we had 2 on a I worked as an apprentice but we called them quad 9s . 1970 was the first time I saw alligator master link tracks and it sure made putting tracks on a quad easier .
one of my favorite sounds, are those large cat engines throttling up. Music to my ears
I started out at Caterpillar in 1974 East Peoria plant building LL and worked briefly as a tractor shuttle driver, moving units from one area to another. The last of these sets we built were called D9 SXS ( side by side ) as they could be set either parallel or in tandem as seen here. The last ones were built I believe in the late 70's after Cat started pushing the original D10 high rise as the most powerful tractor on the market at that time.