Tom Swift and His Air Scout Part 9

"I'm pretty sure Gale heard me mention what I was going to try to invent, and he may get ahead of me, and put a silent motor on the market first. Not that I'm afraid of being done out of any profits, but I simply don't want to be beaten."

The details of Tom's invention cannot be gone into, but, roughly, it was based on the principle of not only a m.u.f.fler but also of producing less noise when the charges of gasoline exploded in the cylinders. It is, of course, the explosion of gasoline mixed with air that causes an internal combustion engine to operate. And it is the expulsion of the burned gases that causes the exhaust and makes the noise that is heard.

Tom was working along the well-known line of the rate of travel of sound, which progresses at the rate of about 1090 feet a second when air is at the freezing point. And, roughly, with every degree increase in the atmosphere's temperature the velocity of sound increases by one foot. Thus at a temperature of 100 degrees Fahrenheit, or 68 degrees above freezing, there would be added to the 1090 feet the 68 feet, making sound travel at 100 degrees Fahrenheit about 1158 feet a second.

Tom had set up in his shop a powerful, but not very speedy, old aeroplane engine, and had attached to it the device he hoped would help him toward solving his problem of cutting down the noise. He had had some success with it, and, after days and nights of labor, he invited his father and Ned, as well as Mr. Damon, over to see what he hoped would be a final experiment.

His visitors had a.s.sembled in the shop, and Eradicate was setting out some refreshments which Tom had provided, the colored man being in his element now.

"What's all this figuring, Tom?" asked Mr. Damon, as he saw a series of calculations on some sheets of paper lying on Tom's desk.

"That's where I worked out how much faster sound traveled in hydrogen gas than in the ordinary atmosphere," was the answer. "It goes about four times as fast, or nearly four thousand two hundred feet a second.

You remember the rule, I suppose. 'The speed of sonorous vibrations through gases varies inversely as the squares of the weights of equal volumes of the gases,' or, in other words--"

"Give it to us chiefly in 'other words,' if you please, Tom!" pleaded Ned, with a laugh. "Let that go and do some tricks. Start the engine and let's see if we can hear it."

"Oh, you can hear it all right," said Tom, as he approached the motor, which was mounted on a testing block. "The thing isn't perfected yet, but I hope to have it soon. Rad! Where is that black rascal? Oh, there you are! Come here, Rad!"

"Yaas sah, Ma.s.sa Tom! Is I gwine to help yo' all in dish yeah job?"

"Yes. Just take hold of this lever, and when I say so pull it as hard as you can."

"Dat's whut I will, Ma.s.sa Tom. Golly! ef dat no 'count giant was heah now he'd see he ain't de only one whut's got muscle. I'll pull good an' hard, Ma.s.sa Tom."

"Yes, that's what I want you to. Now I guess we're all ready. Can you see, Dad--and Ned and Mr. Damon?"

"Yes," they answered. They stood near the side wall of the shop, while Tom and Eradicate were at the testing block, on which the motor, with the noise-eliminating devices attached, had been temporarily mounted.

"All ready," called the young inventor, as he turned on the gas and threw over the electrical switch. "All ready! Pull the starting lever, Rad, and when it's been running a little I'll throw on the silencer and you can see the difference."

The motor began to hum, and there was a deafening roar, just as there always is when the engine of an aeroplane starts. It was as though half a dozen automobile engines were being run with the m.u.f.flers cut out.

"Now I'll show you the difference!" yelled Tom, though such was the noise that not a word could be heard. "This shows you what my silencer will do."

Tom pulled another lever. There was at once a cessation of the deafening racket, though it was not altogether ended. Then, after a moment or two, there suddenly came a roar as though a blast had been let off in the shop.

Tom and Eradicate were tossed backward, head over heels, as though by the giant hands of Koku himself, and Mr. Damon, Ned, and Tom's father saw the motor fly from the testing block and shoot through the roof of the building with a rending, cras.h.i.+ng, and splintering sound that could be heard for a mile.

CHAPTER IX

AFTER A SPY

Curious as it may seem, Eradicate, the oldest and certainly not the most energetic of the party a.s.sembled in the experiment room, was the first to recover himself and arise. Tottering to his feet he gave one look at the testing block, whence the motor had torn itself. Then he looked at the prostrate figures around him, none of them hurt, but all stunned and very much startled. Then the gaze of Eradicate traveled to the hole in the roof. It was a gaping, ragged hole, for the motor was heavy and the roof of flimsy material. And then the colored man exclaimed:

"Good land ob ma.s.sy! Did I do dat?"

His tone was one of such startled contrition, and so tragic, that Tom Swift, rueful as he felt over the failure of his experiment and the danger they had all been in, could not help laughing.

"I take it, hearing that from you, Tom, that we're all right," said Ned Newton, as he recovered himself and brushed some dirt off his coat. Ned was a natty dresser.

"Yes, we seem to be all right," replied Tom slowly. "I can't say what damage the flying motor has done outside, but--"

"Bless my insurance policy! but what happened?" asked Mr. Damon. "I saw Eradicate pull on that lever as you told him to, Tom, and then things all went topsy-turvy! Did he pull the wrong handle?"

"No, it wasn't Rad's fault at all," said Tom. "The trouble was, as I guess I'll find when I investigate, that I put too much power into the motor, and the m.u.f.fler didn't give any chance for the acc.u.mulated exhaust gases to expand and escape. I didn't allow for that, and they simply backed up, compressed and exploded. I guess that's the whole explanation."

"I'm inclined to agree with you, Son," said Mr. Swift dryly. "Don't try to get rid of all the noise at once. Eliminate it by degrees and it will be safer."

"I guess so," agreed Tom.

By this time a score of workmen from the other shops had congregated around the one though the roof of which the motor had been blown. Tom opened the door to a.s.sure Jackson and the others that no one was hurt, and then the young inventor saw the exploded motor had buried in the dirt a short distance away from the experiment building.

"Lucky none of us were standing over it when it went up," said Tom, as he made an inspection of the broken machine. "We'd have gone through the roof with it."

"She certainly went sailing!" commented Ned. "Must have been a lot of power there, Tom."

And this was evidenced by the bent and twisted rods that had held the motor to the testing block, and by the cylinders, some of which were torn apart as though made of paper instead of heavy steel. But for the fact that all the force of the explosion was directly upward, instead of at the sides, none might have been left alive in the shop. All had escaped most fortunately, and they realized this.

"Well," queried Ned, as Tom gave orders to have the damaged machine removed and the roof repaired, "does this end the wonderful silent motor, Tom?"

"End it! What do you mean--"

"I mean are you going to experiment any further?"

"Why, of course! Just because I've had one failure doesn't mean that I'm going to give up. Especially when I know what the matter was--not leaving any vent for the escaping gases. Why this isn't anything. When I was perfecting my giant cannon I was nearly blown up more than once, and you remember how we got stuck in the submarine."

"I should say I did!" exclaimed Ned with a shudder. "I don't want any more of that. But as between being blown through a roof and held at the bottom of the sea, I don't know that there's much choice."

"Well, perhaps not," agreed Tom. "But as for ending my experiments, I wouldn't dream of such a thing! Why, I've only just begun! I'll have a silent motor yet!"

"And a non-explosive one, I hope," added Mr. Damon dryly. "Bless my shoe b.u.t.tons, Tom, but if my wife knew what danger I'd been in she'd never let me come over to see you any more."

"Well, the next time I invite you to a test I'll be more careful,"

promised the young inventor.

"There isn't going to be any next time as far as I'm concerned!"

laughed Ned. "I think it's safer to sell Liberty Bonds."

And, though they joked about it, they all realized the narrow escape they had had. As for Eradicate, once he knew he had not been the one who caused the damage, he felt rather proud of the part he had taken in the mishap, and for many days he boasted about it to Koku.

True to his determination, Tom Swift did not give up his experimental work on the silent motor. The machine that had been blown through the roof was useless now, and it was sent to the sc.r.a.p heap, after as much of it as possible had been salvaged. Then Tom got another piece of apparatus out of his store room and began all over again.

He worked along the same lines as at first--providing a chamber for the escaping gases of the exhaust to expend their noise and energy in, at the same time laboring to cut down the concussion of the explosions in the cylinder without reducing their force any. And that it was no easy problem to do either of these, Tom had to admit as he progressed. All previous types of m.u.f.flers or silencers had to be discarded and a new one evolved.

"Jackson, I need some one to help me," said Tom to his chief mechanician one day. "Haven't you a good man who is used to experimental work that you can let me take from the works?"