Black Magic Cinema 4k CRASH

[Mapoff]

So yeah. I was flying a BMC 4k production camera. I've flown it several times and using a trex 800, HV120 Ice 2, 700mx, 12t/112t and at 1450 it will carry it but not well. The cyclic is very sluggish. I found that 1750 was really smooth and in control. The 1750rpm is something new I've been doing with 700 blades and the smaller cameras to get better vibration isolation with the higher rpms.

Last weekend I put the 800 blades on for a shoot coming soon that required carrying the BMC 4k. I was doing the usual 1450,1600 testing, but went to 1750 and everything seemed perfect. I've measured the current draw at 1750 using the CC Link and the average is no more than 40 amps.

I was doing a medium lift in altitude to about 80-100 ft. I was hovering at that point then decided to come down. When I started coming down I heard the power shut down on the motor. I've had 4 years with this and at least 400 flights and 80 hrs. Its worked so well that when I heard the power shutting down I didn't accept that it was. I was also using a Naza H in GPS. When I started to do an auto I completely forgot to switch to manual and the blades had practically stopped anyway. I was too late in the game and boy did she come down hard. Tons of items are destroyed and will take alot to rebuild.

On the ground I noticed one of the bullets had arc'd right through. Someone with a huge amount of experience seemed to think it had to be a short to another phase or something like that. The other two phases still had heat shrink. There were no other burn marks anywhere except the one bullet. I'm using 4mm EC5 type bullets.

Does anyone have any experience with something like that happening.

For the record the lens was in 4 seperate pieces but the camera is perfectly fine. The BMC, this is NOT the pocket, is a solid piece of aluminum. The gimbal cages were all bent, and the gimbal was D E stroyed.

[Error401]

That sux M. Did that bullet chaff on a frame and ground out? Looks like a lot of amps went through it to burn like that.

Where you been? Seen Prototype at the field a couple times, but missed you. Of course, some of us have started racing quads in the woods, so there's that.

[Mapoff]

He is still working on his copter to get it right. I've been flying at the old middle school location in Blacksburg. Its close and free. It doesn't have the friends though. I'll probably stop in soon and just get a membership so I can stop after work.

I couldn't find a single burn mark anywhere else. I'll probably move on to the solid connectors like the Castle stuff. I think I could have saved everything if I had just reacted faster. I was carrying $3500 in camera equipment alone. It was much heavier than it was ever designed for and I never have done an auto in real life. I've done it alot on the sim but doesn't mean much. So I'm kicking myself but I've actually been practicing autos with my 3d bird which is soon going to become the cameraship until I get my custom frame made up.

[Error401]

Man, my heart sank when I realized it was your main AP ship. Prototype told me a little about it last time he was down. Autos, an essential skill to learn, just not when you need to know. Saved my Logo 550 a good number of times until I figured out the multi-layered issue that was causing my cutoffs.

Hit me up if it's nice in the afternoons, Inverted2112 and I fly at the club field mostly during the weekdays after 4 or 5.

That is really strange about the single sided burn on the bullet. Something had to have grounded. Maybe burned from inside out? Just a thought, but it would probably have fused if that were the case.

[Mapoff]

You'd think. I'm moving to the solid connectors as something different.

I never tried autos with the ship because it's so much heavier. I think I'll get good at the 3d bird from heights higher and higher. Once I get to where I'm falling from a high height, I'll start with the ap ship at a low level and keep starting high and higher. This black magic is really heavy but it was flying great.

[Error401]

Honestly, I'd start like you said, then either add weight to the 3d, or run smaller blades to simulate the heavier loading of the BM. I learned them on an old rex600e runni g 600mm, then ran 550's with the same airframe and batts. Was a whole different feel on the 550s.

[Mapoff]

I really need to fix my castle settings. The headspeed change rate is only 5 I think and castle says 20. Theres no way I could recover from an auto at this minute because it would never speed up in time.

[im4711]

Wow - hurts to just read it. I have seen bullet connectors and wires that rubbed on CF or metal parts. Thats most likely your issue. Those areas I try to protect in addition to just the heat shrink on it. Once you get e wire short out there nis extreme amps and yes if you are lucky its only shut ting down since it allows for an emergency auto landing. I have seen one machine go up in flames.
However - thats you second issue - as many flights as you have you compltly missed practice your auto's. But even as you explained you did not realise until blade stopped - very costly mishap

Sorry to see

[cycled]

I saw a wire connecting a boiler heating element burned most of the way through once. When a wire/connector has high resistance, it will heat up. If there's ever a poor connection, it can start to spark. The sparks will conduct current but eat away at the conducting wire/connector at the same time. It may take minutes or hours to do enough damage to cause a failure, but if a conductor starts sparking it will eventually fail!

That looks expensive!