ELECTRO-MOTIVE MACHINES. 



moveable, being fixed upon a crank or eccentric. In this case the 

 wheel revolves within another, whose diameter exceeds its own 

 by twice the length of the crank, and within this circle it has an 

 hypocycloidal motion. 



Each of these varieties of the application of this power, as yet 

 novel in the practical operations of the engineer and manufacturer, 

 possesses peculiar advantages or convenience, which render it more 

 eligible for special purposes. 



9. Electro-motive machines. To render this general descrip- 

 tion of M. Froment's electro-motive machines more clearly under- 

 stood, we shall add a detailed explanation of two of the most 

 efficient and useful of them. 



In the machine represented in fig. 2, a and b are the two legs 

 of the electro-magnet ; c d is the transverse piece uniting them, 

 which replaces the bend of the horse-shoe; ef is the armature 

 confined by two pins on the summit of the leg a (which prevent 

 any lateral deviation), the end / being jointed to the lever g h, 

 which is connected with a short arm projecting from an axis k by 

 the rod i. When the current passes round the electro-magnet, 

 the lever f is drawn down by the attraction of the leg 6, and 

 draws with it the lever g A, by which i and the short lever pro- 

 jecting from the axis k are also driven down. Attached to the 

 same axis k is a longer arm w, which acts by a connecting rod n 

 upon a crank o and a fly-wheel v. When the machine is in 

 motion, the lever g h and the armature f attached to it recover 

 their position by the momentum of the fly-wheel, after having 

 been attracted downwards. When the current is again esta- 

 blished, the armature / and the lever g h are again attracted 

 downwards, and the same effects ensue. Thus, during each half- 

 revolution of the crank o, it is driven by the force of the electro- 

 magnet acting on f^ and during the other half-revolution it is 

 carried round by the momentum of the fly-wheel. The current 

 is suspended at the moment the crank o arrives at the lowest 

 point of its play, and is re-established when it returns to the 

 highest point. The crank is therefore impelled by the force of 

 the magnet in the descending half of its revolu- Fi 3 

 tion, and by the momentum of the fly-wheel in the 

 ascending half. 



The contrivance called a distributor, by which the 

 current is alternately established and suspended at 

 the proper moments, is represented in fig. 3, where 

 y represents the transverse section of the axis of 

 the fly-wheel ; r, a spring which is kept in con- 

 stant contact with it ; x, an eccentric fixed on the same axis 

 y, and revolving with it and / another spring similar to r, 



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