The Economy of Workshop Manipulation / A logical method of learning constructive mechanics. Arranged with questions for the use of apprentice engineers and students.

by John Richards

To summarise, we have the following propositions relating to steam machinery:—

1. The steam-engine is an agent for utilising the power of heat and applying it to useful purposes.

2. The power of a steam-engine is derived by expanding water in a confining vessel, and employing the force exerted by pressure thus obtained.

3. The power developed is as the difference of volume between the feed-water forced into the boiler, and the volume of the steam that is drawn from the boiler, or as the amount of heat taken up by the water.

4. The heat that may be utilised is what will pass through the plates of the boiler, and be taken up by the water, and is but a small share of what the fuel produces.

5. The boiler is the main part, where power is generated, and the engine is but an agent for transmitting this power to the work performed.

6. The loss of power in a steam-engine arises from the heat carried off in the exhaust steam, loss by radiation, and the friction of the moving parts.

7. By condensing the steam before it leaves the engine, so that the steam is returned to the air in the form of water, and of the same volume as when it entered the boiler, there is a gain effected by avoiding atmospheric pressure, varying according to the perfection of the arrangements employed.

Engines operated by means of hot air, called caloric engines, and engines operated by gas, or explosive substances, all act substantially upon the same general principles as steam-engines; the greatest distinction being between those engines wherein the generation of heat is by the combustion of fuel, and those wherein heat and expansion are produced by chemical action. With the exception of a limited number of caloric or air engines, steam machinery comprises nearly all expansive engines that are employed at this day for motive-power; and it may be safely assumed that a person who has mastered the general principles of steam-engines will find no trouble in analysing and understanding any machinery acting from expansion due to heat, whether air, gas, or explosive agents be employed.

This method of treating the subject of motive-engines will no doubt be presenting it in a new way, but it is merely beginning at an unusual place. A learner who commences with first principles, instead of pistons, valves, connections, and bearings, will find in the end that he has not only adopted the best course, but the shortest one to understand steam and other expansive engines.