Chapter XXXI: Section 38: Friction Gear

Various forms of friction gearing are much used, the chief objection to this kind of gear being the excess of pressure on the bearings required to give sufficient grip to drive the gear.

=664. The common form of flat-faced friction gear= for hoisting purposes, &c. See No. 1211. The required pressure is given by a weighted lever.

=665. Friction bevils,= plain faces, for governor driving, &c.

=666. Friction bevils,= the pinion being usually of hard leather; the pressure may be applied in the direction of either of the arrows.

=667. Multiple ~V~ gear.= A common mistake is to run these too deep in gear; the narrower the surfaces in contact, short of the seizing or crushing point, the less the power wasted in friction.

=668. A very small pinion of leather, wood, or rubber= is frequently driven by a large driving wheel for obtaining high speed with steadiness, for driving dynamos, fans, &c.

=669. Disc wheel and rubber pinion,= arranged to reverse motion or vary speed. See No. 1595. The motion is reversed by throwing either wheel into gear with the pinion, and the speed varied at will by raising or lowering the pinion, used for screw presses.

=670. Wedge friction gear.=

=671. Coupled bearings= for friction gear, to allow of any required pressure or “bite,” the strains being self-contained.

See also No. 737, 738, 1294.