In researching "Vis Major" one thing that was clear, the minor derailments of rotary snow plows was not uncommon even "back in the day" when the plows were new and in constant use, in this case, by the Great Northern. The minor derailments that I researched generally came due to three causes, switch points seemed to be an issue for the lead trucks, short reverse moves could put the trailing plow of a double set on the ground due to snow build-up behind the plow, and the slow speed allowing snow to build up under the trucks and virtually "lifting" the plow off the rail.

I guess the point is, even back when crews used these plows daily during every winter, rotaries on the ground were actually considered just a part of operation. I think it is amazing, and tribute to the men now running these machines that it happens so seldom.

Martin Burwash