468 SEC. 12. APPLIED MECHANICS. 



1998a. Gyrometric Governor for Steam Engines. 



Messrs. Siemens Brothers. 



It consists of an open cup of parabolic shape, fixed upon a vertical spindle, 

 and caused to revolve within the closed chamber containing the liquid, the 

 bottom of the cup being open and always immersed below the surface of the 

 liquid. When the cup is made to revolve rapidly, the liquid contained in it 

 rises round the sides of the cup and sinks in the centre, the surface of the 

 liquid assuming the inverted parabolic form ; and on reaching the edge of the 

 cup it overflows into the surrounding chamber, while at the same time a 

 fresh supply of liquid is drawn into the cup through the opening in the 

 bottom ; and the power absorbed in putting the overflowing liquid into 

 motion offers a continuous resistance to the rotation of the cup. On a level 

 with the edge of the cup, a series of fixed vanes are placed round the cir- 

 cumference of the external chamber, and a corresponding set of blades are 

 also fixed round the outside of the cup just below the rim, so that the sheet 

 of liquid overflowing from the edge of the revolving cup is thrown against the 

 vanes, and by these is thrown back against the blades on the cup, whereby 

 the overflowing liquid is made to offer an additional resistance to the rotation 

 of the cup. 



The internal radial arms uniting the shell of the cup to the centre boss 

 serve to communicate the rotary motion to the liquid inside the cup, \vhile 

 the bottom of the external chamber is provided with a number of radial ribs, 

 for the purpose of checking rotary motion in the liquid outside the cup. 



So long as the cup is driven at a constant speed, the overflow is constant, 

 and produces an absolutely constant resistance ; and, hence, if the cup be 

 driven by a constant driving power, independent of the engine, its speed is 

 as uniform as that of a chronometer, within a very small margin of variation, 

 which is definitely fixed ; and it continues revolving at an unchanging speed, 

 totally independent of the engine, and consequently' affords the means of 

 forming a governor for controlling the speed of the engine to a constantly 

 uniform rate. 



1998b. Chronometric Governor for steam, land, and 

 marine engines, water wheels, turbines, &c. Dr. C. W. Siemens. 



1998c. Gyrometric Governor for a steam engine (size 



adapted for a 4" steam pipe). W. D. Scott- Moncrieff. 



This is an apparatus in which the centrifugal force of a fluid is applied so 

 as to regulate the aperture of a throttle valve through the movements of a 

 loaded piston. It consists of two chambers containing fluid, and communi- 

 cating with each other through a turbine wheel with four or more straight 

 radial arms. The speed of this wheel depends upon that of the prime mover 

 by which it is driven, and the pressure in the front chamber is dependent 

 upon its velocity, and its variations open and shut the throttle valve. 



In the pendulum governor the centrifugal force and the speed necessary to 

 maintain it vary with the different planes of rotation due to different positions 

 of the throttle valve. Such an apparatus can only be correct for one position, 

 and errors of speed must occur for every change in the power of the prime 

 mover or the work it is performing, unless these vary simultaneously and 

 equally. In this governor the centrifugal force of the fluid remains in a 

 fixed ratio to the speed of the engine, and the length of the connexion to the 

 throttle valve varies with the altered length of the fluid column supporting 

 the piston. By adjusting the load upon the piston any speed which the 

 engine is capable of maintaining can be given and will remain constant for 

 all variations of power and work. An index of the speed may be obtained by 

 attaching a glass or Bourdon gauge to show the varying pressures. 



