Page:Popular Science Monthly Volume 92.djvu/609

 Popular Science Montliljj ,>9I?

Caging the Airplane Propeller in Kerosene Can Be "Cracked" to Pro- Case He Gets Too Wild duce Gasoline

IF crude oil yields different liquids when '_ heated to different temperatures, what would happen if the separate distillates were treated again in the same way ? The experiment has been carried out with astonishing results by different chemists — Doctor Burton, Doctor Hall, and Doctor

R i t t m a n.

��our de-

this ex- cage

��THE propeller of a modern flying ma- chine rotates at the rate of about fifteen hundred revolutions a minute. It is mounted directly on the shaft of the powerful motor by which it is driven. When the engine is started, the roar is deafening— so much so that in test- ing an air- planepower plant before is mounted in a machine, the men who con- duct the test must wear ear- protectors, similar to those used by the crews of big coast fense guns

But all does not plain the in which the propeller is re- volved during the test. What is the reason for that?

The cage is a safety device. It protects the men who are conducting the operation. Fly- wheels of steam engines sometimes burst when they spin too fast. Why? Be- cause of the centrifugal force. The greater the speed, the greater is the centrifu- gal force. A propeller which revolves at the rate of fourteen hundred revolu- tions a minute might fly off, even though the utmost precautions are taken to fasten it securely to the shaft. And if it ever flew off — ? A bursting flywheel has many a time wrecked an engine-house as effectively as a high-explosive shell, and a wild airplane propeller would be most unhealthy for anything it encountered upon its wanderings. The eye extends along the edge of the testing platform.

�� ���© Underwood and Underwood

Airplane propellers occasionally have their own ideas about flj^ing. This cage discourages them

��Kerosene, for example, can actually be made to give up gasoline. The process is called "crack- ing." Imagine before you two piles of stones of different sizes. The small stone-pile rep- re sents gas- oline, the large one kerosene. A man with a hammer can obviously crack the larger stones into pieces equal in size to those of the first pile. The chemical equiv- alent of this seems to take place in crack-

��ing kerosene. Since kerosene is so difficult to dispose of, why not crack it and get enough gasoline for the four million auto- mobiles which will be in use this year. Cracking processes actually furnished seven and one-half per cent, of the total gasoline production last year.

In 1918, at least one-fifth of the three billion gallons to be produced will be made by cracking. Their value would pay for ten superdreadnoughts.

Had it not been for the invention and utilization of cracking processes, gasoline would cost more than it does. During the year 1917, approximately 600,000,000 gallons of cracked gasoline were produced.

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