Non insulate 2 rail wheels?

You can,  but the way you suggested won’t work. Normally, rolling stock wheels are insulated by a plastic bushing, getting anywhere near them with a soldering iron is going to melt & distort the insulator rendering the axle set pretty much useless. If you want solid 2 rail axles, the choice is to purchase Intermoutain wheel sets, remove the bushed wheel, and take another solid wheel and press it on the axle, thus giving you a solid axle set. You’ll need quite a few packs to accomplish this, so it won’t be a cheap affair…….you’ll also want to look to check fitment of the Intermountain wheel sets with your rolling stock. Other than that, you might look into some sort of IR detection system to operate track side accessories….

Pat

If you just want the wheels/axle to trigger the circuit, use electrically conductive paint. It is usually sold in auto parts stores for repair of window defroster traces. The copper infused paints are much cheaper than silver infused.

A vote for the IR detection that Pat mentioned. The only negatives would be would be if you had quite a few to do or if the detectors protruding through the roadbed wouldn’t look good. You mentioned shelf layout. Not sure  if it’s overhead.  Azatrax has many solutions on their web site. Maybe even go to a latching relay.

I’ve used Neo Lube before available from Micromark. Not cheap. They caution you about applying it near insulated wheels as it is conductive. Would certainly take the shine out of the axles.

You never know what the future may bring. If you at some point ever decide to go 2 rail. The IR detectors may be the least evasive rather modifying your rolling stock.

I don't have a ready answer to your question, but as I had a similar problem many years ago with 2R equipment on a 3R layout, I'd like to offer two alternatives:

A.  I instituted an Operating Rule:  Either the last car, or next to last car, in a train operating in track circuit territory has to have non-insulated wheelsets.  This just added a bit of 'fun' to the switching/train makeup process.  Track circuit length took this [ eg, max train length ] into account.

B.  Swapping trucks rather than wheelsets, in conjunction with A.  If you wanted to do your cars fleet wide, you might be able to do a swap with a 2Rér or two.....

The simplicity of detection circuitry is one of the great advantages of 3R, and I wouldn't change over to another system unless you had to.  One big problem with an IR system is that they are just point detection -- they can tell you something has passed it, but what and how long is unknown;  there is no 'break in two' protection between the points*.  There is also the problem with intermittent systems like that when powering up a system [ unless you have some sort of latching relay to 'remember' where trains are, etc ].

Best regards, SZ

*Well, in a larger scale, say Ga 1 or LGB, you could combine an IR detector with logic to have a non-contact axle counter system to check in / check out .....

If you have metal trucks, flip one axle in each truck.