Slide rules rule!

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  • #36
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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.
 
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  • #37
anorlunda
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Your post inspire me to look on eBay where I found a Concise Circular sliderule that I bought.
Cool. Post a picture.
 
  • #38
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slide-rule-no300-b.jpg

https://www.sliderule.tokyo/products/detail.php?product_id=8
 
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  • #39
anorlunda
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Very nice. You can challenge your students with that.

Keep it clean and treat it gently so that the markings don't erode.
 
  • #42
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.
 
  • #43
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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.
IMG_1999.JPG
 
  • #44
hutchphd
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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!).
 
  • #45
hutchphd
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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.
 
  • #47
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@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.
 
  • #48
anorlunda
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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.
1620579759387.png
 

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