Possible static issue, gear greasing – long...:^)

[stevehof]

How many of you are greasing your Delrin Gears? Drive set only? Drive and tail set? What is the best type of grease? The goal is to prolong the gear life and reduce drive line noise. There may also be some static electricity reduction as a byproduct of greasing the gear train. The effectiveness of the latter may be dependent on the grease's composition?

I just got through 3 weeks of trying to sort out violent tail kick outs and cyclic glitches. This was occurring on a E7 torque tube setup that had well over 200 trouble free flights as configured. I  replaced every single electronic device and wire on the ship and grounded the boom by sanding the anodizing off the boom at the rearward front boom clamp. I had continuity between the tail case and motor mount. So, I had effectively 'grounded' my boom to the motor mount and CF frame. I also greased all the Delrin gears with white lithium grease.

None of this stuff helped and I continued to get hard tail blow outs with violent stops, along with the occasional cyclic twitches. The Vbar event log was full of checksum errors along with aileron and elevator sensor 'out of range' errors, even sensor disconnect errors that could be tied in the event log time line to tail blowouts and cyclic glitches.

According to Vstabi checksum errors are usually caused by static or the sensor wire being too close to other wires. I live in Southern California and it has been hot and dry the last month. Perfect for static accumulations. I totally isolated the sensor wire and still continued to have problems nearly every time I flew. Now and then I'd get a flight without tail or cyclic glitches but my logs always had lots of checksum errors, sometimes there were 2 to 4 consecutive checksum errors in the log.

When searching Runryder or Helifreak for 'properly grounding' I ran across a post by Dave Dahl. His premise was that you need to ground whatever is suspect to the negative  main power battery wire. When I ran a 24 awg wire between the boom, motor mount and negative battery wire, the checksum errors have been totally eliminated and the ship has flown a dozen perfect flights since, some of them on hot dry days. So, I'm about 99% sure it is now fixed. I think I could have passed on the wire from the boom since my boom was already grounded by the method mentioned above.

Here's the kicker. I have another E7 kitted EXACTLY the same as this one. The logs in that ship are clean and it could be flown on the same day as the one that was wigging out and the other E7 flew fine. So, whether it was static or some weird type of  similar emf generated by a bad bearing somewhere, I have no idea. I do know that giving the carbon fiber chassis a real electrical 'ground' to the negative lead of the power battery (black wire on ESC) fixed the problem. I'm beginning to think that all Carbon fiber framed ships running FBL should be grounded to battery negative. If there is any significant down side to doing this, I'd like to know about it. Thanks!

[Chris Sexton]

One, I am glad you got the issue sorted, although I would have never thought to ground the frame to the battery...

I do run a bit of silicone on my gears, old habbit from my other birds. It helps alot for noise on my X5s. The E7 doesn't make a great deal of noise period, but interesting that I might have been avoiding an issue this whole time by accident.  I didn't think TT systems were prone to static so I have never grounded a boom on my TT birds.

Good information.

[stevehof]

There is some question about the possibility of some types of Delrin being vulnerable to static build up. There was a long thread on this some time ago in RunRyder.

http://rc.runryder.com/helicopter/t696330p1/

Grounding to the power pack battery negative was a revelation to me also. All I've ever heard of was grounding the boom to the motor mount. However, as was pointed out to me in another thread, that does not provide an actual electrical ground. It only provides continuity between those two items. You still have a floating ground at best. This would be particularly true with a plastic frame ship like the Logo. Our E7 CF frames are conductive so if you ground one bolt in the CF frame (true battery negative ground) you will probably have a common chassis ground throughout the frame set due to the metal bearing supports etc.

[Matt Botos]

Hey Steve,

Try mounting your Vbar in the designated mounting spot. The spot you are using right now, even though it is working on the other E7, can be problematic as it is right next to the ESC and motor. The ESC can create tremendous amounts of noise. Each ESC as we all know can be completely different from the next. Unless you remove all of the electronics from the other airframe and place them in the airframe that is suspect it would be very hard to diagnose.

Thanks,

Matt

[stevehof]

I am disinclined to fix something that is no longer broken...:^) I must have 50 flights on the ship since I grounded the frame to battery negative. I looked at the logs AGAIN and there is not one checksum error. The ship is flying fine.

If it was electromagnetic interference from the motor or ESC I don't understand why grounding the frame fixed the problem. However, I can't ague the fact that only a very few others have had similar problems and those problems may have been quite different from whatever was plaguing my ship.

If not caused the Delrin gear set, then maybe some noise generated by the carbon fiber frames themselves. Although the ship hasn't even had a hard landing yet. Having said all this, if this one or other E7 ever acts up again, I will move the Vbar and let you all know the result..:^)

Edit: as for removing the components from the other airframe and putting them in the suspect airframe. Well, for all purposes, I did just that since I did swap out or replace every single electronic component and wire in the ship during my long, frustrating and expensive (new set of HV servos) troubleshooting process.

[Gregor]

When I setup my E7, I take the time that I had continuity from the tailbox to the motor mount, including the TT transmission.  My method was to leverage the carbon fiber on the frame and the TT transmission sides to make the electrical connection.  It looks like the sides are coated with something non-conductive.  The screw holes in the cf seem to provide the best connectivity.  I did have to sand the boom on both ends. This was not to address an issue. Just being proactive about building a more electrically sound model.

Steve does have a point that there are now two different grounds on the model.  The frame, boom, etc is one and the electrical system is the other.  As I see it, the main reason to ground the frame, boom,etc is  to prevent static discharge and the subsequent disruption causes by a "spark" occurring near a sensitive electronic device.  Not to provide  common ground for the electrical system.

The only thing that concerns me regarding connecting the floating ground to the electrical system is that now all positive wires (battery, BEC, servos) if exposed, can short against the frame or metal component on the model.  While this does require the loss of some insulation or exposure of the positive wire, the risk does not exist when the floating ground remains floating.

I'm puzzled by Matts comment about mounting. Perhaps I missed it.  But if the Vbar or sensor is up front, it would seem safer to disconnect the floating ground and move the Vbar and sensor to the back

[stevehof]

Just to reiterate and clarify a little. I had tried 'grounding' the tail boom to the frame by sanding the anodizing off the boom at the most rearward boom clamp. After doing this I measured only a couple of ohms from the tail case to the motor mount screw. This did not fix anything. The Vbar event log was still full of checksum errors and I continued to have un-commanded tail and cyclic movements.

I contacted Matt for help a few weeks ago and he asked to see a photo of my electronics setup. My Vbar controller is up forward on the side of the frame just ahead of the pinion bearing block. Matt suggested I move it away from the ESC and motor. The sensor is on the sensor plate at the rear of the ship. I had already committed to trying the battery negative to frame ground path. The full grounding fixed all my problems so I decided not  to move my Vbar controller.

I am aware of the direct path for a short issue. However, I used one strand 24 awg servo wire for the battery negative to frame ground so I suspect it would melt pretty quick with a full on battery short. I should probably just put an appropriately rated fuse inline on the wire that goes from the negative ESC lead to the frame and not worry about it.