248 



KN()\VLi:nGi':, 



Jll.Y, 1912. 



the drawing tal)lt; wliili.- the upinr (F) slicii'S at ripjlit 

 angles to it. Hcncatli tliisc tables arc two S|)iir 

 wheels identical with those beneath the elliptic table. 

 The lower of these is free and is used when the 



often re(|uired and is obtained by throwing the 

 iip|)er table out of gear, damping it centrally and 

 using only the lower table. Figure 273 was 

 drawn with a circular motion of the central pivot 



FiGUKE 111. 



motions of the tables are not required : the upper has 

 a runner sliding in guides across its diameter. This 

 may be clamped in any position and regulates the 

 motion of the sliding tables — the more eccentric its 

 position the more motion it imparts to the tables 

 above. It is not alwavs desirable to have both 



Figure 274. 



while for Figure 276 only the lower table was used. 



The central pivot of the pantograph is fixed above 

 the tables and is carried along by them, all motion 

 at this point being doubled at the drawing end of 

 the pantograph. 



The gearing inserted between the elliptic table 



Figure 273. 



sliding tables in use, as together the\- impart a 

 circular motion to the central |iivot (G) of the 

 pantograph, whereas a simple harmonic motion is 



I'IGI'RE 275. 



and the central sliding tables has a great influence 

 over the resulting design. 



To the left of the machine is the draw ing table (G), 



