Avoid Locomotive Jack Knife Derailments - Railway Age Magazine

[nkalanaga]

Not directly applicable to model railroads, but it's interesting that the prototype seems to have some of the same problems we do. 

https://www.railwayage.com/news/avoid-locomotive-jack-knife-derailments/?RAchannel=news

"North American railroads have significantly reduced the number and severity of derailments, especially since the Staggers Rail Act economically deregulated U.S. railroads in 1980. But while total derailments have declined, there continue to be a small number of “locomotive jack knife” derailments that can and should be eliminated; accomplishing that will take some decisions and actions.

Research shows at least nine such derailments in the U.S. and Canada in 1992, 1999, 2002, 2005, 2010, 2015, 2018, 2020 and 2023. One of the derailments destroyed a commuter locomotive in transit; another derailed 3 of 5 commuter locomotives; another damaged an unoccupied commuter platform; each damaged the older, shorter locomotives being transported plus freight cars; and one caused a hazmat spill (jet fuel). The 2023 derailment was investigated by the National Transportation Safety Board, and the derailments in 2002, 2005 and 2020 were thoroughly investigated by the Transportation Safety Board of Canada. All involved non-alignment control locomotives with “coupler stop blocks” instead."

[lock4244]

I remember when watching CP at Agincourt Yard in Toronto as a kid, anytime an SW1200RS was being moved between the locomotive servicing shop and it's outpost location it'd be marshalled between two larger units. No idea why at the time, but it looked cool. Years later I caught one in transit during the end of their era on CP, and it was placed between two SD40-2's... I guess CP had had an incident at some point that lead to specific rules regarding placement of them on road freights. Thinking about it, when a few ex MILW MP15's were sent to Montreal for sale or some other reason I caught a few in transit east of Toronto and they were placed between pairs of AC4400/ES44AC's.

You also needed special permission on CP to place more than eight locomotives in a consist, online or dead... was due to a derailment attributed to too much weight spreading the rails.

One of the accidents noted in the article was a CN derailment at Pickering, Ontario, that involved three former GO Transit F59's behind the road power. Guess CN didn't have such marshalling rules regarding non self aligning couplers, or if they did they were ignored.

[learmoia]

A work around for moving units without alignment control couplers is to install stop blocks to hold the coupler in the center position.

[nkalanaga]

Yes, but the article notes that stop blocks don't do as good a job.  They still allow the side pressure from the coupler shank to force the wheels against the rails, which is the issue.  True alignment control couplers keep all of the pushing forces in the draft gear, and transferred directly to the frame.

There are diagrams showing how all of this works, or doesn't work, and I didn't realize there was that much difference between the two methods.  It shows why BN's early Special Instructions included notes on which locos had alignment control couplers.