CONSTRUCTION OF FLYING WHEEL. 305 



with sharp angles they might possibly injure objects against which 

 the wheel flies. To keep the blades in position and prevent their 

 being bent out of shape, solder round them a ring made of two strips 

 of tin-plate 6 mm wide, each being 15 cm long, if the diameter of the 

 wheel is 9 cm . The ring is formed of two strips, in order that it 

 may be soldered at two opposite points ; if there were only one 

 joint, the ring would be heavier on that side than on the other. 

 The ring should allow of being pushed over the wheel with moderate 

 friction ; the two strips, while they are being soldered to the blades 

 should be kept in position by bending an iron wire round the ring and 

 twisting the ends together, for the first joint is apt to break while 

 the other is being made. The wire is removed when the solder is 

 cool and firm. Fig. 201 -4, shows the wheel with the contrivance 

 for letting it off ; B gives a section through the middle of the wheel 

 and its support. The axis is formed by a piece of steel wire, 3 or 

 4" thick, and 4 cm long, with a screw cut upon it from the top to 

 the middle ; l cm below the middle a hole is bored through the axis, 

 aaving a width of I >mm 5. A disc of brass, I 6 in diameter, and 2 mm 

 hick, is screwed upon the axis, and a brass wire, l cm long, is 

 oassed through the transverse hole. The disc forms the support for 

 he wheel, to which it must be soldered as well as to the axis. As 

 he axis is apt to break away unless it is firmly fixed, the disc 

 Cannot be dispensed with, and it is not advisable simply to solder 

 b upon the axis without screwing. The brass wire must also be 

 oldered into the hole. 



Bore an aperture, 15 mm deep, into one end of a piece of brass 

 are, m, which has a thickness of 6 van and a length of 9 cm , the aper- 

 are being wide enough to admit easily the axis a. File a notch 3 mm 

 eep, across the aperture, and wide enough to receive conveniently 

 ie brass wire which passes through the axis ; this portion is shown 

 iore distinctly at than at B. The brass piece is further perforated 

 ;ross its thickness, 12 mm from its lower end, and two discs of brass, 

 m wide, are soldered to it, one l cm from the lower end, the other 

 from the upper one ; the intermediate portion of the brass wire 

 rras thus a short spindle. Two pieces of wood, of the form g and 

 fig. 201 A, are procured from a joiner ; they should be about 12 mm 

 ick, and each have a hole at the projecting ends, 6 mm in diameter ; 

 1 er passing the brass wire through the holes, the piece li is fixed 

 ^g by two screws. 



3ne end of a thin but strong cord, l m< 5 long, is then passed 

 t ough the lower hole and wrapped in smooth and close turns 

 r nd the spindle ; there should be thirty turns forming two layers. 

 A mall handle, shown in fig. 201 D, made of a small piece of steel wire, 



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