T4 Quadcopter Mini 315 (7-8 inch props)

Author: Brendan22, published on 2014-07-27

Click this button to get the 3D model


This quadcopter is about 22mm longer and 2mm taller than the popular T4 Quadcopter Mini 250. It supports up to 8″ props and a 2200mah 3S battery.

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.


  • 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
  • First flight


  • completely 3D printable (without support)
  • fully assembled frame weight less than 130 grams!
  • strong, simple assembly with no bolts to save weight! Everything is secured using 2.5mm zip ties.
  • includes two arm options – 28mm, and 30mm motor cup (inside diameter). The 30mm cup has slots for 3mm motor bolts (the other is 2mm).
  • strong braced tube section arms with plenty of room to conceal motor wiring
  • designed for a 3S battery (up to 2200) located right in the centre of rotation/thrust (110 x 38 x 24mm 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

    Revision History

    2 September 2014
    Legs for your T4 Mini are now available.
    31 August 2014
    Version 1.3
    Added a bridge to T4Mini315VibrationFloatingPlate.stl to make it less flexible. No other files were changed.
    15 August 2014
    Version 1.2
    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:

  • T4Mini315VibrationTopPlate.stl
  • T4Mini315VibrationFloatingPlate.stl
    30 July 2014 – Version 1.01
  • there seem to be a lot more 8″ prop options so I’ve added two arms to suit 8″ props (28mm cup and 30mm cup).
  • extended the 7″ arms by 5mm to give a bit more clearance from the body.
  • modified the body to raise the arm sockets so there is a bit for material in the bottom of the socket – stronger to support longer arms.



I printed all parts in PLA, 0.25mm layers with 40% infill, 2 shells and 3 top/bottom layers. Feel free to experiment. I didn’t play around too much with the settings as these gave me a good strong result.
Fitting the top plate and bottom tray
Both the top plate and bottom tray are designed to slide from front to back (at 45 degrees) as they are being fitted into the body. In particular the top plate needs to be pressed firmly down onto the 8 angled guides as you slide it back. Once in place the top plate will clip onto the smaller bumps near the rear cable tie mount (just above the rear arms). Look closely at the parts and it will all become clear.
Calibration test
T4MiniTestSocket.stl contains a cut-down socket you can use for testing the fit of your arms before committing to the full Body print.
A quick word about scaling
According to Wikipedia apparently “there is no scale information [in STL files], and the units are arbitrary”. There is often confusion with STL files and metric versus imperial (inches) units. I designed these parts in Sketchup using metric units and they import correctly into my slicer (which is also set to metric). If you have issues, check your application to see if has a way to select metric or alternatively scale down by a factor of 25.4.
Also, the Sketchup file contents are scaled up by 1000 (attempt to solve some Sketchup quirks). I scale each component down by 0.001 before exporting the STL so they are in real millimetre sizes.

What you’ll need

  • 4 arms (9 grams, 0.5 hour print each*)
  • 1 body (40 grams, 2.75 hour print*)
  • 1 top plate (12 grams, 1 hour print*)
  • 1 bottom tray (14 grams, 1 hour print*)
  • 1 battery pin (almost nothing, real fast)
  • 2 posts (optional)
  • 1 post plate (optional)
    *times were recorded on my Makergear M2 printer which has a 0.35mm nozzle and was printing at 4500mm/min.
    …and “hardware”…
  • 2,5mm (wide) zip ties (approx 100mm long)
  • some foam for padding the battery compartments. I ended up using self adhesive window draft-stop tape from my local DIY store.
  • some Kyosho Zeal Gel or similar anti-vibration gel and rubber bands for mounting the flight controller and camera.
  • double sided adhesive foam tape (for mounting other electronics)
  • soldering gear and connectors to suit your electrical bits

If your new to RC copters then the ArduCopter wiki is a great place to find out everything you need know.

License: Creative Commons – Attribution – Non-Commercial

Tags: Drone, multicopter, Quadcopter