His auto parts maker Bharat Forge, which son Amit helps him run, suffered a drop in revenue and net profit in a recent quarter due to declining exports. Kalyani attributed the fall to a weak truck market in North America. The tycoon's bet on the defense sector is taking shape: later this year Bharat Forge will be testing 3 howitzer guns it has developed. The company has collaborated with Tata Motors and U.S.-based General Dynamics to bid on a $7.5 billion project to build infantry combat vehicles for the Indian army.