Fun, Learning, Friendship and Mutual Respect
START  HERE


Unregistered
Go Back   HeliFreak > R/C Helicopters > Aerial Videography and Photography


Aerial Videography and Photography Aerial Video/Photo from R/C Helicopters


Reply
 
Thread Tools Display Modes
Old 05-17-2015, 09:51 PM   #1
Mapoff
Registered Users
 
Posts: 368
 

Join Date: Feb 2013
Location: Christiansburg,va
Default Black Magic Cinema 4k CRASH

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.
Attached Thumbnails
Click image for larger version

Name:	IMG_4258.jpg
Views:	36
Size:	75.6 KB
ID:	586456   Click image for larger version

Name:	IMG_4260.jpg
Views:	37
Size:	137.3 KB
ID:	586457  
Mapoff is offline        Reply With Quote
Old 05-18-2015, 07:52 PM   #2
jared_of_atlanta
Registered Users
 
Posts: 599
 
My HF Map location
Join Date: Apr 2007
Location: Atlanta (Stockbridge), GA, USA
Default

Ouch! The bullet could have shorted to the frame. If that happens, the ESC would typically either shut itself off, blow up, or just send all it's juice into the frame. Since it actually burned through, I think we can rule out a safety shut off.
jared_of_atlanta is offline        Reply With Quote
Old 05-18-2015, 08:36 PM   #3
Mapoff
Registered Users
 
Posts: 368
Thread Starter Thread Starter
 

Join Date: Feb 2013
Location: Christiansburg,va
Default

I thought about the frame or motor plate but I still can't figure out the circuit. The frame is isolated from everything. Even if one phase hit the metal on the motor, the motor is isolated from all the wires. It's just a metal housing. It's so bizarre. I'm moving to the solid type of bullets. Part of me wants to do some kind of female to female bullet and solder for a solid connection but would be a pain to seperate later.
Mapoff is offline        Reply With Quote
Old 05-19-2015, 10:24 AM   #4
jared_of_atlanta
Registered Users
 
Posts: 599
 
My HF Map location
Join Date: Apr 2007
Location: Atlanta (Stockbridge), GA, USA
Default

High power and high switching frequency electronics are beyond me but it wouldn't surprise me to find out the ESC can't handle something like this.

Your servos might be grounded to the frame. The receiver is grounded to the servos via the wire. The ESC ground is connected to the receiver ground via the wire. There may be protections to prevent damage to the ESC in this mode but that may include things like "I better shut down." I would be very wary of the ESC.

You can just solder the wires directly to each other. Less resistance, less power waste and higher peak power. If it was a short to frame situation, soldering might not help you because carbon will chew through silicone as easily as polyolefin heat shrink.
jared_of_atlanta is offline        Reply With Quote
Reply




Unregistered
Go Back   HeliFreak > R/C Helicopters > Aerial Videography and Photography


Aerial Videography and Photography Aerial Video/Photo from R/C Helicopters

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


Copyright © 2004-2011 - William James - Helifreak.com