Trifecta - Foldable - RC Groups
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Oct 16, 2017, 02:57 PM
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Build Log

Trifecta - Foldable


Frame: Trifecta Mini Foldable frame : https://hobbyking.com/en_us/quanum-t...frame-kit.html
w/ Expansion pack : https://hobbyking.com/en_us/quanum-t...sion-pack.html
Motors: Multistar 2206 2150kv : https://hobbyking.com/en_us/multista...aby-beast.html
Servo: Turnigy 9018MG : https://hobbyking.com/en_us/turnigyt...10sec-13g.html
Props: Gemfan 6045-Bullnose : https://hobbyking.com/en_us/6045-bul...ccw-black.html
: https://hobbyking.com/en_us/6045-bul...ccw-green.html
ESC: EMAX 20A D-SHOT Bullet : https://hobbyking.com/en_us/emax-d-s...-blheli-s.html
BEC: Spider Pro Series 5V/2A UBEC : https://hobbyking.com/en_us/5v-2a-ubec.html
FC: Frsky XSR4O : https://www.frsky-rc.com/product/xsrf4o/
Battery: Turnigy Graphene 1300mah : https://hobbyking.com/en_us/graphene...5c-w-xt60.html


So before i get to some pics, I do not like the 9018mg servo. It's apparently not fully metal geared like my other servos but those other servos dont fit the gear for the tail. I'd prefer an all metal digital servo. But meh, it works.

I had some basic fpv stuff on this to test but i took it off before maidening because i hated how it looked and the lack of being able to tilt the fpv camera.
Going forward, i would love to get a simple tiny 1axis gimbal for the fpv camera - or maybe just something with a way to fix an angle. Haven't decided on an fpv setup for this tricopter yet.

Configuration wise, It's using the latest betaflight firmware and I have it setup using DShot600.

Maidened the model yesterday. It flew very smoothly. However it did want to drift and I need to do a lot of editing to my tx because it's a little too easy to get it to want to flip and roll. I only had about one battery's worth of flight time with it before the sun went down. So more to come. I didn't get a chance to try out all the available flight modes and I haven't touched the PID's from stock.








and my multi-rotor case has a new member. (same case I use for my transmitter/charger case)
Last edited by cellsafemode; Oct 16, 2017 at 03:23 PM.
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Oct 16, 2017, 03:03 PM
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My flight controller didn't fit on any of the supplied mounting boards or mount points and the tricopter body doesn't lend itself to making your own mounting holes. So my solution was to create a mounting board out of an old PCB breadboard and glue that to the underside of the top.

I have all the power wires from the power distribution board wrapped around ferrite rings and twisted to reduce noise (including the power wires from the servo). The fpv setup will be powered either directly from the battery or via it's own BEC.

The BEC I am powering the flight controller and servo from is the tiny pcb you see glued to the tail. This BEC is rated for 2amps, the flight controller uses 0.2amps and the servo should also use 0.2amps while operating. So there is plenty of headroom. The voltage coming out of this BEC is 4.8volts.

One thing that wasn't very apparent when i was first setting things up is that you can't wire the Servo to motor 4 on the flight controller. You need to wire it to either motor 5 or motor 6 position as there are timers that seem to conflict between the ESC's and servo where 1 and 2 are grouped together and 3 and 4 are grouped together and 5 and 6 are grouped together. Once i moved the servo to motor 5's signal, everything worked great.

DShot600 is awesome. The motors all spin up simultaneously and smoothly compared to pwm modes that i'm used to leading to motors spinning up at different times and not behaving nicely at low rpm even when the esc's are calibrated.

I am unable to activate 32khz sampling mode, guess i dont have the right gyro chip but no big deal. I do have a fairly annoying drift problem that I'll need to look into fixing. But otherwise for a first flight, it went pretty well. Any flight where nothing breaks or catches fire is good

Do any other all metal gear servos work with this frame without modification? Preferrably digital but analog isn't bad if it centers well.
Last edited by cellsafemode; Oct 16, 2017 at 03:24 PM.
Oct 16, 2017, 10:34 PM
Registered User
Another day of test flights. No crashes. This copter flies so smooth.

Couple things I noticed though.

1. The frame's rear leg, which is attached via a thumb screw doesn't have enough structural support to keep itself from bending out of it's locked position if you land with anything but a feather touch down. I'm not sure why a more sturdy leg wasn't utilized like the arms have. They could have made something work.

2. The servo will cause an oscillation on landing sometimes that you have to then hold the frame to stop. I suspect this is due to the long thin legs the frame has. This could be corrected by having the arming feature disable the servo response as well ....wonder if betaflight has a setting to do that.
Oct 31, 2017, 11:23 PM
Registered User
9.5 minutes off a 1800mah liHV. Resting voltage is 3.75v. So still got juice left.

8 minutes with moving around and what not if you're relaxed while fpv'ing.

and I'm a bit heavier than i was aiming for due to going a bit overboard on the voltage cleaning with 2 3200uF caps and a 1000uF cap and 7 ferrites.

Very happy with the trifecta. The tail servo is a bit twitchy though when attempting to maintain position in horizon mode. The craft doesn't end up really jittering though. I still have a lot to learn about pid tuning under bf 3.2. And i still dont have altitude hold really working with the baro sensor. At least I can use the baro to tell me my general height ...it's sometimes hard to gauge when in fpv. Using the baro and horizon mode, i can nail landings in fpv mode despite the camera being angled for forward flight, even during wind. So that's cool.
Nov 06, 2017, 01:14 PM
Registered User
Discovered that you can't, while using betaflight 3.2.1 with dynamic filtering, go full rate yaw spin for a few seconds. The high speed spin seems to confuse the flight control code and it goes into an unrecoverable spin.

I had about 5 seconds or so to try and recover and it just kept up it's spin. All i could do is lower throttle and let it "land" while spinning. Ended up breaking a landing gear. Not bad damage-wise. Servo is working perfectly. But still. Guess I'll have to avoid doing that in the future. No in-place high speed yaw spins.


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