Gimbal arm Mk II

As per our previous article Gimbal arm, we’ve got seriously misled by this project in past three months. There were too many things happening so let’s just go through several highlights.

Design update

Trying to get around that criteria of having our arm light, but still very firm we’ve progressed for a multiple channels arm:

To a single channel arm with clamps and 20% filling:

Current complete 3D model of our arm then looks like this.


While it sounds like a trivial thingy, it took quite an effort to get it right. The thing you are seeing on picture below is practically just a garbage due to poor design, where each of these prints is ~200g of wasted filament + 24-36hrs of printing.

Printing challenge

While printing became somewhat common for us, some of those latest 36hrs prints came in as something new. Particular problem was our garage sound proofing – it is far from perfect and while it can be happily ignored through the day it resonates through a whole house through the night causing some unwelcome family discussions.

Let’s have a look how such print looks like in a time-lapse.

Here you may ask why it is being printed in that most inefficient way – but trust me, this is the best way we identified. Bending forces imposed through the printing due to the temperature differences can come with an incredible power on these lengths and kept ripping the print in a pieces without any problems.

Well at the end we’ve finished having pretty nice collection. 🙂

Cabling mayhem

Blueprint below depicts our cabling plan. Whatever is there – in short it actually means that we needed to get 7 different cables through the arm’s central shaft to have it all working.

In some cases it took up to several hours to make it happen! Chickening out on our first go – I cut out a bit of material to actually make it happen, but it really wasn’t needed later on.

This included also changes to all the connectors around and new power bridge development (I’m keeping this one out of this post as there is more about it). Anyway gimbals ended up needed rewiring as well.

All four arms assembly and cabling completed looked pretty satisfying. It took us two whole weekends just to do this.

Trusses replacement

In comparison to all the other tasks this was a back to basics. Old steel stabiliser rods connecting our thrusters needed to be replaced with a light-weight wooden variant before mounting in our new arms. This could be considered as a cosmetic, but still took us some effort to do it right.

The last bit missing was to drill an oval hole in each support leg to be able to lead our cabling through it.

New arms

Finally we can present you – new arms! Enjoy!

Aren’t they beautiful?

As always, if you read all the way here, please drop us a note on what you think – your feedback is our best motivation. 🙂

Next time – new 6V and 25V power bridges and let’s get back to the ArduPilot again!

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