For slide-rule freaks only, a detailed list of my slide-rules. Instructions for using one are here.

**AW Faber 309**. 250 mm scale. Wooden structure with white plastic facing pinned on. Single-sided with double-sided slide. Two cursors, wooden with plastic window. S, L and T scales can also be read from windows on the back. Scales on the front are unnamed. Made in Bavaria. From the presence of a model number and the solid wood construction, this one is probably from around 1910. Thanks to Emrys for this one.upper stock (A) x ^{2}slide (B) x ^{2}(C) x lower stock (D) x back of slide S arcsin 0.01x ^{2}L 1 - log x (reads log x via window on reverse) T arctan 0.1x **Faber-Castell 167/98 Log-Log**. 125 mm scale. Single-sided one-piece plastic body, with windows on reverse to read S, L and T scales with double-sided slide in normal position. Single-piece plastic cursor with area of circle and (746W) HP to kW. 5-inch scale along ruler-edge at top. Leather slip case. Made in Germany. I bought this one new and carried it always, until Joan sat on it in 1981 and cracked it. It still works.upper stock LL2 e ^{0.1x}A x ^{2}(with extensions, as have B, CI, C and D)slide B x ^{2}CI 10/x C x lower stock D x LL3 e ^{x}Efficiency Efficiency of motor or dynamo based on HP to kW ratio on A and B Volt drop Volt drop in copper cable, based on area, length and current set on A and B using special marks back of slide S arcsin 0.01x ^{2}L 1 - log x (reads log x via window on reverse) T arctan 0.1x **Faber-Castell 167/98b Elektro**. The same as 167/98 above, except: 735W=HP, centimeter ruler scale and plastic slip-case. Also the volt drop and efficiency scales are displaced to reflect metric units and continental HP. Clive Bowman found this one and the next one in London around 1982.upper stock LL2 e ^{0.1x}A x ^{2}(with extensions, as do B, CI, C and D)slide B x ^{2}CI 10/x C x lower stock D x LL3 e ^{x}Efficiency Efficiency of motor or dynamo based on HP to kW ratio on A and B Volt drop Volt drop in copper cable, based on area, length and current set on A and B using special marks back of slide S arcsin 0.01x ^{2}L 1 - log x (reads log x via window on reverse) T arctan 0.1x **Faber-Castell 62/83N Novo Duplex**. 125 mm scale. Double-sided plastic with wrap-around two-piece plastic cursor. All scales have extensions. Cursor has area of circle, kW to HP (746W) and x36. Leather slip case. This and the next two Fabers have metal rod bearings for the cursor. Made in Germany. My favourite.front upper stock T1 arctan 0.1x (and arccot) T2 arctan x (and arccot) K x ^{3}A x ^{2}DF pi.x front of slide CF pi.x B x ^{2}CIF 10/(pi.x) CI 10/x C x front lower stock D x DI 10/x S arcsin 0.1x (and arccos) ST arc 0.01x (arctan or arcsin) P sqrt(1-(0.1x) ^{2})rear upper stock LL03 e ^{-x}LL02 e ^{-0.1x}LL01 e ^{-0.01x}LL00 e ^{-0.001x}W2 sqrt(10x) rear of slide W2' sqrt(10x) CI 10/x L 0.5 log x (use with W scales) C x W1' sqrt x rear lower stock W1 sqrt x D and LL0 x and e ^{0.001x}(ingeniously-marked dual scale)LL1 e ^{0.01x}LL2 e ^{0.1x}LL3 e ^{x}**Faber-Castell 2/82**. 250 mm scale. Double-sided plastic with wrap-around cursor in white plastic with separate windows. Metal adjustable bridge pieces. Cursor lines for area of circle and (735W) HP to kW. Most front scales have extensions. Plastic hinged case. Made in Germany. Thanks to Mike for this one. This one's flawed for me by having C/D and CF/DF on opposite sides; CF/DF should be where the useless paired K scales are and C/D where CF/DF are.front upper stock L log x T1 arctan 0.1x (and arccot) T2 arctan x (and arccot) A x ^{2}front of slide B x ^{2}BI 100/x ^{2}CI 10/x C x front lower stock D x ST arc 0.01x (arctan or arcsin) S arcsin 0.1x (and arccos) P sqrt(1-(0.1x) ^{2})rear upper stock LL03 e ^{-x}LL02 e ^{-0.1x}LL01 e ^{-0.01x}K x ^{3}(unusual paired K for calculations)rear of slide K' x ^{3}C x CIF 10/(pi.x) CF pi.x rear lower stock DF pi.x LL1 e ^{0.01x}LL2 e ^{0.1x}LL3 e ^{x}**Faber-Castell 52/82**. 250 mm scale. Double-sided plastic with 2-piece plastic wrap-around cursor. Cursor has area of circle (746W) HP to kW and x36. Rigid plastic slip case. Made in Switzerland. This one saw me through upper school and university (probably bought about 1969). Before this I used a 125mm Unique and then a 250mm Blundell.front upper stock L log x K x ^{3}A x ^{2}front of slide B x ^{2}CI 10/x C x front lower stock D x LL1 e ^{0.01x}LL2 e ^{0.1x}LL3 e ^{x}rear upper stock T1 arctan 0.1x (and arccot) T2 arctan x (and arccot) DF pi.x rear of slide CF pi.x CIF 10/(pi.x) CI 10/x C x rear lower stock D x S arcsin 0.1x (and arccos) ST arc 0.01x (arctan or arcsin) P sqrt(1-(0.1x) ^{2})**Pickett N 3-T**. 250 mm scale. Double-sided aluminium body with adjustable metal bridge pieces. Thin and rather wobbly cursor with separate windows. Scales apparently printed on rather than engraved. Strange spring friction devices near centre position of slide make setting awkward at some positions. Compared with the other rules above, the slide is relatively much wider; also the two parts of the stock are of different widths. Sturdy leather carrying case with belt loop. Made in USA. Thanks to John for this one.front upper stock square root x ^{1/2}(odd number of digits)square root (10x) ^{1/2}(even number of digits)K x ^{3}A x ^{2}front of slide B x ^{2}ST arc 0.01x (arctan or arcsin) S arcsin 0.1x (and arccos) T arctan 0.1x T arctan x CI 10/x C x front lower stock D x DI 10/x cube root x ^{1/3}(for 1-4-7.. digits)cube root (10x) ^{1/3}(for 2-5-8.. digits)cube root (100x) ^{1/3}(for 3-6-9.. digits)rear upper stock LL0+ e ^{0.001x}(Faber LL0)LL0- e ^{-0.001x}(Faber LL00)LL1+ e ^{0.01x}LL1- e ^{-0.01x}DF pi.x rear of slide CF pi.x CIF 10/(pi.x) Ln ln x L log x CI 10/x C x rear lower stock D x LL2+ e ^{0.1x}LL2- e ^{-0.1x}LL3+ e ^{x}LL3- e ^{-x}**Aristo 0908 Trilog**. 251 mm scale. Double-sided plastic, with bridge pieces on one side only. Wrap-around cursor with separate windows. Cursor lines for area of circle and x36. Upper and lower stock of different widths. Rigid plastic slip case. Made in Austria. Thanks to Dave (#1) for this one and the Jakar.front upper stock LL1 e ^{0.01x}LL2 e ^{0.1x}LL3 e ^{x}DF pi.x front of slide CF pi.x CIF 10/(pi.x) CI 10/x C x front lower stock D x L log x K x ^{3}rear upper stock T1 arctan 0.1x (and arccot) T2 arctan x (and arccot) A x ^{2}rear of slide B x ^{2}BI 100/x ^{2}CI 10/x C x rear lower stock D x P sqrt(1-(0.1x) ^{2})S arcsin 0.1x (and arccos) ST arc 0.01x (arcsin or arctan and arccot or arccos) **Jakar No 1005**. 250 mm scale. Single-sided plastic with one-piece plastic cursor. Flimsy clear plastic slip case. Made in Japan.

Larger: Frontupper stock S arcsin 0.01x ^{2}K x ^{3}A x ^{2}slide B x ^{2}CI 10/x C x lower stock D x L log x T arctan 0.1x **Logarex 4542-27501**. 498 mm scale. Single-sided plastic with one-piece rather vague cursor. Cursor has area of circle line. Scales appear to be printed on and varnished over. Extensions on A, B, C and D. Scales unnamed, though formula appears at left-hand end. My brother found this in Romania, at the equivalent of about 50p UK in 1991. It may be genuine, or a cheap local version. Showy fake skin fold-around case.

Larger: Frontupper stock log x log x x ^{3}x ^{3}x ^{2}x ^{2}slide x _{z}^{2}x ^{2}1/x 10/x x _{z}x lower stock x x sin arcsin 0.01x ^{2}(yes based on A, though at the bottom)tg arctan 0.1x e ^{x}e ^{x}**School teaching rule**. 1500 mm scale. Solid wooden construction, with large graduation marks, basically a 250mm rule magnified six times. Scales painted on. Found in a school's maths department cupboard. Probably dates from 1950s, and unused for twenty years. Thanks to Rusty for this one.

Larger: Frontupper stock A x ^{2}slide B x ^{2}C x lower stock D x **Faber Castell 380**. Scale 500 mm. Wooden slide and stock with engraved plastic faces and brass pins. Double-sided slide with trig windows on the back. Metal cursor with a single line. Conversion factors and properties of materials on the back. Wood and canvas rigid case. Made in Bavaria. No scale values or names on the front, but has "Quot +1" at LH end of D and "Prod -1" at RH end to remind of index change. Inch and mm scales on stock. Stock is in two pieces with metal springs between. From the type of logo, this one probably dates from the early 1920s. Thanks to Mike for this one and the next one.

Larger: Frontupper stock (A) x ^{2}slide (B) x ^{2}(C) x lower stock (D) x back of slide S arcsin 0.01x ^{2}L 1 - log x (reads log x via window on reverse) T arctan 0.01x ^{2}**Unique "Brighton"**. Scale 254 mm. Wooden slide and stock. Stock halves joined by springy metal plate with printed formulae. Log-log on reverse of slide. Trig scales on separate scale on lower edge of lower stock, read using a special extra window on the cursor; cm scale at upper stock. Made in England. This one is a bit tired and barely useableupper stock cube x ^{3}A x ^{2}slide B x ^{2}1/x 10/x C x lower stock D x L log x sqrt(1-x ^{2})sqrt(1-(0.1x) ^{2})lower edge S arcsin 0.1x T arctan 0.1x back of slide LL1 e ^{0.01x}LL2 e ^{0.1x}LL3 e ^{x}**Blundell Descal 310 circular**. Effective scale length about 180 mm for C and D scales. Two plastic disks and clear cursor, pivoted at centre. Cicular slide rules avoid the need to reverse the slide and are easier to carry for a given scale length (this one's about 75 mm diameter), but they're not so easy to manipulate. Thanks to Malcolm for this one.

Larger: Frontouter rotor L log x D x inner rotor C x CI 10/x A x ^{2}K x ^{3}**Sterling Mannheim**. Scale 250 mm. A basic plastic rule aimed at students, made in the USA. No frills, no cursor lines, not even a pi mark on the C and D scales (though oddly there is one on the A and B scales). This one is still in its original bubble pack priced at 1.49USD, probably early 1970s. Thanks to Santiago in Spain for this one and the next one.

Larger: Frontupper stock A x ^{2}slide B x ^{2}CI 10/x C x lower stock D x K x ^{3}back of slide S arcsin 0.01x ^{2}L log x T arctan x **Sterling Mannheim De-Luxe**. Scale 250 mm. The same slide rule as the one above but bonded to an extra plastic base with ruler edges, 1/16-inch at the top and 0.05-inch at the bottom. In a plastic slip case.

Larger: Frontupper stock A x ^{2}slide B x ^{2}CI 10/x C x lower stock D x K x ^{3}back of slide S arcsin 0.01x ^{2}L log x T arctan x **Fuller Calculator**. This beauty is a helical slide rule with a scale length of around 13 metres. It has only the one scale, equivalent to a C, and effectively two linked cursors. Thanks to Joan for this one. Probably 1946.

Larger: Front**Academy 310 circular**. Effective scale length about 180 mm for C and D scales. Two plastic disks and clear cursor, pivoted at centre. Possibly useful conversion factors on backouter rotor D x inner rotor C x CI 10/x A x ^{2}K x ^{3}**Concise No28 circular**. Effective scale length about 210 mm for C and D scales. Two plastic disks and clear cursor, pivoted at centre. Possibly useful conversion factors on backouter rotor D x inner rotor C x CI 10/x A x ^{2}K x ^{3}**Fowler long scale calculator**. Effective scale length for the short scale about 190 mm. Effective length for the 6-rev long-scale about 750 mm. A single-scale slide-rule with 2 pointers, in operation more like the Fuller rather than the other circular slide rules. Serial number 12435. Possibly 1930s, the combination of case style, scales and knob shape suggests ~1938 (from http://osgalleries.org/journal/pdf_files/7.2/v7.2p43.pdf). The serial number is sometimes a date code, which would give Friday 1935-04-12.**Moonstick**. This is not a general-purpose slide rule like the others on this page, but it's a member of the same family. It's a modern device, which tells the phase of the moon for any date and time within a few thousand years before or after now. It is not logarithmic and performs only addition modulo one lunar cycle.It consists of six triangular slides that fit together in guides to make a hexagonal stack. The first four slides select the four digits of the year, with multiple scales on each slide selected by a colour code. The fifth slide selects the month and time zone (ref UTC); then the moon phase can be read off against the date and approximate local time on the sixth segment.

It's quite hard to photograph in its assembled form. The "parts" image below shows one face of each slide separated out; some of the slides have markings on all three faces and can be used either way round.

Moonsticks and other fascinating toys are available from wwwmoonstick.com.

**Aristo 0903 VS**. 250 mm scale. Double-sided plastic, with bridge pieces on one side only. Wrap-around cursor, cursor lines for area of circle and x36. Upper and lower stock of different widths. Rigid plastic slip case. Made in Austria. Thanks to Dave (#2) for this one and the next one.The odd twisted look in the images is the result of scanning it diagonally across the scanner platen in an attempt to get it all on. Scanners are designed to scan flat surfaces; when you try to scan 3-D objects you see the effect of looking at the object from different directions from one side of the platen to the other.

front upper stock L log x K x ^{3}A x ^{2}front of slide B x ^{2}CI 10/x C x front lower stock D x S arcsin 0.1x (and arccos) ST arc 0.01x (arcsin or arctan and arccot or arccos) T tan 0.1x (and arccot) rear upper stock cm scale 0..25cm DF pi.x rear of slide CF pi.x C x rear lower stock D x scale of whole inches with short sections for 1/32 and 1/20 inches (upside down) **Faber-Castell 67/98b Elektro**. 125 mm scale. Single-sided one-piece plastic body, with windows on reverse to read sin, lg and tg scales with double-sided slide in normal position. Single-piece plastic cursor with area of circle and (746W) HP to kW. 5-inch scale along ruler-edge at top. Leather slip case. Made in Germany. Very similar to 167/98 above except this one has 2-colour engraving, missing or non-standard scale names and no scale formulae. It also, like the metric 167/98b above, has a crib near the left-hand index of A and B scales for the units to be used for voltage drop calculations. Although the scales are the same length, the body is about 5mm shorter than the 167/98.upper stock (LL2) e ^{0.1x}(A) x ^{2}(with extensions, as have B, CI, C and D)slide (B) x ^{2}(CI) 10/x (C) x lower stock (D) x (LL3) e ^{x}Efficiency Efficiency of motor or dynamo based on HP to kW ratio on A and B Volt drop Volt drop in copper cable, based on area, length and current set on A and B using special marks back of slide sin arcsin 0.01x ^{2}lg 1 - log x (reads log x via window on reverse) tg arctan 0.1x **Otis King model K**. A pocket spiral slide rule with a scale length of about 1.6 metres. Rather similar to the Fuller but instead of a single scale and two variable pointers this one has two pointers a fixed distance apart and two scales, one moving and one fixed. Z prefix serial number makes this one 1969.**Thornton PIC No 121**. 250 mm scale. Split wooden stock and wooden slide with plastic facings, pinned at ends. In addition to the conventional scales this one has some interesting idiosyncratic scales. Instead of the conventional sine scale for example, which is usually plotted as x = 0.1 * sin(T), this one plots x = 0.1 * T / sin(T) where T is in degrees. This makes the scales more compact, so that sine, tangent, arcsine and arctangent all fit into the space of one scale. There are also some extra short scales and pointers to the left of the rule which facilitate the setting up of interest rates using the log-log scales or simple percentages on the C and D scales. The metal cursor has a single rather fine line. Date might be 1949. Thanks to Dave (#3) for this one.upper stock scale of millimetres (LL2) e ^{0.1x}(LL3) e ^{x}(A) x ^{2}slide (B) x ^{2}(CI) 10/x IDS, IDT, DS, DT special trig scales (C) x lower stock (D) x (K) x ^{3}scale of inches and twentieths **Unique Universal**. Split wooden stock with metal spring, 254 mm scales printed under plastic laminate, pinned at ends. Cursor missing. Properties of materials and fractional conversions on the reverse. British. Probably 1930s or 1940s. Card slip case. No formulae; only S and T are named. Thanks to Glyn for this one.upper stock (LL2) e ^{0.1x}S arcsin 0.01x ^{2}(based on A)(A) x ^{2}slide (B) x ^{2}(CI) 10/x (C) x lower stock (D) x T arctan 0.1x (LL3) e ^{x}**Fearns Calculator**. A conventional circular slide rule from a prolific maker of specialist calculators. This one is unusual in having two full-size disks, with the front one clear and printed in red on the back surface; this allows the "slide" to have two edges, more like a conventional slide rule. The three-and-a-bit decade spiral log-log scale is also unusual, but very easy to use. This one was about to be thrown away when uncovered in a recent move at work. The rear has unit conversions for a small set of non-fundamental units.upper stator cube scale x ^{3}(D) x rotor (C) x (B) x ^{2}lower stator (A) x ^{2}Log.log. e ^{0.01x}to e^{x}Sine arcsin 0.1x Tangent arctan 0.1x **AW Faber 360**. 250 mm scale. Wooden split stock with metal spring and plastic facing pinned on. Single-sided with double-sided slide. Metal and glass cursor with a single line. S, L and T scales can also be read from windows on the back. Scales on the front are unnamed. 10-inch ruler angled on top edge and 30 cm perpendicular on lower edge. 2-piece tubular card case. Interesting to see even on these very old Faber rules, which lack many of the features of later ones, the special scale marks C, C1 and M. C is at 1.128 = sqrt(4/pi), C1 is at 3.568 = sqrt(10)*C (both used in finding the area of a circle from its diameter), M is at 100/pi. Made in Bavaria. Probably between 1913 and 1920. Thanks to Clive for this one and the next one.upper stock (A) x ^{2}slide (B) x ^{2}(C) x lower stock (D) x back of slide S arcsin 0.01x ^{2}L 1 - log x (reads log x via window on reverse) T arctan 0.1x **Frederick Post 1452P**. 253 mm scale. Plastic structure with lower stock screwed on separately, allowing adjustment of friction. Single-sided with double-sided slide. Metal and glass cursor with a single line. S, L and T scales can also be read from a single window on the back (L against an edge). 10-inch ruler at top and 30 cm at bottom, both angled. Rigid case with press-stud flap closure. Made in USA by Grafton Plastics WI and badged for Post. 1940s or 1950s probably.upper stock A x ^{2}slide B x ^{2}CI 10/x C x lower stock D x K x ^{3}back of slide S arcsin 0.01x ^{2}L 1 - log x (reads log x via window on reverse) T arctan 0.1x **Airtour CRP-1 Computer**. Effective scale length about 290 mm for C and D scales. Clear plastic disk and clear cursor, pivoted at centre. Thanks to Clive for this one.This is a special computer for pilots of small aircraft. There is a conventional circular slide rule, though the scales are marked unusually with C scaled 10 to 60 then 7 to 10 and D scaled 10 to 100; this is because the C (inner) scale is often used to read minutes, and its most prominent index mark is at 60. These scales are mainly used for simple ratio calculations such as converting miles to nautical miles, litres to US gallons, pounds fuel to gallons (using the specfic gravity offset sub-scales) or remaining fuel to remaining flight time. There are various marks to facilitate these conversions without having to remember the ratios. Several inset windows allow calculations of airspeed and altitude depending on temperature and true pressure.

The reverse is a vector calculator. There is a vertical slide behind a rotating clear window. If the slide is set to ground speed, a pencil mark made offset by the wind speed and the screen then rotated to the wind direction, the vector sum, both magnitude and direction, can be read off. Similarly, groundspeed or wind velocity can be found from the other two.

**Unique Universal I**. 253 mm scale. Split wooden stock with metal spring. Very similar to #26 above but this one is newer, scales are glued on rather than pinned, and all named but not yet quite conventionally. Probably 1940s or 1950s. Cardboard 2-piece case. Faint print on the case gives a fixed price for sale in the UK of 11/6 (11s 6d or 52½p). This one came from the indoor market in Barnstaple for £3.upper stock LU e ^{0.1x}S arcsin 0.01x ^{2}(based on A)A x ^{2}slide B x ^{2}R 10/x C x lower stock D x T arctan 0.1x LL e ^{x}**Royal Artillery VF0129**. 250 mm scale. Split wooden stock with wooden spring. My father's from his time with the 9th Survey Reg. Very simple scales, unlabelled on front side. Lots of special marks, including some which appear to be hand-marked, presumably for some repetitive field calculations. Made I assume in the 1930s or early 1940s and well used, it has survived well except for a gap between slide and stock. Cardboard and leatherette case has not lasted so well. Manufacturer's logo looks like "PIC" which indicates it is an A G Thornton rule.upper stock (A) x ^{2}slide (B) x ^{2}(C) x lower stock (D) x back of slide S arcsin 0.01x ^{2}ST arc 0.001x ^{2}T arctan 0.1x **Methane Flow Calculator**from the National Coal Board. Another one that Clive found, in Barnsley. This is a true slide rule, but set up to perform one calculation only and without any general-purpose scales. The instructions are printed on the face, and it calculates the flow rate of methane gas through an orifice in a pipe, in two stages. The first stage is done on the rear, and generates an orifice factor from the ratio of the diameters of the orifice and the pipe. The second stage on the front works out:Flow rate = (orifice diameter)

^{2}* (orifice factor) * sqrt(differential pressure) * FAP * FDE * KWhere FAP is a non-linear factor dependent on pressure to atmosphere, FDE is a non-linear factor dependent of percentage of methane in the gas and K is a unit-matching constant. A third stage calculation can be done using the cursor to calculate the flow rate of methane as a fraction of the total flow rate.

It can be seen that the power and square root required in the calculation are done by casting from scales that variously have 2, 4 and 8 decades around the full circle, and that one of the scales is reversed so that a division-like operation is in fact a multiplication.

A neat little device. It's well-made with engraved scales, thick solid-feeling plastic disks and a screw and boss centre pivot.

*(Images of 12 and 25 cm rules are mostly from a scanner; others are from a
digital camera)*

1997-08-03 .. 2020-09-30 (+44 7010 700642)