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.

[Larger plate.]

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

Section 39.—GUIDES, SLIDES, &c.

PISTON-ROD GUIDES.

[672]. Two bars and crosshead; these must be far enough apart to allow for the angle of the connecting rod.

[673]. Four bars, crosshead, and slide blocks; the connecting rod working between the two pairs of guides. The bottom guides are often cast solid with the bedplate.

[674]. Bar and slipper.

[675]. Adjustable slipper; there are other adjustments for wear by wedge pieces, similar to [No. 19]. See also [No. 21].

A plain guide bush is sometimes used as [No. 682], and a forked connecting rod with long fork coupled to the gudgeon or crosshead.

[676]. Section of [No. 673] and alternative crosshead for two round bar guides.

[677]. Slide bed and slipper.

[678]. Section of trunk guide, cast with engine bed and bored out.

[679]. Oscillating cylinder piston head guides.

[680]. Oscillating fulcrum in lieu of guides.

[681]. Diagonal crosshead and guide bars, to allow the crank and connecting rod end to pass the guide bars.

VALVE ROD GUIDES.

[682], [683], [684], & [685].

GUIDE ROLLERS.

[686] & [687]. Guide rollers for ropes, &c.

[688] & [689]. Guide rollers for bars of various sections.

LIFT AND HOIST GUIDES.

[690]. Cage guided by four corner posts.

[691] & [692]. Cage runs on two vertical rails, and is steadied by a third guide. For large cages. Small cages only require guides on one side, as [692].

[Larger plate.]

[693]. Iron wire or rod guides, strained tight, are sometimes used, especially in mines, as guides for the cage; two are used to guide the cage and two for the balance weight.

[694]. Planished round iron guides, with half round fixing brackets and runners attached to cage; these guides are equal to planed bars and much less costly; two are usually sufficient for any cage.

[695]. T L or ⊔ iron guides, for goods lifts.

[696]. Wire rope guides, with separate pair of wood guides for balance weight.

[697]. Intermediate guides for double cage lifts; for large cages extra guides at each side should be used.

[698]. Sloping carriage guides.

[699]. Vertical bracket cage guides.

MACHINE GUIDE BEDS.

[700]. Double V bed, with set screw adjustments.

[701]. Guide bed for planing machine, or any machine where the bed is not liable to lift in working.

[702]. Round bar and flat guide bed.

[703]. Deep V guide; much used for crossheads, tool boxes, &c., requiring accurate movement.

[704]. Lathe bed with square guides and adjustments for wear.

[705]. Planing machine, double V bed.

[706]. Crosshead for two single bar guides, with renewable wearing strips and square guide surfaces.

[707]. Radial slide for tool box, usually of same section as [No. 700].

ROPE GUIDES.

[708], [709], & [710]; in [709] the rope can be threaded without passing the end through.