Read Ebook: The Engineer's Sketch-Book Of Mechanical Movements Devices Appliances Contrivances and Details Employed in the Design and Construction of Machinery for Every Purpose Classified & Arranged for Reference for the Use of Engineers Mechanical Draughtsmen Manag by Barber Thomas Walter

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For producing, from plain circular, or reciprocating motion, variable speed or motion, also intermittent and every kind of irregular motion. Cams are either open or covered. Nos. 131, 132, and 133 are open cams; Nos. 137 and 138, covered cams.

Section 10.--CRANK AND ECCENTRIC GEAR.

See also Nos. 606, 712, 720, 728, 729.

See also Sections 40 and 79.

Section 11.--CHAINS AND LINKS.

For Hooks, Swivels, &c., see Section 43.

Section 12.--CARRIAGES AND CARS.

The design and details of these must always be suited to circumstances. We only propose here to indicate the various types of under-framing and wheels in use, and to give sketch sections of bodies or cars for different purposes.

UNDER-FRAMES.

A car with four wheels arranged as No. 217, but with the leading and trailing wheels slightly raised off the ground, is used as a goods car or hand truck, and is very readily swivelled about, running, of course, actually on three wheels only.

Note that in Nos. 221, 223, & 224 the centre pairs, if running on rails, must have either end play in the bearings or flat broad tyres.

Section 13.--CRUSHING, GRINDING, AND DISINTEGRATING.

Section 14.--CENTRIFUGAL FORCE, APPLICATIONS OF.

Section 15.--CLUTCHES.

Several other forms of this clutch are in use. Edwards', Stevens and Major's, and others may be consulted.

Numerous forms of friction clutches are in use, modifications chiefly of Nos. 38, 59, and 282. See also Section 5.

Section 16.--COUPLINGS FOR SHAFTING.

Section 17.--CONNECTING RODS AND LINKS.

The shafts or rods are sometimes of cast iron of cross or ~T~ section, but are usually of a circular or flat section and swelled in the middle, similar to No. 299. See Struts and Ties, Section 102.

There are innumerable varieties of the illustrated types of heads in use, every engineer having his own design.

Section 18.--CRANES, TYPES OF.

Our object here is to indicate or suggest general design or arrangement only, from which a selection can be made to suit requirements.

Section 19.--CONVEYING MESSAGES.

Messages can be conveyed by--

Section 20.--COMPENSATING AND BALANCE WEIGHTS.

It is of the utmost importance that every revolving or reciprocating part of any machine should be as nearly as possible balanced, to obtain smooth running with the least amount of wear.

The following are types of the most important devices and their applications:--

Hoisting and winding engines are balanced by having an ascending and descending cage, and two ropes, one winding on as the other winds off the drums.

Double cage hoists similarly balance themselves. Heavy slide valves, and other reciprocating parts of steam engines, are balanced by small steam pistons. See Nos. 1651-1654.

Foot treadles, when required to always stop at a point off the dead centre, have a balance weight fixed to fly-wheel, at right angles to the dead centre.

A water tank is often used to serve as a counterpoise, or balance, and may be made variable by varying the quantity of water by a siphon or other device.

For Balanced Valves, see Section 89.

Section 21.--CIRCULAR AND RECIPROCATING MOTION.

See also Sections 62, 31, and 74.

Section 22.--CONCENTRATED POWER.

Knapping toggle motion. See Nos. 269, 251.

Section 23.--CONVEYING MOTION TO MOVABLE PARTS OF MACHINERY.

Motion may be conveyed to such parts of a machine as require to be movable, or to distinct machinery which has no fixed location, by the following means:--

See also Nos. 348, 349.

Endless rubber or wire coil belts are used to give motion to machines having some amount of freedom of movement as regards the fixed position of the driving pulley.

Section 24.--CUTTING TOOLS.

Besides the ordinary cutting tools in use in the workshop, such as the chisel, gouge, plane, saw, drawknife, scissors, shears, scythe, and others, and which do not properly belong to machine devices, there are others, some of them mere modifications of the ordinary tools that are sometimes needed in the design of machines, and are illustrated here.

Other appliances are--Shears: see the ordinary shearing machines, bookbinder's shears, No. 462, and other modifications. In some the shears are hinged at one end, in others the movable blade moves either with equal or unequal motion at either end by cam or crank motion

Section 25.--CONDENSING AND COOLING APPLIANCES.

Their uses generally are to condense steam, to cool heated gases, air, or articles of food requiring a low temperature; distilling, and other purposes. For cooling purposes, compressed air machines are in most demand. The air is compressed in a cylinder, then cooled to ordinary temperature again in a surface condenser, such as No. 468, and then expanded into the cooling chamber, through a cylinder and piston, the expansion reducing its temperature usually to 10? or 20? below zero. Other cooling appliances are ammonia machines, fans, and blowers of all kinds, punkahs, or waving fans, freezing mixtures, &c.

See Morton's ejector condenser, which requires no air pump; Hayward's exhaust condenser, which employs the water in suction pipe of a pumping engine to condense the steam. See Messrs. Tangye's list. Water tube cooling coils are used for tuyeres and other hot surfaces.

Air-compressing and gas engine cylinders are water jacketed to carry off the heat of the compressed air or gas. Cooling by exposing a large surface to air is sometimes employed for exhaust steam on tram car engines &c., the apparatus consisting generally of numerous wrought-iron tubes or coils.

Section 26.--CONCENTRATING AND SEPARATING.

Sifting, riddling, and screening are treated of under Section 72. For concentrating ores many methods are in use, of which the water processes are the most important.

The ordinary magneting machine, for separating particles of iron or steel from mixed borings, &c., consists of a series of magnets drawn through the material, and then through fixed brushes, which brush off the iron particles adhering to the magnets.

Filtration through various substances--as sand, charcoal, calcined ores, &c., is employed to separate suspended matter from liquids.

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