Tractor-trailer king-pin cast-iron lockdown fracture

Stage-direction case — Tom holds up a cast-iron lockdown component from a tractor-trailer fifth-wheel king pin assembly. The part bounced out, causing an accident; Tom is running tests for an active forensic case. Used to motivate why cast iron is fine for complex shapes despite brittleness.

[Tom holds up a cast-iron part.] This is a piece of cast iron. This part was in my office when I showed up Friday night after my travels. I need it back — I have to do some tests on it — but it's part of a big tractor-trailer. It actually holds the king pin, the big six-inch-diameter pin that holds the trailer to the tractor on the fifth wheel. This was the lockdown to keep the thing from bouncing out, and it turns out it did bounce out in one case. We don't have to get into the accident that caused. But there are complex shapes for which making something out of cast iron is fine.