An unsuccesful early WW2 heavy tank of HLK, the Titan Heavy Tank.
Based on the Vickers Independent A1E1, development of the Titan started in 1931.
https://en.m.wikipedia.org/wiki/Vickers ... ndependent
Two prototypes were tested in 1933, powered by the same Armstrong Siddeley engine and gearbox with the A1E1, as also the hydraulic braking system. However, the front small turrets were eliminated and a large single turret was installed, a revolutionary concept for that era. A small batch of Titan was produced in 1935-37, with a 57mm/L70 cannon, a modified Hotchkiss 6-pounder early 1890's/early 1900's naval gun which was produced under license by Pyrkal. There were also twin Hotchkiss/Pyrkal Y1926/32 8mm machine guns in hull. That was a heavy barrel local derivative of the M1922/24/26 Hotchkiss chambered for the 8mmX56 Mannlicher cartridge.
https://www.forgottenweapons.com/light- ... m19222426/
Late production Titan from 1938-41 had the 75mm/L42 gun, which was a modified French Anti-Aircraft cannon. Early production untis were also refitted with the 75mm gun.
Pyrkal had production license from these 2:
https://en.m.wikipedia.org/wiki/Canon_d ... %A8le_1897
https://en.m.wikipedia.org/wiki/Canon_d ... _Schneider
The most siginificant change was the replacement of the petrol engine with a water cooled McDowall MachineWorks diesel, based on the Rolls Royce Condor C.I and the Hipano Suiza 12X/Y. The McD 12V-CI only shared valves, pistons/connecting rods and crankshaft with the Condor, all other were new or derived from Hispano Suiza. For the Ttitan, the McD 12V-CI was rated at 420 hp. In total 3 tank regiments were equipped with Titan tanks, each with 40 tanks plus a number of Titan with a crane instead of turret.
https://en.m.wikipedia.org/wiki/Hispano-Suiza_12Y
https://en.m.wikipedia.org/wiki/Rolls-Royce_Condor
Although the gearbox was adopted to the new engine, the much higher torgue of the 12V-CI led to transmission failures. Brakes also failed occasionally, while its armor was not adequate for the German Panzer III and IV. Therefore, the Titan was slaughtered in the Battle of Thessaloniki, only a handful escape south. But there were several successful shots, destroying German tanks with the 75mm cannon, which lead to further developement of the antitank 75mm cannon.
Only one Titan tank survive today from about 160 built.
The failure of the Titan lead to the development of a new heavy tank, the Talos, which entered service in mid 1944.