PELAW MAIN COLLIERY. 



351 



less, consequently the efficiency in actual work done for the 

 power supplied is much more. The detrimental eddies which 

 occur in otlier fans are obviated by the construction of the 

 Sirocco. This fan has a double inlet, and is 190in. in dia- 

 meter. It is driven at 200 r.p.ni., and is capable of exhausting 

 350,000 cubic feet of air per minute, against 5Jin. water gauge. 

 This requires 230 b.h.p. It is driven by ropes from a 3 

 phase, 50 period, 3300 volt motor, of 500 h.p. Ropes are bet- 

 ter than belts for driving fans, for if a rope breaks the others 

 will drive the fan till the men have time to get out of the mine 

 before it is necessary to stop for repairs. The bearing surfaces 



Fig. 220. Locomotive Built in 1858. 



for the shafting of the fan are very wide, and lined with white 

 metal. They are fitted with leather washers at each end to 

 make them dust proof. The bearings are lubricated by auto- 

 matic ring lubricators. An adjustable sole plate is provided, 

 which is wedge-shaped. By screwing this in or out, the bear- 

 ings can be aligned in a very short time should the foundation 

 settle. It is also useful when the lower bush has to be re- 

 moved, for, by dropping the lower half of the bearing, the 

 bush can be slipped round the shafting and taken out. 



