Re: Working with copper
I'm no expert with this, but thought I'd relate a negative experience I had while trying to make a copper exhaust pipe. (I thought it would look cool.) I soldered my fittings together with silver solder and it did look good! Boy, was I please.
I fired up the engine and liked the sound, too. Got about thirty feet down the drive and the pieces started coming apart, beginning with whatever was closest to the engine. The exhaust heat melted the solder. Maybe there's a way around this or a better solder to use, but my thinking is you might be better off using something other than copper. I hope you can make it work.
Someday when I grow up I will probably lose interest in toys with wheels, but until then...