Perhaps its the way the tracks move past the operator's station. Perhaps it is the "Clacking" noise paired with the bouncing of the tracks moving that fascinates me.
On the farm, we are using a Cat D6D to clear land and keep the driveway cleaned. When operating it, I seem to "Zone Out" a little, where I don't really think about what I am doing - rather, I think of what the machine is doing. You feel every vibration; hear every noise; Sense the load on the engine and the position of the blade; It's a bit of a neat experience.
I think for me it is a form of meditation. The concentration needed to make the machine flatten ground or knock something down forces you to forget the outside world and focus on your immediate area. Sure, you can think of other things during a long push, but a lot of those thoughts are forced to be "Background Processes"
So I leave you with a poem:
STUDY OF A BULLDOZER
Abominable machination.
A destructive reputation.
Angry figure of claws and blade.
Yellow paint and rust, polished blade and tracks,
it does not care what others think.
It tries to understand the earth,
by carving into the ground.
Strong willed,
it goes where it pleases,
shaping the earth with its art.
-Chris Pritchard (2011)