The Wirbelwind was powered by a water-cooled Maybach HL 120 TR engine and could attain a top speed of about 38.6 km/h (24 mph). The Wirbelwind anti-aircraft armament came from its four FlaK 38 anti-aircraft guns mounted in an octogonal open-air compartment mounted on top of the Panzer IV chassis. To protect itself from infantry attack, the Wirbelwind also had an MG 34 mounted in a hull position.  However, the way the guns were placed, it was certainly possible for all four anti-aircraft guns to be used against ground targets such as other enemy vehicles and groups of infantry as was common in a combat situation.
The weight of the Wirbelwind was about 21,772 kg and the length was 5.92 meters. It had a 6 speed forward, 1 speed reverse transmission and it was also capable of storing up to about 3,200 rounds for the main AA guns. The armor varied between 7.6 cm in the front to 2.5 cm in the sides. The Wirbelwind had no other variants besides the main production model. However, there was an attempt to put the Wirbelwind turret or the Ostwind turret on a Panzer III body, but the war ended in Europe before this could happen.
More Info: German Flakpanzer Development
The Flakpanzer IV Wirbelwind's first prototype appeared in 1944 and mainly all Wirbelwinds were then assigned to Flugabwehrzüge units or mobile air defense units designed to protect standard Wehrmacht units from low flying aircraft. By the time World War II ended in Europe, around 105-110 Wirbelwinds had been produced. They were produced by Ostbau and in 1945 Soviet troops forced the Ostbau factory to move from Silesia to Teplitz which is northwest of Berlin. However, the shift left production at a halt and the further Wirbelwind contracts were cancelled regardless in favor of the newer Flakpanzer IV Kugelblitz with two high-velocity 30 mm anti-aircraft guns to take on tougher, more advanced aircraft.
- ↑ http://www.wwiivehicles.com/germany/flak-panzers/wirbelwind.asp
- ↑ http://www.achtungpanzer.com/flak4.htm
- ↑ http://www.historyofwar.org/articles/weapons_wirbelwind.html