Thread: Memory teaser

Hi kraits
Its called a slide rule, I'm sure if you google you will find info on how to use it. If not let me know and I'll put something together. You could make it a puzzle for you to work out how it works?
The longer they are the more accurate, the longest I have heard of was 7" (BTW you can also get round ones)

Staurt

Hi Stuart, Kraits,

The slide rule brings back memories, I used one all the time back in the 60's, that one looks fairly primitive being wood, the ones I used were plastic log-log slide rules ("sly drool" we used to call them).. log-log type meant you could do exponents.

I still think slide rules are good for quick calculations, you get a feel for the sensitivity of a calculation to different variables, because you can see instantly not just the result but all the numbers either side of the result.

Good find.

Regards
Ray

PS. Stuart, good to catch up on the weekend, enjoyed it greatly, now I'm just about to start putting some of that scraping instruction into practice on an angle plate..

I have one here that is white plastic and in a cardboard box. It's from my father in law who was a draftsman for the mines.
It has been years since I looked at it, but from memory my one was a sliding rule for drawing to scale, but I am not 100% on that.
I also got his old drafting board with it and many other drawing pieces.

Dave

any benifits to learning how to use this tool? regardless, i would be interested to know how, so let me have it.

Originally Posted by kraits

found a couple of books in the shed that the old man gave me about 15 years back,the newmans is dated 1949 and the 17th edition is 1966, the newmans is full of ads, really interesting to see.

also found a calculator ruler he gave me way back and i never learn't to use it, anyone ever come across one before,familliar with it?

Kraits
The Machinery Handbook is invaluable for looking up reference info on all sorts of Engineering.
Please keep it in safe keeping.
I have the 15th Edition I purchased new in 1958 I was 14 at that time. Still use the book frequently. There is a wealth of info in it. Always discovering new things in it & continually learning.
Also have the Slide Rule but its more of a memory.
The Newnes Ref book would also have a lot of good Eng Data that does not change much through time.
All good stuff !
Bruce

Hi Ray,
I've only ever used them for "entertainment" so I was always somewhat slow with them.

Stuart

p.s. sorry to run off but I'd been having some issues with one of my dogs, all good now it seems. Also I just remembered I said I would whip my vice apart and take some pictures for you, I'll get on it as soon as I finish another post.

The first thing you need to do is remove the slide and turn it around so that all the numbers are the same way up.

To do a basic mutiplication

find "2" on the fixed scale, slide the moving scale along until the "1" is adjacent to the "2", now slide the cursor along to the "3" on the sliding scale, look down to the fixed scale under the cursor and you will see that it coincides with "6" - 2x3=6.

If you slide the cursor to other points on the sliding scale you will see that wherever you place it 2 x the number on the sliding scale is equal to the number under the cursor on the fixed scale.

To divide, just reverse the procedure.


for some more comprehensive instructions try here

Eric's Introduction to the Slide Rule page


When I was in high school, just before electronic calculators were available, we did a whole year of slide rule instruction using rules that had all sorts of scales that performed all sorts of calculations. Then along came Texas instruments and Messrs. Hewlett&Packard and calculators became relatively cheap and common. I think I paid about $300 for my first HP calculator. I still have a couple (a 12C and a 98 I think), and I still speak fluent Reverse Polish Notation.

I wonder how many here no what that is?...

Originally Posted by Avery

. I still have a couple (a 12C and a 98 I think), and I still speak fluent Reverse Polish Notation.

Hi Avery,

Is one of those HPs a desk top, programable one? Isn't that where RPN comes in?

My father has one, still wokring last I heard. Back then I could program it if I had the book but certainly not off the top of my head. Wouldnt know where to start now.

Stuart

Originally Posted by Stustoys

Hi Avery,

Is one of those HPs a desk top, programable one? Isn't that where RPN comes in?

My father has one, still wokring last I heard. Back then I could program it if I had the book but certainly not off the top of my head. Wouldnt know where to start now.

Stuart

Both my calculators are pocket versions. The 12C is a financial calculator and the other, which I cannot find, is a scientific calculator, I think now an HP45.. Both use RPN. HP did make some desktop calculators, the 98xx series some with printers built in. All of HPs calculators used RPN . It was Bill Hewlett's baby.

RPN really has nothing to do with the programability, it is the method of doing the calculations. The calculators used a stack of memory registers the lower two being the x and y registers. The x was the register that held the display contents and the y was the one above it.

RPN calculators do not have a "=" key.

They do have an "enter" key.

to multiply 2 x 3 the sequence is "2" "enter" (the enter shifts the 2 from the x to the y register) then "3" then the function key, in this case the multply key. The result appears in the display (x register). A subsequent calculation requires the number to be entered and a function key pressed. This method , for a sequential calculation, means less keystrokes and the interim results being shifted up through the registers for later retrieval.

It sounds complex but the actual use is amazingly simple.

Most of the above, except the longest slide rule I've used was 24". In olden times, maths classrooms had jumbo slide rules for instruction, mounted above the chalkboard (also a relic I suppose). IIRC, it was about 6 FEET long.

I have a 12" plastic one right here at my desk, for very quick calculations including trig functions. The number scales are logarithmic, so multiplication is achieved by adding logarithms; division by subtracting. For square root, read directly across from the doubled scale (B to C, or A to D). Similarly, read C^2 on the B scale, or D^2 on the A scale.

In many calculations, intermediate or final results are beyond the scale, so you reset the index by moving the slider bar. See Avery's link for guidance. This is where the circular slide rule comes into its own: The index is automatically reset. Several years ago, I had need for a circular slide rule, but couldn't find one commercially. So I made my own, using a computer of course. I prepared a spreadsheet of logarithms for all the tick marks as radial lines. The output was a roster of x-y coordinates of all the lines. I incorporated them in an AutoCAD script to draw the picture for printing. Much fun watching the animated drawing.

The supreme benefit of using the slide rule is no more precision than needed, and also providing a sense of significance. Downside is you must provide the location of the decimal point by feeling the magnitude.

My HP-35, -45, and -41CV have all died, and I really miss the RPN.

Cheers,
Joe

this is bull sh#t, i can do 2x2 in my head, are you guys kidding me or what?

Hi Avery,
Thanks for that, its sort of coming back to me now that you say it. I'm pretty sure its a scientific calculator, certainly no printer.
They were programmable though right?
You could enter the formula as a program and then just key the variables each time instead of the whole formula?
Would be 20+ years since I used it for real.

Stuart

Joe,

I had forgotten circular slide rules. I am sure I must have one somewhere, probably in the same place as my HP45, hence I will probably never find it.

I think you can still buy HP calculators, I know the 12C was still being sold a couple of years ago.



"you must provide the location of the decimal point by feeling the magnitude."

I think I will use this!

Talk about a blast from the past!!

Used to use a circular slide rule all day every day in the 60s and early 70s, then we bought a Facit electrio-mechanical calculator and I thought it was Christmas.

Still have the circular slide rule somewhere, I'd have to put my thinking cap back on to get up to speed again.