Another Tractor Sketch From the Past

This is another tractor sketch I made some time ago and published to my old sketching blog but not to this blog, so here it is now;

"Orange Tractor"

Pen & watercolor on paper, 5" X 8"

This is actually the same tractor in the pencil sketch from the previous post at Wheeler Farm, just a different angle and different time of year.

What is it about old tractors that make them such appealing art subjects?  Is it the nostalgia for the "simple life" of the independent American farmer?  Or is it the interesting shapes and colorful patina?  Or is it both?