Page:Popular Science Monthly Volume 90.djvu/458

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442

��Popular Science Monthly

��Magnetic Base for a Machinist's Electric Light

ELECTRIC light has become the one illuminant for the machine-shop, be- cause it can be handled readily and moved

to the best lo- cation for throw- ing the rays on the work. Hooks, arms and adjust- ers are many for this purpose, but the magnetic base seems to outshadow them all. It consists of a coil with a soft iron core which is con- nected in series with the socket. When the current is turned on in the lamp its base can be set in any position on a machine-tool and the lamp will be held securely in that position by magnetic attrac- tion. — Jesse J. Nachman.

���The current in the coil makes the base magnetic

��The Protection and Care of Shop Belts

THE best man in the plant should have special charge of the belts. He should be a man capable of using his imagination as to what a belt has to undergo on a drive. The belt swings around the pulley on the driving machine, and the strain on it rises from almost nothing in a tenth of a second to a pull of several hundred pounds as the belt leaves the drive-pulley on its trip to the shaft-pulley.

Suppose the belt is driving a machine with a jerky power driver, not balanced by a flywheel, and while the belt is tightly stretched under this pull it is violently jerked and tugged as well. This puts a big strain on the belt at the moment when it is least able to stand it. The belt for such a drive should be broad and thin, if it runs on a small pulley.

When the belt reaches the shaft-pulley the strain drops to almost nothing, and it runs back slack to the machine-pulley. But, if this machine is not running smooth- ly, the belt is alternately let down and tightened up on the slack side, and each tightening makes a sharp, sudden strain which tends more and more to tear the belt to pieces the slacker the belt is, acting just like a whip in its sudden fautening. One

��can readily see how this destroys the belt at the fasteners and joints.

The size of pulleys makes a difference in favor of belt service. The larger they are the less the strain and the better they hug the additional length of pulley surface. If a belt on 5-in. pulleys breaks down fre- quently, the pull on the same belt running over lo-in. pulleys will be just one-half, and the pulley adhesion just twice as great. Of course, the speed of the belt will be doubled. Furthermore, a double belt may be used on the enlarged pulleys to convey still more power, if necessary. Such a double belt would quickly wear out on the small pulleys.

��Carrying Two Large Cans of Water with Little Effort

IN a very old but flourishing mining town in California, a most interesting labor- saving device was seen recently. It made a comparatively easy task of carrying two 5 gal. kerosene-cans full of water. The device consisted of a light wood frame made of slats or thin boards, 3 ft. square, and braced in the corners. This frame separated the two containers from the

���The frame keeps the containers away from the carrier and lightens the work considerably

carrier as shown. Practically no strength is required in carrying the load, since the tendency is for buckets or cans to come together instead of exerting a vertical strain. — Austin Armer.

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