I will be adding more slide rules to these pages as my collecting progresses as there are more than a hundred known rules by Blundell Rules Ltd and Blundell Harling, as well as hundreds of slide charts and other specials.
Blundell Rules Ltd Humidity Slide Rule Mk 6, Ref No MET 22000, MO 3247/68. A specialist plastic slide rule with reversible cursor for scales on reverse. For calculating relative humidity from wet and dry bulb thermometer readings. Complete with card case.
Blundell Rules Ltd, Met Office Humidity Slide Rule Mk IV. Farenheit version, the Celsius Mk 6 is shown below. A duplex plastic rule with reversible cursor. The scales are: used to calculate vapour pressure, relative humidity and dew point from psychrometer readings. It has a green, cloth covered card case.
Paper Facts & Figures Paper Calculating Rule ©1965. Open frame plastic construction slide rule with instructions and further scales on reverse. For calculating the weight of various quantities of paper in both standard and non-standard sizes. Complete with blue cloth covered card case. Although not marked as such was almost certainly made by Blundell Harling who also made a metric version, see below. The blank is that used for the Academy 300 series.
Wavin Pipe Friction Computer and Metrication Converter made by Blundell Harling no. P3259 for Wavin Pipes United Kingdom Ltd, ©1969, designed by A D Calthorpe, C.Eng, MICE, AMIWE. Ii is based on an Academy Duplex blank and has a card stiffened vinyl wallet case and a laminated instruction slip. One side is imperial and the other metric but both sides perform the same function and the double sided cursor can be used to convert any parameter from imperial to metric or vice versa., Scales are labelled A to G with outside them inch or cm scales (above) and gallons or litres scales (below). The computing scales are: A - gauge marks for different classes of BS PVC pipe and nominal diameter, B - pipe internal diameter, C and D - flow rate in different units, E - pipe length, F - friction loss (head), G - friction loss {pressure).
Fisher Control Valve Sizing Rule Mark VII made by Blundell Harling (P2734) for GEC-Elliott Control Valves Ltd, Rochester, England. ©1967. This duplex plastic rule has 17 specialist scales for gases, steam and liquids from which the size parameters Cv, Cg or Cs can be determined given pressure drop, inlet pressure and flow rate, specific gravity (liquid) or inlet density (gas/vapour), temperature and degree of superheat (steam). The rule has a fabric backed PVC slip case. This is an imperial rule. A metric mark VIE by IWA is illustrated in the “Other German” page. Several versions of the Fisher rule were made including one by Pickett for the American Fisher company.
Blakeborough Valve Sizing Slide Rule and valve chart made by Blundell Rules Ltd in Weymouth. The chart is dated October 1959. The upper face was used for liquid flow to calculate the flow coefficient Cv on which basis the correct size of valve could be selected from the chart. The lower face was for gas and steam flow.
Blundell Rules Ltd, Weymouth, P1442 Friction Loss Calculator made for Shell-Mex and BP Ltd. Fabricated from plastic, there is no cursor and the slide is reversible. The scales on the body front are: pipe length ft actual, pipe length ft equiv, friction loss ins W G (inches water gauge). The slide has instructions on one side together with scales of flow rate in BTU/HR for three values of temperature difference and in gallons/hr for 3/4” copper pipe, and similar scales for 1/2” copper pipe on the reverse. The back of the rule has tables on it for emission for radiators, and 1/2” and 3/4” copper pipe. Ca.1962.
Blundell Omega Slide Rule Artillery 10” Mils Mk 2. A closed frame slide rule made of plastic with two plastic cursors (replacements). Scales are A{B,C}D//{S,ST,T}. The trig scales are in mils (6400 mils = 360 degrees). There is a metres at 1/50,000 rule on the upper edge extension and there are instructions and formulae on the back. NATO stock number 1290-99-960-0933. Green cloth covered card case
Blundell Rules Ltd P2297 Torpedo Spreading Slide Rule Pattn. No. 0552-160221 dating from about 1964, made for the Royal Navy. It has two slides and was used to calculate the firing interval for a salvo of torpedoes given the target range and speed, its length and the desired spread, as well as angle to bow on firing. It has a varnished wood case.
The metric version of the Paper Facts & Figures Paper Calculating Slide Rule ©1969, P3188. This is a duplex rule with fifteen specialist scales covering both paper and board. It has a quality vinyl wallet and instruction booklet.