956 



Popular Science Monthly 



B B, equal to width of V-ring. Connect 

 lines B and C on both sides, extending 

 lines to A A. Call this intersection 

 point F, or "apparent apex of cone." 



Using F as the center and B as the 

 radius, describe a large arc. Repeat this 

 operation using C as the radius. This 

 gives us proper curve and width of the 



Oiam. large end 

 Diam.5mallend j 



Width of ring... 



/ / Apparent opex 

 /,/.- —■' of core 



f 



Method of laying out a pattern for cutting 

 the mica V-rings used on armatures 



mica V-ring, but to eliminate waste the 

 length should also be known; the exact 

 length is not needed and would be im- 

 practical for two reasons; first, it would 

 involve too much figuring for the average 

 armature winder and take up too much 

 time; second, because provision must be 

 made for welding mica V-ring ends to- 

 gether. 



Therefore the exact length would be too 

 short. To get the required length, en- 

 circle the large end of a V-ring with a piece 

 of banding wire, allowing an extra inch 

 for welding. Set this measurement on the 

 large arc, and mark off the points, D D. 

 Connect points D D with the apex, F. 

 The V-ring is now all laid out and ready- 

 to cut. 



A Holding Clip for Making Tests 

 on Spark Plugs 



WHEN testing the spark on a set of 

 exposed sparking plugs most car 

 owners feel the need of special clips to 

 grip the plugs, which have a habit of 

 tumbling out of contact, more particu- 

 larly when single plugs are being tested 

 with the engine running. Under these 



circumstances, too, there is a risk of 

 straining the magneto or coil if a plug 

 swings past its wire without a ground. 

 An ordinary bicycle pump clip of the 

 double spring type makes an excellent 

 plug holder. One end may be sprung 

 over any convenient pipe or bolt and the 

 inverted plug dropped into the empty end. 



Controlling an Oil Cup by Means 

 of an Electromagnet 



THE magnetically operated oil cup 

 described herewith will be found to 

 be a very convenient means of controlling 

 oil feed in partially inaccessible places. 



An electromagnet is used in this scheme, 

 as shown in the sketch. To open the oil 

 cup, energize the magnet by control 

 switch or push button. The iron disk, ad- 

 jacent to the electromagnet, becomes mag- 

 netized and draws up the iron cap on the 

 top of the oil feed pipe, and the oil will 

 commence to drip. Upon breaking the 

 circuit, the disk is demagnetized and the 

 oil feed pipe, being no longer attracted, 

 again falls and closes the feed hole. 



Regulation of the flow can be obtained 

 by adjustment of the iron disk, which is 



-Electro magnet , 



Saaaaaaw 



Adjustoble resistance 





Remote control (hey or s*) 

 -Iron screw rod 



■Iron disc. 



Iron car 



-—Oil feed pipe 

 -- Oil cup 



A serviceable elec- 

 tromagnet that 

 draws the oil cup 

 plunger by electric 

 current controlled at 

 a convenient point 



connected to a screw rod, as shown. A 

 small electromagnet and a rheostat in 

 series in the circuit will render the control 

 of the oil cup quite precise. This device has 

 considerable worth.— Peter J. M. Clute. 



