Conductive paint for wheelset resistors - updated with video

[Bill H]

Group:
I am installing resistors on another batch of wheelsets and my silver conductive paint pen has dried up. Checking the replacement options on Amazon, all of them seem to have a 50-50 mix of reviews ok or doa/garbage. In other words, most seem like a real crap shoot.  Any suggestions on conductive paint pens that might be repeatable?

Kind regards,
Bill

[woodone]

Do not know about a paint-have you tried silver epoxy? It is a conductive epoxy that can be used for electrical connections. It a bit thick so it should hold your resistor in place until the epoxy cures. NOT CHEAP!

[Bill H]

Thanks, but unfortunately most smd resistors conduct on both the bottom and the tabs on the top - so epoxying them to the metal axle would cause a short. I put a layer of gel CA on the axle first - as an insulator, then CA the resistor itself to that base CA, then use conductive paint to connect one end of the resistor to the axle, the other end to the metal part of the insulated wheel. From what I have read, that is pretty typical of what most are doing.

Here is link to a video on youtube that fairly well defines the process. Yes, I know Daryl went over to the dark side, but at least at the time of the video he was modelling normal scale.

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Kind regards,
Bill

[Bill H]

Do not know about a paint-have you tried silver epoxy? It is a conductive epoxy that can be used for electrical connections. It a bit thick so it should hold your resistor in place until the epoxy cures. NOT CHEAP!

[woodone]

Well if you put the resistor to the axle and lean it up against the back of the wheel at an angle you will not have a short.
You are laying the resistor flat on the axle with both ends touching the axle therefore making a short.
Try sitting your resistor at an angle. The epoxy is thick enough to hold its self in this position until the epoxy cures.

[mmagliaro]

These folks are my new best friends for conductive inks, paints, glues.

https://www.applied-technologies.net/copy-of-paints-5

I don't know where they distribute their products, but they sell on eBay.  That's where I get it.
Here's one of their bottles of conductive silver paint for $15.00.  So it's not "cheap", but it's not outrageous, either.
https://www.ebay.com/itm/124488315234

If you check out their website, they have a dizzying array of thicknesses, formulations, and adhesive properties.
You might want to even call them, tell them what you are doing, and ask them which of their products would work the best.

It works really well.  Conductivity after it dries is excellent.  I would still recommend overcoating it with some sort of sturdy enamel paint, or even a smear of 2-part epoxy, to protect it, but I'd say that for any conductive paint that is going to live on exposed axles under rolling stock.

[Bill H]

Hi Max;
Thanks for the suggestion. I will take a look at that product on eBay soon, as my last working silver pen is about empty.  Have you tried the one on eBay yet? Rather curious as to its viscosity.

Kind regards,
Bill

[mmagliaro]

Hi Max;
Thanks for the suggestion. I will take a look at that product on eBay soon, as my last working silver pen is about empty.  Have you tried the one on eBay yet? Rather curious as to its viscosity.

Kind regards,
Bill

I have that exact one: 7737-W.  It goes on like fingernail polish, so it's like a thick brush-on paint.

[Bill H]

Max - that's perfect! As soon as I get this batch done with the last pen, I will order it.