When my WLToys V939 quadcopter stopped performing well, I didn't want to just scrap it. I wanted to salvage the flight controller and try my hand at building a custom frame. The pager motors used on most mini/micro quadcopters are only rated for a certain amount of hours before they lose their strength and functionality. The batteries also wear out with moderate use. I put in an order for some replacement motors and batteries and got to work building a mini quadcopter from the ground up.