Blundell Harling 4

Blundell Rules Ltd started making slide rules in about 1947 in Luton. In 1956 they moved to Weymouth. They merged with W H Harling of London, who were established drawing instrument makers, to form Blundell Harling Ltd, and moved the Harling business to Weymouth in 1964. They are still in business today at 9 Albany Road, Granby Industrial Estate, Weymouth, although they no longer make general purpose slide rules.

Double sided plastic slide chart made by Blundell Harling (P2537) for the British Standards Institution. A Conversion Slide in accordance with BS350. Conversions catered for are Area, Volume, Mass, Force, Pressure and Stress, Capacity, Length, Temperature and Gauges (wire). It has a blue/clear PVC sleeve and an instruction sheet.

Blundell Harling M958D Percentage Calculator ©1970. This plastic rule consists of a white bottom scale disc, a clear interleaf, a clear upper scale disc and a clear cursor. It was intended for use for calculating discounts and uplifts and instructions are printed on the reverse. It has a blue/clear PVC wallet.

Calculator Radiac No. 1 Mk. 2, 6665-99-780-8137 made by Blundell Harling. The five inch diameter plastic calculator has two rotatable discs for calculating the radiation dose received over a period of time from a nuclear explosion. These two discs are reversible, the red side being for use on land and the green at sea. It is housed in a khaki green wallet. The instructions are printed on the reverse of the calculator.

Radiac Calculator No.2 6665-99-949-1446 made by Blundell Rules Ltd. The five inch diameter card calculator has two rotatable discs for calculating the radiation dose received over a period of time from a nuclear explosion. The instructions are printed on the reverse of the calculator. This one is believed to have been made for Civil Defence use. Units are Roentgens/hour instead of the later Centigray/hour used on the calculator above.

Blundell Rules Ltd S121 Concrete Volume Computer. Made of folded plastic, the scales are 7 inches long. It has scales for thickness, width or height, length and cubic yards. This one was made for Brett’s Ready Mixed Concrete. The scales are similar to those on the Unique Concrete Volume Computer which can be seen on the Unique page

P2388 Flow Calculator for Everite Asbestos Cement Pressure Pipes made to BS486/1956. Made for Turners Asbestos Cement Co via Maxwell Jackson Ltd, Manchester.

Two versions of the Blundell Harling 0490-75 Concrete Volume Computer, ©1970. The upper one is branded for Diddimix Concrete of Leicester whilst the lower one is plain. BHL would make batches of these for various concrete firms and print the firms details on them. These were probably factory development items as they are unfinished and the plain one is not quite folded correctly (I have some unfolded blanks for that one).
The ‘A’ side of the calculator is for imperial - metric calculations and the ‘B’ side is for metric - metric calculations.

Blundell Harling 0655-31 Portland Speed-Time-Distance Calculator. It also carries a NATO stock number 6605-99-527-7217. This folded plastic slide chart was a standard catalogue item.

P5718 Imperial/metric conversion slide chart dating from the 1980s made for Texaco. A folded plastic outer with a plain card slide.

Blundell Harling P4174 slide chart for the sizes of pipe flanges and other fittings made for Shaikhan, Kuwait. It measures 10.6 x 5 inches.

Blundell Harling Metriverter M1769P made for G T Drawing Services Ltd. The conversions are the same as on the ELGA one above. These were made for several companies. It has a blue/clear PVC wallet.

Blundell Harling M3364D Pocket Discount & Profit Calculator. A 4.25 inch diameter plastic rule, it has a blue/clear PVC wallet. It is essentially a smaller,cheaper version of the Percentage Calculator above.

Slide chart made by BRL for Vickerys Ltd, London ca.1959/60 for the Bauer Centri-Clean. It is complete with instruction card and a vinyl slip case.

Paper-Machine-Production Calculator made by BRL in the 1950s for the Black-Clawson Company.

BRL S134 Timber Computer for calculating the volume of timber, trenches, etc.

Blundell Harling P4241 slide chart made for Broome & Wellington for textile property conversion from Imperial to Metric

Another Blundell Harling P4241 slide chart, this time made for Shirley Developments Ltd. The conversions are the same as the one above and the slide has been borrowed from that one as it is missing from this example.

Blundell Harling slide chart P3680 made for Panocean ©1971. The upper face is for weight calculation from the volume and specific gravity whilst the lower face is a metric/imperial converter. It has a red/clear PVC slip case.

Blundell Harling P5705 Theoretical Torque Calculator made for MHH Engineering Co Ltd (Torqueleader) for calculating the torque required to develop a particular percentage of the proof stress in a bolt given the proof stress (or bolt grade), stress area (or bolt size), friction coefficient (from table on reverse) and % of proof stress required. Made of plastic it has two rotating discs and a rotating cursor. The instructions are on the reverse. It has a clear plastic sleeve. ©1990. SI Metric Units for metric bolts.

Blundell Harling P5706 Theoretical Torque Calculator made for MHH Engineering Co Ltd (Torqueleader) for calculating the torque required to develop a particular percentage of the proof stress in a bolt given the proof stress (from table on the reverse), stress area (from table on reverse), friction coefficient (from table on reverse) and % of proof stress required. Made of plastic it has two rotating discs and a rotating cursor. The instructions are on the reverse. It has a clear plastic sleeve. ©1990. For Imperial Units (BS and Unified bolts)