Slide Rules. Collecting and discussing. 13

[Skogsgurra]

Hello all,

You are invited to share views and thoughts about slide rules. I have been collecting these devices on a rather small scale and had fifteen of them when my collection took a quantum jump. I was visiting the local book store to buy a book on flowers (yes, flowers) when I happened to ask the store-keeper if he perhaps had any slide rules. He gave me a puzzled look and then said "Yes, I found a box with some forty old slide rules yesterday. I haven't decided what to do with them yet".

Need I say that I saved them from the scrapheap? I got a substantial addition to my collection at a price that we both were very pleased with. He because he got anything at all and I because I paid about a tenth of what I had expected to pay.

I have mostly European and Japanese slide rules. Faber-Castell, Aristo, Sun-Hemmi and some less known makes like Graphoplex (French), Diwa (Danish), Royal Slide Rule (British) and Eco Bra (can't make out from where it comes).

There is a certain standardisation among slide rules. There are the scale systems; Mannheim, Rietz, Darmstadt, Electro, Disponent and some other special systems. There is one that intrigues me. It is called Tachymeter and seems to have been used by surveyors. And there are probably many more that I haven't discovered yet.

The slide rules from the BHP era look very much the same except for the introduction of the Duplex slide rules in the late fifties/early sixties. That was also when some colour was added - except for the "reversed" scales (increasing from right to left instead of from left to right) which seems to have been coloured red for a very long time.

It was only AHP that design people started to make the slide rules more and more attractive. Mild colour coding, more scales and cursor lines, extra functions, friction areas to ease handling, table stands and more was added to keep a market that everyone probably already knew was lost. The last slide rules produced were sometimes monsters - or beauties - depending on your personal preferences. I, myself, think that the Faber-Castell 2/83 N (the N is important here) is a beauty. It is the longest 1 foot SR produced, I think. It has 30 scales and it even smells good!

Another favourite is the little FC 67/38b 400 grad Tachymeter. It is a favourite mostly because it is so enigmatic. What are sin.cos and cos2 scales used for? They are probably there for some very valid reason - as is the 1-cos2 scale. Anyone that has information about these scales?

Collecting slide rules appears to be the retired engineer's perfect hobby. We know a lot, but not all, about the objects. We can appreciate the good workmanship, the precision, the artistery and the ingenuity that went into their design and production. And we know how to use them!

There are a few other reasons that make them ideal collector's objects: They are no more produced. They are still available - although in limited quantity. They are not bulky - can be carried with you when meeting like-minded. There will probably never be a fake slide rule - it takes a very complex production facility to make slide rules and the last factory was closed in 1975.

It is a little like collecting Fabergé eggs - only so much cheaper and more interesting.

Comments and answers invited! Do you collect slide rules? Do you have specific knowledge about any special slide rule? What makes do you know about? How do you find them?

BHP = Before HP.

Gunnar Englund

http://www.gke.org

 

[swertel]

I have one slide rule. It was my grandfathers. I keep it because I one point in time I remembered how to use it, now it's just a momento of him. It's also a great conversation piece to all those young engineers (and I'm only 29) that have never seen one before but "heard stories" about them.

I'd like the collect slide rules, but my wife already thinks I'm right on the edge of being an enginerd. I think that hobby would throw me down the cliff.

--Scott

--Scott

For some pleasure reading, try FAQ731-376

 

[Skogsgurra]

Sorry for that Scott. You know what? I taught my wife to use a slide rule. She's fascinated with them and we are going to look for some tomorrow. She prefers little "cute" ones in leather holsters. I guess we are both enginerds - she would probably be proud to hear that. She never touched engineering in her whole life.

Gunnar Englund

http://www.gke.org

 

[UKpete]

I have no slide rules! When I was at school I think my year was the first not to use them (on the other hand my brother who was at the same school but two years ahead, used it a lot, and did teach me). I am 49 now so that tells you how long ago it was; before electronic calculators certainly - we used log tables.

There was a slide rule that I was given some years ago by my old manager at work when he retired (unfortunately I eventually passed it on to someone else who was interested). It was a special one designed to do train performance calculations. Before computers were available, in the railway traction field the ratings of the machines were calculated over a particular route by several people working together solidly for a week or so with their traction calculators, in order to get RMS values of motor current etc.. I am not sure how the slide rule differed from a conventional slide rule, also I don't know who made it. Sorry I can't be more specific.

 

[Skogsgurra]

Traction? Brings back pleasant memories from the Orion project that I was part of at Adtranz, Bombardier to be.

Gunnar Englund

http://www.gke.org

 

[SlideRuleEra]

If I don't participate in this thread, I would have to change my "handle"!

I have seven, mostly aluminium alloy Pickett. Three of these are "mine" - purchased new, with the intent of using them on the job. The others are recent purchases from E-bay.

As a college freshman, bought the first one, a 10 inch, top-of-the-line, Pickett Model N4-ES Log Log. Used it thoughout college and on my first job. It has 34 scales, but that is somewhat misleading. Pickett had a unique way of displaying the scales by folding them. For example the Square/Square Root scale is 20 inches long (two scales at 10 inches each).

I have always been proud of the fact that I used every scale on this rule, at least once (and sometimes only once, such as the hyperbolic cosine & hyperbolic tangent scales).

Because of the all metal construction, Pickett rules required routine maintenance. I remember taking the disassembled rule to the college dorm bathroom sink, washing it with dishwashing liquid, reassembling it, and lubricating with Vaseline - all per the manufacturer's recommendations. One other thing, this rule is yellow (the "ES" in the model number is an abbreviation for "Eye Saver"). Pickett offered both white & yellow rules, but promoted the yellow color as easier to read.

The other two rules that I obtained in the "old days" are both circular. One is a very small Pickett, the other is a nice plastic Concise. Turns out that I never used either one of these very much - they have very limited capability (fewer scales) and the concentric scales get smaller (less accurate) as you move toward the center. It is also a nightmare to keep the cursor & scales lined up.

For the E-bay rules, one is a Pickett Model N4P-T Log Log. This is the 6 inch (pocket) version of rule described above. It has the same 34 scales.

My wife gave me 20 inch long K&E a few years ago - I always admired one of my contemporaries who used a 20 inch rule and could get positive 3-digit accuracy, even when working at the extreme right end of the rule.

The 6" Pickett Model N600-ES Log Log is the type that went to the moon, literally. This model rule was carried by astronauts on all Apollo moon missions.

The final Pickett is a basic Simplex Trig rule that I gave my wife - she knows how to use a slide rule, too.

I still use the "big" Pickett from time to time, mostly to impress my continuing education students and other younger engineers. However there is still a lot of value to being able to do what I call the "approximate mental math" needed to use a slide rule effectively.

Thanks, skogsgurra, for starting this Thread!

http://www.SlideRuleEra.net

 

[vzeos]

I have acquired a few slide rules over the years. Probably the most interesting is the Cylindrical Pocket Slide Rule. See attached link...Also check out the Oughtred Society link.

http://www.svpal.org/~dickel/OK/OtisKing.html

http://www.oughtred.org/

 

[Skogsgurra]

Do you also use your slide rules? I keep a little pocket SR in my car. It is handy for many purposes, the cm scale is what I use the most (why is there no cm scale on calculators?). Before the cars got on-board computers I also used it to check MPG (or rather liters/100 km) and such things. It is also borrowed by the grandchildren and they pick up the functions gradually and we sometimes play "Guess log" where I buy them an ice-cream or similar every time I'm off more than five percent (another use; find if the answer is within 5 %). I even use it to do calculations with. I guess that this is about as enginerdish as you can get?

Gunnar Englund

http://www.gke.org

 

[notnats]

I just finished reading Ben Rich's "Skunk Works" about Lockheed's development centre.

The Stealth Bomber was the first aircraft designed there with computers. The others including the U2 and the Blackbird were designed using slide rules for all the calculations. He said that slide rule accuracy was all that was needed for all this work.

In an earlier thread, I commented that the author Neville Shute, in his day job was an aeronautical engineer. He worked with Barnes Wallace at Vickers. He describes all the calculations done on 6ft slide rules with teams of 3 checking each other.

Unfortunately I have lost all my slide rules. I remember one made from bamboo that would jam unless you forced it open with a finger in the middle of its back.

 

[Skogsgurra]

notnats,

That was designed in. All wooden SRs were built like that. The "Three Finger Grip" (thumb on D and index on A with long finger beneath, pressing slightly upwards) was among the first things taught in SR classes. I think that it was to keep the slide steady in the frame. A sliding slide would be most irritating and given that wood (or grass, which I think that bamboo is) is hygroscopic and swells cross fibre, it would be difficult to have a "just right" friction under all weather conditions. So, by making the frame grip the slide and machining a slot at the back side the problem was solved. High friction when needed and low friction when moving the slide. Plastic and duplex SRs didn't need that.

An interesting variation can be seen on Graphoplex SRs. They have two little balls with springs and adjustment screws inserted in the frame. Friction can be adjusted by setting the screws. Metal SRs had to be cared (read SlideRuleEra's description) and greased with vaseline. Vaseline is also used with plastic SRs.

Gunnar Englund

http://www.gke.org

 

[sms]

I have four, covering some of the major developments, a bamboo Post, a yellow aluminum allow Pickett, a six inch bamboo Ricoh, and a plastic Sterling. The plastic Sterling is probably among the last of the production slide rules to be made, it was my sister in law's freshman ChemE slide rule, but it was quickly replaced with a calculator somewhere toward the end of the 70's and was probably only used for a year.

 

[swertel]

I remember seeing a picture of a classroom with a giant slide rule above the black board. Those must of have been the days. I wish I could find it somewhere to post a link.

--Scott

For some pleasure reading, try FAQ731-376

 

[SlideRuleEra]

swertel - Here are a two photos of classroom slide rules

http://www4.ncsu.edu/~njrose/Special/Images/Cell&SlideRule.jpeg

http://www.sliderules.org.uk/magazine/ph-musing-02.jpg

http://www.SlideRuleEra.net

 

[haggis]

I only have one. The one I used before calculators and I can't remeber if it is a Staedtler -Mars, Keufell and Esser or Faber-Castell. All I know it was made in Germany and I inherited it from my brother in-law when he suddenly quit engineering. I'll have to get to the box in the basement.
I get a kick out of reading things like "I've heard stories about them" and "It was my grandfather's". How time flies when you're having fun!!

 

[drawoh]

I still have my slide rule from high school and my first year of college. I still have my Texas SR51 too. Try to guess which one works.

I read somewhere that Reginald Mitchell (died 1938) estimated the top speed of all his aircraft to within 5%. That definitely is within sliderule accuracy.

Once of my instructors at college in the early seventies claimed that people were writing out ten digit dimensions on drawings. This problem must have disappeared quickly because I never saw it.

JHG

 

[IRstuff]

On homework, maybe, but any such abuse on drawings would quickly get beaten down, since machining tolerances, particularly 30 yrs ago, would never support more than 3 decimal places.

TTFN

 

[plasgears]

I still have my compact Faber-Castell rechenschieber from Germany. It had unique preset factors for common calculations. I bought it at the Kaufhof in Frankfurt when I was stationed there.

 

[Skogsgurra]

Plasgear,

Would that be a 62/82 or 62/83? One of my favourites.

Gunnar Englund

http://www.gke.org

 

[IRstuff]

My best slideruler was an aluminum Pickett, given out as a consolation prize in an Engineers' Week competition.

Sadly, that was the same yr that the HP-25 was introduced, so I never really used it much.

TTFN

 

[Skogsgurra]

The HP 25! Still have it. What a wonderful machine. My first programmable device. A pity that programs went poof when it was switched off. And no storage devices - just pen and paper. But the programs were short and easily entered. Those were the times.

Gunnar Englund

http://www.gke.org