# Before There Was Calculators.



## Grumpy Gator (Jun 11, 2015)

Found this round slide rule under the bottom drawer of a Kennedy box. I had a hard enough time learning the basics of a normal slide rule many years ago.



*********Just Saying**********G*****************


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## Dinosaur Engineer (Jun 11, 2015)

The flat disc slide rule works on the exact similar principal to that of the linear slide rule. If you can use a straight linear slide rule you should be able to use type.
A further more accurate slide rule was the drum slide rule used by a lot of Drawing offices. These had the logarithmic scales on the outside of a drum which could have a scale length of 500 " as opposed to the 10" normal straight linear type. Sure was a lot quicker (though not as accurate) as using log / anti-log tables ( 7 fig. tables in the D.O. !)
Happy days !


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## silence dogood (Jun 11, 2015)

In hi school, I had one of those.  As for being accurate, yes and no.  In  1972,  I took an electronics theory course.  In many cases, there were a series of calculations.  The guys who spent about 250 bucks for a scientific calculator many times were farther from the answer than I was with my old slip stick.  The calculator took it to too many decimal points where as the slide rule  would automatically round it off.   Mark


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## kvt (Jun 11, 2015)

Ok,  are we dating our selves again,  Now days I do not think they know how to use a slide rule,   (it would take me a little to remember as it has been so long).   I had one like that that I used in high school doing engineering and drafting.   Of course we had the old T square, Bottled ink with the dropper, and such.   None of the fancy stuff.


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## Smithdoor (Jun 11, 2015)

I still have one today use it back in the late 60's 
Still works today and battier need

Dave


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## Danb (Jun 11, 2015)

Had one in high school, used one for the first two years of college--couldn't afford a calc.  Carried one in my shirt pocket as an engr in gas plants--because it was intrinsically safe.  Probably still some chicken scratch on the I-beams of those plants where I was trying to keep track of the decimal points.  The good old days.  Still have a couple and still use them.


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## davidh (Jun 12, 2015)

i can certainly relate, remembering the first electric calculator we got. . . i think it was a remington.  still have my slide rules in the desk.


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## Cactus Farmer (Jun 12, 2015)

Rule #1, Slide rules need no batteries!
My first really good calculator was an HP35. Reverse polish is better in my opinion..........I miss it still.


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## David S (Jun 12, 2015)

I grew up using the linear slide rule at University.  Mine was a K&E, others preferred the Picket, and there was a laminated bamboo Japanese.  My first work term was with a British Engineer and he was using a Curta.  I never mastered that one.
https://en.wikipedia.org/wiki/Curta

David


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## RJSakowski (Jun 12, 2015)

I still have my first Picket N902 and the over-the-top Picket N4 Log Log Dual Base Speed Rule along with its holster.  I can't remember having used the hyperbolic or log-log scales but I did use the rest of the 29 scales.

One of the problems with linear slide rules was when performing  chain multiplications or divisions, you could run off the scale so you had to slide the slide over to the side to continue.  The circular slide rule just wrapped around so it eliminated that inconvenience.

I designed and built a custom circular slide rule for my ex, many years ago.  It calculated the length of bar stock required to make a horse shoe, based on the dimensions of the horse's hoof.  The scales were printed on adhesive backed Mylar and glued to aluminum backing , the product being sold to farriers.

It is amusing to show the slide rule to some of the newer engineers.  I like the quizzical looks it generates.  Same goes for log and trig tables.


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## Chip Hacket (Sep 7, 2018)

Cactus Farmer said:


> Rule #1, Slide rules need no batteries!
> My first really good calculator was an HP35. Reverse polish is better in my opinion..........I miss it still.



Need help! I can’t find the Equal Sign.


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## vocatexas (Sep 7, 2018)

Several years ago I had taken my mother to a doctor out of town and she saw an antique shop she wanted to stop at. I went in too, and saw a strange device like I had never seen before. I think it was marked $25; if that isn't it, it wasn't much more. I didn't have a clue what that thing was and left it on the shelf. About three years ago I ran across something about Curtas somewhere and remembered seeing that one in the antique store. Still kick myself for not buying it. I just had a feeling it was worth something and talked myself out of buying it.


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## homebrewed (Sep 8, 2018)

I used a circular slide rule all through college.  The HP35 was introduced when I was a Senior EE student but was way too pricey.  I still have the circular (somewhere).  At work I'd occasionally drag it out to show to my younger colleagues, telling them it was a calculator that worked without batteries.


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## DiscoDan (Sep 8, 2018)

I was at an antique store in Frederick, Maryland yesterday and the guy had a very large slide rule that looked to be maybe a teaching aid and it was about 4 feet long by about 10 inches wide and everything worked. He "only" wanted $495!


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## Bi11Hudson (Sep 8, 2018)

Still have my Deitzgen engineering slide rule. And still like RPN over algebraic calculators. My slide-rule is in a glass front case with a hammer attached. And a sign saying "*In case of computer failure, Break Glass*". Never went to high school, picked up the EE offshore a few years later. Guess I missed all the fun of high school... ...


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## higgite (Sep 9, 2018)

I still have my Post bamboo slide rule from when I was in college 100 years ago, complete with leather scabbard. If you ask today’s kids, “If Joe and 10 of his friends each had 4 calculators, how many calculators did Joe have?”, they’d reach for their calculator.

Tom


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## tcarrington (Sep 9, 2018)

Took course in engineering curriculum - nomography - we learned how to construct the "on paper" calculators that you laid a ruler across and connected the quantities you had making the ruler cross another line with the quantity(ies) you wished. Miles per gallon calculators are an easy example. Design of pressure vessels is a complicated one. Any equation can be represented with such a chart. It was a very informative course taught by an excellent professor and it explained a whole lot about how the world works and how we approximate it to our best benefit. Now we use spreadsheets and apps to generate these types of short cuts.


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## RJSakowski (Sep 9, 2018)

tcarrington said:


> Took course in engineering curriculum - nomography - we learned how to construct the "on paper" calculators that you laid a ruler across and connected the quantities you had making the ruler cross another line with the quantity(ies) you wished. Miles per gallon calculators are an easy example. Design of pressure vessels is a complicated one. Any equation can be represented with such a chart. It was a very informative course taught by an excellent professor and it explained a whole lot about how the world works and how we approximate it to our best benefit. Now we use spreadsheets and apps to generate these types of short cuts.


Back in the eighties, I designed a circular slide rule the would calculate the length of bar stock required to make a shoe for a horse, based on two measurements of the horse's hoof.  My ex, who was a farrier, made and sold quite a few of these to other farriers.


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## Downunder Bob (Sep 9, 2018)

Slide rules, used to love them. As a Marine Engineering student at Sydney Uni (Australia) in the early seventies, calculators were very basic and we weren't allowed to use them anyway. So it was Long hand, Log tables or a slide rule. The slide rule was by far the quickest, you just had to be careful when keeping track of the decimal point. They were in their own when it came to doing calculations involving raising a value to a power that was not a whole number as in 2, 3, 4 etc. calculations on the expansion and compression of gases in particular often involve a power of 1.3 or 1.4 etc.

I still have a couple of good old Japanese bamboo slide rules, they were the best. And a circular one as shown above, they were particularly good at trig calculations,


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## RJSakowski (Sep 9, 2018)

Dinosaur Engineer said:


> A further more accurate slide rule was the drum slide rule used by a lot of Drawing offices. These had the logarithmic scales on the outside of a drum which could have a scale length of 500 " as opposed to the 10" normal straight linear type. Sure was a lot quicker (though not as accurate) as using log / anti-log tables ( 7 fig. tables in the D.O. !)
> Happy days !


I used five place log tables a lot on college when we needed more precision than the slide rule would provide.  One can appreciate the seven place tables when you realize that every additional place multiplies the number of pages of tables by ten.  My five place tables in the CRC Math Handbook require 20 pages.
One can also appreciate the power of the modern calculator.  The Android calculator on my phone displays 11 decimal places. To replace it with a set of log tables would require 20 million pages.


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## JPMacG (Oct 17, 2018)

I was taught to use a slide rule, trig tables and log tables in high school.  Scientific calculators were just becoming affordable when I started college in 1974.   I think the day I got my first scientific calculator rates among the happiest days of my life, along with the birth of my children, etc.  I have never looked back with nostalgia at slide rules or tables.  I have not used them since 1974 and I have no desire to ever again


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## ch2co (Oct 19, 2018)

You guys got me thinkin' (dangerous) about the distant past when slide rules ruled. I went digging around in my calculator drawer and found 
a circular slide rule (from high school) my dad's very old wooden slide rule, three 6" mini slide rules??, my trusty log log decitrig that was a requirement to have hanging on your belt if you were a dedicted engineering student, and somewhere i have a cilendrical slide rule that if "unrolled"
woul be like 5 foot long (for greater accurcy). Then came my piece de resistance, my Curta mechanical hand cranked calculator which was a dream to use when I was on surveying crews. Then of course came the HP electronic hand held wonder that I have 4 different models of. jeese! Totally rediculous, except for the fact that I looked up Curta calculators online and the dang things are going for  between 1000 to 2000 bucks! Thanks for making me dig into the collection!

one last thing I have to mention that I learned in high school: 
As the animals left the ark, Noah told them to go forth and multiply. After some while, Noah happened upon two snakes sunning themselves. "Why aren't you multiplying?" Noah asked. The snakes replied, "We can't, we're adders."
So Noah and his sons went into the nearby forest and felled some trees. They made a platform of logs onto which they placed the snakes. You see, even adders can multiply on a log table.

Sorry


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## Downunder Bob (Oct 19, 2018)

ch2co said:


> You guys got me thinkin' (dangerous) about the distant past when slide rules ruled. I went digging around in my calculator drawer and found
> a circular slide rule (from high school) my dad's very old wooden slide rule, three 6" mini slide rules??, my trusty log log decitrig that was a requirement to have hanging on your belt if you were a dedicted engineering student, and somewhere i have a cilendrical slide rule that if "unrolled"
> woul be like 5 foot long (for greater accurcy). Then came my piece de resistance, my Curta mechanical hand cranked calculator which was a dream to use when I was on surveying crews. Then of course came the HP electronic hand held wonder that I have 4 different models of. jeese! Totally rediculous, except for the fact that I looked up Curta calculators online and the dang things are going for  between 1000 to 2000 bucks! Thanks for making me dig into the collection!
> 
> ...


Yes I also have a few old slide rules including a circular trigonometry special, and a Sun Hemmi, a very nice engineering model from around 1970. 

That story about the ark is very funny, do you mind if I copy and share it with some friends here in downunderland.


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## ch2co (Oct 19, 2018)

Well I stole it from somebody so steal away! It’s too good not to share.


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## magicniner (Oct 20, 2018)

I still have my slide rule, it's great for very quick, fairly accurate figures.


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## Downunder Bob (Oct 20, 2018)

Deleted member 18150 said:


> Found this round slide rule under the bottom drawer of a Kennedy box. I had a hard enough time learning the basics of a normal slide rule many years ago.
> View attachment 105559
> View attachment 105560
> 
> *********Just Saying**********G*****************



I have one just like that, but please tell, what is a Kennedy box?


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## ch2co (Oct 21, 2018)

silly!  A Kennedy Box is a box you keep Kennedys in. 

Kennedy is a brand of tool boxes. Typically painted brown with many drawers to keep (and loose) tools in.
Considered as a must have by many.


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## Downunder Bob (Oct 21, 2018)

ch2co said:


> silly!  A Kennedy Box is a box you keep Kennedys in.
> 
> Kennedy is a brand of tool boxes. Typically painted brown with many drawers to keep (and loose) tools in.
> Considered as a must have by many.



As in used politicians.

I get it It's just a brand name fro a generic draw type tool box. We have similar here but different brand names usually named after the big box hardware, and auto parts stores that sell them. And if you've got more money than brains, you can get them with names like Snap on.

In my day we made ours out of scrap timber, still got mine was made in 1961 while first year apprentice.


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## ch2co (Oct 21, 2018)

Yeah Kennedy’s have almost a cult following. They go WAY BACK in time.  I have two of them. They are primarily used for bench top small tools.  They also make a lot of other style general tool boxes I’ve got several. One for plumbing, one for electrical, one for general carpentry etc. 3 of these are red and two are brown., but when I think of Kennedy cases I usually think if the bench top units.


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## Downunder Bob (Oct 22, 2018)

I get it. As I said mine is similar style but made out of wood, i'll get a photo of up here sometime. Some guys who were good at sheet metal work made their own in that style, Nowadays they just buy them fro the big box store.


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## Bi11Hudson (Oct 22, 2018)

An afterthought that I happened to remember;

Had an instructer way back when calculators first came out. Since I never went to high school, I was forced to take remedial mathematics even though I already knew much of the material. In any case, the instructor had a system where a calculator could be used but wouldn't provide the exact answer he wanted. Such as ["Pi" times 4]. If any number showed up, the answer was wrong. So, I *did* learn something new. I would have calculated the answer out longhand and still gotten it wrong. A Mr Tate, whom I'm sure is no more.


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