How to use your frame as a wire

[rdlohr]

As many have said, carbon fiber is conductive but getting good connectivity to it can be difficult. If you use an ohm meter to measure across a frame, if you go from end to end on the edges, or between two holes, mine reads between 20 and 40 ohms. If you go to the shiny surface you get no conductivity at all since it acts as an insulater.

Here is from a hole to a hole:
http://img2.putfile.com/thumb/3/8023110618.jpg (http://www.putfile.com/pic/7862006)

To overcome this, I used a conductive ink pen to make pads give you direct connectivity to the carbon fiber. This gets you to about 4-5 ohms which is almost 10X better than without the pad. A wire will typically measure under 1 ohm. You simply drill a hole(s) half way through the frame then use conductive ink to fill the hole(s) and make a pad. The pads are the little round white spots you see my probes on.
http://img2.putfile.com/thumb/3/8023110684.jpg (http://www.putfile.com/pic/7862007)

I plan to use this technique to connect my boom block copper foil to the frame.
See this thread for how I put the foil on the boom block:
http://www.helifreak.com/showthread.php?p=598507#post598507

You can get the Conductive Ink pen from Radio Shack for about $7.
Here is what it looks like:
http://img2.putfile.com/thumb/3/8023110699.jpg (http://www.putfile.com/pic/7862008)

Make these pads underneath anything metal that you want to have continuity to. I plan to put these under my metal main bearing blocks, my motor mount, and my boom block. It may be overkill but my entire heli is going to be at the same potential so I should have minimal chance of ESD problems.

Sorry my focus wasn't better. I needed a few extra hands to hold everything and snap the photos at the same time.


Rick

[dieselracer]

Sounds good. I have everything grounded on my 500. Maybe be overkill but i feel more safe that way. I think you may need to sand some parts of the frame to get the the part that is conductive. I dont know much about the carbon. I went ahead and used a aluminum frame on mine. Good luck with the Build!!

[rdlohr]

Sounds good. I have everything grounded on my 500. Maybe be overkill but i feel more safe that way. I think you may need to sand some parts of the frame to get the the part that is conductive. I dont know much about the carbon. I went ahead and used a aluminum frame on mine. Good luck with the Build!!
Yep, I drill a small hole under the pad to get to the conductive fiber.
Rick

[dieselracer]

Did you try running a current through the frame just to see how much its drops? I did that with my set up, with a AA battery. I checked the batterys voltage. Then i ran it through the frame. and see if it droped any. IN my case it didnt. Maybe the resistance you get from the frame isn't enough to matter.

[rdlohr]

Did you try running a current through the frame just to see how much its drops? I did that with my set up, with a AA battery. I checked the batterys voltage. Then i ran it through the frame. and see if it droped any. IN my case it didnt. Maybe the resistance you get from the frame isn't enough to matter.
As long as you get a good connection to the frame it should be fine. I was looked for the "Best" connection.

Since V = I * R, the voltage drop would only be noticable with a higher current. I don't think much current would be involved here unless there was a spark. I'm trying to avoid the charge buildup so that a spark doesn't occur. I have to believe as long as you get a decent connection to the frame you would be OK without making a conductive pad. I'm just taking no chances since its so easy to do.

Rick

[dieselracer]

Yep. Sounds good. Thats what i did. I grounded everything. Down the the pinion when i had the stock motor. (couldn't get a connection between the motor case and motor shaft on the Medusa.) so far i have 88 flights problem free. I happen to have an aluminum frame so it made it easyier to ground.

[chichiuno]

(couldn't get a connection between the motor case and motor shaft on the Medusa.)

PERFECT example! Why bearings are NOT ideal to ground through.
And people are doing this with the bearings on the tail boom grounding mod.:clappp

[dieselracer]

PERFECT example! Why bearings are NOT ideal to ground through.
And people are doing this with the bearings on the tail boom grounding mod.:clappp
its weird. I got a perfect connection with the stock 500l. I get a perfect conection through all my other grounds through bearings. I wonder if the medusa was annodized before the bearings were put on??

[rdlohr]

PERFECT example! Why bearings are NOT ideal to ground through.
And people are doing this with the bearings on the tail boom grounding mod.:clappp
You are correct that bearings are not ideal to ground through but they will suffice. They will make often enough connection when turning to bleed off the static before it builds up enough potential to cause a problem. I'm not concerned about there ever being enough current running through them to cause pitting.

Rick

[rdlohr]

its weird. I got a perfect connection with the stock 500l. I get a perfect conection through all my other grounds through bearings. I wonder if the medusa was annodized before the bearings were put on??
Turn them when check for conductivity. If you get intermittent connectivity you should be OK. If you get none, you need another way to do it.

Rick

[dieselracer]

Turn them when check for conductivity. If you get intermittent connectivity you should be OK. If you get none, you need another way to do it.

Rick

The Medusa doesnt ground from its case to the pinion. I'm not going to worry about it. I got the case grounded. Its fine. I have 35 flights on the Medusa now with no problems.

[rdlohr]

The Medusa doesnt ground from its case to the pinion. I'm not going to worry about it. I got the case grounded. Its fine. I have 35 flights on the Medusa now with no problems.
Cool.

[dieselracer]

Cool.
I am also using using the rhino gear. that is conductive. Unlike the align one.

[rdlohr]

Just got some new measurements between screws on my TREX 500 and it looks to be about 5 ohms without conductive ink pads which is fine for our purposes. I would only use the conductive ink pad if you have a problem spot that doesn't want to make good connection.

Also, I'm not going to run my black wire to the frame. New data says its not necessary and the side affect of doing it is that now other wires could short against it.

Rick

[jutrast]

The conductive ink is interesting. I'm early enough in my build that i can do it, but the pens seem to be discontinued at Radio Shack, and local stores don't have any.

I'm wondering if this is a reasonable alternative - drill a dimple into the frame where the metal bearing blocks would contact, and fill it with tin solder. Perhaps leave just above the surface. When i sand away the anodizing on the bearing block, this is sure to make contact, no?

Interested in your thoughts.

[TGibe]

The conductive ink is interesting. I'm early enough in my build that i can do it, but the pens seem to be discontinued at Radio Shack, and local stores don't have any.

I'm wondering if this is a reasonable alternative - drill a dimple into the frame where the metal bearing blocks would contact, and fill it with tin solder. Perhaps leave just above the surface. When i sand away the anodizing on the bearing block, this is sure to make contact, no?

Interested in your thoughts.

I could not find a conductive pen either. I filed down the metal bearing block areas that contact the frame and filed the parts of the frame that contacted the blocks. Then I put aluminum foil over the bearing block area that contacts the frame and screwed it all together. It may seem a little strange, but it gave me the continuity I was looking for...Plus you can't see the foil except in the small hole that the nub on the bearing block goes into...

I would have probably gone the solder route if I had thought of it.... Good idea :thumbup:

[ChasHeliCop]

Here you go, radio shack, says in store only....

http://www.radioshack.com/search/index.jsp?kwCatId=&kw=conductive%20pen&origkw=conductive%20pen&sr=1

http://rsk.imageg.net/graphics/product_images/pRS1C-2264866w345.jpg

[michael503]

Here you go, radio shack, says in store only....

http://www.radioshack.com/search/index.jsp?kwCatId=&kw=conductive%20pen&origkw=conductive%20pen&sr=1

http://rsk.imageg.net/graphics/product_images/pRS1C-2264866w345.jpg

Great find!
My experience was less than satisfactory, not with the mod but with the product. These things have a shelf life and apparently don't sell well in my area. I got one and had to cut it open to get the paint out and then added lacquer thinner to it to make it brushable. I used some old Aerogloss thinner (showing my age), but anything similar will work, lacquer thinner, acetone, etc. I keep the remains in a small jar now.
I like the product, you might want to check it in store, or be prepared to cut it open and use a brush.

[TGibe]

Here you go, radio shack, says in store only....



Yeah, not available in my area and I have passed that point in this build. I eventually located one at an electronics parts store, but decided not to take my bird back apart as I had continuity already between the frames...

But thanks for the link! :thumbup: