Jl-I.Y, 19U. 



KNOWLEDGE. 



w hich is mounted over a large spur wheel. Beneath 

 this again is a smaller wheel wliich can, by means of 

 an eccentric, cause the upper portion of the drawing 

 table to move across the lower in a straight line 



the resulting design, as also does the direction in 

 which the drawing table rotates. Figures 278 

 and 279 require almost the same setting, except 

 that the draw iuL; table revolves in opposite directions. 



backwards and forwards. The distance it travels is 

 easih' controlled by the eccentric, while the upper 

 spur wheel is clamped when this motion is required. 

 Usualh- the drawing table revolves centrally, but 

 by clamping the lower spur wheel and throwing the 

 up[)er part of the drawing table eccentric an 



This, of course, is not responsible for there being 

 six arms in the former and onl\- three in the latter. 



\\"hen we consider the number of simple and 

 complex motions which can be brought into action 

 together or independentlv in varying ratios and 

 opposite directions, it is not surprising that the 



designs 



Figure 279. 

 should be almost limitless 



elliptical motion is obtained. (See Figure 274.) resulting; 

 The gearing between the central tables and the variety, 

 drawing table plays an important [sart in the form of In order to make a little clearer what part each of 



