WATER :METERS. The Thomson Wetter Meter is shown in Fig. 1. The displacing or measuring member consists of a fiat disk, having a ball-and-socket bearing, and is adapted to oscillate in a chamber, comprised of two sections joined together, in which each of the inside faces approximates the frustum of a cone, the exterior confining wall assuming the form of a circular zone. The disk has a single slot projecting radially from the ball, which embraces a fixed metallic diaphragm, set with in and crosswise of one side of the chamber, the disk being thus prevented from rotating ; but when it is caused to oscillate in contact with the cone frustums, the chamber, by these means, is divided into sub-compartments, or measuring spaces. Now, if the ports of gress and egress are properly disposed on oppo site sides of the diaphragm, the disk will act as its own valve. The course of the flow through the meter is as follows : Entering the compartment, formed by the upper and lower caps, the current passes on all sides of the chamber, to and through the inlet port : thence through the measuring chamber (causing the oscillation of the disk), then through the outlet port, to the outlet spud and the pipe. At all sections in this path. from the inlet to the outlet, the velocity of flow is much less than that through the pipe. The oscillation of the disk produces in its central axis, at a right angle to the plane of the disk, circular motion. Advantage is taken of this to control its proper rela tive action in respect to the cone frustums, by mounting a conical roller upon a spindle fixed in the ball. This roller impinges upon and rolls around the fixed conical stud or hub, formed on the inner side of t he gear frame. The roller turns upon a conical sleeve which is screwed upon the disk spindle ; the object of this construction being to avoid any tendency to produce end-thrust, consequent upon the angular thrust of the spindle, and also to provide means whereby to obtain the proper relative adjustment between the disk and the cone frustums. The accidental displacement of the adjusting sleeve is prevented by inserting a pin through its shoulder and also the body of the spindle, which is then bent, each end at a right angle to the other, to lock it in place. This circular motion of the spindle is also utilized to drive
the registering mechanism by means of an arm secured to the primary pinion of the train the arm impinging upon and being driven by the lower extension of the roller. The trend of the motion of the disk is to thrust the edge of the slot constantly against the outlet side of the diaphragm.
The diaphragm is made of hard rolled metal, which is shaped very accurately, and is rigidly secured between the two sections of the disk chamber. The internal gearing which connects the disk to the stuffing-box spindle is mounted between two separate plates secured together by pillars, as in clocks, and, in the smaller sizes, the whole as a single structure is secured by screws directly to the disk chamber. The gearing stands in the upper portion of the compartment, and is thus out of the direct path of the current.
The Venturi Neter, made by the Builder's Iron Foundry, Providence, 1.. is shown in Fig. 2. It is the invention of Mr. Clemens Herschel, and was first described by him at the December, 1887, meeting of the American Society of Civil Engineers. Its action is founded on the well-known property of a Venturi tube to exercise a sucking action through holes bored into its narrowest section. The construction of the meter, as shown by the accompanying cut,is merely a contraction of the main pipe, to which two ordinary pressure gauges are con nected—one at any convenient point before contraction of pipe begins ; the other at the smallest section. When any flow in the pipe occurs the pressure on throat gauge will fall, if the flow becomes sufficiently rapid, all pressure at the throat may disappear and a vacuum ob tain. The other gauge, however, will continue to indicate the pressure due to the supply. By mathematical calculation and experimental confirmation, a formula, based on the different pressures on the gauges, has been obtained, which accurately indicates the velocity of flow through the throat of the meter. An ordi nary self-recording differential gauge may be used to obtain a diagram of these variations in pressure, from which both the velocity at any given time, and the total quantity passed in any interval, may be readily determined.
Water Tower : see Fire Appliances.