Here's something to remember when you are at trackside watching a train pass, and you hear the thunder of a harsh slack adjustment. Maybe none of those knuckles broke right then, but hairline cracks result, and -someday, somewhere after months or years of oxidation in those cracks - that knuckle will break. Of all the broken couplers and knuckles I analyzed as an official, very few were all new breakage.
Also, I would challenge your statement that knuckles break with some regularity. Let's be fair to our North American Locomotive Engineers, who -- in my experience -- do not regularly break couplers. The failure rate is actually pretty low when looked at as incidents per thousand car miles, and our contemporary Engineers are pretty skilled at train handling.
Tom,
Sounds like the cases where breakage does occur are low cycle fatigue. What safety measures are in place to keep a consist from running away if a coupler break occurs?
