Section 60.—MOTIVE POWER.
It is assumed that all physical energy is derived more or less directly from the sun, whose rays combine: 1, heat; 2, light; 3, actinic or chemical power.
Heat may be obtained:
a.
By direct use of the sun’s rays.
b.
From any combustible material.
c.
From chemical reaction.
a. By direct use of the sun’s rays.
b. From any combustible material.
c. From chemical reaction.
Light does not separately develop power.
Chemical reactions are employed to develop heat, combustion, contraction, or expansion, as means of developing power.
From the foregoing elementary physical sources the following are the practical sources of our power for mechanical purposes.
- Electrical power.
- Magnetic power.
- Tidal motion.
- Falling water.
- Descending weights.
- Wave motion.
- Wind.
- Expansion of air or other gases.
- Steam.
- Explosives.
- Fuels, hydrocarbons, &c.
These are employed in producing power by the following apparatus or motors:—
Electric motors driven from a dynamo, battery, or accumulator.
Magnetic power cannot be employed continuously as a motor, as it gives out only as much as it receives.
Tidal motion can be utilised to drive any kind of wheel, see Water Wheels, [Section 90]. It can also be stored in a reservoir, driving a water engine as it flows in and out on the flood and ebb; or a floating vessel may, by its rise and fall, communicate motion to machines.
Falling water; for machines employed to utilise, see Water Wheels, [Section 90]; Turbines, Water-pressure Engines, &c., [Section 93].
Descending weights must first of course be raised, absorbing as much power in raising as they give out in falling, neglecting friction. Clockwork; water; or compression of a spring (see [Section 80]); multiplying pulleys (see [Section 42]), are the apparatus employed to utilise this form of energy.
Wave motion is too uncertain and erratic to be a practicable source of power. Rocking air-compressing chambers, rocking pumps, &c., have obtained some small measure of success.
Wind, windmills. See [Section 95].
Expansion of air and gases. Ascending currents of hot air from a fire are used to drive a light screw motor, fan, &c. Hot-air engines, see Ryder’s patent and numerous others, which depend upon alternate expansion and contraction of air by heating and cooling. Air compressed in an accumulator or reservoir is employed to give motion to multiplying pulleys or an air engine.
Expansion of liquids, other than water (by heat), into the gaseous form. Engines in which the fuel is burnt under pressure and the total products of combustion employed (with or without steam) to drive a motor.
Steam is in reality one of the last-mentioned sources of power; it is employed by direct pressure on a piston or ram (see [Section 32]); or to produce direct rotary motion (see [Section 75]); also in the jet pump, [No. 801]; or injector (see [Section 45]); or by direct pressure on a body of water contained in a closed vessel, as in the pulsometer, steam accumulator, &c.
Explosives are substances which, by application of flame, heat, percussion, &c., suddenly assume the gaseous form, thus increasing their bulk many hundred times, usually in a small fraction of a second of time. A second class comprise explosive mixtures of gases, such as hydrogen, and oxygen, carburetted hydrogen, and air. Some attempts have been made to employ explosive substances to drive engines in various ways, but with no permanent success. The second class of explosive mixtures of gases are largely employed in the gas engine, petroleum engine, and their varieties.
Fuels, hydrocarbons, &c., are employed to evaporate water into steam; to expand air or other gases, or convert liquids into gases; and also by vaporisation to supply gas for use in some forms of gas engine.