank could be detached at a moment notice to operate autonomously from the armoured train, and provide outer reconnaissance. The program was approved as the "medium rail-and-ground armoured draisine "R" the letter standing for the tank's manufacturer, Renault.

A first prototype was tested in 1932 with the 1st Armoured Train Unit, another in 1933, three three more chassis ordered, until in 1939; some thirty nine Draisine R had been provided. Initial successes after the first tests encouraged broader use, extended to the TK (TK-3) and TKS tankettes, both very cheap reconnaissance tankettes derived from the Vickers Carden Lloyd family.

A different appraich though, as WIBI developed this time just light rail guides and no longer a full rail chassis like for the Draisine R (FT-17). It was essentially a trolley holding the tankette on rails so that it can run on its own tracks. The bogies were just her for additional support. The prototype was built in mid-1932. In August it was showed to the commission under General Wacław Wieczorkiewicz, the same day as the R draisine.

Tests and fixes went on in 1933-35. On April 22, 1936, four more of these were ordered from Lilpop workshops in Rau, as well as Loewenstein plants in Warsaw. The price was only 6,321 slotys per draisine, as compared to 12.400 złoty for the Drezyna R, so half the price. In September 1936, they were adopted by the army as the "TK light armored track and off-road draisine" simplified as "TK and TK-S tank rail guide" (prowadnica szynowa czołga TK i TK-S). In October 1936, 38 serie draisines were ordered. It is estimated today that about 50 were produced before the war broke out in 1939.

Design

The main difference was that for the tankettes, two models were to be used, either the TK and TKS very close together, with differences in engines, transmission and armour design. In order to place on the rail guide, it was necessary to screw extension caps on side horizontal suspension beams. The operation took about 10 min. with a trained crew. The main supporting element was a frame, welded from steel profiles. This frame rested on two standard bogies, using semi-elliptic springs. Inside the frame was a movable spar which supported the tankette's own floor. It was hinged from the rear edge of the frame, lifted by a hydraulic mechanism.

There was an oil crane attached to its front lifting part to lift it through gears and chains, both manually driven. When traveling, the spar was partially raised to manage an even pressure of the guide bogie wheels. When towed by another rail vehicle or second carriage, the tankette was completely raised above the tracks with the guide having two front entry ramps held above the rails by flat springs, folding upwards by chains. The operation could be prformed under fire, from inside the tankette with a small floor hatch behind the driver's seat (15x 40 cm) ensuring a constant air flow to the radiator and to operated the manual oil pump attached to the spar, and rail brake lever.

Anither lever on the oil drain lever prevented the spar from falling down. The brake lever was removable. The tankette was locked on the beam with a wedge, resting on the edge of the floor opening. The tank was resting on the guide bumper at the rear and the crew could get off the guide 1.5 min. The brake acting on the rear wheels was activated to do so, then removed the brake lever and wedge connected by a chain were removed and after unlocking the latch, the girder was lowered by gravity and pump, then moved off the braked guide. It took two minutes to get back on rail, raising the chassis. To enter the frame, the tankette had to drive backwards onto the guide, guided by its side plates until the wedge and brake lever were connected, as well as the pump oil crane to lift the spar.

The draisine was as fast forward as the original vehicle, 46 kph for the TK3 down to the 40 for the TKS. But it had a low reverse speed of 5 kph. In order to change the direction of travel the whole carriage was to be reversed on track. For this, a separate oil-pump lift was used. After the tankette slided off the guide, the operation needed a turntable with lift placed under the guide beam, lifting, rotated and replaced, after which the tankette had to mount it again.

The same principle was applied to move to a parallel track as well. Additional rails were needed to be placed under the wheels like for the Tatra T18. The guides had sprung couplings forward and at the rear to connect all compatible railcars and took place into any armoured train. In a trolley there were colored lights inside the tankette connected by electric cable to the guide socket. Some tankettes were also equipped with a short-range radio station RKB/c, operated by the commander. They were heavenly distributed to armoured trains to ensure at least one radio Draisine R was available at all times.

Draisine K specs
Dimensions (L-W-H)	6.3 x 2.15 x 1.33m, span 3.85 m, wheel 0.32 m
Weight	1.5 t (wit tankette 4.15 t)
Crew	2 (tankette)
Armament	1x wz. 25 7.92 mm (0.3 in) machine-gun
Armor	4-6 (TK-3) or 3-10 mm (TKS)

Combat Use

In 1939, each armored train (except No. 13 and 15) had five TK/TKS tankettes, four of them were draisines, a fifth carried on a flatcar as a reserve in the utility storage section. however, photos of No. 12 showed all five were Draisines TK. By July 15, 1939, the 1st Armored Train Division had 19 of these, the 2nd Division 29 of these, two draisines per platoon, with regulations of 1938 specify at least one of these armored draisine would be equipped with a radio.

The Polish armoured trains mobilized in 1939 each had a platoon of armoured draisines to patrol the track before and behind it and generally was standardized at two medium armoured draisines R and four light armoured draisines TK/TKS plus a 5th reserve tankette at least on paper. Typically the arrangement was two TK-R-TK units (one R, two TK/TKS) for a crew of 17 comprising one officer, six NCO, 10 soldiers, 12 onboard the draisines. The Draisine K camouflage mirrored those iof the tankettes they carried. In 1939 they were airbrushed with the standard greyish sand and dark brownover brown-green pattern in irregular patches with a few still in the old 1920s pattern with black outlines.

Gallery

TK-3 tankette

Draisine K

The combined Drayzina K-R-K in 1939. Platoons often operated combined two TK-R-TK on both ends of the armoured train and one of the four of these tankettes had a radio. The TK-R-TK made for a powerful yet very flexible universal reconnaissance unit but the more powerful FT tanks through the Draisine R usually towed the other two as the tankettes were lifted upon the rails. If needed, the trio was dectached, both tankettes venturing either side of the "R" that acted as advanced command. Plus they only needed a coupled on minute to be detached compared to the Renault FT and venture inland. The Draisines R stayed in support by gunfire the rest of time. In 1939 rthey were most often all three seen in ground operations, and were detached to support ground units and so had crippling losses.