This is a mini version of my T4 Quadcopter design. It uses the same concepts but is completely redesigned to fit into the "250" class of mini quadcopters.
This design is suitable for 5" props. If you are after something a little bigger there is now also the T4 Quadcopter Mini 315 that supports up to 8" props and a 2200mah battery - or just use the longer arms on this model if you don't need the battery space.
Check out the whole "T" copter family:

• TX8 Octocopter
• T6 Hexacopter
• T4 Quadcopter (10" props)
• T4 Quadcopter Mini 315 (7-8" props)
• T4 Quadcopter Mini 250 (5" props)
• Tubular Crossfire 2 quadcopter
  I've added a post on the forums over at DIY Drones for discussing and improving these designs.

  Videos

• FPV flight by Abormor
• Build video playlist
• Build video 1: Body assembly
• Build video 2: Install motors
• Build video 3: ESCs and power
• Build video 4: Flight control
• Frame strength testing

Features:

• completely 3D printable (without support)
• fully assembled frame weight less than 110 grams!
• strong, simple assembly with no bolts to save weight! Everything is secured using 2.5mm zip ties.
• includes three arm options - 24mm, 28mm, and 30mm motor cup (inside diameter). The 30mm cup has slots for 3mm motor bolts (the others are 2mm).
• strong braced tube section arms with plenty of room to conceal motor wiring
• designed for a 3S battery (1000 - 1500mah) located right in the centre of rotation/thrust (88 x 38 x 22mm capacity).
• plenty of space to mount ESCs - concealed but still well ventilated for cooling.
• top plate has space for a variety of flight controllers and a Mobius style camera. It also features 3mm mounting holes so stand-offs could be used to add an additional deck of components. Alternatively two hex holes are available to add 3D printed posts and rear upper deck.
• RF "invisible" frame - as opposed to carbon fiber or aluminium
• Sketchup file included so you can make changes to suit yourself

  History

  2 September 2014
  Legs for your T4 Mini are now available.
  12 August 2014
  Version 1.4
  New vibration isolating top plate option. This option is compatible with previous body and all other components. It replaces the top plate with one that has mounting points for 65 gram vibration damping balls that then connect to a new floating plate to hold your flight controller and camera.
  New files:

• T4MiniVibrationTopPlate.stl
• T4MiniVibrationFloatingPlate.stl
  Also updated Body.stl to slightly raise the arms giving a bit more strength in the arm sockets.
  20 July 2014
• Added T4MiniArm30mm7inch.stl so that "blackdice" can experiment with bigger (7") props. Also added T4MiniArm28mm7inch.stl
  12 July 2014
  Version 1.3
• Added T4MiniTrayShallow.stl as requested by "p25o1". This low profile bottom tray reduces the available height to 7mm (compared to 14mm original).
  (no other files have changed)
  1 June 2014
  Version 1.2
• added T4MiniArm30mm.stl which has a 30mm internal cup to fit motors such as the Lumenier 2206-11. This arm also has slots for 3mm motor bolts (the others are 2mm).
• T4MiniBatteryPin.stl has also been updated to add a small tab to make it easier to install and remove the battery pin.
  (no other files have changed)
  31 May 2014
  No changes to the files but I've just replaced my Multistar ESCs with 12amp Afro ESCs (SimonK firmware) and its made a huge improvement. Even the cheapo Multistar 1704 motors sound better. I'm about to fit some Lumenier 2206-11 motors so we'll see how that goes...
  26 April 2014
  Version 1.1
• improved method for attaching top plate and bottom tray to the body.
• slightly increased zip tie hole sizes to make them easier to thread through.
• thicker top plate (2mm) with rearranged rubber band and hex post mounting points at the rear.
• new posts and plate added to give an additional layer for mounting the receiver or other items.
• new slots in the rear of the bottom tray so cables can be threaded up the back of the T4 to suit some flight controllers.