Project description and CAD images in part 1.
Short summary: the Black Widow is a scratch-built, heavy FPV spider quadcopter. I designed the frame taking some inspiration from the Quaternium Spidex v2, but incorporating a lot of changes including carbon tubes for arms and helicopter landing skids. Frame plates were cut on a CNC machine for me by a colleague from my designs. It is intended as a replacement for an old X525-based FPV quad I used until recently, and uses all the same electronics (NTM 2830-750, 11x5 Graupner, Blue Series 30A, Crius SE, 4S4500).
Black Widow
Without further adieu, here's pictures of the final result. Detailed build log further below.
Build log
Most parts laid out neatly on the table. The order didn't last long...
Using a sharp fine-toothed saw and taping the cut lines over with paper tape, cutting the pipes was easy enough. Chosen arm lengths of 22 and 28cm allow cutting all arms from a single 1m piece of tube, cutting costs a little.
First bolts are put into place. Custom designed and CNC'd bottom plate, Flyduino FCP HL clamps.
Screwed the center together to check that everything fits. It does.
Bolted on the rest of the frame. Again, all plates custom designed and CNC'd. Looks like it's almost ready, right? Wrong...
Motor shafts of the NTM motors are on the wrong side and had to go, so the motors would fit over the tubes. Taping them up to prevent metal filings from going into the motor magnets and applying some Dremel power...
A clean cut. Dremel goes through 3mm shafts like a hot knife through butter. Don't forget eye protection when doing this!
Stripping old ESCs of their covers and getting ready to fix the cables as needed.
Cut to length and bullet connectors soldered on. A total of 12 motor cables, that's quite some soldering to do... and this is only for a quad.
Placing ESCs onto the frame where they will go.
Motor bolted onto the holder and cables laid through the arm. It fits!
Applying new protection heat shrink to the ESCs after the cables are all re-soldered.
Installing ESCs, routing cables. Not perfect, but clean enough for me.
Power distribution inspired by RCExplorer. The cables are first all put together...
... then tighly wound together using thin copper wire ...
... and then soldered and wrapped in heat shrink. The connection is solid both mechanically and electrically, and works well.
Test-fitting the complete assembly: seems to fit well! Both halves aren't connected yet, the top simply rests on the screw tops of the bottom part.
Top subassembly, including the top center plate with the electronics (Crius SE, Drotek I2C GPS) and the vibrodampened tubes carrying the GoPro on the front and battery on the back.
Video chain on the bottom side of the top subassembly: GoPro with a live-out cable, a MinimOSD flashed with KV Team OSD firmware for MultiWii 2.2 compatibility, and an ImmersionRC 5.8G 25mw transmitter.
Bottom subassembly is prepared for joining with the top. Motors are propped up on various items to keep the clamps in the middle from coming apart when temporary screws are removed.
Top subassembly is lowered onto the bottom and screwed down. Tighten everything down, plug in all the cables...
... all done! Ready to fly, once the weather permits to do so.
Build results
The build largely succeeded as planned. All the components found their place within the frame, and the assembly is very stiff, which will allow for good flight performance.
On the downside, the goal of lightening the quad vs. the previous X525-based version was missed, badly. The final all-up weight including the GoPro and the 4S4500 NanoTech battery is 1.9kg, 100g more than the old build - it seems that "carbon tubes + clamps + tons of screws" principle doesn't work out as lightweight as expected. Still, it is well within the performance envelope of the drive hardware.
Maiden flight results
Two words... EPIC SUCCESS. Stable in the air on the very first takeoff, great in FPV. Flight time: just over 14 minutes until the LiPo alarm kicked in, so over 40 minutes per outing with the 3 batteries that I have. PID values need a little fine tuning, P for roll seems a bit high - but overall it flies much, much nicer than the X525-based predecessor did.
I'm definitely very happy with this build, and will be using it a lot in the coming weeks.
Any comments, suggestions, critique or any other kind of feedback are greatly appreciated :)
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Did you flashed your ESC's with simonk firmware?
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How did you power the FPV setup, Ive been looking around for hours for an answer :)
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This weekend I'll be building a brushless gimbal setup for the Black Widow, the power distribution gets a bit more complicated there - I'll power the gimbal with a 12V UBEC, and a new FPV camera with a 5V->12V step-up converter from the ImmersionRC transmitter 5V output.
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