Chapter 8

THE SKY-BIRD II

"Well, Mr. Giddings, what do you think of Sky-Bird II?" asked John Ross, one memorable day.

There was a smile of deep satisfaction on John's own bronzed features as he put the question, a smile which was duplicated on the faces of his three co-workers--Paul, Bob, and Tom Meeks. It was the latter part of March, Easter vacation week for Paul and Bob, and the two chums had been working every one of the last three days helping John and Tom put the finishing touches on the big new airplane. And now this Friday morning it rested gracefully upon its own rubber-tired wheels, its great stretch of wings spread out as airily as those of a monster bird, its huge two-bladed propeller glistening like burnished silver, and its body running backward in a splendid symmetrical taper, to end at the well-proportioned tail. Sky-Bird II was done at last.

Mr. Giddings was so lost in admiration at the beautiful lines of the craft that he did not reply immediately to John's question. He had not seen it for almost two weeks, and in that time, under the onslaughts of the four boys, it had changed appearance in a striking way, numerous finished parts having been connected and paint and varnish having been applied.

"All I have to say, young men, is that if she performs anywhere near as well as she looks, I shall be thoroughly satisfied with the money I have invested thus far," declared the great newspaper man with an enthusiasm which he did not try to conceal. His eyes were shining, as he walked around the craft looking at it from all sides. He rubbed his fingers lingeringly over the smooth fuselage, and smiled quietly as he regarded the name "Sky-Bird II" lettered in large blue characters on her sides and underneath each long bird-like wing. Then he mounted a folding step and went through a neat door into the glass-surrounded cabin. This was deep enough to stand up in, and provided comfortable upholstered cane seats for the pilot and four passengers or assistants. All of these seats except the pilot's and observer's were convertible, forming supports for the swinging of as many hammocks, and in a small space at the rear was a neat little gasoline-burner, and over it a built-in cupboard containing some simple aluminum cooking ware.

"Well, I declare!" said Mr. Giddings in amazement at the convenience of things, "it looks as if you fellows hadn't left out a single item needed in a long and enjoyable cruise."

"There's nothing like being fixed up for all emergencies, sir," laughed John. "As you notice, we have everything for night-flying as well as day-flying. With such a machine as this there is no reason why a crew of four or five could not run nights as well as days, two operating while the others sleep in the hammocks. Cold foods can be cooked or warmed up on the gas-stove when needed, and the enclosed cabin protects all hands from the worst effects of bad storms."

"Wouldn't this glass break in a hailstorm?" asked Mr. Giddings. "It seems to be pretty thin."

"It is thin," said Paul; "that is to give it lightness. It might check some in a hailstorm, but it could not break out, as it is made of two layers of glass between which is cemented a thin sheet of celluloid."

"I think you had two Liberty motors here in the hangar when I was here last. I neglected to ask you the power of these, and what you need two for," observed Mr. Giddings. "I thought you said in the beginning that you considered one 400 horse-power engine of sufficient strength to carry this plane at a fast clip."

"It is this way, sir," responded John. "The regular big biplane of the bomber type carries two propellers with an engine for each propeller. If one motor fails them when flying, about all the other is good for is to make a landing with. By reason of the great lightness of our airplane one good 400 horse-power motor is all we need for pulling purposes. But suppose this should fail, as any motor might do? We could not continue, any more than the other fellow, and would have to volplane to the ground. Again, suppose we wished to fly continuously more than twelve hours? We could not do so, as such a steady run would heat the best motor and ruin it. These two Liberty motors, which we have, overcome all these troubles. Both are so arranged that a simple switch connects and disconnects either one with the propeller, and both can be put at work at the one time if needed in a bad storm. If one stalls, the other can immediately be thrown in and a forced landing obviated. Moreover, if we could get fuel when needed, with this arrangement I am safe in saying we could fly steadily day and night, resting one motor and working its mate, for a week or more."

"What is this?" As he spoke the publisher touched a peculiar-looking helmet hanging from a hook near the pilot's seat.

Bob laughed. "Why, don't you recognize the products of your talented son, dad?" he cried, as he took the object down and clapped it over his father's iron-gray head. "That's my new wireless telephone headpiece, and right underneath it here is the mahogany cabinet containing the sending and receiving instruments. You see, these two wires run from the plug up to the receivers, there being one receiver in each side of the helmet, right over your ear, pressing against the ear tightly by means of a sponge-rubber gasket."

"A man looks like a padded football player with this thing on," said Mr. Giddings with a smile. "Why is a helmet required at all?"

"We wouldn't require it so much with these motors, as they are equipped with a new kind of muffler which shuts out about four-fifths of the noise other airplanes get," explained Bob. "But for all that there are always noises in airplanes; for instance, they say the whirr of the propeller when it is revolving about 1450 revolutions per minute, or at the full speed of this one, makes quite a roar; so you see the need of the helmet to shut out all undesirable sounds possible. In ordinary planes the crew cannot talk to each other except by using phones or putting their lips to each other's ears and yelling at the top of their voices, according to what John and Tom tell me. But we don't expect to have that trouble in this enclosed cabin and with this new muffler working, do we, fellows?"

"I'm sure we won't," said John.

"Not if I'm any judge," grinned Tom.

"Can you talk with a ground station when you're flying, say a couple of miles high?" asked Mr. Giddings, examining a transmitter attached to a yoked wire support which his son slipped over his shoulders.

"Farther than that. With this particular vacuum tube, which will amplify sounds three or four times over any other I have tried, we expect to talk with ground stations or other aircraft at a distance of three thousand miles. Notice what a simple thing it is, dad," and Bob indicated a little glass bulb which looked a lot like an ordinary incandescent light, but which had a peculiar arrangement of wires and substances inside.

"Is the transmitter or receiver made just like the ordinary kind?" asked Mr. Giddings.

"Practically the same, dad. The wireless transmitter, like that of the wire telephone, contains a sensitive diaphragm which your voice strikes and sets to vibrating. These vibrations compress and release a capsule of carbon granules which agitate and set in motion an electrical current in two magnets connecting with them. The magnets convey the sound-waves in the form of electrical waves, along wires out to the tip of each wing, where the wires hang down a little way. When a message comes in it is caught by a webbing of antennae wires in our wings."

"Then I suppose these sound-waves, in other words the words one speaks, run out of the end of these wires into the atmosphere?"

"Exactly, sir," agreed Bob. "That is, the electrical waves are projected into the air and disturb this air in a way to make it pulsate in the same manner as your voice makes the diaphragm pulsate. These waves are then carried through the atmosphere in every direction, and sooner or later reach the antennae wires of some station equipped to receive them. Down these wires they dash, are registered and magnified in the wonderfully delicate vacuum tube, and from it are carried up into the receivers at your ears."

"I should think they would be electrical impulses when they reach the receivers," argued Mr. Giddings. "How can a person hear _words_ from electrical discharges?"

Bob smiled. "Easy enough, dad," he went on. "You see, this vacuum tube does the business. The electrical current agitates this in unison, and the impulses are immediately converted into words again,--and there you are!"

"I acknowledge my understanding now," admitted Mr. Giddings, with a hearty laugh; "but there's just one thing yet I want light on: Where do you get your electrical current? It takes a dynamo to make electricity, else storage batteries. I don't see either."

"Come outside here a moment, dad."

Bob smiled as he led the little party out of the Sky-Bird's cabin. When they once more stood on the hangar floor, he pointed to a peculiar T-shaped object just beneath the nose of the airplane. This had escaped the gentleman's observation until now.

"It looks like a small propeller with a torpedo sticking out from the middle of it," laughed Mr. Giddings.

"So it does, dad," agreed Bob. "Well, that's our wireless dynamo. You will notice that the propeller faces ahead, like the big fellow here. When the airplane is flying, the rush of wind spins the fan at a terrific rate, its axle operates a little dynamo in this torpedo-like case and manufactures electric current. The current then passes into this small apparatus here with a bulb attached, which regulates the voltage and sends it up to the instruments in a uniform flow, no matter at what speed the airplane may be going."

"That's a cheap way of getting current," declared the newspaper man, "and a mighty good one, too." He now changed the subject by asking: "How much do you suppose this machine weighs?"

"I have been in smaller ones which weighed, unloaded, as much as three thousand pounds," admitted John Ross, with a peculiar smile. "Put your hands under the Sky-Bird's nose here and see if you can lift her, Mr. Giddings."

"Don't joke that way, John," expostulated Mr. Giddings. "Why, her engines are right above this portion of her, and I couldn't lift one of them alone."

"Just try it anyhow, dad," persisted Bob, who also wore that queer smile.

More to accommodate them than because he expected to accomplish anything, the publisher half-heartedly braced himself in a crouching position and pushed upward on the airplane's front. To his amazement the whole forward part of the machine rose upward a foot in the air, as if it were made of paper.

"My word!" exclaimed Mr. Giddings, letting the craft back upon its wheels. "Who would have thought such a thing? I had faith in this principle of the hollow wings and helium-gas, boys, but I never thought it could reduce the normal weight of the plane to such a vast extent, It is truly a wonderful idea."

"You might not believe it, but the Sky-Bird weighs less than two hundred pounds as she stands," said Paul. "Just before you came today, Mr. Giddings, Bob and I, one at each end, easily lifted her clear off the floor."

"It's what we aimed for, and we've got it," added John with satisfaction, while Tom Meeks nodded his head and ejaculated, "I'd say so! I'd say so!" his whole broad face abeam. "This feather lightness means great lift, great speed, and great cruising range."

"I should think so surely," was the decided response of the newspaper man. "I notice you have installed that 'automatic pilot' too. And what's that up here in front on top of the cabin? A searchlight, as I live!"

"Yes, dad," said Bob; "we thought that would be a good thing in case we do any night traveling on this tour of the world. It ought to have good power, being operated with current from the storage batteries of the wireless wind-dynamo."

After a little more inspection and further questions, Mr. Giddings took his departure, promising to be on hand at the hangar the following morning for the test flight.