Refer to article in June 2021 Model Railroader page 54 and 55. Going the resistance soldering route. I have the gel flux and feeder wire but trying to find the .031 solid core solder as mentioned in the article and need sources for the solder.
I have twice purchased .031 Kester solder from Dave on eBay. Found him to be a very reliable and honest seller. https://www.ebay.com/str/davejohn007
Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.
Note that he wants solid-core .031, perhaps lead-free. Most of the commercial .031 wire is 'optimized' with some kind of no-clean flux or RA core, and I suspect this is his actual difficulty.
Dave at AggressiveFun could certainly provide the necessary 'stuff' if asked, and might be a useful source of information about the best current products for resistance soldering.
Used to be that you would use one of the 'specialty' soldering-supply companies like SRA for less-usual products. Amazon is now highly useful BUT you have to know what you want, carefully read to be sure that's actually what you'd be getting, and then go through the crapshoot that so much online-order fulfillment has turned into.
And be very careful with what is quoted for shipping.
Remember that soldering for 'electronics' is different from soldering for 'structural integrity' and for the latter you might benefit from a jeweler's supply company like Kernowcraft. My understanding is that it used to be much more common to use either solder paste (which is powdered solder alloy in gel flux) or small chips positioned with tools in those 'applications' than to use fine machine solder wire, but with the rise of automated solder feeding as an alternative to wavesoldering it's getting easier and easier to source.
That's a good point, Overmod. I wasn't doing resistance soldering, and my response did not take that part of the OP's plan into account. Thanks for the follow up.