Quadcopter – Revision I

Revision One
Revision One

At the time of designing this quadcopter, it wasn’t often you could find a 3D printable multicopter frame perfect for any user level experience to both build and fly. Fortunately, the frame designed here is not only simple to put together, it’s also insanely durable. Capable of surviving the most abusive crash landings without even bending an arm or breaking a motor mount. Seriously!

Thanks to the ever-expanding 3D printer movement, I was able to design from scratch a full quadcopter kit on a budget and get right into the RC aeronautics hobby. Now you can to!
If you are already flying in the multicopter hobby, then great! Here’s another frame you can fly on a budget.

 The story of how this came to be


With commercial store-bought multicopters far outside the price range of an entry-level pilot, and with reliable kits few and far between (at the time of inception), I pressured myself into designing my very own quadcopter from scratch. In a matter of weeks, and some trial and error, I not only had a working prototype, I also managed to teach myself to fly! Without 3D printing I probably would never have met such an awe inspiring hobby. And ever since, I’ve wanted to share this gift with the world.

Build it yourself


The frame was designed entirely in Tinkercad back in early 2012. All the pieces are available here on Thingiverse or downloadable in .zip form here. You will also need some additional metric hardware listed below.

Essential hardware you will need for the frame includes: (Available at Mc-MasterCarr if not at your local hardware store)

  • 24x 35mm M4 socket-cap screws (For mounting center hub to arms and landing gear to arms)
  • 16x 25mm M4 socket-cap screws (For mounting arms to motor mounts)
  • 16x 14mm M3 socket-cap screws (For mounting motor cross-plates to motor mounts.)
  • 4x 6mm M3 socket-cap screws (For mounting flight controller)
  • 4x 20mm M3 nylon standoffs (Also for mounting flight controller)
  • M3 nylon nuts (Also for mounting flight controller)
  • M3 and M4 nylock nuts (To hold everything together)
  • At least 1m of 19mm / 1.5mm square aluminium tubing (Will be measured, cut, and drilled to form the arms)

 

Printing


Printing these pieces is pretty straight forward, nonetheless I will explain some key settings you’ll want to consider. Your build platform must be no less then 100mm² and you can print in any rigid plastic you desire.

The “shelves” (as I call them), pictured below in the bottom left, are optional add-ons available for your choosing. You can have up to four shelves per frame. There are currently two options available. A GoPro mount that offsets the camera so its lens remains centered, as well as a slotted expansion shelf perfect for FPV or radio gear.

3D rendered of kit
3D render of kit

 


Any experienced 3D printer-er knows how to tune their slicer to get optimum strength out of the finished prints. The motor mounts, landing gear, and cable-clips should be printed at a fairly high infill. 30% or more should do.  The center hub and add-on shelves should be printed at no less then 18% infill with four shells/perimeters (0.3-0.5mm nozzle).

You’ll want these extra shells (how many paths the extruder makes on the edges/walls of parts.) to act as a kind of buffer when refining the tight-fitting edges of parts or boring out holes. The frame was designed this way in order to be snug and sturdy with no loose joints. (Reads: poor design..)

Most of the holes in this kit, especially the ones on the bottom plate, will need to be bored out with a drill or drill press. The holes on the bottom plate are intentionally blocked to allow the slicing software and 3D printers more cleanly reproduce the recessed holes for the screw heads.

When picking fractional drill bits, 1/8inch and 5/32inch would be your best bets for boring the M3 and M4 holes respectively.


Assembly


Building the frame is pretty self-explanatory. It is made even easier with the included hole drilling template you can print used for precisely marking where to drill your holes in the aluminium tubing; using this is highly recommended. Also included with the files is a small miter box for making perfectly perpendicular cuts when using a hand saw. Refer to the diagram below when measuring, cutting, and drilling your aluminium tubing. Four pieces of tubing should be cut and filed down to 235mm in length. You can use a 5/32inch bit for these 4mm holes.

Reference for making arms.
Reference for making arms.

 


Pro Tip: Unless you have a drill press, it is recommended that you do not drill through the entire bar in one shot, but rather stop when you go through the first wall, remove the drill bit, flip the bar over, re-mark then drill from the outside again.

 

Piece it all together


We are almost done. Lets start with the four motor mounts. Line up the holes on a motor mount with those on an aluminium arm and press the two together. The end of the bar should stop when it meets the tab on the underside of the motor mount. Once you have all motor mounts in place, take some 25mm M4 socket-cap screws with respective M4 lock-nuts and firmly bolt them in place. You may have to clear out these holes with 4mm or equivalent drill bit if your holes don’t quite match up.

Bolting on a motor mount.
Bolting on a motor mount.

After you have all four motor mounts each installed on their own arm, it is time to move on to the center hub. Take eight 35mm M4 socket-cap screws and from the bottom, insert them into the holes on the bottom hub. The heads should sit flush with the rest of the piece. Lay this assembly down on a flat surface and one by one start fitting each arm to the protruding screws. The flat part of the motor mounts should be facing upwards. If you plan to use a long Velcro strap to secure the battery(s) you can thread that through slots on the bottom hub now. I however recommend using the medium Pure-Tech Xtreme Double Strap or any other adhesive/Velcro battery strap for affixing a battery  to the bottom hub later on.

If you are having trouble getting a bar to sit flush in its cavity, don’t force it! Instead, get some sand paper or a file and and make slight adjustments until it all fits. You may need to repeat this step for the top hub as well.

Fitting arms to hub
Fitting arms to hub. Fun fact: I used only one aluminum bar to make this picture.

Now that your quad is taking shape, grab the top hub and desired add-on shelves, if any. Determine which side will be facing forwards and try to press the shelves into the triangular cavities. Chances are you will have to file and/or sand down the joints to make them fit. You want these to fit relatively snugly, but still loose enough should you need to replace or remove one later on. Should you need to remove a shelf for any reason, do not pull it back out, but instead push it out by applying force to the trapezoidal tab.

Insert shelf
Insert shelf

The last step for readying the top hub is to get four 6mm M3 socket-cap screws and insert them in to the recessed holes on the underside of the top hub. Anchor these in firmly from the other side with four 20mm M3 nylon standoffs. Should you choose to used a different flight controller that does not have 45mm x 45mm hole spacing, you can alter or omit this step now. Also, if you want your wiring to look neat and you have a wire harness ready for the four ESCs, I suggest you feed that through now as seen below.

Completed top hub assembly
Completed top hub assembly

Now it’s time to line up and mate these two halves. If you refined and test-fitted your parts already this should be pretty easy. Simply align the eight screws protruding from the bar/bottom hub assembly and seat firmly. Now get a few M4 nylock nuts and gingerly tighten them to all the screws. DO NOT over tighten these, you will risk breaking something. The shelves and four bars should sit flush in their cavities, the hubs on the other hand should have a slight space between the two as seen below.

Unfinished frame assembly
Unfinished frame assembly

Lastly we will want to loosely attach the landing gear to the arms. Each landing gear assembly has a spot to clip in any ESC with a 24mm width. I suggest you use Turnigy Plush 18amp or 25amp ESCs. We want to attach the gear loosely in order to manage any slack in the ESC wires later on.
Grab four 35mm M3 socket-cap screws and corresponding nuts for each arm and attach the landing gear as seem below. Again, DO NOT over tighten these, you will break something.

Semi-complete arm
Semi-complete arm

That’s it! Your quadcopter frame is complete. All the electronics and software on the other hand is up to you due to the innumerable different combinations of hardware you can use on it. A brief list of the hardware I use and know works swimmingly is listed below.

 

Electronics (and propellers)


For a superb flying quadcopter, I use the following. The stores listed below are where I purchased my stuff, your local hobby store may have a more convenient selection.

From HobbyKing

From RCDude Hobbies

From RCTimer

From your local hobby store

From your local hardware store

  • Assorted zip-ties
  • High strength outdoor Velcro
  • High strength outdoor adhesive strips
  • Clear tape (for prop balancing)

 

Additional notes


Note: When attaching your motors, you will use the threaded shaft that gets bolted to the top of the motor to attach your props. You will also need to attach your motor to its provided cross plate (sometimes hardware add-ons are sold separately, watch out) before bolting it to the motor mounts with the 14mm M3 socket-cap screws and nylock nuts.

Note: Review previous images at the beginning for proper use of the printed cable clips. These are pretty self-explanatory nonetheless. They clip on over any wires that will reside in the gap and should primarily keep wires out of the propellers.

Note: Use the M3 nylon nuts to secure your Crius MultiWii board to the nylon stand offs.

Note: You must program your ESCs before flight, otherwise your quad may will plummet to earth (or any  other celestial body for that matter) unexpectedly. Observe the following image and use your ESC programming card and its manual to duplicate these settings on all four of your ESCs.

Program settings for all ESCs
Program settings for all ESCs

Note: If you are using the MultiWii flight controller like me, open up the MultiWii.ino file through the Arduino IDE and click on the config.h tab. You will need to change the lines stated below. This is only applicable to the hardware used and the specific version of software available at the time of this writeup. Search around the net for instructions and tutorials that match your specific setup.

  • First, uncomment (remove the “//”) the line for the X type of multicopter,
    #define QUADX
  • Then adjust the minthrottle line so it reads
    #define MINTHROTTLE 1032
  • Below that, you will need to change the line for mincommand to
    #define MINCOMMAND 900
  • Now you want to comment-out the line
    //#define I2C_SPEED 100000L
  • And uncomment the line reading
    #define I2C_SPEED 400000L
  • Now scroll down a few lines and uncomment the line
    #define CRIUS_SE
  • Finally, scroll down a ways and uncomment the line reading
    #define RCAUXPIN8

Once you are done editing the code, you are now free to upload the sketch to the flight board via an FTDI cable. Make sure the FTDI cable is set for +3.3V logic level and VCC output voltages with DTR enabled.

Note: Observe this screenshot for a reference in PID calibration. Seen here are my settings that seem to work flawlessly with my specific setup. Finding these often unique variables is a general procedure many DIY multycopter enthusiasts have to go through.

My MultiWii Config settings
My MultiWii Config settings

Note: Finally, get an AMA card (or equivalent) and go fly!

 

Additional media


Here is a timelapse of me building of this quadcopter.

 

Watch a complete amateur fly this RC aircraft for the first time. The center hub finished printing just minutes prior and the landing gear hasn’t even been designed yet.

 

Finally, laugh at the world’s lowest altitude multicopter crash caused by me accidentally inverting the ESC signal cables.

 

5 thoughts on “Quadcopter – Revision I”

  1. Hi, do you have sketchup/solidworks etc. files for this? If so can you post it? I wanna customize this for 15mm square profiles.
    Thanks

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