Isochronous Governors

A governor is said to be isochronous when the equilibrium speed is constant (i.e. range of speed is zero) for all radii of rotation of the balls within the working range, neglecting friction. The isochronism is the stage of infinite sensitivity.

Let us consider the case of a Porter governor running at speeds N1 and N2 r.p.m.

For isochronism, range of speed should be zero i.e. N2 – N1 = 0 or N2 = N1. Therefore from equations above, h1 = h2, which is impossible in case of a Porter governor. Hence a Porter governor cannot be

isochronous.

Note : The isochronous governor is not of practical use because the sleeve will move to one of its extreme positions immediately the speed deviates from the isochronous speed.