A Smoking Bolt?

The investigation has begun. What caused parts of the engine shaft of a diesel express train to fall onto the tracks, leading to a fire and derailment, not to mention 36 injured passengers? It is too soon to say officially, but the most likely outcome is a maintenance error.

Trains that travel at high speeds on metal rails laid on the earth's surface are bound to vibrate. They can't help it. Parts will eventually fall off, unless the bolts that hold parts in place are kept fastened. This requires a lot of work by human hands.

Wouldn't it be great to have a bolt that, the more it vibrated, the tighter it fastened itself?

Guess what? There IS such a bolt. It is called the "perfect lock bolt", and it is as good as it gets in the world of metal fasteners.