By virtual_stephen on Jan 30, 2020

12  428  5

I learned to fly quads with the Hubsan H107L and when I heard about the H107D I thought it was the best thing in the world. A tiny micro with a camera that transmitted video. Amazing, at that time I hadn't seen anything like it and I had to have it. Many crashes later I am building my own quads and have a fleet of brushless craft but I wanted to go back to where is started.
H107D-hack was born. The body of an H107D plus the best brushed motors I could fit and it had to have a proper betaflight setup and of course a camera and VTX with OSD!

Now, there isn't much space inside an H107D so some small sacrifices were made but relatively few. I sourced a tiny brushed F3 board with onboard frsky RX and after shaving some weight off the bottom of the internal battery tray I was able to slide the FC under the battery tray and leave it with the micro-USB plug accessible from the rear without needing to open the frame. The entire FC+RX fits into the space that was used for the hubsan VTX!
Likewise, to fit the camera required a little shaving of the internals but with some patient work it fitted.

Then the maiden. Sadness. Frame seems so flexible that uncontrolled oscillations make FPV impossible. I try to tune, to filter, to do anything but nothing works. I started on Betaflight 3.2, then try 3.5 then in desparation try the cut-down 4.0.6 release even though the F3 has lost many features. Nothing works. Just oscillations all the time.

I shelved the project with a sigh and went back to making brushless models for a while. After learning how to use RPM filter and JESC I noticed the Betaflight "F3 Performance Edition" which is used to enable RPM filter for older F3 FCs. Interesting I thought, didn't really think much of it. Then I thought "what about the H107D-hack?". Sure enough after loading the performance edition of 4.1.1 for F3 I was able to tame the oscillations. Whatever dynamic notch magic was included is exactly what this little quad needs!



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virtual_stephen   Feb 02, 2020  

First outdoor flight - it works but power is low and the camera angle makes fast flight impossible. Still, it's a fun experiment and it runs ok with acro mode at a modest distance. Vibrations are definitely an issue and I am trying to dampen them by gluing the two halves of the frame (top and bottom plates) together with welder. Anyone who flew the old Hubsans will remember how the arms would pop apart all the time, and I'm sure that this doesn't help smooth flight.

virtual_stephen   Feb 02, 2020  

Update - First outdoor flight and it works but the oscillations are still problematic. Power is also an issue, after flying brushless I forgot how underpowered brushed motors can be, and crashed mid-roll. Trying to dampen vibrations by gluing the two halves of the frame together.

virtual_stephen   Feb 01, 2020  

VTX was persuaded into life and after a few lipos it appears that increasing P & D gain and lowering the filtering produced stable flight. These plastic frames have their own rules for vibration and it seems that attempting to filter is a waste of time.
The little guy has some power, keen to maiden this around the park. Lipo placement is less-than-ideal, sandwiching the lipo between FC and VTX is a great way to heat the lipo so this is gonna be a bonafide battery killer!

virtual_stephen   Feb 01, 2020 

Sidenote: It appears that Red Ones do indeed go faster. These motors are badass.

virtual_stephen   Jan 31, 2020  

Looks like I hit the VTX connection to the FC when inserting a lipo, no video! Time to take it apart again then.

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