There are lots of cool things going on in this photo. The draw works and rotary table are all mounted on a permanent skid that slid into place on a wooden platform, under the wooden derrick and I love how the gears and sprockets are all aligned and tightened with turnbuckles. The 55 gallon drum racks are cool. The rig lights are single bulbs. There are individual chains driving the draw works, cat heads, rotary table, etc, and it is clear there is a secondary drive system behind the big Waukesha engine, perhaps to a mud pump that we cannot see in this photo. In addition to that there is slick wheel on the secondary system with the belt off and laying on the deck; that might be to run a little generator that is now down in the daylight, don't know. There appears to be a throw-out bearing of sorts on the main drive, along with what looks like a brake band, likely both related to the draw works drum.
All this stuff needs constant oiling and adjusting and all of it would grind your fingers, or your hand into hamburger meat in a millisecond if you were tired, sleepy or guilty of a brain fart and made a mistake. The guy in the foreground, with the coffee cup, has been up all night and is grumpy. The driller, or whoever that is over near the brake handle is guilty of blatant photo bombing.