A 250-mini quad racer is small and can be built to be inexpensive and durable. I designed my first drone in this category in 2015, and helped a couple of friends with their projects some months later.
My last 250 quad was ready in the beginning of september, featuring 15 min airtime and FPV (first person view, using a camera for live video transfer) in a 692 g unit.
The frame is designed in SolidWorks and water jet cut form 1/8 inch aluminum. This gives great stiffness at low weight. Modeling all components in CAD enables easy assembly, as all holes and mountings have been designed to fit the components. 3D printed separators maintain the connection between the upper and lower frames.
The HobbyKing KK-mini board is a small, light and inexpensive flight controller. Combined with upgraded firmware, it gives good customizability. All four 12 A Afro speed-controllers are located internally in the body, beneath the primary 1400 mAh 4-cell LiPo battery. A smaller LiPo-cell is used to power the FatShark 5.8 GHz 25 mW video transmitter.
Four Multistar BabyBeast V2 brushless motors running at about 16 V provides a significant amount of lift. The setup has been able to handle steady coastal winds exceeding 16 m/s.
The GoPro camera is mounted internally in the body for protection and to maintain an even weight distribution. It can record video directly and provides analogue video out for the video downlink.
All required components fit into a 300x400 mm carrying case that makes the setup possible to bring along to remote locations.