crankshaft

[spro]

No intention to come between previous advise only an appreciation for the work you already did. That was some job to get it that far. I note you only roughed out the center main and it didn't collapse there. The rod bearing throws seemed to have shifted during the machining and thrown the works. I think that the answers to this area of machining the eccentrics/rod areas will be helpful.
The crash must have been more intense than you mention.

[davec43]

My first thought was also that it must have been an exciting moment!

[oldbrock]

Rick has it. Spacers are essential in all spaces not being worked on, my senior students in high school all built a twin cylinder double acting steam engine from barstock. We did have one crank destroyed but that's not bad in a class of 20 students. My draughting class designed it and some of them were also in the machine class. ( that's limey for drafting) Peter