Hi guys,

I was hoping you can help. I have recently got back into RC Flying after a long break. Having dived into FPV, I also fancied combining my 3D printer and creating something that flew. I printed and built the Avatar Bi-Copter but I am having a bit of an issue. I am new to flight controllers and betaFlight and can’t fathom what’s causing the issues.

Problem 1: When I arm the copter, occasionally motor 2 struggles to start. This seems to gets worse after a couple of hard ish landings (the reason for which is below).

Problem 2: when I start to power up the copter, the blades, controlled by 2 servos, twitch and start to angle backwards. You can see the behaviour when the copter isn’t armed and I simply push the throttle forwards in the first video.

Problem 3: the main one and the reason for the firm landings. If I manage to get the copter off the floor, the blades, alternate flipping forwards and backwards and essentially make the copter shake violently and you have to put it back on the deck. When this does happen, the blade lock into a position normally pouting towards the rear.. the o my way to reset them is to disarm the copter and they reset. I have attached a video showing the behaviours listed above.

I am using a Matesky F4 Flight controller using motor positions 1 & 2 for the motors and 3 & 4 signals for the servos. All of this is set up in BetaFlight.

If anyone can point me in the direction of possibly curing this I would be so grateful as it is driving me insane!!

your videos arent available, you can load it to youtube, dropbox... and paste the link inhere. attachements are limited in size.

bi copter is still uncommon and therefor more difficult. i tried to build a tricopter, but the servo i used and the mount of the servo was an issue, its still on my todo list.
there arent to much examples for bi- and tricopters, maybe you can find some additional infos by searching on rotorbuilds.com and contact some builders with bicopter experience

how did you mount the servos? what kind of servo do you use?
what motors and esc are in use? tell us more pls

Hey,

Thanks for your reply. I totally forgot to add the videos. Here they are:

https://youtube.com/shorts/-lA5qo4Ya78?feature=share



The servos are mounted in the side of the body and are totally solid. The servos twitch when you move the copter round where the fc is trying to correct the movement. The way they move seems correct as well. I don’t know if I need to set the pid settings?

The servos are Emax micro servos, the motors are iFlight and the escs are HobbyFlight 40a

first of all, very nice, it looks awesome :-) https://rotorbuilds.com/search/bicopter here are some examples and maybe some help for tuning.

rcexplorer is a frame designer and builder. he did tricopter designs and also one for bicopters. he might be one of the experts for that kind of build in betaflight: https://rcexplorer.se/

tuning might be it, i would suggest to start lifting with area between ground and props, the downward airflow has no room to go away and change the pidwork there, you shouldnt try to tune it for that situation. room between ground and props would true true flightsituation and show the work of the servo better.

i will mention about it and come back here, not sure if i can help.
my start for tuning would be, lower all pid values by about a third and add some d-term to yaw. as yaw works different on a bicopter, it might need the dampening of d-term. i would try a low value of about 5 on yaw d term and see if there is any improvement

You said you were using Beta Flight? Check to see your not in airmode. It can do strange things when it supposed to be sitting still. I think it’s now a default to have on.

Thanks for the replies guys. Apologies for the slow responses.

@kevin2112 - I have tried it in Angle, horizon & in default, which I assume is airmode. Still the same behaviour.

@hugnosed_bat - Thanks for that. I will head over there and see if I can fond some pointers. When I get 5 minutes I will give the PID values a crack to see if that can sort it