Quadcopter style drone originally designed in 2017 for computer controlled swarm acrobatics. You can't buy the original electronics anymore but upgrading to newer ESCs and flight controllers should be easy. The original cost was < $200 per drone to build. The frame is simple (3d printed + carbon fiber rods) but rock solid and has survived 20ft free falls without damage.

Parts MUST be SLA printed in tough resin or SLS Nylon printed (recommended) (e.g. order from Shapeways).

Components 

• Frame
  • 4 x 138mm (length), 5mm (diameter) carbon fiber rods
  • Loctite or other two part epoxy
  • 2 x M2 10mm Stainless Steel Screws
  • 2 x M2 Generic Stainless Steel Nuts
• Lift
  • 4 x 6 inch diameter, 3 inch pitch propellers.
  • 4 x M4 2.2mm Thick Stainless Steel Nut
  • 4 x T-Motor MN1806 2300KV Motors
• Electronics Mounting Hardware
  • 4 x Generic Stainless Steel M3 nuts
  • 8 x M3 6mm (length) Aluminum Standoffs
  • 16 x M3 Electrical Insulating Washers
  • 4 x M3 4mm (length) Low Profile (2mm head height) Stainless Steel Screws
• Electronics
  • 1 x ThunderPower TP2000-2SPXRX Battery
  • 1 x PixRacer flight controller
  • 1 x ACSP5 Power Board
  • 1 x AfroESC Quattro 4 in 1 ESC
  • 1 x FrSky XM Receiver

Build Instructions:

• Sand down the circumference of the ends of carbon fiber rods by ~0.5mm by hand to prepare to improve epoxy adhesion in the later steps.
• Cover the M3 nut pocket holes in the xframe top piece with scotch tape
  • This is to prevent epoxy from getting into the holes later.
  • When the two xframe halves are sandwiched together, the tape shouldn't touch the bottom half.
• Use 2 part epoxy to glue the carbon fiber rods and printed parts together as shown in the photo.
• Wait for the epoxy to dry.
  • The assembly should lay completely flat on a table.
  • Press down the xframe with a heavy weight while it is drying.
• Attach the motors
  • Note that all screws needed for this come in the box for the motor. The box contains two main screw types (a short M2 and long M2 variant).
  • Assemble the motors with the M4 prop adapter with 4 of the 'short' M2 screws.
  • Use 2 'short' and 2 ‘long’ M2 screws to attach the motors to the frame.
• Assemble the center electronics stack
  • The order of the layers starting from the bottom is as follows:
    • M3 Nut (in the xframe pocket)
    • Xframe plastic part
    • 6mm standoff
    • Washer
    • ESC board
    • Washer
    • 6mm standoff
    • Washer
    • Flight Control Board
    • Washer
    • M3 4mm screw
• Attach the shell
  • Use the M2 10mm screws and nuts

Notes:

• Aluminum standoffs were chosen for weight savings and because Nylon standoffs will break during crashes before the frame breaks. You can swap with Nylon standoffs for cost savings.
• You can use non-low profile versions of the screws/nuts too. The chosen parts are mainly chosen for weight savings and to provide space for mounting M4 IR markers on the motors.
• The center stack is 25 degrees skewed along the Z-axis. You will need to configure this in your flight controller settings.
• Use velcro or zipties to attach the battery.
• The other 2 unused holes on the xframe can be used for mounting extra accessories such as lighting. The provided LED holder is for Adafruit 3W Pixie LEDs and a downward facing lenses