Jack Straw in Mexico: How the Engineers Defended the Great Hydro-Electric Plant

by Irving Crump

Nedham was right. It was some time after midnight before the big generators were in condition to operate again. For hours the men toiled to get every vestige of the gritty substance out of the machines. Mr. Ryder went at the task with the rest, and Jack, unwilling to remain idle, rolled up his sleeves and seized a piece of cotton waste also. With the steel jacket removed, an excellent opportunity was afforded the lad for a better acquaintance with the mechanism of a water turbine generator, and as he worked beside Mr. Ryder, the engineer briefly explained the details.

“This is not really a generator that we are working on, Jack,” said Mr. Ryder, “because a generator is supposed to create energy. This does not do that. The real energy is in the water that turns the turbine, and this machine merely converts that energy into electric current, so you see the word ‘generator’ is a misnomer in this case. It is the same in a steam plant. Steam furnishes energy which is converted into electricity by the so-called generators. In fact, man-made electricity is nothing more or less than some other kind of energy in a new and more useful form. I guess you follow me.”

“I understand all right,” said Jack, “for it is very simple, though I must confess I had never considered electricity in that way before.”

“The energy here comes from the water that plunges over the dam we built across the river about a mile back in the mountains. The dam is sixty-odd feet high and the water that is stored up behind it is carried down to the plant here through a very large flume. The flume is built at the same level as the dam and brings the water around the mountain to the north of the plant and into the big forebay or reservoir just back of the station.

“The water in the forebay is kept at about the same height as the dam also, so it can get a sixty-foot direct drop to the turbines here in the building. The stream rushes down through the large penstocks, or feeders, and strikes against the mass of concaved blades on the waterwheel or turbine. The blades are set across the drum of the wheel and at a slight angle, thus giving the turbine the full benefit of the force of the water striking against them as well as the suction of the water after it leaves the blades. This is known as the reaction type of turbine and is only used in plants where the fall of water is less than 100 feet. There is another type of waterwheel on which buckets take the place of blades. This is known as the impact type and is driven entirely by the pelting of the water against the bottom of each cup. This wheel is used chiefly where the fall of water is more than 100 feet.

“The armature of the generator is also mounted on the shaft or axle of the turbine. The armature, you know, is composed of coils of wire wound very close together on an iron frame, or spider. Since the turbine whirls around very fast the armature is bound to turn at the same rate of speed. Now, the armature is surrounded by electrically excited magnets, which are the positive and negative poles of the generator. And as the coils of wire on the armature rush past the magnets the attraction or lines of force between the poles are cut abruptly and immediately electricity is created. By means of those brass collecting rings which you see on the armature the coils are connected to the transmission lines and the electricity flows through them to the lights in Mexico City.”

Mr. Ryder’s description of the hydro-electric plant was so simple and so easily understood that Jack was able to follow the entire process of converting water power into electrical energy. The conversation had also helped to lighten the rather disagreeable task of cleaning the generator and it was midnight almost before they realized it.

At this hour Mr. Ryder gave up all hope of using the generator that night, for, as he explained to Jack, the lights were fast being put out in the houses and stores of Mexico City, thus cutting down the load on the power plant to a point where the supply could be easily furnished by the remaining four machines. That being the case, he suggested they quit work and leave the task entirely to the peons and other workmen under Nedham. Jack’s arms were black to the elbow with dirty oil when he finally tossed his piece of waste away, and Mr. Ryder’s condition was little better.

“Come on, we’ll wash up a bit and start for the cottage; I am rather tired and I fancy you are too.”

Together they proceeded to the washroom and a few moments later left the station building and started up the short dusty street that led between the two rows of cottages. The searchlight was still playing from the roof and here and there a lonesome sentinel could be seen silhouetted against the skyline. Otherwise the little community was quite lifeless.