Page:Popular Science Monthly Volume 91.djvu/471

 �FOR PRACTICAL WORKERS

��Dust Proofing the Priming Cup on Automobile Engines

AS motorists well know, the presence of l small particles of grit and dust in the cylinders of an automobile motor causes much trouble. Unfortunately most prim- ing cups are the source of this trouble. They collect dust which is washed into the cylinder when priming the motor. Here- with is shown a cup designed to prevent such trouble. It consists of a brass body A threaded on the end so that it can be screwed into the cylin- der. Just below the small tapped hole in the body is a conical seat for the needle- valve C, which is made of steel. The upper end of the needle-valve is riveted into the cap B, which is knurled on the outside so as to present a good gripping surface. The needle-valve is seated by screwing down on the knurled cap. — W. Burr Bennett.

���Cap for the cup with needle-valve

��Proper Care of Inner Tubes to Prevent Chafing

IF tire users better understood the con- struction of inner tubes, and factors which contribute to their wearing out, it would be easy to secure more and better service. Spare tubes should not be carried in the cardboard boxes furnished from the dealers' shelves. There is much danger of their being chafed. Tube bags can be secured for this purpose.

If the car is equipped with smaller tires on the front wheels than on the rear wheels, an extra tube should be secured for each size. The cross-sections of inner tubes are made a little smaller than the normal air

��space inside of the cases. It is not advis- able to use a 4^-in. tube in a 4-in. case. This usually wrinkles and creases the rub- ber, with bad results. Do not use a 4-in. tube in a 4^-in. case for any length of time. When this is done the rubber is stretched too much and the effect of heat and displacement of air in the tire quickly uses up the life of the tube.

If put into usage for which it was not designed, the tube will not, as a usual thing, render efficient service. If it were practical to use one size of tube in another size of case, tire manufacturers could effect a big saving in equipment and furnish only a few sizes of tubes.

Lubrication is most important to con- servation of the tube, but it is a matter that is given the least attention. Practically all tire manufacturers treat the inside of cases with a white solution to prevent tubes from sticking to the adhesive "fric- tion" of the fabric. A good lubricant, however, should also be used.

Some tire users neglect dusting soap- stone inside of the case when changing a tube. Others use the soapstone so sparingly that it does but little, if any good, or they may use so much that it does more harm than good. If a quantity of it be dumped into the case it will collect at one point, and during the hot weather will heat up to such extent as to burn the rubber of the tube, making it thin, brittle and lifeless. This results in a honeycombed appearance. Soapstone is the lubricant most used for tires and is satisfactory, but not lasting. Therefore, a fresh supply should be put in the tires at least two or three times during the season. Powdered mica has proven a more durable lubricant than soapstone, and quite as effective as graphite, and is much more pleasant to handle. It should be dusted on the fabric all around the case and on the inner tube to cover every par- ticle of the surface.

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