Making the case for grounding

[jrman83]

I have a 420 that I bought brand new and built in December of last year. I got about 20 really good flights on it and then started having issues with losing power mid-flight. Luckily I was always able to at least get skids pointed down and didn't suffer catastrophic damage. It was enough.

Using the logging ability that comes on the Ikon 2 it would show a loss of radio signal and then the system would go into fail safe and power down.

I replaced the rcvrs at first and thought that would fix it. Happened again after about 4 flights.

Started testing on the bench. I had purchased upgrades to the KST servos I had and at the same time changed the ESC (HW80A) to rule out any possible power issues to the rcvrs. Tested with new rcvrs, servos, and ESC and issue still occurred. Eventually swapped out motor with new one as well, no change.

What I noticed was that with a DVM I could read 700mv from tail case to main frame while the system was running. I wasn't sure if this was normal and checked across my G380 and the result was less but still a little voltage (never had an issue with it).

Anyway, with a complete electronics changeout, even FBL, the issue remained. With some assistance on here I was advised to try and ground the boom. I was reading about 800 ohms from main frame to tail case.

What I did was sand down the part where the boom mates to the frame. Some of the booms I have this area has paint on it and others don't. I sanded down to the nice solid black area that is the cf. Initially this didn't make any difference as I believe the mating areas may not have been perfect on frame or boom. So what I did was to take a folded piece of aluminum foil and place between boom and frame to close the gap. After that I was reading nearly zero ohms from case to frame and zero voltage when system was running on the bench. Took less than 10min to do it all.

I have only 6 good actual flights with it and about 18 5min periods on the bench but the system no longer looses power.

Just a suggestion, but I would devise a way to properly ground your boom to your frame. I plan to do it to all of my SAB setups. It is usually not an issue, until it is. I don't want to go through that again. Just thought I would provide my experience. Not a good feeling when you loose power while inverted 10ft off the ground. Time will tell if the issue is completely resolved on my 420, but I am hopeful.

[mattbeau]

Are you using the belt tensioner? Curious because the belt might run on the boom otherwise. Let us know how it goes. It seems like a simple fix. It's the first I've heard of this and surprised that so much time has passed without a problem.

________________________________
sactownhobby.com

[jrman83]

Yes, using the tensioner. The 420 kits came with them. I couldn't see where the belt or the tensioner was touching the boom, or could I see why it would be happening. Like I said, it basically was good one day and bad the next.

[toadiscoil]

Although what you say makes a lot of sense, Matt's comment that he has never heard of that is also strange. Why has this never been an issue with Goblins?

Also it seems like yours was working fine and all of a sudden you started having issues. Some other part that got loose and causing the static? I don't really know.

As you said time will tell, so I will be looking for your findings.

[jrman83]

No, no issues with anything. In fact, when I would test on the bench and it would shut down after only a few seconds of starting to spool up, I could remove the tail belt and the power loss would not occur.

There is nothing that could have come loose or anything else, considering a complete change of electronics, that would cause a 700mv drop across the boom.

I think that most systems are probably okay as long as the top mating surface of the boom is making good contact with your frame. However, even a little clear coat or paint overspray on it and that is null.

I recommend that everyone sand that surface down to make sure there is nothing there but bare cf. My boom was a factory boom that had some paint and clear coat on it. Going by nobody else having the issue has risk. One loss of power in the middle of some move you may be performing can cost you hundreds with SAB. The fix takes no time to complete to ensure you don't have it arise like I did.

[mattbeau]

Keep us posted on how it goes. I'm willing to check the same thing. Are you sanding tge boom where the plastic bolt goes through the frame to mount the tailboom?

________________________________
sactownhobby.com

[jrman83]

Originally Posted by mattbeau

Keep us posted on how it goes. I'm willing to check the same thing. Are you sanding tge boom where the plastic bolt goes through the frame to mount the tailboom?

________________________________
sactownhobby.com

Yes. The only place that the boom makes direct contact with the frame.

[Inverted Hokie]

This is out of my league for sure, but here's a thought...
I built a Van der Graff generator when I was in high school and it used a rubber belt to cause a static build up in the globe. Could a static charge be building up? Not sure where & how it would collect though.

[jrman83]

I only know what I seen on the digital volt meter and how the heli did. More than that I can't hypothesize.

Sent from my SM-G955U using Tapatalk

[cool cat]

This sounds so familiar to what I have happening on my 360mm stretched Mini P.

Replaced all electronics minus motor and batteries. Had the bird fall out of the sky and replaced the frame and went through it all.

1st hover and got it again while just putting around the drive way.

Taped the motor lead wires at each connection and then the 3 wires to the frame.

Did 4 packs in yard all hovering 18" just in case and no stalls yet. I soo wanna throw this thing into tic tocs and flips but just cant trust it yet.

I am thinking the static may be zapping my electronics as my vbar reads switching and dropped packets and hi vibration.
For sure not hi vibes, I spin up with no blades and hold tail and frame to feel and this bird is smooth.

[Pygmaeus]

I have been following you threads for a while on this. A while back I had a car that would give a traction control failure indicator when making left turns. Turns out right hand wheel bearing was going bad causing increased friction and static build up during left hand turns. The static would hit the wheel speed sensor causing the indicator. As nothing mechanical has changed on your setup, wear on existing components is really all that left. What is amazing is that you would get hit within 2 seconds of starting.

[Shogun71]

My approach is that all helis have a grounded boom and tail case!!!!

I had a Compass Atom 500 nose dive due to a static hit which was supposed to be static proof.

When I build a goblin I check the tail shaft for continuity with the motor mount. All my other goblins have had full continuity out of the box on the build.

My 380 did not. I ran a thin wire on the inside of the boom from the tail case to the frame and go continuity. Good enough for me.

My impression is that the 380/420 use fiberglass rather than CF for the boom and therefore it is an insulator...

I have even seen static issues on some torque tube setups.

Better to be safe and take a few minutes in the beginning rather than lose a model or do all of the stuff in this post...

No blame, just a warning.

[msallua]

Originally Posted by jrman83

I have a 420 that I bought brand new and built in December of last year. I got about 20 really good flights on it and then started having issues with losing power mid-flight. Luckily I was always able to at least get skids pointed down and didn't suffer catastrophic damage. It was enough.

Using the logging ability that comes on the Ikon 2 it would show a loss of radio signal and then the system would go into fail safe and power down.

I replaced the rcvrs at first and thought that would fix it. Happened again after about 4 flights.

Started testing on the bench. I had purchased upgrades to the KST servos I had and at the same time changed the ESC (HW80A) to rule out any possible power issues to the rcvrs. Tested with new rcvrs, servos, and ESC and issue still occurred. Eventually swapped out motor with new one as well, no change.

What I noticed was that with a DVM I could read 700mv from tail case to main frame while the system was running. I wasn't sure if this was normal and checked across my G380 and the result was less but still a little voltage (never had an issue with it).

Anyway, with a complete electronics changeout, even FBL, the issue remained. With some assistance on here I was advised to try and ground the boom. I was reading about 800 ohms from main frame to tail case.

What I did was sand down the part where the boom mates to the frame. Some of the booms I have this area has paint on it and others don't. I sanded down to the nice solid black area that is the cf. Initially this didn't make any difference as I believe the mating areas may not have been perfect on frame or boom. So what I did was to take a folded piece of aluminum foil and place between boom and frame to close the gap. After that I was reading nearly zero ohms from case to frame and zero voltage when system was running on the bench. Took less than 10min to do it all.

I have only 6 good actual flights with it and about 18 5min periods on the bench but the system no longer looses power.

Just a suggestion, but I would devise a way to properly ground your boom to your frame. I plan to do it to all of my SAB setups. It is usually not an issue, until it is. I don't want to go through that again. Just thought I would provide my experience. Not a good feeling when you loose power while inverted 10ft off the ground. Time will tell if the issue is completely resolved on my 420, but I am hopeful.

I have the same problem in my G420... Subscribed!...

Thanks!

[whitewater]

My 380 is isolated at the front end of the boom and so I will sand the finish off as described. How far does continuity need to go? My motor is isolated from the motor mount according to my multimeter. Do I need to worry about exposing the motor mount threads for continuity? Where is ground on this system? I wish I knew more.

[frenchusa]

i had similar issues, but it was coming from ESC Platinum 100A (same 80A), check your voltage cutoff.

From manual: The ESC will gradually reduce the output to 50% of the full power in 3 seconds after the voltage cutoff protection is activated, if soft mode is selected. It will immediately cut off all the output when hard mode is selected.

http://www.hobbywing.com/products/en...-120A-V4en.pdf

[msallua]

Originally Posted by whitewater

My 380 is isolated at the front end of the boom and so I will sand the finish off as described. How far does continuity need to go? My motor is isolated from the motor mount according to my multimeter. Do I need to worry about exposing the motor mount threads for continuity? Where is ground on this system? I wish I knew more.

First I try sand in an old crashed boom , but don't like because the boom is very thin and loses strength.

I prefer a wire from the tail to the aluminium main plate.

Works perfect!

[mgrezmer]

I have been suffering a similar problem with my stretched and belted Gaui X3. Extremely intermittent power cutouts. Have not been able to arrive at a solution.

Tonite I will go home and run a wire from the tailcase (aluminum) to the aluminum motor base plate. I would love to solve this problem and be able to fly with complete confidence. It has been baffling and has consumed a lot of time and resources. Glad I stumbled onto this thread. Thanks!

[jrman83]

Originally Posted by msallua

First I try sand in an old crashed boom , but don't like because the boom is very thin and loses strength.

I prefer a wire from the tail to the aluminium main plate.

Works perfect!

When you sand the portion of the boom that meets the frame, it is just enough to remove the paint. No more needed. That should not weaken anything.

As far as ESC setup, I would disable any type of voltage cut.

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[Thickfog]

Weird. Posted this issue on the main forum.

On my 470l for the past 2 months and today on my compass exo. Totally trashed the compass. Frame is two pieces. Canopy is 3.

[jrman83]

Wow. Sorry to hear about that. Just a total power loss?