This thin booklet, 12×16 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 the left cover, and a 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’ ”.
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.
The photo at right below shows the calculator set up to execute Example I in the instruction sheet shown at the left.
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.
Hello Sir. My name is Bruce Laughlen. My grandmother was sister to R.O. Wynne-Roberts. We have some pictures of South Africa from his time there but curious where you saw this calculator. I would love to find one to have in the family as quite a few family members are also engineers in Canada and a couple in UK and elsewhere.
Thank you for reaching out! I found this on eBay, so you may want to have a saved search for this there – you never know when one may pop up!