With a copy in their possession, the Ross boys hurried home, after having dinner with the Giddings family, to acquaint Mrs. Ross with the good news.

CHAPTER IV

PLANNING A BIG AIRPLANE

As planned, the much-talked-of Air Derby around the world took place from Mineola Field, New York, on the 4th of July. A great crowd had been attracted, owing to the extensive accounts of the affair in the big newspapers for the past several months, and a thrilling hush fell over the a.s.semblage as, at high noon, one after another of the famous flyers took off in various types of aircraft. There were four big dirigibles, two of which started to cross the Atlantic at once, while the others took a northerly course with the intention of making the final hop from St. John's, Newfoundland, in accordance with several previous attempts of other aircraft. Besides these, seven heavier-than-air machines started, all making for Newfoundland also.

Four of these were flying-boats, two were seaplanes, and the other was a double-propellered biplane.

Needless to say, the Ross boys and Bob Giddings and his father were present to see the machines off. They had arrived in the big automobile of the publisher, and were greatly interested in every detail of the departure. Several of the contestants John Ross knew, having met them at some time during his flying periods, and it gave him a chance briefly to renew old acquaintanceship and personally to wish them good luck on their long journey. Of course our friends would have given a whole lot to have been able to compete in the novel contest themselves, but that was out of the question.

When the last machine had disappeared from sight, they took their departure. Mr. Giddings left them at the office of the _Daily Independent_, following which Bob drove Paul and John out to some of the city's beautiful parks. Late in the afternoon they again stopped at the newspaper building and picked up Bob's father, thereupon turning the car in the direction of Yonkers. Altogether they had pa.s.sed a very pleasant holiday.

"Robert tells me that your plans for the new airplane, the Sky-Bird II, are just about finished, John," remarked Mr. Giddings, as they sped northward along the smooth surface of Riverside Drive, with its beautiful greenery on the left and its fine residences at the right.

"Yes, sir," said John; "we have been devoting every spare moment to them. Of course a good many changes had to be made to adapt conditions from the little airplane to the big fellow, and to incorporate the extra pet features we all agreed upon were desirable. You know it never pays to start building an important and costly affair like an airplane without having every detail thoroughly planned out, and perfect working drawings in hand. I think Paul will complete the drawings early next week, including copies for accompanying the specifications when we apply to Washington for patent rights. As soon as the drawings are done, we will drop in at your home in the evening and show them to you."

"Good!" said Mr. Giddings. "I shall await them with great interest. I suppose as soon as I approve these drawings, you fellows will all pitch into the actual work."

"We surely will, sir," laughed Paul, while Bob, at the wheel in front, having caught some of the conversation, called back with energy: "That's just the size of it, dad."

"We have everything all ready," continued Paul. "The balsa-wood and spruce we ordered some time ago is on hand, and that will keep us busy until other needed materials arrive. We have repaired the big exhibition building in the old fair-grounds, put on new double doors and purchased a good Yale lock for them. John and I have taken our workbench and tools over there, and Bob has helped us rig up a nice little five-horse power motor and small handsaw, also a circular saw, home-made sand-drum, a small planer, and a boring-machine. That building is dry, and has lots of room in it for housing the new airplane as it grows to maturity. When cold weather comes we can easily install a couple of heating-stoves to keep ourselves comfortable and protect our materials and the machine from frost damage."

Mr. Giddings expressed himself as well pleased with these arrangements.

As he noted the foresightedness of the young mechanics his confidence in them expanded.

"Don't hesitate to order anything you need, young men," he said warmly.

"Have them send the bills to me. If my trust in you is misplaced, I am willing to stand the consequences. This is not only the best kind of a practical education for Bob, but it is good business training for all of us. Go ahead; go ahead!"

With such strong encouragement, is it any wonder that the three young men continued their operations vigorously? Not one of them scarcely wanted to stop long enough to eat and sleep, _a la_ Edison; and as it was now summer vacation time, Paul and Bob were able to be with John all day long in the old exhibition building. Neighboring boys and even older people hung around the open doors to watch operations, but the builders were careful not to let them get close enough to gain any ideas which might be harmful to their interests.

On Tuesday evening of the week following the start of the Air Derby, John and his brother put on their best clothes and hied themselves over to the Giddings home. In Paul's hand was an envelope containing the precious plans for the Sky-Bird II--completed at last by the young draftsman, and ready to be shown to the financial member of the quartet.

When they were all seated in the Giddings library a little later, Mr.

Giddings scrutinized the plans with every evidence of satisfaction written upon his strong features. Now and then he would ask a question, as Paul explained view after view and detail after detail.

At length he pointed to an oblong object situated in the pilot's c.o.c.kpit just under the dashboard. "What is that?" he asked, curiously.

"That is what John and I call an 'automatic pilot,'" answered Paul.

"It is a new form of stabilizer, and made so as to overcome the defects of others which are on the market. A stabilizer should automatically keep an airplane on a fairly level keel no matter how air conditions are, even so steady that it will travel along on its course for a considerable distance with the pilot paying no attention to his controls, perhaps eating his lunch or reading his orders."

"A mighty useful contrivance," commented Mr. Giddings. "I should think that would also prevent lots of accidents in bad winds."

"It will--if it turns out as we expect," Paul remarked.

"Give me the full details of this," was the request. "Remember, I am not much of an airplane man."

"Well," said Paul, "you know, sir, that it is far more difficult to drive an airplane than to guide an automobile, not merely because you have two steering-gears or rudders to take care of, one for sidewise and the other for up-and-down travel, but also because there are movable planes in the wings of the machine, which have to be worked to tip or 'bank' it when making a turn or to keep it on an even keel when a gust of wind strikes it. The 'rudder' is the vertical plane at the tail of the machine, and is used for steering sideways, while the 'elevators' are the two horizontal movable planes just below the rudder, which are used for steering up and down. Similar planes to the latter, one situated in the back edge of each upper wing, are called 'ailerons,' and one or the other is raised or depressed according to whether the aviator wishes to bank to the right or left.

"The driver of an automobile has nothing to do but watch his steering-wheel, and be ready to touch a pedal when he wishes to slow up or go faster or stop. If he makes a curve he does not have to bank his machine owing to his comparatively slow speed; but the aviator, traveling much faster through the air, must do this, bringing his airplane to a steep angle if he makes a very short turn. If he does not calculate just right, he is likely to turn upside down and meet this death in a nasty fall.

"While the careful automobilist can always see the road in front of him and avoid rough spots or obstacles before he reaches them, the aviator cannot do this. It is true that he can see another airplane if it gets in his way, or a church steeple when he is flying low; but his greatest dangers are in the clear air itself, where they cannot be detected. He may suddenly drop into a 'hole,' which is really a downward current of air, or he may get a terrific b.u.mp when he strikes a rising current. A freakish whim of the winds may unexpectedly take away the air support from under one of the wings, and he will lurch and dip sharply to one side."

"And I suppose sometimes lose all control?" said Mr. Giddings.

"Yes, sir; that has very often happened," put in John. "A flyer friend of mine took a nasty tumble that way near Cleveland last year, breaking three ribs. It's a wonder he wasn't killed."

"The pilot is blind to these pitfalls," went on Paul. "He must control his machine largely by intuition and the sense of feeling, although the veteran airman, John says, can tell a good deal about what to expect from the nature of the earth or clouds below him."

"That's true," averred John. "The closer you are to the earth the more you will feel the 'b.u.mps,' as we call them. They are a whole lot like the waves of the ocean, only invisible, and there will be one straight over every protuberance or depression of size in the surface of the earth. Mountains, hills, houses, lakes, valleys, rivers, forests, all cause b.u.mps or holes in the air up above them. At one thousand feet they are pretty bad. At ten thousand feet they are scarcely noticeable. That's why most pilots prefer to fly high whenever they can."

"What causes the air to act in this way over such configurations?"

propounded the publisher.

John looked helpless, and smiled. "You've got me there," he admitted.

"I haven't had the opportunity to study aerostatics the same as Paul here. He can probably tell us."

"I'm not through my course yet," reminded his brother, "but I think I can answer that. The air surrounding the earth is a great belt forty or more miles through and is of an even thickness. As our globe sweeps through it, the lower stratum of air naturally sinks down into the valleys and like depressions. This action pulls down the upper stretches of air, thus creating what are termed 'air-pockets' or 'air-holes.' Very dangerous they are, too."

"That is plain enough," declared Bob. "Now, dad, let Paul go on explaining this 'automatic pilot.'"

"If the aviator is enshrouded in fog or tries to sail through a heavy bank of clouds, he is quite likely to lose all sense of direction,"

continued Paul. "He will not know whether he is banking or traveling on an even keel. Sometimes pilots have come out of a low cloud to find themselves dangerously close to the earth and in an awkward position, perhaps in a steep bank, a side-slip, or even in the terrifying nose-dive, and they have not had time to right themselves before crashing to earth. So you see that before flying can become reasonably safe, some way must be found of keeping the machine automatically on a level keel.

"To operate this stabilizer of ours all the pilot will have to do is to guide the rudder with his feet. The automatic pilot works the elevator and the ailerons. It takes care of 'b.u.mps' and 'holes' and sees that the machine banks at just the right angle on the turns. This makes the operation of an airplane containing the stabilizer even more simple than running a motor-car, because you do not have to worry about going into different speed gears when climbing or descending. You will notice on this drawing that strong piano-wires connect the instruments with all the necessary controlling planes of the machine."

"Instruments?" interrogated Mr. Giddings. "I thought there was but one."

"No; there are two stabilizers, as you will see,--here, and here," was Paul's response, pointing his finger to the parts. "But, as each one is exactly like the other in its construction, only the one has been drawn in detail. The other stabilizer runs lengthwise of the c.o.c.kpit and takes care of the elevator. Both of these are operated by compressed air, which proceeds from a little tank, right here. The tank is kept supplied by two tubes which lead into it, and each of which joins a small pump operated by a fan which is right here on each side of the fuselage where the onrush of wind will keep it humming as the airplane travels.

"Each equalizer has a bore in it half-filled with mercury, working a good deal like a carpenter's level. If the airplane tilts to one side or the other, the mercury will try to keep its level and will immediately flow to the high side of the bore. At each end of this mercury tube there are electrical contact points. As one becomes submerged in the mercury by a tilting of the plane, a connection is made whereby two electro-magnets are energized on that side. One of these magnets closes an exhaust-valve, and the other opens an inlet-valve, in the compressed air tank. At once air is forced into this double cylinder, which you see at the bottom of the stabilizer, filling the half which is to operate its own set of rudders; and a piston begins to work inside. The piston is connected to a toothed rack, as you will note, causing this to turn a sector engaging it. The control wires connect with this sector."

"Very clever arrangement; but I don't quite see how, in banking, the ailerons can be brought back automatically to a neutral position as soon as the turn has been completed," ventured Mr. Giddings.

"John and I have provided for that, while Bob is responsible for the electrical features I have just mentioned," said Paul. "You will notice that at the top of the mercury channel there is a dividing wall.

A tube runs from the left side of this wall to the right wing of the airplane, also from the right side of the wall to the left wing. At the end of each tube there is what we call a 'venturi tube.' This is a kind of suction device operated by the wind. The wind which blows through the left venturi tube sucks the air out of the right-hand side of the mercury tube, and the right venturi tube sucks the air out of the left-hand side of the mercury tube. The stronger the wind, the greater the suction. Now, when making a turn to the right the left wing must travel faster than the right wing, and so there must be more suction in the left venturi. This produces a greater suction in the right-hand side of the mercury tube, which draws the mercury up on that side and down on the other, until the proper electrical contact is broken and the ailerons are returned to neutral position."

"Can the mechanism be thrown out of gear when desired? I should think such a feature might be desirable," remarked Mr. Giddings.

"Indeed it is desirable, sir," declared Paul. "No red-blooded pilot wishes to sit still and let his machine run itself all the time, no more than an automobilist. That would spoil all the sport. By merely disengaging the automatic pilot's wires here at the sector--the work of a couple of seconds--the airplane is ready for hand control."

"How much does it weigh?" was the gentleman's next query.

"A trifle less than a hundred pounds."

"That oughtn't to handicap an airplane any."