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CHAPTER X
POWER AND ITS APPLICATION
THIS is a phase of the flying machine which has the greatest interest to the boy. He instinctively sees the direction in which the machine has its life,--its moving principle. Planes have their fascination, and propellers their mysterious elements, but power is the great and absorbing question with him.
We shall try to make its application plain in the following pages. We have nothing to do here with the construction and operation of the motor itself, as, to do that justice, would require pages.
FEATURES IN POWER APPLICATION.--It will be more directly to the point to consider the following features of the power and its application:
1. The amount of power necessary.
2. How to calculate the power applied.
3. Its mounting.
WHAT AMOUNT OF POWER IS NECESSARY.--In the consideration of any power plant certain calculations must be made to determine what is required. A horse power means the lifting of a certain weight, a definite distance, within a specified time.
If the weight of the vehicle, with its load, are known, and its resistance, or the character of the roadway is understood, it is a comparatively easy matter to calculate just how much power must be exerted to overcome that resistance, and move the vehicle a certain speed.
In a flying machine the same thing is true, but while these problems may be known in a general way, the aviator has several unknown elements ever present, which make estimates difficult to solve.
THE PULL OF THE PROPELLER.--Two such factors are ever present. The first is the propeller pull. The energy of a motor, when put into a propeller, gives a pull of less than eight pounds for every horse power exerted.
FOOT POUNDS.--The work produced by a motor is calculated in Foot Pounds. If 550 pounds should be lifted, or pulled, one foot in one second of time, it would be equal to one horse power.
But here we have a case where one horse power pu
