24 April, 2019 at 02:49 #61587
I’m here in the Northern Hemisphere and it is gorgeous spring weather (not that we can’t fly in the winter, but that is indoor project weather). Time to fly!!! In prepping for the season it’s time to revisit my beloved RCExplorer models (Baby TriCopter and the newer BiCopter). We have a thread on the Tri and DRoni; need to give that a try (pun). In searching for the next tuning adventure on the BiCopter (and a new place to collect unmodified kit tunings) I created this thread.
So the first item in my search I came across is this YouTube video:
The gentleman that posted it provides his settings in the description area (make sure you use the correct resource mapping for your board).
Eight things of interests:
1. It looks somewhat like an RCExplorer when you look at the parts he used to build and he even references Dave’s site, but it is not completely the RCExplorer design. In fact his copter has the FC mounted upside down on the bottom below the arms (maybe part of the secret sauce to mount the FC below the motor rotational axis). I may print some parts to try this on the stock design.
2. The flight video at the end looks really promising for the tune he has. You can hear some oscillation, but it never feeds back and runs out of control. And !!!! he flies in all directions (including backward) without issue and at a reasonable speed.
3. He’s running BetaFlight 3.5.1 set to Bi-Copter.
4. Only his Yaw D Term is set to 0
5. Not using feedback servos (which in Betaflight would not help anyhow)
6. He’s using the cheaper BangGood racestar motors
7. The tilt mechanism is different than Dave’s design but same orientation.
8. The prop rotation is opposite default for Betaflight, but matches what Dave suggested.
Thoughts. I will be trying this tune by the weekend with BetaFlight 4 to see if there is any improvement to the stock setup. If you use BF4 reference Joshua Bardwell’s video on BF4 trying to kill you so it does not kill you!! https://www.youtube.com/watch?v=wLAfYNTYPiw&24 April, 2019 at 11:07 #61590
Not to be rude but i have a hard time trying to understand the purpose of your post…
Are you asking for help, are you promoting what looks like a knock off of Davids design? I ask because, normally folks come here to either ask for help or showcase “their” builds. However every once in a while there are those that assume its ok to post promotional content of some form, which isnt cool. Please clarify your original post so we may better help you.24 April, 2019 at 13:46 #61593
If you’ll check my previous posts you’ll see that I was onboard with the Bicopter from the beginning last year and helped to route out original mapping for the kakute FC. I applaud everyone’s efforts to improve the bicopter with all kinds of sOAT mods and ducts but I’m intested in getting back to tweaking the stock setup whether hardware placement or software tuning. I’ve been following these threads, but have not seen this yet. The video linked above is not an ad or someone promoting a competing product and he even references David’s site. What I found interesting is he seams to have a relatively good tune on a pseudo rcexplorer design but his FC is hanging upside down and below the carbon arm. Upside down is no big deal, but how far away the FC is from the center of rotation is intriguing.
So no, I’m not promoting anything but trying to improve the stock setup with minimal changes to the baseline design which hopefully feeds back a result that Dave can release a V2 on. Think of it as a new github development branch.
Thanks for asking.24 April, 2019 at 14:09 #61594
OK just checking…24 April, 2019 at 14:25 #61595
Rotational rates are not influenced by how far the rate gyros are from the center of rotation, the whole vehicle, every point on it, rotates at the same rate.
Accelerations are a different story, and moving the accelerometers away from the center of rotation can have some very undesirable effects, which are usually compensated for by what’s called lever arm corrections. Our scales (offset by maybe a couple of cm), coupled with the noisy environment, it’s likely a don’t care.
The difference is the mass distribution, the copter presented in the video will have it’s CG below the center of rotation, which gives the dynamic system some damping, which the bicopter really needs in pitch. On my RCE BiCopter, I’ve printed a simple spacer, about 30 mm deep, which suspends the battery below the frame. This has shown the most promising improvement on flight characteristics of all the things I’ve tried so far, although I’m still in the tuning and setup stage. I’m considering rebuilding the BiCopter and removing the sOAT motor mounts to really quantify the change.
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