In 1937 the Czechoslovakian army wanted a replacement for the LT vz 35. Two designs were developed by Skoda and CKD (Ceskomoravska Kolben Danek of Prague, after 1940 Böhmisch-Mährische Maschinenfabrik AG). The Skoda was the S-11-a and S-11-b. The CKD model was basically an improved LT vz 35 with the transmission and engine from a TNH tank.
The floor under the fuel tanks were secured by small bolts. This was made to blow out the floor if an explosion happened inside the tank to reduce the damage internally.
There were 4 large bogie wheels mounted in pairs on each side on longitudinal leaf springs. The drive was in the front by sprockets with 19 teeth. These were attached via a pinion to a cross-shaft. This was attached to the gearbox which then had a propeller shaft go to the rear and meet up with the engine.
The coaxial MG could be fired independently of the main armament as it was ball mounted.
The 37.2 mm Skoda A7 L47.8 gun's elevation gear could be locked for firing.
The engine was mounted vertically in the center of the rear compartment.
The drive sprocket was in the front with the idler in the rear.
A Praga-Wilson pre-selector gearbox simplified the gear changing and drove the front sprocket by a 2-stage epicyclic steering gear.
The driver sat on the right and the machine gunner to the left.
After the Germans took possession of the TNHPs they removed some of the ammunition to make room for a loader.
The hull and turret were riveted with the superstructure bolted in place.
The commander's cupola didn't rotate and had four periscopes.
Between the driver and the hull machine gunner was the gearbox.
New Designs T-15 and T-25
In 1942 or 1943 the Heereswaffenamt (Wa.Prüf.6) gave Skoda specifications for a 10.5 ton reconnaissance tank and a 22 ton medium tank. They were to be based on a longer and wider TNHP-S chassis.
The T-15 was to have a 50 mm gun. Its armor protection was to be 50 mm in front, 20 mm in the sides, and 15 mm protecting the rear. The armor plates were angled more.
The T-25 was to be armed with a semi-automatic 75 mm gun.