=784 & 785. Hand (portable) indicator,= to indicate speed of revolution
of a shaft, &c., by simple wheel work and dial plate.
=786. Governor gauge,= indicates the speed by the angle of the balls
moving a finger on a vertical scale.
=787. Steam engine indicator,= of which there are many varieties.
Macnaught’s, Richards’, Darke’s, Kraft’s, Casartelli’s, &c., are
examples, in which a small steam piston operates a marking point by the
varying pressure of steam acting against a spring; the paper is usually
coiled on a cylinder having a reciprocating motion by a string from the
engine.
=788. Morin’s dynamometer.= Consists of two belt pulleys connected by a
spring; one receives the strain of driving belt, and the other transmits
it, the spring indicating the tension on the belts.
=789. Regnier’s dynamometer= indicates the tension on the connections by
contraction of the spring operating a dial plate.
=790. Bourdon tube pressure indicator.= The tube is of flat section, and
its curved portion expands with the pressure, operating a finger on the
dial by rackwork.
=791. Worm gear and dial= to register the number of revolutions. See No.
1559.
Other forms of pressure gauges are--1st. The mercurial gauge, in which
the pressure is indicated by the height of a column of mercury in a
glass tube. 2nd. The water gauge, in which a column of water replaces
the mercury. 3rd. The spring balance (see No. 1729). See also Nos.
1730, 1728.
[Illustration: 770.-791.]
=792 & 793. Winding engines= are provided with indicators on the
principle of No. 744. The travelling nut has a pointer whose position on
a vertical graduated scale shows the position of the cage in the pit.
Vertical scale indicators are also employed to show the level of water
in tanks, reservoirs, &c. See No. 1730.
Water tube indicators are employed to show the level of water in
boilers, &c., as also gauge cocks fixed at various heights in the
boiler.