- 455 Martinson, Los Angeles
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A man must have a hobby….
This non-commercial website was an amazing 60th birthday present from my soulmate Ros. But the website name is thanks to another family member - our daughter Siân. When asked as a teenager what I did, she often told her friends: “My dad? Oh, he collects expensive sticks of wood!”
When the latest computer is out-of-date inside 6 months, it may come as a surprise that the Rev. William Oughtred (1575-1660) invented his Circles of Proportion calculator around 1621. This analogue principle was in continual use for nigh on the next 400 years. My hobby is collecting and writing about this analogue calculating wonder - the SLIDE RULE. Over the years the concept was successfully adopted and adapted by many trades and professions. Remarkably being able to use such an elegant analogue instrument from a bygone age is still a licensing condition for all private and commercial pilots.
This website is a virtual “display cabinet” for my collection (as it gets uploaded) of slide rules, slide charts and mechanical calculating aids and a virtual “bookshelf” for my published articles.
My wish list
| Maker | Model(s) |
|---|---|
| A.W. Faber-Castell | 1/38, 8/13, 8/14, 8/15, 20/44/3 & 51/88 |
| Addiator GmbH | Octadat |
| AHREND (Wed. J. Ahrend & Zoon) | 649, 651, 696, 698, 699 & 701 |
| ALRO (All-Round) | 101, 10 RL, Beton, Cycloop, GoA, Ha.C/P/Q/V, Philips Calendar, Nomographie, Van Leer, Vonderlingenplaat & WeR4 |
| AWF (Ausschuss fuer Wirtschaftliche Fertigung) | SR703, SR705-709, & SR754 |
| Controller Calculator | 200 R |
| DARGUE Bros. Ltd. / Simplon | Sub-Ivory SR-1 & SR-4 + Honduras SD10, WR-2A, WR-5 & WR-7 |
| Fearns Calculators | Barber Shop Harmony Calculator |
| Fowler | Nautical, Artillery, Kearns & Mackay |
| Inglis | any FLASH RECKONER |
| ITAB (Internationaler Tabellenverlag) | Multicalor Flachheizkorper & Styropor-Vollwarmeschutz |
| IWA (Ingenieurbuero fuer wirtschaftliches Arbeiten) | 09102 Wiredrawing &15489 Harmonik |
| Johann Faber | 180/080, 180/082, 9201, 9202, 9203 & 9204 |
| Keuffel & Esser (K&E) | 4081-3 Braille version |
| KOSMOS | Book: "De Rekenliniaal" - 11th & 12th Editions |
| L&C Hardtmuth / Classic | 10" Series III |
| Lawrence Engineering Services | S-M (C.V. Ore) & Exposure (MIT) |
| LOGA Calculator A.G. | TF, TR, T150, T300, O2 Calculator, 30 TxC & 75 Terminator |
| LOGAREX | 27705 |
| Logomat Rechengeräte | 1300/1303 |
| Nestler | RP 75, Kreisrechner & Disc-O-Lator |
| S.R.&S.E. (Slide Rule & Scale Eng. Co.) | - any - |
| Systeem Matthijssen | - any - |
| Unique | Junior, Study 500/700/900 & J180/181/182 |
The history of the slide rule - how it all began ....
To learn more about the history of this calculating wonder check out the “Slide Rule History” by the Oughtred Society (OS) or my 2-page summary (in Dutch).
Need a “memory jogger” or just intrigued how such bygone analogue calculators worked, then the International Slide Rule Museum (ISRM) offers an online teach yourself course: “How To Use The Slide Rule”. Alternatively download the self-running 35mm “slide show” Training Programme with synchronised audio commentary I digitalised. Afterwards try out some test calculations using Robert Wolf's online simulation of the classic Nestler 23R wooden slide rule. If this gets you thinking about starting your own collection, then the UKSRC/OS “Beginner’s Guide to Collecting Slide Rules” is a must read.
For educators looking for maths related inspiration and teaching aids/material then you need to look no further than Nicola Marras’ slide rule inspired website. But if you are just looking for reference works/published books on slide rules try one of these inventories: List 1 or List 2.
news - So far 1612 items are loaded from my collection
Dr. Günter Kugel 1930 – 2025
Renowned German collector, Günter Kugel, sadly passed away in his home town of Moers on May 18th 2025. Günter was 94 and for many years had been a close friend and to the whole slide rule community, a respected and valued expert. He will be sorely missed.
LOGA dating
The linear and circular models of Swiss slide rule maker LOGA Calculator AG are notoriously difficult to date. Serial numbers were often used but rarely help. Based on some great detective work Jacques Perregaux has published in German a new insightful dating guide freely downloadable from here …
LATEST ADDITIONS – ARISTO SPECIALS
Like many of the quality slide rule makers in Europe, German maker ARISTO took orders for once-off models. Most specially commissioned designs were radically non-standard and unique. Luckily ARISTO had a fairly consistent product numbering system for everything. So their specially commissioned models are easily identifiable – see my 25 examples here …
Preannouncement IM2025
After 5 years of only ZOOM meetings, the 2025 annual International Meeting of Collectors will be a face-to-face event!
So put into your diary: 24-26 October in Boston, USA.
SAD NEWS - Robert Colin Adams (05/01/1954-22/10/2024)
Born in Blythe Southern Australia, Bob as he was known to everyone was the partner of Di Pearce who unexpectedly passed away a year ago. Bob was still mourning when early this year he was diagnosed with cancer. He was receiving treatment but was recently hospitalised when vital organs started terminally failing. After bouts of partial recovery Bob’s body finally gave out and he tragically passed away pain-free in Adelaide hospital. His slide rule legacy is the Electronic Archive.
ALRO book - RELAUNCHED
Dutch maker ALRO is famous for its circular slide rules where the lid doubles up as a desk stand. Otto van Poelje has meticulously catalogued and photographed every model (disc or chart) ALRO ever made. At the recent online 2023 Int. Meeting the book was relaunched. Watch the short video clip about the book here … and order your copy here …
MAJOR MAKERS IN PICTURES
Rod Lovett’s facility listing the slide rule models of 14 major makers has been expanded with 7 new image archives – click HERE to take a look.
TWO IMPORTANT NEW e-BOOKS!
Thanks to Jose G. Fernández collectors can now download free-of-charge English & Spanish translations of Rechenschieber im Wandel der Zeit - a book published in 2009 by Guus Craenen. It charts the development and evolution of the slide rule from 1787 to 1905. Click HERE to go to the download webpage.
MAGICAL SLIDE RULES
Did you know a special model exists for each house of Hogwarts School of Witchcraft & Wizardry? Depending on your Gryffindor, Ravenclaw, Hufflepuff or Slytherin affiliations select your Harry Potter inspired sorcerous slide rule simulation from Robert Wolf’s website ...
The IMPOSSIBLE is POSSIBLE!
Generically a slide rule can solve complex calculations but CANNOT do simple arithmetic. A rare and unusual exception is the newest addition to the collection - a System Korte slide rule that CAN add and subtract!
TOP SECRET !!
Lawrence made the only known slide rule considered so vital to the WWII effort that the UK & US governments had it classified - based on research from MIT it calculated radar antenna beam patterns, beam width, gain, etc.
