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. 



