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Blundell-Harling (BRL) Slide Rules


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Blundell Rules Limited (B.R.L.) was a British manufacturer of slide rules in Luton, England. BRL originated as an effort to create ongoing post-war work for a machine shop created during WW2. The Blundell G1, was their first slide rule (c.1947-1949) which was made of laminated black Bakelite. This highly brittle material was used for two years before switching to Astralon (PVC) as the prior material had a 40% reject rate. BRL later moved to Weymouth in the UK in January of 1956 and refined their rule making techniques, with the British government as a prime customer. The B.R.L. logo was used at this time. In January of 1964, BRL purchased the assets of W.H. Harling Limited of Clapton, London, and with it, a line of precision drawing instruments, T-squares and related items. Harling had previously made wooden slide rules, but dropped them in favor of its other instruments. The resulting company became Blundell-Harling, and stayed in Weymouth which still manufactures specialist drawing equipment.

See the 24.5" long BRL and Blundell-Harling Pilot Balloon Slide Rules in the Aerospace gallery


P146 Blundell-Luton TypeP8
Blundell-Luton TypeP8 (c1947-49)
Made in England - Bakelite and paper veneer construction
Front Scale
A [ B, CI, C ] D
Back: Conversions


REF Blundell-Luton TypeP10
Blundell-Luton TypeP10 (c1947-49)
Made in England
Front Scale
6in // Cube (K), A [ B, REC (CI), C ] D, MAN (L)
BackScale
[ S, S&T, T ]
Archive - Owned by Brailsford Sykes. Scan and photo donated by son John Sykes (UK)
Brailsford Sykes, born 1926 in Huddersfield, Yorkshire. He joined Brook Motors at age 16 as an apprentice, and subsequently "graduated" with a gold medal in 1946. He became an expert in the theory and practical application of induction motors, and was rapidly promoted to a managerial position in the company, running the Sheffield technical sales office. This was from 1950 to 1974, and the attached photo was probably taken mid-60's at his office desk. You can see the Blundell in his top pocket. He retired from the company (taken over by Hawker Sidley and then amalgamated with Crompton Parkinson) in 1984.


REF Blundell Type G1
Blundell Type G1 (c.1947)
Made in England - Blundell's first slide rule model
Stock made of black Bakelite with laminated scales
Front Scale
K, A [ B, Reciprocal(CI), C ] D, L
Back : Blank


S367 BRL Students Type-1
BRL Students Type-1 (c.1950's)
Made in England - Stock made of Astrolon
Note: the BRL text was scratched out of the logo
Front Scale
K, A [ B, R, C ] D, M
Back: Simple instructions
Multiple hairlines


BRL AL4

ISRM 14.02.10.02

BRL AL4 (c1956)
Made in England
Front Scale: 10in // UL, A [ B, REC (CI), C ] D, LL
BackScale: 26cm
Note the two steel rods that are putting tension on the slide and keeping it tight.
Gift of Jane Northcote, UK, in memory of her father Donald Northcote
Donald Henry Northcote (1921-2004), Professor of Plant Biochemistry, University of Cambridge, England, and Master of Sidney Sussex College Cambridge, from 1976 to 1992. He used the aove slide rule in his scientific work. Prof. Northcote was a laboratory scientist: a chemist and electron microscopist. His laboratory was in the Department of Biochemistry, Tennis Court Road, Cambridge, England. He has another slide rule in the Aristo gallery. His daughters, Jane and Mary, also have slide rules displayed on ISRM in the Thornton and Hemmi galleries.


S214 BRL G29 - Students Model
Blundell Rules Ltd. G29
Made in England, Luton Beds - Pat. No. 644944
Front Scale (extended)
10in // A [ B, R, C ] D
Back Side: [ S1 cos, L, T  ctg ] 26cm
Back Adv: The British Inst. Of Engineering Technology


BRL P2361 - Westec Electronics Slide Rule

ISRM 13.04.26.02
BRL P2361 - Westec Electronics Slide Rule
Made in England by B.R.L. (ref P2361) for Westechno. Ltd., Exmouth, Devon, England
Patents: Provisional No.49828
Front Scale
(Lr)H, K, (fx)2π, A [ (Cr)B, S Cos, T Cot, (Lx or Cx)CI, XL or fr) C ] D (XC), L, Ln, ST
Back: Design aids for Reactance, Resonance, Temperature, Ohm's Law, Frequency and Wavelength, Equivalents, etc.
Note: This is the only slide rule, besides those made by Pickett, to have an 'Ln' scale
Gift of Phillip Rodley, Upper Hutt, NZ
Phillip Rodley


B-R-L T.50 Janus Series Duplex

REF
B-R-L T.50 Janus Series Duplex
Made in England by BRL
Front Scale:
L, LL1, DF [ CF, CIF, CI, C ] D, LL3, LL2
Back Scale:
LL0, LL00, A [ B, T, Cot, ST, S, Cos ] D,
DI
, K
Scan provided by the Steve Seale Collection, Nashville, Tennessee


Blundell Harling T-50 Janus Series Duplex

REF
Blundell Harling T-50 Janus Series Duplex
Made in England by Blundell Harling
Note: has BRL T.50 model number but with different scales
Front Scale:
S1, A [ B, Ta, Tb, ST, S, C ] D, K, L.
Back Scale:
ICAN temperature, temperature conversion, altimeter correction, P&D alt.[ Temp., Air temp.,C1, Dens.alt., C ] D, SM, KM.
Scan provided by the Steve Seale Collection, Nashville, Tennessee


BRL N52 Aviation Janus Series Duplex

ISRM 14.07.22.03
BRL N52 Aviation Janus Series Duplex
Made in England by Blundell Harling
S1, A [ B, Ta, Tb, ST, S, C ] D, K, L.
Back Scale:
ICAN temperature, temperature conversion, altimeter correction, P&D alt.[ Temp., Air temp.,C1, Dens.alt., C ] D, SM, KM.
Gift of Phillip Rodley of Upperhutt, New Zealand.


Blundell Harling S143-20

ISRM 09.01.12.100
Blundell Harling S143-20
Made in England
Front Scale
K, A [ B, CI, C ] D, L
Back Scale: Blank
Multiple hairlines
Donated by David Hecht,Alexandria, VA


S237 BRL Academy 304 Darmstadt
BRL Academy 304 Darmstadt
Made in England - Blundell Rules Ltd.
Front Scale
L, K, A [ B, CI, C ] D, P, S, T
Back Scale: [ L1, L2, L3 ]
Original Owner: P. Burt/England, England


S359 Blundell Omega 401 Rietz
Blundell Omega 401 Rietz
Made in England
Front Scale
11in // K, A [ B, CI, C ] D, L
Back Slide: [ S, S&T, T ]
Original Owner: D.H. Carpenter, England


Blundell Omega 405 Basic

ISRM 09.01.12.101
Blundell Omega 405 Basic
Made in England
Front Scale
11in // A [ B, C ] D
Back: Blank
Donated by David Hecht,Alexandria, VA


Blundell Harling A504 Super Duplex

REF
Blundell Harling A504 Super Duplex
Made in England
Front Scale:
Gauge Points, S1 Cos1, A [ B, TA, TB, ST, S, Cos, C ] D, K, L
Back Scale:
P, DF [ CF, CIF, CI, C ] D, LL3, LL2
Multiple hairlines
Scan provided by the Steve Seale Collection, Nashville, Tennessee


Blundell Harling 506 Academy Duplex

REF
Blundell Harling 506 Academy Duplex
Made in England
Front Scale:
LL01, LL02, LL03, DF [ CF, CIF, CI, C ] D, LL3, LL2, LL1
Back Scale:Sinh1, Sinh2, Tanh, A [ B, T, Cot, ST, S, Cos ] D,
DI
, K, L
Multiple hairlines
Scan provided by the Steve Seale Collection, Nashville, Tennessee


Blundell Omega 602 Log-Log

ISRM 09.01.12.102
Blundell Omega 602 Log-Log
Made in England
Front Scale
6in // LL2, A [ B, CI, C ] D, LL3
Back Slide: [ S, S&T, T ]
Donated by David Hecht, Alexandria, VA


P166 Blundell 604 Electro
Blundell 604 Electro (Omega Series)
Made in England
Front Scale
6in // LL2, A(Kw) [ B, CI, C ] D, LL3
Well: Voltage Drop, Gen Eff/Mot Eff, Gen/Mot
Back Slide: [ S, L, T ]
Back Adv: Northern Electric
Orig Owner: H.A. Ashton


P049 Blundell Omega 606
Blundell Omega 606
Made in England
Front Scale
6in // A [ B, CI, C ] D
Back Slide: [ S, S&T, T ]
Back Adv: Dustraction Ltd. Leicester


S092 Blundell Harling 803
Blundell Harling 803
Made in England
Front Scale
L, K, A [ B, CI, C ] D, S, T, ST
Back: Blank
Multiple hairlines
Original Owner/Location: NIB/England


Blundell Harling Classmate 812-1

ISRM 09.01.12.103
Blundell Harling Classmate 812-1
Made in England
Front Scale
S, T, A [ B, CI, C ] D, K, L
Back Scale: Blank
Multiple hairlines
Donated by David Hecht,Alexandria, VA


Blundell Harling Classmate 813

ISRM 09.01.12.104
Blundell Harling Classmate 813
Made in England
Front Scale
S, T, A [ B, CI, C ] D, K, L
Back Scale: Blank
Multiple hairlines
Donated by David Hecht,Alexandria, VA


S347 Blundell Harling 904 Academy
Blundell Harling 904 Academy
Made in England
Front Scale
ST, A [ B, CI, C ] D, S, T
Back Scale:
K, L, DF [ CF, CIF, C ] D, LL2, LL3
Multiple hairlines
Original Owner/Location: NIB/England
Note: (per David M. Riches, UK) This appears to have been made using the school series S143-10 blank which is narrower than the 800 series blank, but still part of the 'Academy' series.


REF Blundell Omega 909 Left-handed
Blundell Omega 909 Left-handed
Reversed scales (compare with Blundell 606)
Made in England (c.1970)
Front Scale
6in // A [ B, C, C ] D
Back Slide (not verified): [ S, S&T, T ]
Archive - Ron Manley collection


REF BRL S100
Blundell Rules Ltd S100
Made in England
Front Scale (extended)
A [ B, C ] D
Back Adv: Pirelli General (tire)
Archive - Chris Gillings collection


REF BRL S101
Blundell Rules Ltd S101
Made in England
Front Scale (extended)
6in // Cube(K), A [ B, Rec (CI), C ] D Man.(L)
Back: Unknown
Archive - Peter Owen collection (England)


P155 Donkin S101
Donkin S101 (circa 1977)
Made in England by BRL for Donkin and Company Ltd (Marine Steering Eng)
Front Scale:  6inch // Cube, A [ B, Rec, C ] D, Man
Back: Blank


P022 BRL P19
Blundell Rules Ltd P19
Made in England
Front Scale
6inch // A [ B, REC, C ] D
Back: 15cm, Adv: Automatic Telephone and Electric Co, Ltd.
Original Owner/Location: Unk/England


P007 BRL Avergi
Blundell Rules Ltd Avergi
Made in England
Front Scale
13cm // A [ B, CI, C ] D, K || 5inch
Back Slide: [ S, L, T]
Original Owner/Location: Unk/England


Fisher Controls - Valve Sizing Slide Rule Blundell Harling FC3540

ISRM 12.07.16.01
Fisher Controls - Valve Sizing Slide Rule Blundell Harling FC3540
Made in England for Fisher Controls (1967)
Front Scale (Side A)
P (Pressure Drop - PSI), %QC2 [ P1 (Inlet Pressure), Gas Specific Gravity, Temp, Super Heat, C1, Q (Flow) ] Cg-Gas, Cs-Steam, %QC1
Back Scale (Side B)
P (Liquid Pressure Drop), %QC2 [ P1 (Inlet Pressure), Inlet Density, Flow, Q ] Liquid Cv, Gas Cg


Blundell Harling P3867 POST OFFICE TELECOMMS Voltage Drop Calculator

REF
Blundell Harling P3867 POST OFFICE TELECOMMS Voltage Drop Calculator
Made in England.
Front Scale (Inches - Feet)
A (AREA Square inches) [ L (GO & RETURN LENGTH), V (VOLTAGE DROP) ] IAl (CURRENT - Aluminum), ICu (CURRENT - Copper)
Back Scale (Millimetres - Metres)
A (AREA Square inches) [ L (GO & RETURN LENGTH), V (VOLTAGE DROP) ] IAl (CURRENT - Aluminum), ICu (CURRENT - Copper)
Archive - Scan by Steve Seale Collection, Nashville, Tennessee


Nelson-Jones Circuit Designers Slide Rule 1974 Key Electronics

REF
Nelson-Jones Circuit Designers Slide Rule 1974 Key Electronics
Made in England by Blundell Harling for Key Electronics 1974, England.
Front Scale: dB, A [ B, CI, C ] D, LL3, LL2
Back Scale (Impedance Calculator): Ohms [ L&C, Frequency ] Ohms
Archive
Instructions

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