T4 Quadcopter

Author: Brendan22, published on 2014-03-01

Click this button to get the 3D model


Check out the whole “T” copter family:


  • completely 3D printable (without support)
  • simple assembly
  • includes a single motor arm or optionally use the coaxial arms from the T6 and create an X8!!
  • strong braced tube section arms with plenty of room to conceal motor wiring
  • designed for a single 3S or 4S battery located right in the center of rotation/thrust with room for up to a 6000mah 3S or 4200mah 4S battery (155 x 50 x 30mm capacity).
  • easy cable routing with beveled cable “tunnels” (and even a few cable tie mounts)
  • plenty of space to mount ESCs – concealed but still well ventilated for cooling – perfect for a 4-in-1 ESC too.
  • top plate is designed for the new Pixhawk flight controller from 3D Robotics – but is also fine with APM, KK2 and others
  • mounting holes available on the “nose” that can be used to attach things like the included Go Pro vibration mount.
  • RF “invisible” frame – as opposed to carbon fiber or aluminium
  • All-up-weight 1,011 grams (excluding battery of your choice – including 3DR 880KV motors, 4-in-1 ESC, Pixhawk with GPS and telemetry). Still flies great when loaded with another 1kg of batteries and camera gear (see video).
  • Sketchup file included so you can make changes to suit yourself


I’ve been experimenting to find a strong “tubular” profile that could be printed reliably. The angled sections in these designs are 35 degrees to vertical – so well within the typical 45 degree capability of most printers. They arms only present about 11mm of flat surface to minimize obstruction to airflow.
The rest of the design are a collection of ideas that have accumulated over the past year building various quadcopters and Y6 configurations (3D printed, aluminium and bought frames).



3 August 2014
Version 1.05
Just a small change to add slots to the arm motor mount holes so that 4 bolts can be used (in a 16-19mm pattern) regardless of which “corner” of the motor the wires exit.
1 April 2014
Added a T4 univeral camera plate accessory as a separate thing.

22 March 2014
Version 1.04.1

  • No changes to any existing parts
  • Added a vibration reducing mount for a GoPro Hero 3 – for folks who don’t want to set up a full camera gimbal. I used these dampeners because I had them lying around. They removed all vibration “jello” but may be a bit too soft for aggressive flying. I think these ones would be a better option. Anyway, I’ve included several STLs with different hole sizes which will hopefully suit most dampeners out there (5mm, 7mm, 8.5mm). Flight video is above.
    15 March 2014
    Version 1.04
  • about 12mm narrower “waist” for a small reduction in plastic/weight
  • additional cable tunnels at the front of the flight controller
  • slots in the side and rear of body.stl provide another option to cable tie accessories (eg transmitters with aerials pointing down)
  • small notches out of the bottom tray provide an outlet for cables to run under each arm (eg for lighting strips)
    The following files have been updated:
  • T4Body.stl
  • T4TopPlate.stl
  • T4BottomTray.stl
    I’m also adding the component weights and print time in the instructions.

8 March 2014
I flew a few different batteries today to compare. This is with my 880kv 3DR motors which is a bit over-weight as it is version 1.00 and has most of the power components from my T6 inside. I’m guessing a 1.02+ version with something like the 3DR 850kv motors would weigh at least 100 grams less with longer flight time.
The results:

  • 3S 3500mah = 10 minutes (only used 2472 mah – old battery)
  • 3S 6000mah = 18 minutes (used 5676 mah)
  • 4S 4200mah = 16.5 minutes (used 4027 mah)
    Version 1.03: A small update that adds two more holes to the body and top plate near the front cable tunnel. This provides a triangle of fixing points on the “nose” which could be used for “accessories” such as a simple camera mount.

7 March 2014
CRASHED HARD!! But this frame handled it well (see photo above). I printed off another arm after work, reassembled and had time for a quick test flight – all back to normal. Replacing the arm was about a 10 minute job.
5 March 2014
I just noticed a hole missing at the front of the top plate. It’s not required (or any real issue if missing) so I’ve just updated T4TopPlate.stl and the Sketchup file without changing version numbers.
4 March 2014
Version 1.02: I’ve spent another full day drawing on this thing. The biggest parts are now 199mm long and 140mm wide. Hopefully that will squeeze onto a few more print beds out there. The arm will also fit onto that sized bed if you rotate it a bit.
I’ve started to version the Sketchup files and left older ones in the files if anyone prefers an earlier design.
3 March 2014
Version 1.01: As requested I’ve put this thing on a diet. It now only requires a 140mm wide (and 220mm long) build platform so it should fit easily on a Replicator 2.
Also I’ve updated T4Arm.stl adding a small hole to allow a cable tie to be used for strain relief where the wires exit the motor.



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.
Calibration test
TubeSocketArm.stl contains a cut-down socket you can use for testing the fit of your arms before committing to the full Body print. I found a 0.1mm clearance between the arm and socket provides a firm press fit. Some light sanding may help if you find the fit too tight but I recommend keeping the tolerance as small as possible.
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 (40 grams, 2 hour print each*)
  • 1 body (147 grams, 8.5 hour print*)
  • 1 top plate (35 grams, 1.75 hour print*)
  • 1 bottom tray (52 grams, 2.9 hour print*)
  • 1 battery peg
  • 4 legs (optional – long, short, or none)
  • 1 GPS post and plate (optional)
    *times were recorded on my Makergear M2 printer which has a 0.35mm nozzle and was printing at 4500mm/min.
    …and “hardware”…
  • 8 M3 x 40mm+ bolts (arms to body)
  • 8 M3 x ~5mm bolts (motors to arms)
  • 8 M3 Nyloc nuts and washers
  • approx 3mm x 10mm self-tapping screws (attach top plate and bottom tray)
  • some Kyosho Zeal Gel or similar anti-vibration gel and rubber bands for mounting the flight controller and camera.
  • some foam for padding the battery compartments. I ended up using self adhesive window draft-stop tape from my local DIY store.
  • double sided adhesive foam tape (for mounting other electronics)
  • some cable ties
  • soldering gear and connectors to suit your electrical bits
    …and stuff to make it fly…
  • 4 motors** (I had some 880KV ones lying around but something like these 850kv ones would be a match)
  • 2 normal propellers and 2 pusher propellers (10 x 4.7 slowfly)
  • 4 20A+ ESC (speed controllers) or a 4-in-1 ESC
  • 1 power distribution assembly (if not using 4-in-1 ESC). I prefer to make my own compact version (like this or this) but you might be able to squash in something like this or this.
  • 1 3DR power module (or BEC – often built in to your ESCs)
  • 1 3S (up to 6000mah) or 4S (up to 4200mah) battery
  • 1 3DR Pixhawk, APM (or other flight controller)
  • 1 Radio control receiver (and transmitter) (eg a Taranis)
  • 1 3DR GPS/compass (optional)
  • a pair of 3DR telemetry radios (optional)
    ** the arms will suit any motor up to 30mm diameter (typically they’re 28mm) and with a pair of 19mm mounting holes. This sized motor typically has a 16x19mm mounting pattern but unfortunately the wires on different models exit the motors from different corners so the only way to work with all motors was to provide a 19x19mm hole pattern and mount the motors using only 2 bolts (with Locktite). Experience has proven this is not a problem and, in fact, seems to be common practice – for example all 3D Robotics off-the-shelf vehicles only use 2 bolts to mount their motors.

If your new to RC copters then the ArduCopter wiki is a great place to find out everything you need know.
The default APM parameters for the 3DR Iris should be very close for this quadcopter.
Some tips from maverik0106:

  • you may need to look quite a distance from the print bed to find the objects in some of these STLs. (I’ll work on improving that).
  • he also suggests that Makerbot/Replicator users “do not resize the objects”.

License: Creative Commons – Attribution – Non-Commercial

Tags: Drone, multicopter, Pixhawk, Quadcopter