| At the end of 1943, the firm of Zahnradfabrik Augsburg received turret less hulk of an old Panzerkampfwagen IV Ausf G that had been badly damaged during combat operations. The old Panzer IV hull was to be rebuilt as the test bed for a new type of drive system. The new thoma drive was in principle similar to Porsche the system used in the Ferdinand/Elephant Tank Destroyer. Like the Porsche system the new test vehicle would use a standard tank engine bolted to a generator that in turn drove motors that propelled the tank, however unlike the Porsche petrol/electrical system the new test vehicle would have a new petrol/hydraulic system. This gave the benefits of the Porsche system without the fire risk that plagued the Porsche system. The old Pz.Kfw.IV Ausf.G. hull underwent major refurbishment to accommodate this new drive system. The main area of modification was the rear of the hull, which was completely re-manufactured to accept the new power plant and drive units. Within the fighting compartment, all the old drive shafts were removed along with the large gearbox and final drive assembly. New driving controls were installed and two large 780mm adjustable toothed idlers replaced the original Pz.Kfw.IV drive sprockets. By mid 1944, the hull was completed and the prototype was fitted with a new Pz.Kfw.IV Ausf.H. turret. This new turret was unique as it was powered hydraulically by the new hydrostatic drive. During the remainder of 1944/5 tests carried on but were never concluded. During April 1945 the US 3rd Infantry Division, part of the US 7th Army (patch) was advancing through southern Germany and into Bavaria. The 3rd secured Augsburg on the 28th and with it the Zahnradfabrik Werk and the test vehicle. At the end of hostilities, the vehicle was shipped back to the United States where it was subjected to thorough tests by Vickers Inc. Detroit, Michigan as the company was at the time working on a similar design for an American tank. Testing in America with the US Army finally ended on account of the lack of spare parts for the experimental drive system. The vehicle still remains at Aberdeen U.S Army Proving Grounds in Maryland to this day along with many other rare German vehicles and guns. |
