154 PORTABLE WIND MOTOES APPLIED TO 



in a solid wood block so as to form two isosceles triangles, the 

 front one being rather higher than that at the rear. Braces 

 and cross-beam are mortised to the four uprights to secure 

 the necessary rigidity. 



Other braces, HIT, IP (Figs. 97 and 98), contribute to the 

 strength of the structure, and at the same time serve to carry 

 different collars and bearings ; finally a beam J projects 

 horizontally to a distance of 4ft. lOin. at the rear, so as to 

 receive a prop or stay in case the wind is too strong, or, in 

 any case, to protect the mechanism should the machine be 

 blown over. Up to the present this has not been much 

 required. 



The frame of the Windmill. A cast-iron plate K, 3ft. Sin. 

 in diameter, and ^ inch in thickness, is fixed on the main 

 shaft by a brace and cotter. On the front part of this plate 

 are eight lodgments, to receive eight arms L, 2 T 3 - x 1 J inches 

 section near the centre, and 2^- x -fa inches at the circum- 

 ference. They are fixed in the lodgments by iron braces, 

 bolted at the rear of the plate K. Three rings are braced to 

 these arms M M / M x/ , made of angle-iron riveted on flat iron. 

 The first ring M (Fig. 99) forms a cylinder concentric to the 

 shaft 0, 6ft. 6in. in diameter, and 5 J inches in height, provided 

 with 32 openings to receive the vanes, the second ring M' is 

 13 feet in diameter, the third M" 19ft. Sin. They are both 

 provided with 32 large notches, the curve of which corre- 

 sponds to that of the vane which it supports. Fig. 99 shows 

 the shape of these notches. The vanes are secured on the ring 

 M" by means of an iron pin ab, with a handle at #, and 

 threaded at #, screwing in a brace c, by means of which the 

 vane is compressed on the curvature of the notch. . 



Vanes. The frame above described carries 32 vanes (four 

 on each arm), made of pine-boards ^ inch thick, 6 inches 

 wide at the centre, and 32J inches wide at the periphery, 

 forming a vane lift. Sin. in length, the small end of which 

 is rounded to help the placing in position. 



The vanes, instead of being plane as in other wind-motors, 

 form an helicoidal curve, and as the mill revolves, the wind 

 presses against the surface, less and less inclined towards the 

 centre, where it is almost normal to the plane of the mill. 

 In this way the shock of the wind is reduced in the first part 

 of the curve, and gradually loses its speed to escape in the 

 centre, after having transmitted to the motor all its motive 

 energy. 



