Here's my first car for my planned industrial layout, a small flat made from a paper mache box lid (idea taken from a post in this forum - thanks!) painted with rattle can primer and weathered with poster paints . The wood work is from popcicle sticks stained with ink/alcohol mixture, the couplers are pop rivets:
The underbelly reveals my "no-tech" wheel mounting systems, On30 wheelsets held in place by nylon clips. The two fishing weights add great stability and help it track pretty well.
At 2.25 inches wide, it is arguably too wide for 16.5mm track, but I like how it came out anyway. Total cost was around $3, so even if it ends up sitting on a siding or shelf, it was worth it.
Have a gnice day.