Black Widow - a heavy FPV spider quad project, #1

I've been flying my X525-based FPV converted quad for a couple months now, and I'm pretty happy with what I learned with it. However, I've been noticing more and more negative points about the frame and the general construction for my purposes. The main three problems with the X525 for me are:

• Space. There simply isn't enough to make room for all the FPV equipment (GoPro, video TX, OSD & co.) without making complex and heavy modifications to the frame.
• Weight. The X525 with its aluminum arms and ridiculous sprung landing gear is simply way too heavy to carry much payload.
• Stability. Although heavy, the aluminum arms bend slightly after multiple flights. The motor holders are useless.

So taking all this into account, I've decided to go for a scratch-designed frame. My inspiration came in form of the Spidex v2 frame by Quaternium, and my design strongly resembles it. However, I've made some important changes. Here's the results of my first ever encounter with LibreCAD:

 Overall top view of the frame

Top and bottom center plates

Motor mount

Battery and GoPro holders

Propellers drawn into the top picture are 11". Larger size could be possible with longer arms.

The most important difference to the Spidex is the fact that I'll be using 16mm carbon tubes for the arms instead of alunimum. They will be held in place with pipe clamps from the Flyduino FCP HL frame (23mm hole center distance). Plates will be all cut from 1.5mm strong GRP on a CNC machine by a colleague later today.

Motor distance is 58cm diagonal. The arm lengths are chosen so that all 4 arms can be cut from one 1m tube - 22cm on the front, 28 on the back.

An important feature are the two 50cm long tubes running along the frame. Those will be mounted on top of the top center plate using clamps and vibration dampeners, and the battery and GoPro holders will be attached to them on the front and rear of the frame. This way, the camera is isolated from eventual vibration of the drive, and the battery acts as a counterweight and can be moved forwards and backwards along the tubes to tune the CG.

Later, the camera mount on the front will be replaced by a 2-axis brushless gimbal. Haven't decided on the controller yet - either AlexMos or the open-source brushlessgimbal.de controller.

A simple heli landing gear will be fixed underneath.

Now, for the electronics that will be flying this beauty. I'll re-use everything currently mounted on my X525 frame, which is:

• Motors: NTM 28-30 750kv
• Props: Graupner E-Props, 11x5
• ESCs: HK Blue Series 30A
• FC: Crius SE v0.1 w/ MultiWii 2.2
• GPS: Drotek I2C GPS
• LiPo: Nanotech 4S 4500mAh
• Camera: GoPro 2
• Video TX: ImmersionRC 5.8G 25mw
• OSD: MinimOSD w/ KV-Team-OSD firmware for MultiWii

All in all, I hope to be able to keep this frame under the current all-up weight of the X525, that is 1.8kg. Flight time of the X525 is ~15 minutes right now, so with a little less weight I hope to get 16-17 minutes per battery out of this build.

Last but not least, the current state of things: almost all the parts are already here and ready to be mounted. I'm only missing the CNC plates, those will be done this evening by a colleague, and with any luck I can pick them up tomorrow to start the build. Prototype plates were already cut from hard foam to make sure the design works with the CNC machine, and it worked flawlessly:

After the build is done and somewhat tested, if there is interest, I will gladly publish the DXF files for the frame, so anyone can cut the plates and build one of these.

Progress updates coming up, stay tuned!