Motors
  ------
  Conrad Electronics, 1-3v 25mA 249:1 gearbox
 
  gears
               teeth  material	
      motor        7  steel 
               42:13  nylon
               36:12  nylon
               37:12  brass/steel
               37:19  brass/steel
               30     brass
  overall ratio 249.41295 : 1 => 249:1