Buy a slide rule…. really. we’re not crazy


One like this went to the moon. That’s how useful they are.

Slide rules were IT for decades. No engineer could be without one.

Okay, this may sound odd to some, but in case you didn’t know, without the slide rule calculating device the engineers would not have been able to make the atom bomb, or go into space.  And guess what, if our power grid ever comes under stress from solar storms or just plain overuse, one of these could come in REALLY handy for engineers.  No batteries required.  These things last a really long time, too, because they were carefully crafted, precision made.    Many were made from bamboo, then later aluminum or other metal.   Some were over a foot long.

Slide rules come in a wide variety, from short and simple to big and complicated.   Some are geared toward trigonometry, with an easy way to read sine/cosine   tan/cotangent, logarithms.    There are scales for square root and square, cube and cube root, division/multiplication.  When you see the result on a slide rule, you can slide the viewer up and down the scale and immediately see proportions and ratios.

So, look around on ebay and pick up a classic by Pickett, Koeffell, Faber, Hemmi, or others.   Keep it around, in a drawer or on display.   Power out  and your iPhone calculator on the fritz ?   no problem.    The really good ones hold their value well as a small investment.. condition, condition, condition is the rule.  The more scales, and the older, the more valuable.



And, don’t ignore the extremely useful circular slide rules, calculators.   They come in a large variety, usually plastic or thin metal, with several concentric rings of scales and a sliding pointer.    For example, see Concise Circular rules.  still being made.  For many professionals in engineering, drafting, electronics, or even business math, these devices are still extremely useful, partly because of their speed.  no need to punch buttons.

Ode to Slide Rules

SLIDE RULES.. are very cool. Okay, so we have computers and iPhones.. BUT, we all must pay some honor to the fine precision devices that allowed engineers to invent the a-bomb, early electronic gadgets, and so much more that we totally depend on today.   So, if you get the urge to insult them, or laugh at them, hold it in.     They are built extremely well so they last a very long time. plus, if the power ever goes out… … and it does… you can grab a slide rule. OR a solar powered calculator, to crunch the numbers.    Oh, well, I still like slide rules.  they’re cool I have a few, maybe more than a few.     They’re like tube radios…  yeah, they’re old, but way cool.    retro.

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 But REALLY, there are some really good reasons to own a slide rule !

        Easy to use, and FAST.   Slide rules may look complicated at first glance, but they are quite easy to use.   Once you learn a few basic principles, you apply them to all the various scales on the rule.   Slide rules have been made customized to various industries, or types of calculations done, such as pipe flow, electronics, etc, to enable fast calculations.

           SO, why a slide rule, when one can use a modern scientific calculator ?    Well, for one thing, it’s very interesting to learn about how we all got our fantastic electronics gadgets.   There are people living today who remember having almost no access to a calculator.   At that time cash registers and adding machines had hundreds of moving parts, very heavy, and were used only in industry and government.    Indeed, some types of calculators were kept hidden.  It was a military or business secret advantage.    Back then you had to learn your numbers in school and know how to do mental calculations, and paper and pencil, to do math.   Once slide rules were invented, it enabled a tremendous boost in math productivity over many decades, because more people could make precise calculations.  That’s extremely important in engineering and business.  A slide rule was like Lotus 1,2,3, the first spreadsheets, in the effect it had.    So, slide rules enabled us to have all the modern gizmos that need tons of math.   They enabled engineers to design electronic circuits much faster, leading to our modern computers.

        To most people, using a slide rule seems weird.    It’s just a different way of looking at calculating.    Remember, the abacus was used for a very long time, because it worked, plain and simple.   Slide rules are like that.    A simple system, used repetitively.   Once you learn it, it’s easy.   A lot of people need to use basic math during daily activities.   Perhaps you need to calculate square feet, or know how many inches in 50 centimeters.   Or maybe calculate gas mileage.   Beyond that, many professionals need to determine rations quickly, such as artists, engineers, draftsman, and so on.   For specific tasks, a slide rule is very effective and fast.   Plus, they are cool.  Never need batteries.

       Advantages of a slide rule.    All math is just a combination of four basic relationships.   add / multiply   and subtract / divide    Multiplying is just a lot of adding at once,     and  dividing is a bunch of subtracting.     When calculating moving systems, like speed, motion, direction and for 3 dimensions such as volume, one often needs to determine roots…squares, cubes.  This can be done easily on a slide rule.    

        Using the ‘slip-stick’ to great advantage.  The slide in a slide rule can position numbers in relation to another number, and you get the result on the vertical line.    One advantage of this system is in determining factors and ratios, since you can slide the vertical indicator back and forth and look for common factors and ratios.     With an electronic calculator, you may have to reenter a bunch of numbers, trying to get close to the result you are looking for.   On a slide rule you can move the slide back and forth to come to a quick conclusion, such as for estimating square feet, or cubic meters, etc.

Compasses – they’re really important.

Sextants were once incredibly important. They enabled sailors to explore the world for centuries. Now they are rarely used.

Navigation article

Do you know how to navigate ? Click on article link above..

Compasses are a pilot’s best friend because they don’t use any electronics, for one thing.      If you do much hiking, boating, flying, driving, or biking, it’s a good idea to have a quality compass in your gear.

Get a GOOD compass. click to shop

 Compasses come in a wide variety, depending on the use.  

 See our reviews and discussion about navigation on YouTube.    Above is a good selection of samples, and below is some information about each of them.

A.  Airguide liquid fill auto or boat compass.   These may be affected by metals in the vehicle, so will show some deviation, especially while in motion.

B.   Airguide, large, for a boat.    The bigger the better, more accurate, doesn’t spin as much.   Liquid filled.    Great paperweight, but also useful.

C.   This is a fascinating hand bearing compass, with a radio receiver for what’s known as Non-Directional-Beacons, or ADF, long used by pilots but fading out now because of GPS.  many of these beacons are near shore, so boats can get a bearing on a beacon, move, get another bearing, and determine speed and direction.   It works, uses a small headphone, earbuds.     I would take it in a plane or boat.

Lensatic, vintage marching

D.  Lensatic sighting compass.    Many styles have been made, better ones are liquid filled and have pointers that glow in dark with a bit of flashlight for a few seconds.   You sight along a wire, line up a slot, look down and take a reading.   Great for hiking, rescue work, and going out into the boonies.

E.  A military sighting compass, unique design, declination adjustable, measured in degrees.   Kind of a marching compass.  very durable, this one’s at least 50 years old.

Brunton Eclipse, Vintage artillery/surveying,   clone, surveying

F.   Brunton Eclipse.  the prize of Brunton orienteering and sighting type compass.  very light, durable, has an inclinometer feature, nice instruction pack that’s attached.  Declination adjustable.   Long lasting.  increments of 1 degree.

G.  German artillery and surveying compass, measures in mills.  declination adjustable, tripod mount with level for doing angle and distance readings, calculations.    Aluminum     This will last another few decades I’m sure.

H.   Chinese clone of a very good surveying compass by Brunton and a military version, the M-2.   It’s not as good quality as the genuine, but the needle is accurate and fast to settle.  It works fine.   If you know what you’re doing, you could do some serious work with one of these or the M-2, like build a bridge or road.   This and a telescopic transit, and some measuring rods.   The Brunton surveying compass is very costly, but you can find them used sometimes for great prices.

walking compass, hand bearing for kayak

I.   Old walking compass.   back in the day….. really, people actually carried a compass, because if you didn’t, you could wander off somewhere, like the countryside of England.   This one is sealed, water bathed needle, very durable, probably at least 40 years old.

J.  Marine hand bearing compass.   You hold it up to your eye, and read off the bearing to  the point in the background.    very sturdy, for boats and canoes mainly.

Silva sightmaster, Brunton racing, simple baseplate

K.   Silva’s jewel, the  Sight Master surveying compass and inclinometer.   fine construction, site in one end to read precise degree increments, and inbetween.   Other end you sight for angle tilt.   Easy to read, for the pros.

L.  Brunton racing compass, also a good baseplate for orienteering.    very easy to read quickly.   declination adjustable, liquid filled.  has several scales with detail triangles for precisely locating oneself on a map, such as a marine offshore chart or in a forest in difficult terrain.   Take a few sightings, triangulate, place the bearings on the map, and use the small scales to precisely locate.

M.  another simple baseplate compass.  ANY compass is better than none.   but get one that is easy to read, liquid filled, declination adjustable, durable.


The Brunton brand is well known and they make good stuff.

If you buy a compass, get one that’s well made and keep it away from magnets, and electromagnets, and electric motors.

Also good..

Suunto, Silva, military compasses, and those used by surveyors.   There are many good  digital compasses including those on watches, but beware… what if the batteries go out ?

Watch video, review of types of compasses.



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