GoPro Gimbal 4th Axis - CNC Router Project

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GoPro Gimbal 4th Axis - CNC Router Project

Postby OakLines » Fri Dec 15, 2017 11:42 am

4th Axis handle for a GoPro Gimbal - Take the bounce out of your step and create drone like walking shots that almost seem to hover along.

4thAxis-Title.Still001.jpg (643.79 KiB) Viewed 4355 times

Posts: 265
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Re: GoPro Gimbal 4th Axis - CNC Router Project

Postby 4DThinker » Sat Dec 16, 2017 7:52 am

Thanks for posting. Good use of a CNC for making the parts. Great video. :)

You talked about tuning the system. I'm wondering what your options were for tweaking it if it had needed tweaking? Different spring? Different attachment points for the same spring? If you change to a camera that weighs more or less than the current one, does you gimbal have "room" to keep working across those differences?


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Re: GoPro Gimbal 4th Axis - CNC Router Project

Postby OakLines » Mon Dec 18, 2017 8:20 pm

Hi 4D, thanks for the kind words…

In this example - the natural frequency was baked into the design via some trial and error. ;-)

Generally speaking, you have two options for adjusting the natural frequency (fn) - the stiffness of the spring and/or the mass of the system.
The fn for a simple single degree of freedom spring mass system is proportional to the square root of K over m
Where K is the stiffness of the spring - and m is the mass.

So thinking about it...
stiffer spring - higher fn, softer spring - lower fn
more mass - lower fn - less mass higher fn

So there are lots of ways to maneuver here using both the numerator and denominator –

I wanted to keep it as light as possible, so I didn’t consider adding or removing weight as a viable option. The gimbal and camera weigh what they weigh - and I couldn’t remove any more mass from it - and I didn’t want to add any extra either. Well actually, I did play around with adding some weights to lower the frequency at one point – but once it started getting too heavy, I decided it was just silly to make it heavier.

So what I did (off camera – not in the video) was measure my walking and running cadenced with some instruments that we manufacture - to provided a reference frequency to work around. Then with TTV4 and the vibration test system I could measure the response of the system as I experimented with various configurations.

Initially I was using bungee cord in various sizes and configurations, but I couldn’t get that to work in the range I wanted. So I switched to wire springs, and sampled all the ones in my collection to no avail. They were all either too soft, too stiff, too long, or too short.

So eventually – I got the bright idea to wind my own – of the stiffness and length I needed. It was actually pretty fun, just formed it around a dowel in the drill press.

It was fun - and good background project to tinker around with.

If I changed the gimbal/camera setup – or the expected working conditions – I’d probably have to wind a new spring for it to keep it in the working range.

Thanks for the reply! ;-)

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