WATEK METERS 



739 



Counter 



raised surface is a portion of a parabola. The arrangement is shown 

 diagrammatically in Fig. 358. A roller R receives vertical motion from the 

 float mechanism, and is pressed against the drum by a rocking frame F, 

 This frame carries a pinion P which actuates the counter mechanism, 

 and which does, or does not, gear with the teeth of a spur wheel carried 

 by the drum according as the roller is on the recessed or the raised portion 

 of its surface. 



Thus when the roller is at the highest point it engages only with the 

 raised surface, so that in this position corresponding to no flow the 

 counter is not actuated. At the lowest' 

 position the roller is entirely upon the 

 recessed surface, and the counter is 

 actuated continuously. In any inter- 

 mediate position the counter revolves 

 only while the roller is in contact with 

 the recessed surface, so that the fraction 

 of the period of revolution of the drums 

 during which the counter rotates is pro- 

 portional to x/ h. Thus since the velocity 

 of flow is also proportional to *J h, the 

 discharge is summed or integrated, and 

 can be read directly from the counter. 



Another type of velocity recorder is 

 shown in Fig. 359, while where a com- 

 bined velocity and discharge recorder is 

 required, a modification of this in which 

 a cast-iron U, having both legs of the 

 same area and containing mercury, may 



be used. These contain iron floats which carry light racks gearing 

 with pinions, which convey their motion to corresponding racks placed 

 outside the tubes. The racks carry light rods which pass up to the 

 recording mechanism. That connected to the float in the throat chamber 

 regulates the amount of registration by the counter, while the second 

 carries the pencil of the velocity recorder. 



EXAMPLES. 



(1) Determine the H.P. transmitted through a 6-inch pipe if the 

 velocity of flow is 3 feet per second, and the delivery pressure 1,000 Ibs. 

 per square inch. 



Answer. 154 H.P. 



FIG. 359. Recording Mechanism for 

 Venturi Meter. 



B 2 



