It is not often we are called upon to put vibrations in; the problems mostly consist of taking them out.
The following persons are most vitally interested: (a) the designer and the builder of the machine structure, which may be easily discredited by a bad vibration, even if perfect in every other particular. (b) the buyer of the machinery, or the owner of a hotel or factory, or any like building, where a bad vibration may mean general annoyance, defective product, undue wear and tear or even actual danger.
A badly vibrating turbine may often cause an explosion of the steam main feeling it. In some rotor explosions, the cause was merely vibration, "running a little rough," as a practical man may sometimes put it.
In a gas engine, a bad vibration may mean excessive wear of the bearings, needless strain on the engine and connections, loss of power or lack of "pick-up." Most of these conditions are absolutely unnecessary.