SECTION III 

 CHAPTER XIII 



Hydraulic Prime Movers Water-Wheels The Overshot Breast Side Undershot and 

 Poncelet Wheels The Pelton Wheel Losses Form and Number of Buckets Speed 

 Regulation Jets from Needle-nozzles Typical Installations Summary. 



ART. 119. HYDRAULIC PRIME MOVERS, WATER-WHEELS. 



ALTHOUGH the question of the utilization of natural water powers has 

 always been one of great economic importance, the introduction and per- 

 fection of electrical manufacturing processes, and the possibility of. 

 transmitting electrical energy without great loss or expense to a great 

 distance from the place of its generation, has of recent years made it 

 practicable to take advantage of many water powers far remote from large 

 centres of industry and has raised the whole question to an altogether 

 higher plane of importance, while the consequent demand for hydraulic 

 prime movers capable of developing large powers in single units, and of 

 satisfying the exhaustive demands of such installations in the way of 

 speed regulation and efficiency, has led to a great transformation in the 

 design of such motors. 



The first hydraulic prime mover consisted of a wooden paddle water- 

 wheel dipping into the current of a stream, and as such a motor was only 

 required to do the work previously performed by an animate agency, the 

 power required was small and the efficiency of only secondary importance. 



The construction was at first of the most primitive type, but was 

 gradually improved ; iron took the place of wood ; improvements in design 

 led to increased efficiency ; the demand for greater powers led to the 

 necessity for utilizing larger falls and the consequent development of the 

 breast and overshot wheels, until a type of wheel was evolved, which 

 within its limitations was as efficient as the most modern of turbines. 

 Its chief disadvantages lay in its slow speed of rotation, the impossibility 

 of close speed regulation, and in the large size of wheel required for even 

 small powers ; and while for the purposes for which the motor was first 

 required these were not serious, the introduction of more modern 

 machinery, more particularly for textile purposes, involved the necessity 

 for a motor which, having a fairly high speed of rotation in order to avoid 



