I'm Designing an Open Source 5" FPV Freestyle Miniquad Frame!

I've been doing a bad job here at Patreon.  It has been several months since I made my last post.  That means I'm also doing a bad job at figuring out how to have my Kestrel frame manufactured.  Aside from any potential tweaks needed to cut the frame on someone else's properly professional CNC machine, it has been ready to go since April.  What am I waiting for?

We'll talk about that in the next post.  For now, lets talk about the new 5" frame I'm designing.  I'm calling it the Falcon.

There's the current 6" layout with a placeholder 1300 mAh 5S battery and GoPro Session for scale.

The American Kestrel is a pigeon-sized falcon, and they inhabit the local park that I fly at.  You can see the park from my back yard!  Being birds of prey, Kestrels should have good vision, and my tiny Kestrel frame is designed to carry an HD FPV camera, so the name seemed like a good fit to me.

This new frame is bigger, and I couldn't find any particular species of Falcon that I liked, so we're just going more generic this time.  The Kestrel's heavier, sturdier, bigger sister will be the Falcon.

The Falcon Isn't All That Unique

The starting point for my design is the frame I fly every day.  My favorite frame.  The Hyperlite Flowride.  The proportions are similar.  The layout is similar.  I'm even making sure that the Falcon uses the same TPU GoPro mounts, because I have so many lying around.

Like many freestyle frames, the Falcon has is two plates separated by standoffs.  This is a simple design, but it is still my favorite.  If your electronics don't take up a lot of room, you can lower your center of gravity by using shorter standoffs.  If you can't quite fit your stack into the frame, you can just swap in taller standoffs.  No fuss, no muss.  I like that kind of versatility.

What is Unique About the Falcon?

I could just say that it is Open Source, right?  I think I can count the number of Open Source freestyle miniquad frames on one hand, and two of those frames are my designs.  I don't think that's a good enough reason to spend the time designing a frame.

Like the Kestrel, the arms on the Falcon are easily configurable.  You don't need any CAD experience to adjust the frame to your liking.  If you can edit a text file, you can adjust the length and angle of the Falcon's arms.  Do you want a 5" stretch-x layout?  A 7" wide-x layout?  You can make that happen.  You just have to find a way to have the arms cut for you.

With the Kestrel, I wanted the fuselage to always be the same.  I'm straying from that for the Falcon.  I want the arm mounting holes to be compatible with every Falcon, but there will be three fuselage configurations.

There will be a long layout with three stacks: a 30.5x30.5 stack (with 20x20 holes as well) in the center, a 20x20 stack up front, and a 20x20 stack in the back.

There will be a truncated layout that completely eliminates the rear stack.

There will be a partially truncated plate that eliminates the rear 20x20 stack, but still leaves room for an extra battery strap.

My plan is to use the top and bottom plate to be identical.  That means you won't have to cut or buy as many spare parts.  I plan to fly with a fully truncated bottom plate and a partially truncated top plate.  That's the layout in the above screenshot.

How Much Code is Shared with the Kestrel?

A lot of code is shared!  I thought for sure that I would be starting from scratch with the Falcon, and I'd just be borrowing small parts of the Kestrel.  Parametric motor mounts were tough to get right, so I knew I'd be stealing those, but what other parts could I pilfer?

Even though the two frames look quite different, they are similar enough that I decided it would be best to build them together in the same source tree.  If you want a Kestrel, you "include" one of the Kestrel configuration files.  If you want a Falcon, you "include" one of the Falcon files.  Easy peasy.

I'm excited about this, because it means I won't have to port changes from one model to the other.  When one frame is improved, the other will be improved right along with it!

How Far Along is the Design?

Far enough along that I'm thinking about cutting my first prototype Falcon this week.  Everything looks reasonable on my screen, but how will it look in real life?


I thought my very first Kestrel prototype looked good on screen, too, but the side plates were way too sturdy and heavy in real life.  I'm expecting to have the opposite problem with the Falcon.  Parts that I think look just about durable enough will be flimsy.  At least it will be easy to fix!

What do you think of the Falcon so far?  It is a little rough around the edges.  Getting the more aesthetic elements right will have to wait until I cut a frame and see how it feels.  Do you think I'm on the right track?  Should I give up?  Let me know what you think!

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