Blundell Harling

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.

Blundell, Luton, G2 closed frame, Bakelite slide rule with metal & glass cursor. Scales are: K,A{B,C1,C}D,L. Dating from 1947-9 it has a very novel, and heavy, Bakelite case which opens from the side.

Blundell Rules Ltd AG1 plastic, closed frame 10” slide rule. Scales are in\K,A{B,C1,C}D,L. Batch No. 4826. Dates from the 1950s.

Blundell Rules Ltd L4 simplex, 10” closed frame slide rule, made of Bakelite with a metal and glass 2 line cursor. It dates from 1947-9. Scales are UL,A{B,C1,C}D,LL. It is complete with instruction booklet and imitation leather covered wood, hinged case. Batch number 1547.

Blundell Rules Ltd L6 simplex, 10” closed frame slide rule, made of Bakelite with a metal and glass 3 line cursor. It dates from 1947-9. Scales are UL,A{B,C1,C}D,LL//{S,ST,T}. There is a cursor in the rear of the body for the trig scales on the slide and there are tables on the back. The card case is worn and very faded from its original green colour. Batch no. 2164

Blundell Rules Ltd P14 five inch closed frame slide rule, made of Astralon, with a metal and glass cursor. It dates from the 1950s. Scales are K,A{B,C1,C}D,L//{S,ST.T}. There is a cursor in the rear of the body for the trig scales on the slide and there is an advert on the back for Damson-Alliance, Crane Builders. It has a leather slip case.

Blundell Rules Ltd G22/2 ten inch plastic closed frame slide rule with blue card case. An extremely basic rule with just A{B,C}D scales. It was made for the Stationary Office, having S crown O stamped on the back.

Blundell Rules Ltd G29 10” closed frame slide rule, made of Astralon with Diakon cursor. Scales are in\A{B,R,C}D//cm{S,L,T}. Students Model made for the British Institute of Engineering Technology. Complete with battered card case.

Blundell Rules Ltd Academy 302 Log Log ten inch plastic open frame simplex slide rule. It has a buff coloured, cloth covered card case and instruction leaflet. The scales are: K,LL2,LL3,A{B,C1,C}D,L,T,S. It dates from about 1960. The 300 series were replaced by the Blundell Harling 800 series of which there are examples on the next page.

Blundell Rules Ltd Academy 300 open frame simplex 10” plastic slide rule. It has a blue/clear vinyl case and instruction leaflet B19. Scales are: K,A{B,C1,C}D,L.

Blundell Rules Ltd Academy 304 Darmstadt open frame, simplex 10” plastic slide rule. It has a blue/clear vinyl case. Scales are L,K,A{B,C1,C}D,P,S,T//{LL1,LL2,LL3}.

Blundell Rules Ltd Academy 307 Air Navigation ten inch plastic open frame simplex slide rule. It has a card case, instruction leaflet and instruction card and dates from circa 1960. The general scales are T,A{B,S,C}D. The specialist scales include: temperature, air temperature, altitude, ICAN temperature, temperature conversion, and altimeter correction. There are formulae on the reverse of the slide and a series of gauge points along the top of the body in addition to those on the scales.

Blundell Rules Ltd Academy 305 Electro 10” open frame, plastic slide rule. Scales are Voltage Drop, Motor & Dynamo efficiency, 3 phase motor efficiency, A{B,C1,C}D,K,LL2,LL3//{S,L,T}. It has a blue/clear vinyl case, instructions, guarantee certificate and retail carton. Early 1960s.

Blundell Rules Ltd Academy 306 Tarrant Hydraulic Slide Rule: Flow in Pipes and Circular Sewers supplied by the Paterson Engineering Co Ltd, Kingsway London WC2. 10” open frame plastic slide rule with a buff coloured card case, BNIB, ca.1960. Based on the Hazen-Williams formula.

BRL Janus HF55 Tarrant Hydraulic Slide Rule: Flow in Pipes & Circular Sewers; Flow in Open Channels with blue card case, missing cursor, supplied by Paterson Engineering Co. Duplex plastic rule with metal end braces. Pipes side based on Hazen Williams formula, open channel side based on Manning formula.

Blundell Rules Ltd Academy 303 Rietz ten inch plastic open frame slide rule. It has a light blue cloth covered card case. The scales are: L,K,A{B,C1,C}D,S,ST,T.

Blundell Omega 401 Rietz slide rule. It is closed frame, plastic and ten inch scale length and has a blue cloth covered card case. Scales are in\K,A{B,C1,C}D,L//{S,ST,T}.

BRL Janus T50 10” duplex slide rule. It has a black, imitation leather covered, hinged wood case. The 22 scales are: LL01,LL02,LL03,DF{CF,C1F,C1,C}D,LL3,LL2,LL1//L,P,A{B,T,ST,S}D,D1,K.

Blundell Rules Ltd P19D slide rule. An all plastic 5” closed frame rule with Diakon cursor dating from the 1950s, its scales are: inches\A{B,C1,C}D. It has a leather slip case. On the back of the rule “Geon” is printed, it being a promotional rule for them.

Blundell Rules Ltd T20 slide rule. This laminated PVC slide rule has a twenty inch scale length and a metal framed cursor. The scales are LL1,LL2,A{B,C1,C}D,L,LL3 in current nomenclature, although they are actually designated L,UL,A{B,R,C}D,M,LL.

Blundell Rules Ltd P15 five inch closed frame slide rule, made of Astralon, with metal and glass cursor, and a leather slip case, dating from the 1950s. Its scales are: in\A{B,C1,C}D//(S,ST,T}.

Blundell Rules Ltd P16-C five inch, closed frame electrical slide rule, made of Astralon, with plastic cursor, and a leather slip case, dating from the 1950s. Its scales are cm\UL,A{B,Cos,°F,°C,C}D,LL//{S,ST,T}in//D&M,V(in well)

Blundell Rules Ltd P16 five inch, closed frame electrical slide rule, made of Astralon, with a leather slip case, dating from the 1950s. Its scales are in\UL,A{B,Cos,°F,°C,C}D,LL//{S,ST,T}cm//D&M,V(in well)

BRL P17 five inch, closed frame log-log slide rule made of Astralon, with a leather slip case, dating from the 1950s. Its scales are in\LL2,A{B,C1,C}D,LL3//{S,ST,T}cm

Blundell Rules Ltd T11 ten inch Astralon slide rule with patent tension adjustment for the slide. This was one of their “Technicians” rules dating from 1955. Scales are inches\LL1,LL2,A{B,C1,C}D,P,LL3//{S,ST,T}cm. It has an imitation leather covered wood case. Batch No. 4373.

Blundell Rules Ltd P8 closed frame Bakelite 5” slide rule. It has a leather slip case. Scales are: A{B,C1,C}D. Batch number 1843. Promotional rule for ICL Combustion (International Combustion Ltd).

5” plastic closed frame slide rule with metal framed cursor “Made in England” unsigned but by BRL. Printed on the back “John Thompson Water Tube Boilers Limited, Wolverhampton”. Scales are A{B,C}D. Black PVC slip case, possibly not original as it is rather too wide. Stator and slide dimensionally identical to BRL P8 above but different material. Some P8s had this type of cursor rather than that above.

Blundell Rules Ltd AL6 closed frame 10” Astralon slide rule with three line cursor. This is the plastic version of the earlier Bakelite L6 slide rule illustrated above. It dates from the 1950s. It has a card case. Scales are: inches/UL,A{B,C1,C}D,LL//{S,ST,T}.

Blundell Rules Ltd U7 simplex, 10” closed frame slide rule, made of Bakelite with a metal and plastic 2 line cursor. It dates from 1947-9. Scales are UL,Cube,A{B,S,S&T,T,Rec,C}D,Man,LL. It is complete with instruction booklet (with three supplementary leaflets) and cloth covered card case (battered). Batch number 609.

Blundell Rules Ltd AG5, 10” closed frame slide rule made of Astralon, with a metal and glass 3 line cursor. It dates from the 1950s. The Rietz pattern scales are in\K,A{B,C1,C}D,M//{S,ST,T}. It has an imitation leather covered wood, hinged case.

BRL G5 Bakelite slide rule dating from 1947-9. The Rietz pattern scales are K,A{B,C1,C}D,L//{S,ST,T}. Batch number 413. Two line metal & glass cursor.

This S100 slide rule is identical to the one above apart from the cursor design and the addition of the ‘S100’ model number at the bottom left. It has a brown leatherette slip case. It has “Weston Oil Seals” on the reverse. It too is unsigned but is known to be Blundell model.

BRL E13 ten inch electrical slide rule with patent tension adjustment for the slide. Scales are: inches\K,LL1,LL2,DF{CF,C1F,C1,C}D,P,LL3,A//{S,ST,T,L}cm. It has an imitation leather covered wood case.

BRL Rule Slide RA 10” VF0129. It has a green cloth covered card case. The scales are in\A{B,C}D//S,L,T

BRL Student’s slide rule Type 2. A 10” closed frame plastic slide rule, it has a black card box. The scales are: UL,A{B,R,C}D,LL with inch and cm rulers on the back.

Blundell Rules Ltd E3 closed frame, 10” electrician’s Bakelite slide rule with metal & glass cursor. Scales are:Voltage drop{A{B,S&T,C}D,motor/dynamo. It dates from 1947-9 and has a black card case.

Blundell Omega 405 Basic closed frame ten inch plastic slide rule. Scales are in\A{B,C}D. Complete with blue cloth covered card case, instruction booklet and adjusting screwdriver.

Blundell Rules Ltd Omega 406 Simplified Rietz plastic 10” closed frame slide rule. Scales are: in\A{B,C1,C}D//{S,ST,T}. It has a blue card case.

Blundell Omega 606 Simplified Rietz 5” closed frame simplex slide rule made of plastic. It has a leather slip case with the “AVRO” logo on. Scales are: in\A{B,C1,C}D//{S,ST,T}.

Blundell Rules Ltd Omega 410 ten inch, closed frame, plastic slide rule. The special feature of this rule is the folded CF and DF scales Its scales are: in\A,DF{CF,C1,C}D,K//{S,L,T}. It has a blue cloth covered card case, typical of Omega ten inch rules. Probably ca.1960.

Blundell Rules Ltd Omega 601 Rietz five inch, closed frame, plastic slide rule. It has a leather slip case. Its scales are: in\K,A{B,C1,C}D,L//{S,ST,T}. 1960s. Promotional for Woodhead-Monroe shock absorbers.

Blundell S125 5” plastic slide rule for school use. Scales are: K,A{B,C1,C}D,L. It is complete with paper sleeve and instruction leaflet. It is laminated from alternate layers of white and clear plastic, as is the slide.

Blundell Harling Descal 315 circular slide rule, 7.8 inches diameter, made about 1970. It has a brown PVC wallet. The scales are: LL(2 turn), D/C,C1,A,K.

Blundell Academy Duplex 505 ten-inch plastic slide rule. It has a blue velvet lined PVC wallet. The scales are: LL01,LL02,LL03,A{B,L,C1,C}D,LL3,LL2,LL1//T,ST,DF{CF,C1F,C1,C}D,P,S. One end brace has a piece missing and the other has been broken and glued together, but it still functions OK. Complete with BRL instruction booklet and Blundell Harling guarantee, it will date from ca.1964.

BRL Janus N52 Air Navigation 10” duplex slide rule dating from ca.1960. It has a blue cloth covered card case. The front scales are: S1,A{B,Ta,Tb,ST,S,C}D,K,L. The scales on the back are: ICAN temperature, temperature conversion, altimeter correction, P&D alt.{Temp., Air temp.,C1, Dens.alt., C}D,SM,KM.

Blundell Academy Duplex 502 10” plastic slide rule. It has a black PVC press stud fastening case. The scales are: L,K,A{B,C1,C}D,LL3,LL2,LL1//T,ST,DF{CF,C1F,C1,C}D,P,S. Complete with Blundell Harling instruction booklet and guarantee.

Blundell Omega 604 Electro slide rule. A 5” slide rule with a leather slip case probably ca.1960, promotional for Permali whose name is on the back of the rule. Scales are in\LL2,A{B,C1,C}D,LL3\voltage drop, motor & dynamo efficiency, ditto 3 phase//{S,L,T}. There is a clear plastic index on the left end of the slide for reading the scales in the well.

BRL Omega 603 Darmstadt closed frame 5” plastic slide rule.It has a leather slip case with the Rolls Royce logo on it. Scales are: in\L,K,A{B,C1,C}D,P,S,T//{LL1,LL2,LL3}. Rolls Royce Ltd printed on back of slide rule

Blundell Academy Duplex 500 slide rule. A 10” plastic rule with the following scales: L,K,A{B,C1,C}D,LL3,LL2//T,ST,DF{CF,C1,C}D,P,S. It has a blue/clear PVC wallet. J W Stafford was presumably the original owner who stamped his name into the rule. A black marker had been used to obliterate this (hence the staining) and to write another owners name but I have removed these.

BRL S101 5” plastic slide rule made for Gibbon Brothers Limited whose name appears on the reverse. The scales are: in\K,A{B,C1,C}D,L. It has a leather slip case. Although only marked with the model number and “Made in England” it is clearly made by Blundell. See also the S100 near the top of this page.

BRL PG54 (Janus) duplex slide rule for the interpretation of aerial photos. Plastic with metal end braces. Made for MoD W10/WK/00148. It has a black leatherette covered, hinged wooden fitted case.

BRL A312 5” plastic open frame slide rule with plastic cursor. Scales are K,A{B,C1,C}D,L. It has a blue/clear PVC slip case.

Blundell Omega 605 Basic 5” closed frame plastic slide rule. Scales are: in\A{B,C}D. It has a leather slip case and also a polythene sleeve and guarantee slip.

Blundell Rules Ltd Omega 407 Technico plastic 10” closed frame slide rule. It has a blue cloth covered card case. Scales are: in\K,LL1,LL2,DF{CF,C1F,C1,C}D,P,LL3,A//{S,ST,T,L}.

Blundell Omega 404 Electro slide rule. A 10” slide rule with a blue cloth covered card case probably ca.1960. Scales are in\LL2,A{B,C1,C}D,LL3\voltage drop, motor & dynamo efficiency, ditto 3 phase//{S,L,T}. There is a clear plastic index on the left end of the slide for reading the scales in the well.

Blundell Rules Ltd Omega 409 Mercantile plastic 10” closed frame slide rule. It has a blue cloth covered card case. Scales are in\M1,month(days weeks,decrease and profit on return increase and profit on cost,C)D,M2,M3. M1, M2, and M3 are money scales from 1/- to £80 in three stages.

Blundell Rules Ltd Omega 602 Log Log five inch, closed frame, plastic slide rule. It has a leather slip case. Its scales are: in\LL2,A{B,C1,C}D,LL3//{S,ST,T}. 19060s

Blundell Omega 403 Darmstadt slide rule. It is closed frame, plastic and ten inch scale length and has a blue cloth covered card case. Scales are: in\L,K,A{B,C!,C}D,P,S,T//{LL1,LL2,LL3}.