Page:Popular Science Monthly Volume 91.djvu/789

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Popular Science Monthly


��be taken to keep the red lead from working up into the paint above it, if the latter is a light color; hence the coat next to the red lead should be rather stout. Or you may make the second coat of paint with plaster of Paris and boiled linseed oil to the con- sistency of buttermilk, added to *a batch of white lead paint made of the same consistency as the plaster paint; mix well together, and thin out to a brushing con- sistency with turpentine. This coat should be made as heavy as you can well brush it out. The next or finishing coat should be ordinary oil paint, drying with a gloss, the same as used on outside woodwork. The reason for applying the plaster paint is that it prevents the subsequent coats of paint from wrinkling or running where much paint is to be applied. It must be made to dry quickly, by means of dryers, so that you will not make the mistake of applying the succeeding coat prematurely, in which event there would be cracking of the paint. Observe particularly that no plaster is to be added to the last coat.

It should be said, in conclusion, that no oil paint is really waterproof, because linseed oil is not proof against moisture. This can readily be demonstrated by sub- jecting a dry coating of linseed oil paint to the action of water. Note how the coat whitens and swells, showing that the oil has taken up water. — A. Ashmun Kelly.

��Two- Speed and Reverse Countershaft for a Small Lathe

THE countershaft illustrated was de- vised and built for a small screw cutting lathe which was used for a great variety of work, from turning hard steel to high-speed wood turning, thus requiring

���Countershaft cone

��Pulleys of different diameters with three ship- per levers to provide many different speeds

a wide range of speed. Two forward speeds and one reverse were provided, and as the lathe was furnished with back gears, the arrangement gave twelve speeds for normal

��use and six for the reverse, the speed range running from 30 to 1000 r. p. m.

The three shipper levers were arranged conveniently near the head of the lathe, one behind the other, the low-speed lever


���Three levers to op- erate the belts for two- speed forward and one backward

��in front, next the high speed and then the reverse, which happened to be an iron lever. Had it not been of iron it would have been provided with a different shaped handle so that the operator would not be likely to throw it in by mistake. Tight and loose pulleys without friction clutches were used, those on the countershaft being of the same size, of iron, while the line shaft pulleys were of different diameters, and were of the straight face wooden type. — H. H. Parker.

��The Damage Caused by Running Tires Deflated

RUNNING a tire deflated for even a . short distance is harmful to the tire and extravagant. When traveling at a very high rate of speed it may of course require some time to bring the car to a stop. But a certain amount of damage is done every second of deflation. A soft or flat tire on a front wheel can always be noticed by the difficulty in steering the car in a straight course — the steering wheel naturally veers toward the side of the flat or soft tire. If there is a deflated tire on the rear wheel, pounding and bumping will be noticeable. A rear tire ridden flat very far will result in damage to the differential.

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