The crank shaft carries a pinion which gears into a toothed wheel of a coarse pitch, carrying cutters at the ends of the teeth.
The smallest number of teeth in a pinion for epicycloidal teeth ought to be twelve (see 49)but it is better, for smoothness of motion, not to go below fifteen; and for involute teeth the smallest number is about twenty-four.
The rotation of the cam shaft continues till the cam has again heaved up the flitch-plate, when the pinion on the cam shaft is thrown out of gear with the wheel on the counter shaft, and the cam remains steady till another charge of coal is dropped into the hopper and the action is renewed.
The signal coil is suspended by fibres and is mounted together with a fixed soft iron core on a brass plate affixed to a rack, with which a pinion operated by a milled head screw engages.
Since, however, only relatively low powers are now employed, the ordinary rack and pinion movement for focusing suffices, and for the illuminating the object only a mirror below the stage is required when the object is transparent, and a condensing lens above the stage when opaque.
This ring runs between friction wheels and is provided with teeth on its inner periphery, and these teeth transmit motion to a pinion on a spindle having at its other end another pinion which, through an intermediate wheel, rotates the heliometer tube.
The sleeve of the pinion which carries M also carries the dial finger, and if the dial is properly graduated its finger will indicate the weight.
If now a small weight, as a penny, be passed through the slot, H, it falls into the small box, I, and causes the lever, J, to turn; the lever, J, which turns in friction wheels at K, and is counterbalanced at 0, carries a toothed segment, L, which actuates a small pinion on the same axle as F, and is free to turn on that axle by a sleeve.
The rocking-bar is moved by a rack g into which a pinion on a cross-spindle j gears; the cross-spindle is moved by means of a worm-wheel into which a worm on the longitudinal FIG.
A spur pinion D, gearing with both wheels, is carried loosely upon an eccentric E forming part of the central pin, so that when this latter is turned by the hand-wheel F and chain G the axis of the pinion describes a circle the diameter of which equals the throw of the eccentric, and a small relative motion of the two sheaves takes place, depending on the number of the teeth of the annular wheels.