The chains are periodically replaced. They recieve a tremendous amount of wear and tear during the course of a season. Remember the old saying "a chain is only as strong as it's weakest link"? Watch what happens when a train hooks up.Watch the chain jump. The old PTC three bench cars weigh in around two tons. A three car train ( six tons) plus the weight of the riders equals a lot of stress, not only on the chain but on the spockets and the motor and gearbox as well.
It happened to a new coaster (Superman at SFA) twice in its first couple of weeks... the first time while I was on it!
I don't know how often parks replace chains, but I think Cedar Point generally replaces theirs at least every two or three seasons, necessary or not. Given the length of Magnum's chain, I'm surprised it doesn't happen more often. It's been several years since it happened last... perhaps someone can remember which year?
------------- Jeff Webmaster/Admin - CoasterBuzz.com