Design a Quadcopter, Become a Maker

I'm far from classifying myself as a Maker, but I figure that shouldn't exclude anyone from having a go and seeing just what the maker process feels like.

It all started with a long time curiosity regarding quadcopters (multirotors). I know what they are, have a high level understanding of how they work, and most importantly have been following their relevance and specific applications to the Architectural, Engineering and Construction (AEC) industry.

Then one day I decided that being an idle spectator over the internet was not enough. In order to better understand the use cases of multirotors I needed to better understand the mechanics of how they work. So I started down the path of designing and building one.

Just to be clear, my past experience with multirotors is nothing more than reading about them online and talking to vendors at trade shows, which I've done a lot of. And I've never even flown one, not even as simple as a cheap import toy from China. I don't have an electronics background, nor did I have any idea regarding the core components that makes a multirotor function.

I could already see that this was going to be a steep learning curve.

The Plan

Before starting the design process I decided to outline some simple guidelines:

• It had to be a quadcopter. This is the simplest of the multirotor forms.
• It had to be a simple design. After researching online I found some photos of a design which looked suitable as a starting point.
• It had to be easily repairable. The arms which support the motors needed to be easily replaceable without disassembling the entire center section.
• It had to be upgradable. I wanted the potential to mount a Go-Pro style camera at a later date. I can also easily upgrade to a full telemetry system, like including GPS.
• I wanted to geek out a bit by learning more about Autodesk Inventor design software to design the parts. I work in AEC after all, not manufacturing.
• I wanted to use different manufacturing techniques. This ended up including laser cutting and 3D printing.
• And at the end of the day it needs to perform. I want to have acrobatic fun with this, not just for mindlessly hovering around.

The Design

Before doing anything else, I needed to work out some performance specs. Using an online service called eCalc I was able to enter in some basic information which would estimate a variety of data that I could use to start tweaking my specs until I was happy. For someone new like me this was invaluable, otherwise I would be running blind.

Moving onto the model design phase, coming from the AEC world I already spend most of my day inside virtual design environments. Having ready access to software for product design I figured it would be a perfect chance to expand my software knowledge in this area. Even though in this instance I used a professional grade software product, there are other free alternatives like Autodesk's range of 123D products that can assist a novice in 3D product design.

There were three parts which I needed to build to form the main frame structure; the motor arms, the center plates, and some kind of cover to protect the electronics.

The Build

It was interesting to see that despite how much I virtually designed my idea, it still ended up evolving as I was making and assembling it. As simple as my project was, it gave me a glimpse into the complexities of what a true manufacturing process could be like, and the important roles of rapid prototyping technologies like laser cutting, CNC routing, and 3D printing.

Things just don't feel right until they are tangible.

Here's how the build process went.

Using the maker fabrication service Ponoko I had some acrylic jigs cut. I wanted to make the center plates out of 2mm carbon fiber, but getting a single run of CNC cut carbon fiber was going to be cost prohibitive, so I decided on this more manual and cheaper alternative.

The carbon fiber sheet had two locator holes drilled in it which aligned with the pins on the bottom half of the jig (below photo, right). With the carbon fiber sheet in place, the top half of the jig (below photo, left) was placed on top, once again aligning with the pins.

Using a Dremel tool the carbon fiber sheet was literally routed out. This resulted in two surprisingly neat plates. All they required was a quick tidy up with fine wet and dry sandpaper.

The two center plates were then bolted together and spaced apart with 13mm brass spacers. This provides structural integrity to the center frame while allowing the motor arms to be slotted into the gap and fixed with bolts through the remaining two holes.

I originally planned to have a simple carbon fiber plate to protect the electronics, but due to how it was mounted this now interfered with my plan to easily install and remove the motor arms. It also looked chunky and ugly. So I went back to the design software to figure something else out.

I ended up settling on a slightly more complex solution which in the end resulted in a far more elegant finish. It also allowed for a smaller form factor. The cover I eventually designed fitted very snug over the flight controller board. Both items were then fixed directly to the center bolts thereby again freeing up the two outer bolts as originally planned.

It took an hour to 3D print on an Ultimaker 2. The material used was PLA and was more than solid enough to protect the enclosed board.

And it fitted like a glove... well almost. A few very minor trims with a knife was required. I've since updated the design with a fraction more tolerance.

The center plate arrangement is now much neater and far more compact. I was originally wanting to print it in black, but racing red is much better.

The final steps were to drill all the holes in the motor arms, and then assemble. Surprisingly, learning how it's all wired together and calibrating the electronics took longer than the build of the frame.

Here's the final result.

The Fun

Of course it's not all serious work, so it was time to finally see it in action. Like I said previously, I've not flown a quadcopter before so I had to step into this cautiously. Fortunately, it wasn't as hard as I was expecting.

The Conclusion

Put simply, for me this project checked every box which I set out to achieve. It's not only the satisfaction of building the project, but I now have a slightly deeper understanding of the mechanics and electronics which goes into making a multirotor fly.

Even though my quadcopter is only the bare basics, the research I put into it and the expandable nature of the equipment I've chosen takes me one step further to a better comprehension on the complexities of how autonomous multirotor drones function. These include; payload limitations vs power, manoeuvrability, stability issues, autonomous expandability even at this simple level.

It is this new knowledge which now gives me a clearer insight into the potential applications which drones could play in the AEC industry of the future.

And do I now feel like a maker? Yeah, I think so.

I've designed, iterated, made, and tested my own custom creation. I think there's something to be said for that.

Doing The Maker Thing 

In the true spirit of the maker community I would like to make available all the information I have on the chance someone else wants to be a quadcopter maker too.

Design Files

You can find CAD files from the following Autodesk A360 links.

• Autodesk Inventor Model* (Click to view the model in the browser)
• STL for the Flight Control Cover
• Drawing for the Center Plate
• Drawing for the Arms

*Naze32 Flight Controller model provided by The M Brothers.

Inventory of Parts

Make

• 1 x Flight Controller Cover - 3D Printed
• 2 x Center Plates - 2mm Carbon Fiber
• 4 x Aluminium Arms - Cut and Drilled to Suit

Buy

• 1 x Flight Controller - Naze32 "Acro"
• 1 x 3S 2200mAh LiPo Battery
• 1 x Power Harness (i.e. for Power Distribution)
• 4 x 20A ESC (Electronic Speed Controller) - Afro
• 4 x 1090kv Motor - Turnigy Aerodrive SK3 2822
• 4 x Propeller - 8x4.5
• Various Bolts, Nuts, Spacers, Misc, etc
• Your choice of Radio Equipment