CHAPTER XI
A NIGHT TRIP
Taking a lesson from what had happened, Tom was very much more carefulin the following experiments on his new, silent motor. He made somechanges in his shop, and took Jackson in to help on the new machine,thus insuring perfect secrecy as the apparatus developed.
Tom also changed the safe in which he kept his plans, for the one hehad used previous to the episode in which Bower and the stranger whotook the mud bath figured, was one the combination of which couldeasily be ascertained by an expert. The new safe was more complicated,and Tom felt that his plans, specifications, and formulae which he hadworked out were in less danger.
"I can just about figure out what happened," said Ned Newton to Tom,when told of the circumstances. "These Universal people were provokedbecause you wouldn't give them the benefit of your experience on theirflying machines, and so they sent a spy to get work with you. They,perhaps, hoped to secure some of your ideas for their own, or they mayhave had a deeper motive."
"What deeper motive could they have, Ned?"
"They might have hoped to disable you, or some of your machines, so thatyou couldn't compete with them. They're unscrupulous, I hear, and willdo anything to succeed and make money. So be on your guard againstthem."
"I will," Tom promised. "But I don't believe there's any more dangernow. Anyhow, I have to take some chances."
"Yes, but be as careful as you can. How is the silent motor coming on?"
"Pretty good. I've had a lot of failures, and the thing isn't so easyas I at first imagined it would be. Noise is a funny thing, and I'mjust beginning to understand some of the laws of acoustics we learnedat high school. But I think I'm on the right track with the muffler andthe cutting down of the noise of the explosions in the cylinders. I'mworking both ends, you see--making a motor that doesn't cause as muchracket as those now in use, and also providing means to take care ofthe noise that is made. It isn't possible to make a completely silentmotor of an explosive gas type. The only thing that can be done is tokill the noise after it is made."
"What about the propeller blades?"
"Oh, they aren't giving me any trouble. The noise they make can't beheard a hundred feet in the air, but I am also working on improvementsto the blades. Take it altogether, I'll have an almost silent aeroplaneif my plans come out all right."
"Have you said anything to the government yet?"
"No; I want to have it pretty well perfected before I do. Besides, Idon't want any publicity about it until I'm ready. If these Universalpeople are after me I'll fool 'em."
"That's right, Tom! Well, I must go. Another week of this Liberty Bondcampaign!"
"I suppose you'll be glad when it's over."
"Well, I don't know," said Ned slowly. "It's part of my smallcontribution to Uncle Sam. I'm not like you--I can't invent things."
"But you have an awful smooth line of talk, Ned!" laughed his chum. "Ibelieve you could sell chloride of sodium to some of the fishes in theGreat Salt Lake--that is if it has fishes."
"I don't know that it has, Tom. And, anyhow, I'm not posing as a saltsalesman," and Ned grinned. "But I must really go. Our bank hasn'treached its quota in the sale of Liberty Bonds yet, and it's up to meto see that it doesn't fall down."
"Go to it, Ned! And I'll get busy on my silent motor."
"Getting busy" was Tom Swift's favorite occupation, and when he wasworking on a new idea, as was the case now, he was seldom idle, nightor day.
"I have hardly seen you for two weeks," Mary Nestor wrote him one day."Aren't you ever coming to see me any more, or take me for a ride?"
"Yes," Tom wrote back. "I'll be over soon. And perhaps on the next ridewe take I won't have to shout at you through a speaking tube becausethe motor makes so much noise."
From this it may be gathered that Tom was on the verge of success.While not altogether satisfied with his progress, the young inventorfelt that he was on the right track. There were certain changes thatneeded to be made in the apparatus he was building--certain refinementsthat must be added, and when this should be done Tom was pretty certainthat he would have what would prove to be a very quiet aeroplane, ifnot an absolutely silent one.
The young inventor was engaged one day with some of the last details ofthe experiment. The new motor, with the silencer and the changedcylinders, had been attached to one of Tom's speedy aeroplanes, and hewas making some intricate calculations in relation to a new cylinderblock, to be used when he started to make a completely new machine ofthe improved type.
Tom had set down on paper some computations regarding the cross-sectionof one of the cylinders, and was working out the amount of stress towhich he could subject a shoulder strut, when a shadow was cast acrossthe drawing board he had propped up in his lap.
In an instant Tom pulled a blank sheet over his mass of figures andlooked up, a sudden fear coming over him that another spy was at hand.But a hearty voice reassured him.
"Bless my rice pudding!" cried Mr. Damon, "you shut yourself up here,Tom, like a hermit in the mountains. Why don't you come out and enjoylife?"
"Hello! Glad to see you!" cried Tom, joyfully. "You're just in time!"
"Time for what--dinner?" asked the eccentric man, with a chuckle. "Ifso, my reference to rice pudding was very proper."
"Why, yes, I imagine there must be a dinner in prospect somewhere, Mr.Damon," said Tom with a smile. "We'll have to see Mrs. Baggert aboutthat. But what I meant was that you're just in time to have a ride withme, if you want to go."
"Go where?"
"Oh, up in cloudland. I have just finished my first sample of a silentmotor, and I'm going to try it this evening. Would you like to comealong?"
"I would!" exclaimed Mr. Damon. "Bless my onion soup, Tom, but I would!But why fly at night? Isn't it safer by daylight?"
"Oh, that doesn't make much difference. It's safe enough at any time.The reason I'm going to make my first flight after dark is that I don'twant any spies about."
"Oh, I see! Are they camping on your trail?"
"Not exactly. But I can't tell where they may be. If I should start outin daylight and be forced to make a landing-- Well, you know what acrowd always collects to see a stranded airship."
"That's right, Tom."
"That decided me to start off after dark. Then if we have to come downbecause of some sort of engine trouble or because my new attachmentdoesn't work right, we sha'n't have any prying eyes."
"I see! Well, Tom, I'll go with you. Fortunately I didn't tell my wifewhere I was going when I started out this afternoon, so she won't worryuntil after it's over, and then it won't hurt her. I'm ready any timeyou are."
"Good! Stay to dinner and I'll show you what I've made. Then we'll takea flight after dark."
This suited the eccentric man, and a little later, after he had eatenone of Mrs. Baggert's best meals, including rice pudding, of which hewas very fond, Mr. Damon accompanied Tom to one of the big hangarswhere the new aeroplane had been set up.
"So that's the Air Scout, is it, Tom?" asked Mr. Damon, as he viewedthe machine.
"Yes, that's the girl. 'Air Scout' is as good a name as any, until Isee what she'll do."
"It doesn't look different from one of your regular craft of the skies,Tom."
"No, she isn't. The main difference is here," and Tom showed his friendwhere a peculiar apparatus had been attached to the motor. This was thesilencer--the whole secret of the invention, so to speak.
To Mr. Damon it seemed to consist of an amazing collection of pipes,valves, baffle-plates, chambers, cylinders and reducers, which took thehot exhaust gases as they came from the motor and "ate them up," as heexpressed it.
"The cylinders, too, and the spark plugs are differently arranged inthe motor itself, if you could see them," said Tom to his friend. "Butthe main work of cutting down the noise is done right here," and he puthis hand on the steel case attached to the motor, the case containingthe apparatus already briefly described.
"Well, I'm ready when you
are, Tom," said Mr. Damon.
"We'll go as soon as it's dark," was the reply. "But first I'll giveyou a demonstration. Start the motor, Jackson!" Tom called to his chiefhelper.
Mr. Damon had ridden in aeroplanes before, and had stood near when Tomstarted them; so he was prepared for a great rush of air as thepropellers whirled about, and for deafening explosions from the engine.
The big blades, of new construction, were turned until the gas in thecylinders was sufficiently compressed. Then Jackson stepped back out ofdanger while Tom threw over the switch.
"Contact!" cried the young inventor.
Jackson gave the blades a quarter pull, and, a moment later, as heleaped back out of the way, they began to revolve with the swiftness oflight. There was the familiar rush of air as the wooden wings cutthrough the atmosphere, but there was scarcely any noise. Mr. Damoncould hardly believe his ears.
"I'm not running her at full speed," said Tom. "If I did she'd tearloose from the holding blocks. But you can see what little racket shemakes."
"Bless my fountain pen!" cried Mr. Damon. "You are right, Tom Swift!Why, I can hear you talk almost as easily as if no engine were going.And I don't have to shout my head off, either."
This was perfectly true. Tom could converse with Mr. Damon in almostordinary tones. The exhaust from the motor was nearly completelymuffled.
"Out in the air it will seem even more quiet," said Tom. "I'll soongive you a chance to verify that statement."
He ran the engine a little longer, the aeroplane quivering with thevibrations, but remaining almost silent.
"I'm anxious to see what she'll do when in motion," said Tom, as heshut off the gas and spark.
Soon after supper, when the shades of evening were falling, he and Mr.Damon took their places in the first of the Air Scouts, to give it thepreliminary test in actual flying.
Would Tom's hopes be justified or would he be disappointed?
Tom Swift and His Air Scout; Or, Uncle Sam's Mastery of the Sky Page 11
