A while ago I noticed this piece of heavy equipment sleeping on a job site and decided to sketch a picture of it. It’s a Caterpillar 637 elevating scraper.
For an oil study like this where I’m only interested in the object and not the surroundings, sometimes I start with a piece of masonite primed with white oil paint. A brush works as well as a pencil for laying in the shapes, and you can get to detailed rendering right away.
Here’s a video of one in action, link.