Gimbal Quad Woes?

I've been pretty quiet in regards to development of the Gimbal Quad lately, and that is because there are some issues to iron out. Due to the shorter daylight hours since last month, I haven't had a whole lot of time to fly during the week. Consequently it took me a while to realize a major issue with the setup of the Gimbal Quad. Thankfully it appears to be a hardware issue and not a fundamental design issue with the frame.

It all started with the maiden flights of the quad. Since I am running the Tau Labs Sparky, I was hoping to use the autotune feature to dial in the PID settings. I set everything up in the GUI so that I could enable autotune from my transmitter, took the quad outside, got it into a hover, and flipped the mode toggle switch to autotune. It began to oscillate like it was supposed to in autotune mode, but shortly after one motor/arm took a dip, almost in an insta-flip fashion, and the quad landed on the pavement.

That was very disappointing, but after picking up the frame and inspecting the damage, it was just a couple cosmetic scratches to one of the arms and a broken prop. Unfortunately I was out of props so I had to place an order and wait until I could fly it again. I also figured that since autotune was technically in beta, that maybe it was a bug which caused the crash, since everything seemed to still work ok, and it hovered fine in self level mode.

Once I got the props replaced, I went to maiden flight the quad again assuming this time I was going to end up manually tuning the PIDs myself. It was during this flight that I believe I found the real issue. It seems that one of the ESC's, and I am not sure if it is the same or just a random one, is de-syncing from the motor under higher throttle! This time I was hovering around in auto level, and I decided to give it a little punch of throttle to see how it responded. Just like the first flight in autotune mode, one of the motors/arms dipped and the quad nearly flipped and crashed to the ground. This definitely leads me to believe there is a sync issues with the ESC/motor combo.

I had read about people having issues with this on the forums, and it seems to just depend on the motor/ESC combo. It seems the mini motors of higher kv values are more prone to having issues with different ESCs and firmwares. I currently have a set of Multirotor Superstore branded SimonK 20A ESCs installed. I have ordered another set of KISS 18A ESC's like the ones I am running on my other Mini GoPro Quad to replace these. I am hoping this will solve the issue and also hopefully I can actually try out the autotune mode on the Sparky flight controller.

In the meantime I just have to sit and wait on the parts, but that hasn't stopped me from working on a new project.........more on that in another post though.