Mr Don LeTourneau is RG LeTourneau's grandson
he is restoring and digitizing LeTourneau film archives
The old LeTourneau earth moving equipment was something else , all electric controls. You steered a scraper with a couple of toggle switches while holding onto a bar. Never got to try to operate one but was able to crawl all over several years ago. When I was running a pilot car [escort] for heavy haul/OS I got to operate a few scrapers/loaders/excavators during loading/unloading or stageing them. Fun times !!
Not a couple of switches, there was just one. The dash had a "Jesus bar" to grab and the switch was on the right side of the dash behind the bar (at least on a 111A) where it was convenient for the thumb and forefinger.
The fun started when the machine got a little age on it. The alternator would loose voltage at low engine rpm and the steering contacters wouldn't engage. Most peoples normal reaction when they get into a tight spot is to get off the fuel. But on a LeTourneau (later Wabco), that killed your steering. Lots of stories about accidents due to inexperienced operators and the unusual controls.