Good question about fan drive. A tracked armoured vehicle generally requires 10% of its engine power to drive the fans at max power. A Leo 2 disengages its fans if you kick down the transmission and releases another 200 HP ! 
 
This much power is needed because there is absolutely no natural ventilation in a tank engine bay and no gaps between units so heat just builds up if not removed unlike in a car where it is blown away by the movement of the vehicle and only needs to be extracted from the inside of the engine. 
 
David
		 
		
		
		
		
		
		
		
		
	
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