Use a silver based conductive paint. The stuff is sometimes used to repair a cracked PC board path.
http://www.alliedelec.com/Search/ProductDetail.aspx?SKU=9070009&MPN=2505N&R=9070009&SEARCH=9070009&DESC=2505N
Also, look at windshield defogger repair kits in your local automotive parts store.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
The only exhaust cams I've seen stick to the inside of a drive wheel and will not be visible.
I have never installed one, so would suggest that you direct your question about soldering to the axle to the people at SoundTraxx. The cam contacts will require a power source in order to work, but I think the material from which the cam is made will not withstand soldering.
I'm building a Bowser 4-8-2 Mountain and will be using a SoundTraxx Tsunami decoder in it. I'm considering using a SoundTraxx Exhaust Cam Kit with it and have a few questions for those of you who have installed cams on your locomotives.
I'm a little concerned about the visual appearance of the driver wheel that has the cam installed on it. The cam disc is opaque, but I wonder how noticeable and objectional it will be once the locomotive is placed in service.
The instructions recommend soldering the cam to the axle. This makes me a little nervous. The alternate method is to use conductive epoxy or conductive paint. I would prefer one of those methods. Conductive paint is available in silver, nickel, and copper. The difference being the impedence per square inch. From experience, is one recommended over the other?
Finally, any pitfalls to avoid? Shortcuts not to take? Is the effect worth the effort?
Thanks!