This is a modified version of Punkkills' popular micro 105 FPV quadcopter frame. The original frame, while great, tended to break after fairly small crashes. After going through three frames, I decided to make some modifications to make the design more durable.

I smoothed corners to remove stress concentrations and braced the arms to improve rigidity. I have crashed this frame dozens of times and have only broken the arms in one spot which I simply glued back into place.

This is only the bottom frame. Print the top piece from Punkkills model.

Additionally here is a pro tip to avoid breaking your motors in a crash. Add a spacer between the prop and the motor housing. This prevents the shaft from being rammed into the bottom of the motor casing in a crash, which could result in breaking the bottom piece. Also add a good dab of hot glue under the motor where the motor sits in the frame. This will strengthen the bottom of the motor, hold the motor on the frame, and reduce strain on the motor leads .