The history of the Tiger heavy tank is often presented as a duel between two models: The Tiger H1 designed by Henschel with a mechanical transmission and Tiger (P) designed by Porsche with an electric transmission that allegedly led to its downfall. This common presentation is incorrect. The Germans worked on three Tiger tanks in the spring of 1942: the Tiger H1, Tiger (P) Typ 101 with a Siemens electric transmission, and the Tiger (P) Typ 102 with a Voith hydromechanical transmission. A lot has been written about the first two, but the last remained in the shadow for a long time. Books only contained scattered mentions or dry overviews of this tank without any photographs or blueprints.
|Typ 102 refuelling in the vicinity of the Nibelungenwerke factory. The small fuel tanks and poor fuel economy meant this had to happen quite often. Ferdinand Porsche, director of Steyr Oscar Hacker, and Voith chief engineer Fritz Kugel.
|Maybach SRG 328 145 shaftless gearbox used on Pz.Kpfw.III Ausf.E-Ausf.G and VK 30.01 (H) tanks. The gears are selected via a combination of five levers, four of which have a vacuum actuator. When the gears are changed, the brake and synchronization accelerator are activated automatically. All of these operations take a fraction of a second and require precise manufacturing to work.
|VK 30.01 (P) trials, 1942. This tank offered experience in using an electric transmission with an air cooled engine.
|Voith hydromechanical transmission for the Tiger (P) Typ 102.
|Typ 102 hydromechanical transmission from the side of the torque converters.
|Diagram of the Typ 102 hydromechanical transmission drawn by Vasily Chobitok.
|Torque converter block blueprint. The cooling fan drive can be seen in the top left. Photo via Harold Biondo.
|Hydraulic pumps that filled the torque converters. The water cooling pump can be seen on the upper left. The Tiger (P) had air cooled engines, so it was plugged. Photo via Harold Biondo.
|Turning mechanism blueprint fragment. The quality of the archive document leaves much to be desired. From left to right, this image shows the clutch, drum brake, hydraulic retarder, planetary gear train, forward and reverse conical gears.
|Typ 102 control system. The pneumatic and hydraulic lines are shown in dotted arrows. Photo via Harold Biondo.
|Hitler inspects the Nibelungenwerke factory, June 20th, 1942. Due to a shortage of room the hulls are stacked on top of each other.
|The cowling on the back shows that this is the Typ 102. Stains from leaking oil can be seen underneath. Ferdinand Porsche, Oscar Hacker, and Fritz Kugel stand on the dummy turret. Vicinity of Nibelungenwerke, December 23rd, 1943.
|The rear cowling and dummy turret suggest that this is the Typ 102.
|Further development of Voith's idea: a hydromechanical transmission for the Typ 250 tank. The gearbox and double differential are combined in one compact assembly.
|Typ 101/2 engine with a generator. Two double fans with a belt drive can be seen above. These engines were supposed to be used on the Tiger (P) Typ 103.
|Pz.Kpfw.35(t) transmission. Gear changes and braking are done by a pneumatic system.