810 EEPOEX— 1888. 



Wigzel of Sowerby Bridge. It is furnished with au exceedingly perfect centri- 

 fugal governor, which maintains the speed accurately at seventy-six revolutions in 

 spite of very great fluctuations in the load. The electrical means of stopping the 

 engine have been provided in the shape of Tate's electrical stop-valve, which may 

 be described as an electro-magnet arrangement with the ordinary pushes for com- 

 pleting its circuit, which actuates a steam relay piston set to close the main-stop 

 valve. The fly-wheel of this engine is twenty feet in diameter and weighs thirty- 

 tons, and is geared to the pulley of the dynamo, so that the latter makes live revo- 

 lutions for each revolution of the engine by rope driving gear consisting of eighteen, 

 ropes. 



This engine is an extremely fine specimen of a modern steam-engine ; it works 

 so silently that a visitor standing in the engine-room with his back to the engine 

 railino-s at the time the engine is being started, cannot tell whether it is in motion 

 or not. The dynamo at first sight seems very small when compared with the 

 steam-engine driving it, the fact being that it is dwarfed by the enormous fly 

 wheel of the engine ; it is only when one stands close to the plummer-block bear- 

 ings that one realises the great size of the spindle, and of all the parts required to 

 transmit the power to the armature coils. 



The author was well aware when designing this machine that the mechanical 

 strains on the spindle, core attachments, and winding were likely to be of an extra- 

 ordinary nature. The following precautious were therefore adopted, and as events- 

 have turned out they have been more than justified. The spindle is of steel, 

 18 feet long, with three bearings, one being placed on either side of the driving- 

 pulley. The diameter is 7 inches in the bearings and 10 inches in the part within 

 the core. This part in the original forging was 14 inches diameter, and was planed 

 longitudinally, so as to leave four projecting ribs or radial bars on to which the 

 core discs are driven, each disc having four key ways corresponding to these ribs. 

 There are about 900 of these discs, the external diameter being 20 inches, and the 

 total length of the core 36 inches. Originallj' this core was provided with thirty- 

 two driving-teeth made of steel, each tooth riveted to .sockets attached to eight of 

 the core discs. It may here be mentioned that, as the working has shown, the strain 

 on these driving-teeth was perilously near their factor of safety ; their number has 

 been doubled, so that now the tangential strains are borne by a very considerable 

 percentage of the core discs. 



The armature winding consists of 128 copper bars, each seven-eighths of an 

 inch deep, measured radially, by three-eighths wide. These 128 bars are coupled 

 up so as to form thirty-two conductors only; this arrangement has been adopted 

 to avoid the heating from Foucault currents, which with one-and-a-half inch con- 

 ductors would have been verj' considerable. The bars are coupled at the ends of 

 the core across a certain chord, according to an arrangement patented by the author 

 and Mr. Swinburne, which consists of crescent-shaped bars so formed that the 

 whole surface is thoroughly exposed to tlie current of air passing through the 

 armature ; they are also somewhat shorter than those usually employed on drum- 

 wound armatures. The bars are insulated by a covering of ' tiburite,' a material 

 which has been recently introduced by Messrs. Crompton, and which will stand a 

 temperature of 160° Cent, for long periods without the least discolouration, 

 softening, or alteration of its mechanical and insulating properties. The com- 

 mutator is 20 inches long, has sixty-four parts, and in addition to the usual 

 tightening nuts at the two ends, is provided with a third tightening ring at the 

 centre to prevent the tendency of such long commutator strips to spring when 

 worn down thin. The current is collected by eight brushes mounted on a separate 

 ring placed concentric to the commutator, and the current is led away from these 

 brushes by a large number of thin bands of sheet copper strapped together into 

 convenient groups. 



The field magnets are of the horizontal double type, and were adopted by the 

 author and Mr. Swinburne after a careful series of experiments, which con-vinced 

 them that the fashionable single magnet form was very unsuitable for this kind of 

 machine. 



As this machine is virtually a series wound machine, the magnet coils each con— 



