# HP Forums

Full Version: OT - slide rules
You're currently viewing a stripped down version of our content. View the full version with proper formatting.

I know that more than a few of you are slide rule junkies. Check out the current issue of Scientific American, article "When Slide Rules Ruled."

It even has a picture of the HP-35 which, it says, sounded the death knell for slide rules.

Good article, I finished reading it just a few minutes before going online. A while back they also had an interesting article about the curta calculator. Now I think an article about the hp-35 is due.

Do you mean the edition of April 2006? Sorry, I don't see it there ... d:(

For a while now, i've been using a slide rule for real world use! not as a calculator replacement, but i've found some situations where a rule works really well.

i've taken to carrying around a small 5 inch pocket rule. i quite like the pocket sizes rules. the one i've been carrying is a pickett. this isnt the best pocket rule either; i have a K&E and a Faber Castell that are both nicer, better made and more comprehensive – the picket is just smaller and not very rare or valuable.

anyway, here are my uses. (1) i've noticed that restaurants are dark and there’s almost always a prime number of people to divide by. since the number is usually between 3 and 13, these are all easy on a rule and it gives me an “analogue” result which i ignore anyway and scan forward to the next major division and call that the answer.

(2) supermarkets have taken to making “special offers” sometimes worse value than before. to compare price/quantity ratios on a rule is easy, take the first price, divide by first quantity and multiply by second quantity. compare answer to second price. the divide-multiply is easy on a rule because you don’t worry about the intermediate result – you just slide forward. even quicker is that you often know whether the result is better or worse simply by the direction of travel of the slide on the final multiply. in which case you don't even bother to line it up (assuming you just want a comparitor).

its not worth carrying a 10 inch rule about for these because 2 figure accuracy is fine for this kind of thing. the one thing that i would like tho’ is a 5 inch rule with a folded multiply/divide scale (ie 10 inch precision) but no advanced scales (trigs, logs etc), otherwise it would be too fat.

so there.

Thanks for that recommendation. I was interested enough to download a digital version. A fascinating article.

Delighted to see a Faber 2/83 slide rule featured as I have one of these and it is a really lovely piece of engineering.

My older sister kindly sent me her Farber Castell 2/83 slide rule from Vietnam. She bought and used it while studying to become a civil engineer. It is in perfect condition. I attended college in the US and in 1975 which is after the HP so I didn't have any slide rule.

It's in May 2006

Quote:
to compare price/quantity ratios on a rule is easy, take the first price, divide by first quantity and multiply by second quantity. compare answer to second price. the divide-multiply is easy on a rule because you don’t worry about the intermediate result – you just slide forward. even quicker is that you often know whether the result is better or worse simply by the direction of travel of the slide on the final multiply.

Actually, you don't need to move the rule a second time. Set the first price on the fixed scale over the first quantity on the sliding scale. Then look above the second quantity on the sliding scale and there you'll find the second price. If the actual second price is more, you're getting ripped off.

This is a great example of one of the basic details about how a slide rule works. At any given setting, the ratio of any two values on the adjacent scales is constant for that setting. This didn't really occur to me until I started using my brand new E6B circular slide rule in flight school way back in 2001.

Stefan