The motions of bodies, or of the ultimate parts of bodies, also involve energy, for stopping them would be a source of work.
In steam cranes it is usual to work all the motions from one double cylinder engine.
Much attention has been paid to the improvement of the mechanical details of the lifting and other motions of cranes, and in important installations the gearing is now usually made of cast steel.
The speed of these two motions depends much on the length of the span and of the longitudinal run, and on the nature of the work to be done; in certain cases, e.g.
It is now possible to apply motive power exactly where it is wanted, and to do so economically, so that the crane designer has a perfectly free hand in adding the various motions required by the special circumstances of each case.