# Slide rules rule!

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anorlunda
Staff Emeritus
In case of EMP and no sliderule, there's always the Trachtenberg system of arithmetic to get you through those dark days:

https://en.wikipedia.org/wiki/Trachtenberg_system
Don't forget a backup method to make your PF posts.

jedishrfu
Don't forget a backup method to make your PF posts.
That should be possible with a Z1 computer.

anorlunda
jedishrfu
Mentor
Except the Z1 is electro-mechanical and an EMP might still knock it offline.

https://en.wikipedia.org/wiki/Z1_(computer)

It was a great computer though and ahead of its time.

Except the Z1 is electro-mechanical and an EMP might still knock it offline.
In 1962, the USA carried out a nuclear EMP experiment in high altitude near Hawaii:
Wikipedia said:
Starfish Prime caused an electromagnetic pulse (EMP) that was far larger than expected, so much larger that it drove much of the instrumentation off scale, causing great difficulty in getting accurate measurements. The Starfish Prime electromagnetic pulse also made those effects known to the public by causing electrical damage in Hawaii, about 900 miles (1,450 km) away from the detonation point, knocking out about 300 streetlights,[1](p5) setting off numerous burglar alarms, and damaging a telephone company microwave link.[6] The EMP damage to the microwave link shut down telephone calls from Kauai to the other Hawaiian islands.
Source:
https://en.wikipedia.org/wiki/Starfish_Prime

I think, that electro-mechanical relais are more robust against EMP than transistors or integrated circuits, because their wires have a larger diameter, and so the current density is lower. Solid state equipment has a problem:
Wikipedia said:
Older, vacuum tube (valve) based equipment is generally much less vulnerable to nuclear EMP than solid state equipment, which is much more susceptible to damage by large, brief voltage and current surges. Soviet Cold War-era military aircraft often had avionics based on vacuum tubes because solid-state capabilities were limited and vacuum-tube gear was believed to be more likely to survive.
Source:
https://en.wikipedia.org/wiki/Nuclear_electromagnetic_pulse#Vacuum_tube_vs._solid_state_electronics

On the other hand, computers with smaller size collect less voltage from a certain electric field. So smartphones may work:
Wikipedia said:
An EMP has a smaller effect the shorter the length of an electrical conductor; though other factors affect the vulnerability of electronics as well, so no cutoff length determines whether some piece of equipment will survive. However, small electronic devices, such as wristwatches and cell phones, would most likely withstand an EMP.
Source:
https://en.wikipedia.org/wiki/Nuclear_electromagnetic_pulse#On_small_electronics

The slide rule is often used for multiplication and division, but it can also be used for functions like exponents, roots, logarithms, and trigonometry. It is rarely used for addition or subtraction.

The introduction of the inexpensive, fast, and versatile electronic pocket calculator led to the slide rule's demise.
The owner's slide rule used to have a special status, but that was happily replaced by the equally special status of the dazzling HP-35.

Baluncore
The “General Report On Tunny With Emphasis On Statistical Methods” (1945) from Bletchly Park, GCCS, includes the following inventory item and comment;

“Section 57. Simple Machines.
(a) Slide-rules.
The operations required are multiplication, division, squaring, extracting square roots, and taking logarithms to base 10. Many of the slide-rules used lack logarithms, and have elaborate useless scales.”

Obviously the scales A, B, C & D had no meaning to the author, while the L scale on the rear was not Log because it was Linear !

Keith_McClary
anorlunda
Staff Emeritus
Obviously the scales A, B, C & D had no meaning to the author, while the L scale on the rear was not Log because it was Linear !
Ah the nostalgia. You motivated me to take down my old Post from the wall to see what scales it had. When I used it actively, I knew the purpose of all those scales and I found productive uses for them.

Here are the scale labels:

ex LL0 0.001→0.01
e-x LL/0 -0.001→-0.01
K
DF
CF
CIF
CI
C
D
R1
R2
L
e-x LL/1
e-x LL/2
e-x LL/3

T T
sec T ST
Cos S
e-x LL/1 -0.01→-0.1
e-x LL/2 -0.1→-1.0
e-x LL/3 - 1.0→-10.0
C
X D
ex LL1 1.0→10.0
ex LL2 0.1→1.0
ex LL3 0.01→0.1

Keith_McClary
Mark44
Mentor
That's nothing. I had to use an abacus and record intermediate results on a clay tablet with a stylus.

Lucky bastid! We could only dream of having a stylus
Luxury! We could only count on our fingers...

Staff Emeritus
Luxury! We could only count on our fingers...
Fingers? You had fingers? Why, when I was a lad we hadn't yer evolved fingers....

Baluncore
There are a couple of good historical references here;
“From webbed fingers to the World Wide web” and “From dactylonomy to binary arithmetic”. Both by the scientist and author; Sly Drool.

jedishrfu
Mentor
Not a slide rule, but an old style "flight computer"

Your post inspire me to look on eBay where I found a Concise Circular sliderule that I bought. Concise still has a website and still sells circulars. This one is a model 300 with a 4” diameter which makes it have the roughly same resolution as a 12” stick sliderule.

There are two kinds of circulars that I have found. The first a Post uses two connected cursors. Place one on the index’s point of the scale and the other on the number then use them together preserving the angle to find the second number and at the other end you’ll find the answer.

The concise uses two rotating discs where you move one the smaller disk index point to the first number and then line the cursor on the second number on the smaller disk and read the answer on the larger disk under the cursor.

hutchphd and anorlunda
anorlunda
Staff Emeritus
Your post inspire me to look on eBay where I found a Concise Circular sliderule that I bought.
Cool. Post a picture.

hmmm27
jedishrfu
Mentor
hmmm27, anorlunda and Keith_McClary
anorlunda
Staff Emeritus
Very nice. You can challenge your students with that.

Keep it clean and treat it gently so that the markings don't erode.

Ibix
2020 Award
anorlunda
Staff Emeritus
$3200! 3200 JPY =$29.34

YoungPhysicist, Keith_McClary and Ibix
The fact that Concise is still in business is remarkable. From what I know they have no real market, as with every other kinds of slide rule, and only serve as collectibles nowadays. Even Hemmi(a major Japanese slide rule manufacturer alongside Concise, many of it's products known as POST in the west)has turned into a small enterprise selling PCBs, with almost no evidence of its former glory besides its company name.

https://www.hemmi-inc.co.jp/english/

So either Concise made too many of them and had to get rid of them for decades or maybe there is actually someone buying them for genuine calculation purposes, I think.

Mark44
Mentor
My slide rule collection, plus an HP 11-C that my brother gave me, and that uses RPN (reverse Polish notation).
The yellow one is a Pickett that I've had since the early 60s. The third one down is also a Pickett that someone gave me. Besides the L scale, which I remember using, it also has LL0, LL00, LL1, LL2, and LL3 scales that I'm not familiar with. The one at the bottom belonged to my wife's father.

hutchphd
Homework Helper
Keep it clean and treat it gently so that the markings don't erode.
I always used to put a little talcum powder on my linear rule (probably give me lung cancer!!).

hutchphd
Homework Helper
The third one down is also a Pickett that someone gave me.
Yeah I spent many anguished hours on that machine. As I recall the HP 35 Calculator was around \$400 ....too rich for my sophomore self.

jedishrfu
Mentor
@Mark44 here’s a discussion on the slide scale functions including the LL series.

https://www.math.utah.edu/~alfeld/sliderules/

In high school, a chemistry teacher taught me those after school. I used them in Ph calculations but don’t remember much beyond that.

I also remember using them in an approximation scheme starting with the answer and twiddling the slide to find when the two operands were the same. As an example, the trick could be used to find square roots using the C and D scales that were slightly more accurate but I remember using them on other scales too.

anorlunda
Staff Emeritus
The one at the bottom belonged to my wife's father.
The one on the bottom was a Post rule. That's the kind I had. (see #22 in this thread.) Post was made of bamboo, compared to metal for Pickets or plastic for other brands. Undergrads took great delight arguing which was best.

Bamboo would shrink or swell with the humidity, so the screws holding it tight had to be adjusted often. If I remember, the surface of the metal Pickett was more vulnerable to scratches and abuse.

I too bought a HP-35 on the first day they came out, and I took it with me to Finland on a business trip that same day. I was the envy of every engineer in all of Finland that day.

Does anybody have a fond memory of the mechanical calculators the HP-35 replaced? I hated them, and I hated the noise they made. Slide rules were far superior unless you needed many more digits of precision.