The Museum of HP Calculators

HP Forum Archive 21

[ Return to Index | Top of Index ]

OT: My Slide Rule Collection
Message #1 Posted by Eddie W. Shore on 21 Apr 2013, 4:39 p.m.

http://edspi31415.blogspot.com/2013/04/my-slide-rule-collection.html?m=1

I don't think any of them operate in RPN though. Still, a fun thing to use every once in a while. I have much appreciation of what mathematicians and scientists used before the electronic calculator.

      
Re: OT: My Slide Rule Collection
Message #2 Posted by Garth Wilson on 21 Apr 2013, 7:14 p.m.,
in response to message #1 by Eddie W. Shore

Our daughter-in-law's sister graduated from Cal Poly Pomona in mechanical engineering, in the top 1% of her class a couple of years ago. (Our daughter-in-law is about to graduate in computer science.) The first time this super-smart homechooled family was here at the house, we got to talking about related things, and the sister said, "Someday I'd like to see a slide rule!" I said, "Well, if you can hold on a second, this can be that day," and I went and got my K&E N4080-3S log log duplex trig slide rule (the nicest of my three slide rules) which my grandfather gave me near the end of his life and after most engineers were already onto calculators. The first thing she says is, "OK, now how do you add?" I said, "You're supposed to be able to do that in your head," and proceded to show her the common things slide rules were used for. She seemed impressed, but it was hard for her to relate to this thing from a past world. Those who were proficient at it however did not gain any real time savings when going to a calculator, until calculators became programmable. Programmability was in fact my primary reason to go to the calculator. The slide rule couldn't compete there.

            
Re: OT: My Slide Rule Collection
Message #3 Posted by Jim Horn on 22 Apr 2013, 1:41 p.m.,
in response to message #2 by Garth Wilson

Slide rules were indeed fast, useable and remarkable. But calculators handily beat them in precision. For many purposes the difference in real life is slight, but not always.

When taking a US Air Force orbital perturbations class in 1976, I brought my Post slide rule to the final exam, getting quite a laugh from the others when I said I brought it as a backup to my then-new HP-67. Halfway through the two hour test, though, my '67 battery gave out as I hadn't charged it sufficiently the night before. So the slide rule was ruefully pulled out and used to complete the exam.

A fellow student took pity, though, and loaned me his TI when he finished. Using it to check my answers, I was pleased that the Post had been correct - but the greater precision of a scientific calculator would have made all the difference in computing the long-term perturbations of those orbits. My grade went up accordingly. And I didn't forget to plug in my '67 again.

The slide rule got me through college - I may have been the only EE graduate there in 1975 to not have a calculator. But I was waiting for affordable programmability and bought my first, the HP-25, a month later when it came out.

I still have the Post, and a 5 inch circular one somewhere...

                  
Re: OT: My Slide Rule Collection
Message #4 Posted by Bill (Smithville, NJ) on 22 Apr 2013, 4:56 p.m.,
in response to message #3 by Jim Horn

Hi Jim,

Quote:
But calculators handily beat them in precision.

This is true but... one thing the slide rule did much better than a calculator was to teach the user the importance (might even say necessity) of estimating the final result - what we always called back of the envelop calculation. In my engineering office, you can tell who had grown up with slide rules and who grew up with calculators by their ability to quickly tell if a calculated result makes sense or not.

Quote:
I still have the Post, and a 5 inch circular one somewhere...

Yep, I still have my Post Versalog and the little 5" Post rule with magnifying glass, along with the hard back instruction book. These got me through all my courses at Purdue back in the late 60's.

Bill

Edited: 22 Apr 2013, 5:01 p.m.

                  
Re: OT: My Slide Rule Collection
Message #5 Posted by Peter Murphy (Livermore) on 22 Apr 2013, 8:21 p.m.,
in response to message #3 by Jim Horn

Using a slide rule also required that you learn something about logarithms. And although they're not used for computation anymore, logs still arise in useful mathematics; it was nice that students had the slide rule to help them learn about logs.

You also learned how to read analog scales, which are still used in graphs. Divisions on slide rule scales corresponded to increments of 1, 2, or 5, and graphs need such divisions if they are to be read easily; some graphing programs happily introduce scale divisions that do not meet that criterion. (Try interpolating by eye if the space between 5 and 6 on a graph axis is divided by two tick marks.)

                  
Re: OT: My Slide Rule Collection
Message #6 Posted by Garth Wilson on 22 Apr 2013, 10:47 p.m.,
in response to message #3 by Jim Horn

Slide rules helped the user to understand number relations better.

My close-up vision was always great, and especially before my 40's, it was only a small exaggeration to say I could see germs. I wouldn't have minded if the lines were made much thinner and closer together to get another digit when necessary. It might have required a tiny worm-gear drive on the cursor azimuth adjustment and the position of the upper and lower body pieces relative to each other though to make the accuracy match the precision. I was usually calculating values for electronic circuits though, and even the three to four digits you get from a slide rule were overkill for that.

                        
Re: OT: My Slide Rule Collection
Message #7 Posted by Jim Horn on 23 Apr 2013, 3:21 p.m.,
in response to message #6 by Garth Wilson

I agree with all about the need to have a feel for what an answer should be without any external tools. I've seen way too many examples of orders-of-magnitude errors accepted by others.

One other slide rule benefit was the quickly acquired skill to be able to quickly and accurately position the slide and cursor to great accuracy. In retrospect, the ability to reliably move something within milli-inches (tens of microns) with your thumb can serve in machining, guesstimation of thicknesses and offsets and more.

But yes, if computing the value of a 5% precision resistor, the old slide rule was terrific. Next to my desk I still have two HP ones from the 1970s: a "Mismatch Error Limits and Reflectometer calculator" and a "Pulsed RF Calcualtor", both with the old HP logo (with the commutator brushes above and below) from their Signal Analysis Division in Santa Rosa, California where I was privledged to work. Aah, memories...

Just noticed that these may be simulated on the Web, e.g.:

http://www.hpmemory.org/pict/technics/applet/slide_rule/reflectometer.htm

Science marches on!

                  
Re: OT: My Slide Rule Collection
Message #8 Posted by Mike Morrow on 23 Apr 2013, 9:26 p.m.,
in response to message #3 by Jim Horn

Quote:
When taking a US Air Force orbital perturbations class in 1976, I brought my Post slide rule to the final exam, getting quite a laugh from the others when I said I brought it as a backup to my then-new HP-67.

When I was taking the six-month academic portion of the U.S. Navy officer's nuclear propulsion training in 1974, slide rule use on tests was required...calculators were prohibited. The same policy had been in effect at Georgia Tech, from which I graduated in 1974.

The naval nuclear propulsion school delivered the finest course on slide-rule usage (all the tricks and shortcuts) that I have ever seen. My Dietzgen N1725L could do things I never dreamed, even though I had spent four years with it at Georgia Tech.

You must have gotten one of the very first HP-67 units if you had it in 1976. I was unable to get one until mid-1977, even after going to all the authorized dealers I could find in the Boston area, including MIT and Harvard Coops, for months.

Quote:
The slide rule got me through college - I may have been the only EE graduate there in 1975 to not have a calculator.

In 1974, very few students at Georgia Tech had a calculator unless it was something like the SR-10 or SR-11 with only a square root, square, and inverse as its scientific functions. The SR-50 was not yet available, and that most-desired HP-45 cost the 2013 equivalent of $1900. I had only a four-function Bomar 901B when I graduated.

Quote:
But I was waiting for affordable programmability and bought my first, the HP-25, a month later when it came out.

I waited to buy the TI SR-50 in December 1974. It remains one of my favorite TI calculators of all time. I didn't get a programmable until May 1977...the HP-67.

Quote:
I still have the Post, and a 5 inch circular one somewhere...

I still have my Dietzgen N1725L that I purchased new in 1969 for $35 (very expensive...that's equivalent to $222 in 2013).

Today, when one can get an HP 50G for under $100, and the new HP Prime for $150, it amazes me to no end.

Edited: 23 Apr 2013, 9:34 p.m.

                        
Re: OT: My Slide Rule Collection
Message #9 Posted by Garth Wilson on 23 Apr 2013, 10:05 p.m.,
in response to message #8 by Mike Morrow

I have never seen any video or discussion on how slide rules were made. Does it exist?

                              
Re: OT: My Slide Rule Collection
Message #10 Posted by Mike Morrow on 23 Apr 2013, 11:52 p.m.,
in response to message #9 by Garth Wilson

There's a lot of interesting slide rule information in the 25 Mb pdf book published in 2012 called All About Slide Rules. On page 2 there is a short section on how slide rules are made. There are some manufacturing notes spread throughout its pages.

I consider the Dietzgen N1725 to be the finest example of a scientific slide rule ever made. It uses maple for dimensional stability, and teflon runners for the slide to provide lubrication.

Edited: 24 Apr 2013, 12:11 a.m.

                                    
Re: OT: My Slide Rule Collection
Message #11 Posted by Garth Wilson on 24 Apr 2013, 3:04 a.m.,
in response to message #10 by Mike Morrow

That is a great book! I didn't really see anything about the actual manufactuing methods of slide rules though.

                                    
Re: OT: My Slide Rule Collection
Message #12 Posted by BShoring on 24 Apr 2013, 11:10 p.m.,
in response to message #10 by Mike Morrow

Special thanks to Mike for posting the link to "All About Slide Rules."

It is interesting reading even to someone who has never used a slide rule. A lot of good stuff to learn!

Thanks, Bob

                              
Re: OT: My Slide Rule Collection
Message #13 Posted by Bill (Smithville, NJ) on 24 Apr 2013, 4:27 a.m.,
in response to message #9 by Garth Wilson

Quote:
I have never seen any video or discussion on how slide rules were made. Does it exist?

There's a nice video from the MIT Museum - an interview with "Frank Adorney about the conception, development and fabrication of the Hudson 8 and Hudson 9 slide rule. This rule, invented by James R. "Pop" Bland, a mathematics professor at the U.S. Naval Academy, was the prototype for the famous Keuffel & Esser Deci-Lon slide rule."

MIT Slide Rule Interview

While not a video, the Slide Rule museum has a nice slide Rule course page:

Slide Rule Course

Bill

                              
Re: OT: My Slide Rule Collection
Message #14 Posted by Palmer O. Hanson, Jr. on 25 Apr 2013, 3:25 p.m.,
in response to message #9 by Garth Wilson

Quote:
I have never seen any video or discussion on how slide rules were made. Does it exist?
Pags 20-44 of Dieter von Jezierski's book Slide Rules - A Journey through the Centuries contains some information on construction and manufacture of slide rules. The book was originally in German but there is a translation to English by Roger Shepherd.

The journal of the Oughtred Society published a lot of detailed material on slide rule manufacture. I don't have my copies any more as I sent them to Joerg when I was downsizing my collecting activity.

                  
Re: OT: My Slide Rule Collection
Message #15 Posted by Ingo on 26 Apr 2013, 8:13 a.m.,
in response to message #3 by Jim Horn

I went into collecting slide rules and the HP Voayager series three years ago. I'm too young to have encountered slide rules in University or school. I grew up with pocket calculators, but was never able to afford an HP 11c or 15 c when I was at the university.

Now, an HP15CLE is my daily companion. Plus a beautiful wooden Nestler 251 slide rule in a leather pocket.

When in business meetings both create a lot of attention, esp. among the engineers, although the slide rule catches an order of magnitude higher attention than any new tech gizmo that might enter the scene.

                        
Re: OT: My Slide Rule Collection
Message #16 Posted by Derek Walker (UK) on 26 Apr 2013, 11:21 a.m.,
in response to message #15 by Ingo

Some years ago I used to attend meetings where there would be discussion of what combination of number, diameter and height of cylindrical tank(s) would give a required storage capacity. Using a slide rule with a three line cursor (including a pi/4 constant reading on the A/B scales) I could come up with several combinations before the calculator users had got past inputting the first pi x r^2. I used slide rules up to and including university, but many of my younger colleagues had never seen, let alone used, one.

            
Re: OT: My Slide Rule Collection
Message #17 Posted by Palmer O. Hanson, Jr. on 24 Apr 2013, 10:43 a.m.,
in response to message #2 by Garth Wilson

"OK, now how do you add?"

Really, really old users of slide rules will remember that it was possible to add and subtract 3 digit numbers if the L scale was on the slide.

"Those who were proficient at it however did not gain any real time savings when going to a calculator, until calculators became programmable."

The major deficiency of the slide rule was the inability to concatenate addition, subtraction, multiplication and division without moving back and forth between the slide rule and some method for addition and subtraction.

Edited: 24 Apr 2013, 10:50 a.m.

                  
Re: OT: My Slide Rule Collection
Message #18 Posted by Sílvio A. Bensi on 25 Apr 2013, 7:20 a.m.,
in response to message #17 by Palmer O. Hanson, Jr.

Quote:

"Really, really old users of slide rules will remember that it was possible to add and subtract 3 digit numbers if the L scale was on the slide."


Thank you Palmer!

            
Re: OT: My Slide Rule Collection
Message #19 Posted by Garth Wilson on 25 Apr 2013, 11:47 p.m.,
in response to message #2 by Garth Wilson

Encouraged by this topic, I posted a page about my slide rules on my website, at http://wilsonminesco.com/SlideRules/SlideRules.html . The ink is still wet and I haven't linked it into the rest of the site yet; so if you see glaring errors, email me at wilsonmineszdslextremezcom (replacing the z's with @ and. ).


[ Return to Index | Top of Index ]

Go back to the main exhibit hall