A Slide-rule for Indicating and Facilitating Regulation of Quantities of Water Flowing over Gauge Weirs.
Year: 1896

page_text: Date of Application, 4th Nov., 1896-Accepted, 19th Dec., 1896
A Slide-rule for Indicating and Facilitating Regulation of Quantities
of Water Flowing over Gauge Weirs.
I, JOHN AMBROSE MCPHERSON, of the Engineers Department, Water Works,
Bristol, Civil Engineer, do hereby declare the nature of this invention, and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement :-
This invention consists in a slide-rule for indicating and facilitating regulation of
quantities of water flowing over gauge weirs such as are commonly used in connection
with water supply works, drainage, irrigation and like works.
The slide-rule which constitutes this invention has fixed upper and lower members
between which is a central member or slide which is free to slide longitudinally
between the upper and lower members. The upper member is graduated for quantities
of water into major graduations each indicating, in the case of a rule graduated as
for gallons per 24 hours, I million gallons per 24 hours in respect of a weir of a
given width. The major graduations are subdivided into minor graduations. The
central sliding member of the slide-rule is differentially graduated for depths in
major divisions each indicating, in the case of a rule graduated in inches, one inch
as for a weir of the given width referred to in respect of the graduations for quantities
aforesaid of the upper member.
The graduations in the upper member are read from left to right, as also are the
graduations on the central or sliding member.
The lower member is graduated into exactly similar divisions as the central member,
but the graduations of the lower member are read from right to left.
When the slide-rule is closed, that is to say, when the slide is fully home, the
instrument serves as a table indicating the quantity of water passing over the weir
for any depth indicated on the slide-rule.
Another use of the slide-rule, when the slide is fully home, consists in the indication
thereon of the depths of water required over two or more weirs to make a total
volume of water equal to the same quantity when flowing over one weir. Conversely,
the volumes of water flowing over two or more weirs in respect of given depths
may be read on the rule and the equivalent depth for the total volume as for one
weir ascertained.
By the provision of the sliding central member of the slide-rule the instrument
is adapted to regulate the depth of water where two or more gauge weirs are used
in conjunction, so that when a change is made in the volume passing over one weir,
the alterations necessary in respect of the other weir or weirs to provide for such
change without affecting the original volume are indicated.
The instrument is adapted also for use in regulating the flow of water in cases.
where it is supplied in part over a weir or weirs, and in part by pumping.
The leading feature of the invention consists in the graduations for depths being
divided differentially and in opposite directions upon the slide and the lower member
so that they correspond for varying depths of water with the quantity graduations
of the upper member according to the formula for the flow of water.
As is obvious, the measures of volume and depth appearing on the instrument
may be expressed according to the metrical or other system.
In the accompanying sheet of drawings, Fig. 1 represents, in face view, a slide-
rule made according to this invention and graduated in accordance with the system

page_text: appertaining thereto. The instrument consists of an upper member a, a lower
member b, and a central member c: The members a and b are fixed. The inember c
is free to be slid longitudinally between the members a and b. The instrument
illustrated is graduated in British measures and to adapt it for use in respect of a
weir of a width of 3 feet. For a different width of weir the 'graduations would
require to be re-set. Each major graduation on the member a indicates a million
gallons per 24 hours. These are subdivided into tenths of a million. Each major
graduation on the central member c indicates an inch. These are subdivided into
balyes and again into quarters. The member is similarly graduated, but the
graduations are read from the opposite end.
With the slide e closed, as shown in Fig. 1, the instrument serves as a table
from which to read the quantities of water flowing over the weir at the depths
corresponding, as indicated by the position of the graduations on the member a in
relation to those on the member c. For example, it will be seen that the quantity
of water flowing over the weir at a depth of 7 inches is indicated on the instrument
as 2,500,000 per 24 hours-which is correct.
.
Another use of the slide-rule when the slide c is closed in, as shown at Fig. 1,
consists in the indication thereon of the depths of water required over two or more
weirs to make a total quantity of water equal to that flowing at a given depth over
one weir. For example, if the depth of water flowing over one weir be 12 inches
the quantity is read off as 5,600,000 galious. If it be desired to divide this flow in
equal quantities over two weirs, that is to say, 2,800,000 gallons over each, it
will be seen from the instrument that the depth of water for each is slightly over
7 inches.
Conversely, the depths of water flowing over two or more weirs having been
ascertained, the equivalent depth of water necessary in respect of one weir to give
the same total quantity is indicated.
At Fig. 2 is shown a face view of the instrument in which the slide c is partly
drawn out towards the right. It is shown thus drawn out to illustrate the application
of the instrument in its use for regulating the depth of water where two or more
gauge weirs are used in conjunction, so that on a change being made in the quantity
passing over one weir the alterations necessary in depth of water in respect of the
other weir or weirs can be found from the instrument.
For example, in a case where the depth of water flowing over one weir is 9 inches,
and it is required to increase it to 12 inches and make an equivalent reduction over
another weir over which the depth of water is 6 inches, the slide c is drawn towards
the right until the graduation thereon indicating 64 inches is brought opposite the
graduation on the lower member b indicating 9 inches. It will then be seen, as
shown at Fig. 2, that the graduation on the lower member 6 indicating 12 inches is
opposite the graduation on the slide c indicating 2 inches which is the depth of flow
required over the second' weir.
Similarly, if it be required to decrease, to a given amount, the quantity flowing over
one weir, the equivalent necessary increase in depth over a second weir can be readily
ascertained, being simply the converse of the example last described.
If the quantities set out in the top member a be disregarded, the instrument serves
as a guide for regulating alterations over two weirs of any similar widths when
dividing the total quantity to give the same aggregate.
At Fig. 3 the slide c is shown drawn out towards the left for the purpose of
illustrating the application of the instrument to cases where the supply of water is
in part over a weir and in part by direct pumping.
For this application the upper member a bears, in addition to the graduations
aforesaid and the numerals at the major graduations, other lines, numerals, and
asterisks. In the example shown in the drawings, the numerals 1-120; 1-150; 2-120
and 2-150 appear. These refer respectively to one pumping engine of 120 horse
power, one engine of 150 horse power; two engines of 120 horse power, and two
engines of 150 horse power. The asterisks are placed upon lines which indicate in
gallons per 24 hours the quantities pumped by the respective engines.
:

page_text: Assuming that while the water to the depth of 94 inches is flowing over a gauge
weir, an engine of 150 horse power is started to pump. Now in order to ascertain
the depth to which the water flowing over the gauge weir must be reduced, the slide c
is drawn out to the left until the graduation 9 inches is opposite the line corre-
sponding to 1-150, as shown at Fig. 3. It will then be seen that opposite the zero
of the upper member a is the graduation indicating 6 inches which is the depth to
which the water must be reduced to balance.
Conversely, in cases of cessation of pumping, if the depth of water flowing over
the weir be set opposite the zero of the upper member a, the proper depth to which
the water should he increased will be that opposite the line indicating the engine.
At Fig. 4 is shown a modification of the instrument. According to this modification
the members a, b, and c, are arranged concentrically as a circular disc. The member c
is free to be rotated between the other two which are fixtures. The instrument
being graduated as for a weir of 3 feet in width, the graduations in each member
are of the same value as those shown in the example at Figs. 1, 2 and 3. The instru-
ment is shown as set to the same position as in Fig. 1 and illustrates the same
example.
The central member c is turned between the other members by a pinion carried on
a spindle turned by the means of the milled head e. This pinion gears with a
rack secured to the central member c. The mechanism for turning the member c is
analogous to that employed for winding the spring in a "keyless watch.
As before stated, the instrument hereinabove described and shown in the
accompanying drawings is graduated for use in respect of a weir of 3 feet in width.
For different widths the graduations must be differently set. The system of
differential graduation in opposite directions of the members c and 6 so that they
correspond for varying depths of water with the quantity graduations of the upper
member according to the formula for the flow of water is however maintained in
varying widths of weirs. Similarly, the graduations may be set on the same system
for any form of discharge weir or opening.
Having now particularly described and ascertained the nature of this inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
(1.) A slide-rule for indicating and facilitating regulation of quantities of water
flowing over gauge weirs; consisting of a fixed member a graduated to indicate
quantities of water in respect of a weir of a given width, and members b and c of
which bis fixed and c free to slide, both b and c being differentially graduated from
opposite ends to indicate depths of water flowing over a weir of the said given width
according to the formula for the flow of water, the slide c being situated between
the other two members, substantially as herein before described with reference to
Figs. 1, 2 and 3 of the accompanying drawings.
(2.) The modification under which the members graduated after the same principle
as in the instrument claimed in the foregoing claim are arranged in the form of
rings concentrically disposed, the inner and outer rings or members being fixed and
the intermediate ring or member free to turn between them, substantially as described
with reference to Fig. 4 of the accompanying drawings.
Dated this 3rd day of November 1896.
NICHOLAS WATTS,
Bristol, Chartered Patent Agent.