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          Wynne-Roberts’ hydraulic calculator

    This thin booklet, 12x16 cm in size, is titled “Wynne-Roberts’ Hydraulic Calculator for water mains and circular sewers”, and its red cloth-bound cover hides a surprise: open it, and you see a notebook bound onto on the left cover, and a complicated circular logarithmic slide rule built into the one on the right!
    The calculator is made entirely of cardboard, and consists of five rings, of which the second and fourth can independently rotate about the others (and are equipped with cardboard tabs to push them around by).The rings are calibrated to read velocity, pipe inclination, flow rate, and related pipe diameters. The construction is quite precise, with the two movable green rings rotating smoothly and without any jitter. The entire device, in fact, is produced with meticulous attention to quality and aesthetics.
    The notebook contains the instructions, given as a series of example calculations; there is also a table of “Proportional values of velocity and discharge for circular sewers at various depths” and a list of “Different coefficients for ‘n’ ”.
Wynne-Roberts' hydraulic calculator - cover
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All this takes eight pages, followed by four sheets of blank square ruled paper – divided into inches and eights – for any notes one may want to jot down.
Wynne-Roberts' hydraulic calculator - open
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    The photo at right below shows the calculator set up to execute Example I in the instruction sheet shown at the left.
Wynne-Roberts' hydraulic calculator - instructions  Wynne-Roberts' hydraulic calculator - example I calculation
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    This nifty little calculating device was published in London, and was designed by R.O. Wynne-Roberts. This was Robert Owen Wynne-Roberts, MICE (Member of the Institution of Civil Engineers), FRSI (Fellow of the Royal Sanitary Institute), who was born in Liverpool in 1864, and had a distinguished career as a City and Water Engineer in Wales, South Africa, and Canada. He died in Toronto in 1935.
Exhibit provenance:
    Ebay, from a seller in the UK.
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