Belts were used well into the 50's. The twist in the belt reverses the direction of the drive pulley. The open belt is a hazard, if the belt come off it can also be dangerous. Early blower equipment used at the silo on the farm was belt driven. Eventually the belts went away, all was PTO (Power Take Off) driven with appropriate guards. Most threshing machines were belt driven. Working that close to an open saw blade is also dangerous.
I believe these steam tractors are more closely watched. Several years ago one came apart at an Ohio county fair.
Medina County Fair, Ohio 2001 Steam Tractor explosion.