"Simplex" external spring steam engine indicator, Type B. In case.

"Simplex" external spring steam engine indicator, Type B. In case.

In this steam-engine indicator, which is a modified form of one patented by Mr. M. J. Wayne in 1894, the ordinary helical spring is replaced by a bow spring situated outside the cylinder away from the action of the steam. This can be easily removed and replaced, as its ends simply fit into grooves provided in the top of the extended piston rod and a fixed piece above it, and are retained in position by a small spring pin in one of the grooves engaging with a notch.