Nobody knows what caused the accident that killed Jeffrey Smith on Sept. 8, 2011, in the welding shop of a Wisconsin factory where Caterpillar Inc. builds gigantic strip-mining machinery. All we know is that a crane was moving a 36-ton set of tracks, called a crawler, when the component shifted unexpectedly and crushed Smith.To try and find out what killed one of its members, the United Steel, Paper and Forestry, Rubber, Manufacturing, Energy, Allied Industrial and Service Workers International Union wanted to send Sharon …