Boom Grounding idea

[Jermo]

just tap into the ground for the tail servo and connect it under the servo mount....effectively that would ground it. Would be the shortest path to ground..
Jer

[wanderer56]

Well.... yes it would be the shortest path, but then again your discharging some incredibly high voltages through your rx. Are you sure you'd want to do that? Also you have a screw thats sticking up inside the boom while the belt is bouncing around and risk cutting it on the screw?

Don't mean to sound negative, my brain is just trained to think of worst case scenieros.

Engineers design the circuits and the technicians tell them why it won't work. LOL

[Jermo]

? No screw through the boom. Just lightly sand paint/varnish and insert the jumper. The current would be minimal and It's all common ground.
Jer

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[wanderer56]

Yes there was a picture/post of a boom grounded with a sanded boom and wire inserted under the servo mounting bracket. That would work, but I don't know if I'd tap into the servo ground lead. I would run it back to at least a metal frame part. Just saying.

[Jermo]

But then you aren't grounded.

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[redsoper]

i have never grounded mine, i have been flying in the middle east, where its hot and dry, and never had a brown out problem!

[wanderer56]

Originally Posted by Jermo

But then you aren't grounded.

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Sure it would. Take a DVM and connect one lead to boom block mounting screw and the other lead to the metal motor mount and see what you get. CF is also conductive with very little resistance and usually the screws make contact with the inside of the screw holes in the frame and provide a path for current to flow.

Are you wanting to ground the servo itself?

I'm using an i2 metal boom block and TT, so I really don't have an esd problem but sanded the bottom of the boom where it makes contact the the boom block just for good measures. Another pinning screw in the tail box and now I have continuity from the tail box to any metal part on the heli, motor mount, metal battery tray, metal main bearing blocks, etc. You just need to provide a path from the boom the the frame. Some even run the ground wire all the way to the battery ground lead to ground the esc as well. The rx's only path to ground is through the ground buss in the rx and then through the throttle ground lead running to the esc. I've never tested from the rx through the esc to battery ground lead. Not sure if the esc throttle signal ground is isolated or not?

Just a healthy debate here. Not trying to start an argument.

Check out this thread
http://helifreak.com/showthread.php?t=420612

[wanderer56]

Just to confirm, I checked between rx signal ground and battery ground and I get .5 ohms. So the signal ground from rx and servos are grounded to the battery through the esc, but not to the frame. So grounding boom to frame doesn't ground the boom and frame to the battery ground unless you provide a path. Grounding the boom to rx (via servo ground wire connected to the boom) will ground the boom to the battery itself but not the frame. But I still would not be confortable discharging high esd voltages through the ground buss in the rx. Static esd voltages can kill small electronic componants inside the rx.

If you are comfortable with it, then give it a try.

[Jermo]

Esd voltages won't get large at all since they are bled before they build.

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[wanderer56]

OK. Give it a shot. You might be on to something.

[extrapilot]

Guys

For those who have an ESD problem due to a tail belt, consider how this works. You have electrons being stripped or deposited at the point of belt-to-pulley interface via triboelectric effect. Analogy- the drive pulley is the negative terminal, and the tail pulley is the positive terminal. Your goal is to short that circuit to prevent a potential from developing between those poles. You don’t do it by connecting the tail to the motor (which may or may not have a low-impedance path to the tail drive), you connect the tail to the drive pulley.

There is a separate mechanism, where the blades (main and tail) interact with particles in the air- same basic process (triboelectric). In this version, there is no local ground path- that path is the atmosphere. That leads to a high charge on the entire machine- and St Elmos fire, something common on full-scale machines. It has the potential (pun intended) to cause ESD events, which is why so much effort goes into mitigating it.

In both cases, it makes sense to use a static wick to help bleed electrons. If your electronics are solid, great. But if you have concern, and you want to invest $0.20 in some carbon tow and an eyelet, well- cheap, low weight insurance.

[flerpie]

Originally Posted by extrapilot

In both cases, it makes sense to use a static wick to help bleed electrons. If your electronics are solid, great. But if you have concern, and you want to invest $0.20 in some carbon tow and an eyelet, well- cheap, low weight insurance.

I'd sure like to see a pic of some "carbon tow". Have no cloo what that means.
Maybe even a completed static wick.

The static wicks I've seen are almost $27.00 each and I only ever
found 1 company that makes them. GForce I think.

http://www.amainhobbies.com/product_...ce-Static-Wick

[flerpie]

There are the more simpler ways of dealing with staticE and there are also
things like this - evidently the roller is meant to contact the belt and discharge
the static. I just prefer a metal boom block such as the I2 boom block
and eliminate the problem at it's source.

http://www.amainhobbies.com/product_...orce-ESD-Plate

[extrapilot]

Flerp

Tow is a term which just means unwoven fiber. You can buy this, or just pull out 10 strands from conventional woven carbon cloth and group them up, etc. You can use other materials- but to be effective, the wick needs to have lots of very fine terminations exposed- as electrons can make the jump much more easily with thin/pointed conductors. I use carbon because it qualifies, and I have tons of it around.

Here is a pic- very simple to make, weighs almost nothing, very effective...

Cheers
R

[flerpie]

Thx for the pic. Looks alot like what I pictured - using a crimp wire lug to crimp
the fibers in. Great idea. Looks better than that $27.00 one.

[extrapilot]

Well, there are 6000 fibers in that tow, each of which is only 7 microns in diameter. That makes for a happy electron jumpoff. Im not clear as to why a commercial product would just use a standard tinned wire.

Anyway- if the wick is exposed to moving air, that helps.

Cheers

[Jermo]

Static wicking is used in commercial aircraft and might be an idea to try with a belted model. It's application is generally for communications. I'm not certain of the exact nature of the brownouts caused by ESD in our models. My assumption was that it was due to the static getting into the receiver. If that's the cause then providing a good path to system ground would protect the receiver. If it's actually interfering with reception then static wicking is the solution for that.

Personally just a quick spray of silicon in the tailboom on the belt seems to prevent issues for me. Since I've never had an issue I don't know if what I'm doing is making a difference or not. I can only assume that my preventative measures are working.

good discussion... I really wish we had more data that's accurate as to how the ESD/Static is causing the brownouts.
Jer