The Case of the Runaway Tires
The captain was perplexed. The field reported a runaway tire coming off trailer #17. That trailer was used to haul around rescue boats to various emergency scenes in the rivers and lakes that crisscrossed the region.
While responding to a potential drowning, the tire had simply flown off its mount crashing right through the plate glass window of a local diner. Fortunately, no one was hurt, but the tire missed hitting old John Henry by less than a foot. The town loved that old man. Aside from the human tragedy, it would have been an ugly lawsuit besides.
Funny thing is – that was the sixth runaway tire coming off a trailer in the last twenty months. When the captain went back to ask the team about what could be wrong, they came back with, “Must be a manufacturer’s flaw. We take good care of our trailers.” One guy even suggested the trailers may be haunted with a polite laugh.
The captain kept thinking. The technology behind making a trailer is pretty well known. It’s not very likely that this experienced manufacturer would start producing lemons, just for our group.
The captain went back and pulled up the check records for the trailers. The process was tedious. He had to pull out individual paper forms for three years. Of course, they would have to be filled out again afterwards, but if could save someone like our beloved John Henry, well…it was worth it….
The tattered forms were all stacked up on the lunchroom table. It included weekly check for three years for the unit’s 11 trailers, or about 1,716 sheets of paper. The captain poured himself a fresh cup of joe and started digging through them. His team was right: they had inspected the trailers every week thoroughly for the last 156 straight weeks. There had been a few maintenance events and they were well documented.
The captain went out to talk to one of the guys doing a trailer check that day. He was a new guy who had played linebacker for the local football team and was proud to be serving in his new job. He was eager to help out. About half way through the check, the young guy came to an item: check lug-nuts. He did, giving each nut a quarter turn by hand using the classic star sequence. It was by the book
Something clicked in the captain’s head. If we have lug-nuts that aren’t loose being tightened every week by linebacker-sized checkers, could something go wrong? The captain asked to see the bolts from the most recent runaway tire, and sure enough the threads had been stripped and several bolts had snapped.
Relieved he had an answer, the captain adjusted the check instructions to say, “First loosen the lug-nuts. Then re-tighten them.” He then refiled all 1,716 of the check records.