LitterBug's build of the dRehm dRifter

[LitterBug]

@NickRehm dropped a really cool new YouTube video lately with a new take on an idea I have been wanting to try for a really long time. Adding a pusher prop to a standard race drone. He kicked it up a notch by designing a 3D printed frame, adding a lidar sensor for altitude control, using a standard RC Car controller to drive it like a car, using his own firmware, documenting it all really well, and making it all open source for everyone to build, play, improve upon, etc.. Met up with him at FliteFest and got to see some of his other awesome projects as well.

Check out his video where he was testing it out

It's all documented here https://hackaday.io/project/191240-flying-rc-drift-car

I am using this thread to document my build and shenanigans!

Cheers!
LitterBug

I am half tempted to fly it on dRonin firmware at some time so I can dRive a dRehm dRonin dRifter

 

[LitterBug]

Planned-ish Hardware:
Frame: dRehm dRifter printed by PCBWay
FC: Matek F405-CTR Built in PDB, plenty of IO ports, Plenty of PWM outputs, Baro, 5V & 12V power, SD card
RX: Radiomaster EP2 Nano ELRS (telemetry back to TX so I don't have to tape my phone on for data collection)
GPS: RMRC Mini 220 ( don't want to tape my $200 phone on for recording )
Lidar: Benewake TF Mini plus protected
Battery: 4S Lipo. (plausible Li-Ion)
FPV Camera: Something smallish with wide FOV when ground hugging. will swap for narrow FOV if flying higher.
FPV VTX: 1.3ghz for better penetration cruising through and around ground level stuff
Threaded inserts: Adafruit M3x4MM
ESC(s) - Pusher: 30+A, 4S, (with BEC to plausibly drive servo(s) and accessories?)
ESC(s) - quad: 30+A 4in1 4S
Motors: SunnySky X2207S kv2700

Extras:
Lights: HECK YEAH!
Paint/vinyl: HECK YEAH!
Horn: Don't you know it!

 

[LitterBug]

Planned-ish firmware:
INAV
ArduPilot
DRehmFligh on a Teensy v4.0. (ALL the cool stuff)

I have several of the Teensy boards, but they are currently tied up with other projects. For now I plan to use an OpenPilot revolution since I have a few laying around, has plenty of PWM outputs. Has plenty of serial ports, and it is compatible with the majority of flight control software out there.

 

[NickRehm]

Sweeeeeeet!! Was awesome meeting you and hanging out at FF. Hopefully next year we can race if I don't destroy mine by then

 

[LitterBug]

Sweeeeeeet!! Was awesome meeting you and hanging out at FF. Hopefully next year we can race if I don't destroy mine by then

I already have ideas in case I crash this one too bad, and also some ideas for Combat!!! Like maybe even an upscaled version.... Hmmm. We may need to collaborate on a combat version for next year....

Oh, and Boris the spider will be riding this build for sure! Wile E Coyote is wanting to go for a rip, and I think even Woodstock wants a crack at it. A lot of pilots are already in line to go for a ride! Some of the pilots want me to do yaw vectoring on the pusher motor. One asked for twin EDF differential thrust for the pusher.


Cheers!
LitterBug

 

[LitterBug]

Things are getting heated up in the shop. Some Crazy ACME parts are already showing up, test fitting for a driver's seat, bringing parts mods in, and requesting some cool options

 

[LitterBug]

Been "organizing" my many bins of parts, looking at old quad builds, etc... and evaluating what hardware to use for the initial build. I have been making updates to the 2nd & 3rd posts to reflect what direction looks best without acquiring too much additional hardware. Once i have a clear path forward, I'll start hooking it up on the bench and adding more pictures.

The Quad Motor/ESC gear is my last real decision point. Do I strip an old quad, use stuff laying around, etc....

Cheers!
LitterBug

 

[LitterBug]

Pretty much decided on my final hardware config. The pusher motor is still in the air, but it will be easier to just drop anything in that position since it doesn't need to match the rest of the motors. Have enough unused parts so I will not need to tear other builds down to build this up. The parts I've chosen should also allow me to scale a replacement build up a bit in the event that this one gets destroyed. :-D

Cheers!
LitterBug

 

[LitterBug]

Doing some initial sizing - fitting - arranging to make sure selected components will fit, figure out how much length to add to the rear motor wires, etc... Found the puffiest, most dead, 4S 1550 battery I have, and it still fit.

Will need to slot half of the motor mount holes to use this version of the frame. My motors.do not have 4 equidistant mount points. 2 are correct, 2 are wider. Going to look at @NickRehm 's files to see if there is another version to print and or modify in case this frame goes destructo. After I get the motor mounting and wire length fixed, the top and bottom will be glued together with CA for added strength.

Cheers!
LitterBug

 

[LitterBug]

I've started soldering up the FC, loading firmware, and making slow but steady progress.

Installed latest INAV configurator (6.1.0) on laptop, and installed INAV 6.1.0 on the Matek F405-CTR board

Soldered up Radiomaster RP2 ELRS reciever to RX2/TX2, bound, configured and tested. Getting telemetry back to my TX16S with the INAV LUA script.

Soldered up GPS with MAG to RX4/TX4 and SDA/SCL. Will need to supply power to the board to test.

Calling it a night.

Cheers!
LitterBug

 

[LitterBug]

Not the best GPS in the world. I've been able to pull in satellites down in the cave with super cheap ones. This one while comminicating fine with the FC with good compass data, is coming up NIL on the sats.....

Mmmm. All my other GPSes have a different pinout.... Will repin the connector and try a different GPS.

Mmmmm. bahhh.... switched to a different GPS and no change. Guess I need to get out of the cave for the GPS test.
Cheers!
LitterBug


Edit: the cave seems to be extra fortified against GPS. Worked fine upstairs. Now to add lidar.... :-D

 

[LitterBug]

Bought wrong OD (too small) heat set threaded inserts for the FC mount holes. Nothing some hot glue or epoxy won't fix. (Oops!)

Working on the lidar hookup and testing too.

All sensors present!

LB

 

[LitterBug]

Seriously considering switching to ArduPilot rather than INAV before finishing the build. INAV prioritizes the Accelerometer for althold over sensors like a baro, lidar, and GPS causing very erratic althold behaviour in the presence of vibrations. Due to the 3D printed frame, this could be a real stumbling block potentially causing a crash hazard. Their answer, get rid of vibrations.... REALLY??? >Sigh<

LB

 

[LitterBug]

So, like always, working on about 5 builds at the same time. Really need to cut that out and focus on getting this done! In all fairness, some of the same functionality that will be used for this build may well be used on some of my indoor/winter fly projects as well. Have Diatone Tina-Whoop 1.6" and Diatone Taycan 3" ducted Cine-whoop builds that may get lidar and possibly optical flow. Curious to see how these all deal with me flying off the balcony at work and up down the escalators too. 🙃 Using these as a test bed for ELRS too. Never really had issues with FrSky or DSMX at the indoor flys, but if I am running close to the ground, it may be possible to get behind small hills out at the field, which I HAVE had issues with in the past.

Cheers!
LitterBug

EDIT: also getting all my ESCs updated to the latest BLHeli_32 or BlueJay firmware....

 

[LitterBug]

Needed to extend the rear motor wires since the FC and 4-way ESC is way up front.

 

[LitterBug]

Working on finishing/modding the frame to mount everything up. Need to slot half the motor mount holes to fit my motors, drill out the motor center since the shafts are bottoming out. Have the ESC/FC/GPS threaded inserts glued into the frame.

Cheers!
LB

 

[NickRehm]

Looking good! Make sure you spin props in the tips-out configuration. Those little bumps under the motor mount were an afterthought to give it 2-3 degrees outward tilt for more yaw control.