!?78 



Popular Science Monthly 



are for binding posts. Each element has 

 its own set of binding posts. The rea- 

 son for this is that some experimenters 



have a step 

 down trans- 

 former which 

 would b(' suit- 

 able for the 

 lights but 

 cannot be 

 used in con- 

 nection with 

 the magnet. 



No dimen- 

 sions are giv- 

 armature (H), 

 1), their size 

 magnet used. 



Bearing iwint of semaphore arm 

 Fig. 4. Diagram showing con 



struction of lamp 



en for the spring (G), 

 or projection arm (Fig 

 depending on the size 

 The spring (G) should be made of some 

 spring metal, such as gcrman silver or 

 phosphor bronze. The armature (H) is 

 made of soft iron and the projection 

 arm of aluminum. The spring and arm 

 are riveted to the armature. 



u '"a^ -^'.1. ^".t. ^ 



Fig. 5. 



Plan of arrangement of parts, 

 with dimensions 



An angle arm (J), holds the lamp to 

 the standard. It should be about i/V' 

 wide and each arm about \" long. 



The string (K) attached to the pro- 

 jection arm is the means by which the 

 semaphore arm is moved when the ar- 

 mature is pulled down ])y the magnet. 

 If a light lirass chain is used in place of 

 the string, the appearance is more real- 

 istic. 



Fig. 7 shows the wiring diagram when 

 used with one source of current. The 

 key is a .strap key or push-button, 



placed at a distance from the 

 semaphore. In Fig. 1, the 

 arm is shown with the cur- 

 rent passing through the 

 magnet. 



When completed and as- 

 sembled, if the cover, base 

 and lamp are painted black, 

 the standard painted white 

 and the semaphore arm 

 painted red with two white 

 stripes as showm it gives the 

 semaphore a very realistic 

 appearance. 



The semaphore need not be 

 entirely electric as the sema- 

 phore arm can be constructed 

 so that it will move with a 

 lever instead of an electro- 

 magnet. In such a case, its 

 construction will be much 

 simpler than when electricity 

 is used. 



ti- 



n 



Fig. 6 



Saving Time in Tracing a Design 



NEARLY e\ery worker, from the 

 lady embroiderer to the machine 

 shop designer, at some time has use 

 for a symmetrical design, yet they us- 

 ually go to the trouble of drawing each 

 side out, or tracing one side. A far 

 quicker and easier way is to use the 

 following draughtsman's method : 



Draw one half of the design out on 

 tracing paper, or any strong tissue 

 paper. Fold this over on top of the 

 blank half, being careful that the 

 crease comes exactly along the center 

 line of the whole design. With a silver 

 half-dollar, pass over the top of all us- 

 ing a rapid to-and-fro stroke. The de- 

 sign is now^ reproduced perfectly on 

 the other half of the paper. For this 

 work the pencil should not be too hard, 

 F or B, or a common Xo. 2. 



/ompj^, 



Mopnefs 



Fig. 7. Wiring diagram when semaphore 

 is operated with batteries 



