Motors Part 17
All liquids do not evaporate at the same temperature as water. Some require a great deal more than 212 degrees; others, like, for instance, dioxide-of-carbon, will evaporate at 110 degrees, or about one half the heat necessary to turn water into steam.
On the other hand, all gases act alike so far as their heat absorption is concerned, so that by using a material with a low evaporative unit, less fuel will be required to get the same expansion, which means the same power.
To ill.u.s.trate this, let us a.s.sume that we have equal quant.i.ties of water, and of dioxide-of-carbon, and that is to be converted into a gas.
It will take just double the amount of fuel to convert the water into a gaseous state. As both are now in the same condition, the law of heat absorption is the same from this time on.
The dioxide-of-carbon engine is one, therefore, which uses the vapor of this material, which, after pa.s.sing through the engine, is condensed and pumped back to the boiler to be used over and over.
In like manner, also, ether, which has a low point of vaporization, is used in some engines, the principle being the same as the foregoing type.
Rotary Engines.--Many attempts have been made to produce a rotary type of steam engine, and also to adapt it for use as an internal combustion motor.
The problem is a complicated one for the following reasons: First, it is difficult to provide for cut-off and expansion. A rotating type, to be efficient, must turn at a high rate of speed, and this makes the task a more trying one. Second, the apparent impossibility of properly packing the pistons. The result is a waste of steam, or the gas used to furnish the power. Third, the difficulty in providing a suitable abutment so as to confine the steam or gas, and make it operative against the piston.
[Ill.u.s.tration: _Fig. 115. Simple Rotary Engine._]
In Fig. 115 is shown a type of rotary which is a fair sample of the characteristics of all motors of this form. It comprises an outer cylindrical sh.e.l.l, or casing, A, having a bore through the ends, which is above the true center of the sh.e.l.l, to receive a shaft B.
This shaft carries a revolving drum C of such dimensions that it is in contact with the sh.e.l.l at its upper side only, as shown at D, leaving a channel E around the other portions of the drum.
The steam inlet is at F, which is one-eighth of the distance around the cylinder, and the exhaust is at G, the same distance from the point D, on the other side. The inlet and the outlet pipes are, therefore, at the contracted parts of the channel.
The drum has a pair of radially-movable blades H H', which may move independently of each other, but usually they are connected together, thus dispensing with the use of any springs to keep their ends in contact with the sh.e.l.l.
When steam enters the inlet F the pressure against the blade H drives the drum to the right, and the drum and sh.e.l.l, by contacting at D, form an abutment. Each charge of steam drives the drum a little over a half revolution.
A great deal of ingenuity has been exercised to arrange this abutment so that the blades may pa.s.s and provide a steam s.p.a.ce for a new supply of steam. In certain types a revolving abutment is formed, as shown, for instance, in Fig. 116.
The sh.e.l.l A, in this case, has two oppositely-disposed inlet and outlet ports, B, C, respectively, and between each set of ports is a revolving gate, formed of four wings D, mounted on a shaft E, in a housing outside of the circular path F, between the drum G and sh.e.l.l A.
The drum G is mounted on a shaft H which is centrally within the sh.e.l.l, and it has two oppositely-projecting rigid blades I. When steam enters either of the supply ports B, the drum is rotated, and when the blades reach the revolving gates, the latter are turned by the blades, or, they may be actuated by mechanism connected up with the driving shaft.
[Ill.u.s.tration: _Fig. 116. Double-feed Rotary Engine._]
Caloric Engine.--This is an engine which is dependent on its action upon the elastic force of air which is expanded by heat. The cylinder of such a motor has means for heating it, and thus expanding the air, and a compressor is usually employed which is operated by the engine itself, to force compressed air into the cylinder.
It is not an economical engine to work, but it is frequently used in mines, in which case the compressor is located at the surface, and the engine operated within the mine, thus serving a double purpose, that of supplying power, and also furnishing the interior with fresh air.
All engines of this character must run at a slow speed, for the reason that air does not absorb heat rapidly, and sufficient time must be given to heat up and expand the air, so as to make it effective.
Adhesion Engine.--A curious exhibition of the action of a gas against a solid, is shown in what is called an _Adhesion Engine_. Fig. 117 shows its construction. A plurality of disks A are mounted on a shaft B, these disks being slightly separated from each other.
The steam discharge pipe C is flattened at its emission end, as shown at D, so the steam will contact with all the disks. The steam merely contacts with the sides of the disks, the movement of the steam being substantially on the plane of the disks themselves, and the action sets up a rapid rotation, and develops a wonderful amount of power.
[Ill.u.s.tration: _Fig. 117. Adhesion Motor._]
It will be understood that the disks are enclosed by a suitable casing, so that the steam is carried around and discharged at a point about three quarters of the distance in the circ.u.mference.
This motor is given to ill.u.s.trate a phase of the subject in the application of a motor fluid, like steam, or heated gases, that shows great possibilities. It also points out a third direction in which an expansive fluid may be used.
Thus the two well-known methods, namely, _pressure_, and _impact_ forces, may be supplemented by the principle of _adhesion_, in which the expansive force of a gas, pa.s.sing alongside of and in contact with a plain surface, may drag along the surface in its train.
Such an exhibition of force has an a.n.a.logy in nature by what is known as capillary attraction, which shows _adhesion_. For instance, sap flowing up the pores of trees, or water moving along the fibers of blotting paper, ill.u.s.trates movement of liquids when brought into contact with solids.
CHAPTER XIV
ENGINERY IN THE DEVELOPMENT OF THE HUMAN RACE
The energy of a nation may be expressed by its horse power. It is not numbers, or intellect, or character, or beliefs that indicate the progress of a people in a material sense.
It is curious how closely related enginery is with the advancement of a people. Nothing can be more striking to ill.u.s.trate this than railroads as a feature of development in any country.
Power in Transportation.--Without the construction and maintenance of mechanical power, railroads would be impossible. To be able to quickly and cheaply move from place to place, is the most important factor in human life. The ability of people to interchange commodities, and to a.s.sociate with others who are not in their own intimate community, are the greatest civilizing agencies in the world.
Power vs. Education and the Arts.--Education, the cultivation of the fine arts, and the desire for luxuries, without the capacity for quickly interchanging commodities and to intermingle with each other, are ineffectual to advance the interests of any nation, or to maintain its prosperity.
Lack of Power in the Ancient World.--The Greeks and the Romans had a civilization which is a wonder even to the people of our day. They had the arts and architecture which are now regarded as superb and incomparable. They had schools of philosophy and academies of learning; their sculpture excites the admiration of the world; and they laid the foundation theories of government from which we have obtained the basis of our laws.
The Early Days of the Republic.--When our forefathers established the Republic there were many misgivings as to the wisdom of including within its scope such a large area as the entire Atlantic seacoast. From Maine to Florida the distance is 1250 miles; and from New York to the Mississippi 900 miles, comprising an area of 1,200,000 square miles.
How could such an immense country ever hold itself together? It was an area nearly as large as that controlled by Rome when at the height of her power. If it was impossible for the force of Roman arms to hold such a region within its control, how much more difficult it would be for the Colonies to expect cohesion among their scattered peoples.
Lack of Cohesiveness in a Country Without Power.--Those arguments were based on the knowledge that every country in ancient times broke apart because there was no unity of interest established, and because the different parts of the same empire did not become acquainted or a.s.sociated with each other.
The Railroad as a Factor in Civilization.--The introduction of railroads, by virtue of motive power, changed the whole philosophy of history in this respect. Even in our own country an example of the value of railroads was shown in the binding effect which they produced between the East and the West prior to the Civil War.
All railroads, before that period, ran east and west. Few extended north and south. It is popularly a.s.sumed that the antagonism between the North and the South grew out of the question of slavery. This is, no doubt, largely so, as an immediate cause, but it was the direct cause which prevented the building of railroads between the two sections.
It simply reenforces the argument that the motor, the great power of enginery, was not brought into play to unite people who were antagonistic, and who could not, due to imperfect communication, understand each other.
To-day the United States contains an area nearly as great as the whole of Europe, including Russia, with their twenty, or more, different governments. Here we have a united country, with similar laws, habits, customs and religions throughout. In many of those foreign countries the people of adjoining provinces are totally unlike in their characteristics.
It has been shown that wherever this is the case it is due to lack of quick and cheap intercommunication.
The Wonderful Effects of Power.--This remarkable similarity in the conditions of the people throughout the United States is due to the railroads, that great personification of power, notwithstanding the diverse customs and habits of the people which daily come to our sh.o.r.es and spread out over our vast country.
It has unified the people. It has made San Francisco nearer to New York than Berlin was to Paris in the time of Napoleon. The people in Maine and Texas are neighbors. The results have been so far reaching that it has given stability to the government greater than any other force.
But there is another lesson just as wonderful to contemplate. England has an area of only about 58,000 square miles, about the same size as either Florida, Illinois, or Wisconsin.
England as a User of Power.--The enginery within her borders is greater than the combined energy of all the people on the globe. Through the wonderful force thus set in motion by her remarkable industries she has become the great manufacturing empire of the world, and has called into existence a carrying fleet of vessels, also controlled by motors, so stupendous as to be beyond belief.
We may well contemplate the great changes which have been brought about by the fact that man has developed and is using power in every line of work which engages his activities.
The Automobile.--He does not, in progressive countries, depend on the muscle of the man, or on the sinews of animals. These are too weak and too slow for his needs. Look at the changes brought about by the automobile industry within the past ten years. What will the next century bring forth?