848 



HYDRAULIC MACHINERY, FOR MINES 



1177 



beam in which is formed an abrupt descent for the liberation of the water ; lp, flanking 

 of tail-race. In order that the water may impinge upon the buckets of the wheel with 

 the least possible loss of effect, the bottom of the course, 

 where it approaches the point of impulse, is made with 

 a declination of from 3 to 4 from the horizontal direc- 

 tion. The line of direction m n, of that portion of the 

 water flowing through the sluice opening c, ought there- 

 fore to make with tha tangent lino m o, to the circle of 

 the wheel, an angle of 24 to 25. The surface p h of 

 the water-run is a tangent drawn to the small circular 

 arc p r, which approaches close upon the circumference 

 of the wheel at that part where it passes the vertical 

 plane, and which should bo as long as the distance be- 

 tween two contiguous buckets. At the point r the arc 

 terminates abruptly for the width of the race, allowing 

 a drop for the water equal to half the depth of the 

 shrouding. 



Method of determining the curvature of the buckets. 

 Prom a point a (fig. 1176) in the extreme circumference 

 draw the lino a b, making an angle of 25 with the radius 

 a d, drawn from the centre of the wheel to a. Then 

 with a radius of th of the depth of the shrouding h, less 



1178 



