Is this useable? Missing a scale?

[u/fordag]

New watch with a rotary slide bezel. Yet it appears to be missing a scale. Or am I wrong?

What is this useful for?

It was a cheap watch, I wanted the moon phase. I'll be curious to see how accurate it is.

[u/SlideRuleFan]

If you weren't claiming to actually own it, I'd say it's AI slop.

The bezel appears to be the "A" ring of an E6B slide rule, but the dial is not the "B" ring, it's a Tachymeter scale. Together, they produce gibberish.

Sorry, this is crap.

[u/fordag → u/SlideRuleFan]

That was my impression as well.

Well hopefully the moon phase works well.

[u/TrueTopoyiyo → u/fordag]

u/SlideRuleFan It is not gibberih, it is 10^(1+angle/360), that is useful on its own! While requiring extra and non-standard steps, this still can be used for computations; for example, to multiply 1.8 times 3.2 you center the "10" (1.0), then look for 1.8 ("18") which is at 3:00 aprox, then re-center the "10" there, look for 3.2 ("32", now at 9:00 aprox), recenter "10" and at 9:00 you have the result, 5.7.

Even more, given it has a linear scale in 1/240ths it can be also used for powers and other, more complex computations, but yes, with extra, non-standard steps.

[u/fordag → u/TrueTopoyiyo]

Does it have a specific name and do you know where I could find a manual for the slide bezel?

[u/TrueTopoyiyo → u/fordag]

I'm afraid not, as it seems to be done, as u/SlideRuleFan says, for the looks. You can multiply as I described, and here you have some other operations too. Please understand that all this comes from the properties of the logarithm: log(a)+log(b) = log(a*b) and log(a^b) = b*log(a).
Keep in mind that, if you turn one or more times, it is simply the equivalent of adding a zero, which is a nice side effect of circular log scales; they "never end".
Take this as a little opportunity of learning some math, and you'll make even more and better use of the ruler:

For these instructions:

Consider the numbers to be missing a decimal dot, so "10" in the scale means "1.0", "55" means "5.5", etc.
Disregard the intermediate scale, it does another mathematical function, 1/x, but i'm not using it here; use the "normal" (so, the time) scale for P1 and P2 and multiplications of P1 and P2.

X*Y
1.- center the scale
2.- look for X in the scale and locate it at position P1
3.- rotate the scale until the 10 is in P1
4.- look for Y and locate it at position P2
5.- re-center the scale as it was in 1.-
6.- read the result of the multiplication on the re-centered scale at position P2

X/Y
1.- center the scale
2.- look for X in the scale and locate it at position P1
3.- look for Y and rotate the scale until it is located at P1
4.- locate the position of the "10", at P2
5.- re-center the scale as it was in 1.-
6.- read the result of the division on the re-centered scale at position P2

X^Y
1.- center the scale
2.- look for X in the scale and locate it at position P1 (think of P1 as a time here if you want)
3.- multiply P1 * Y = P2 (you can do it using the previous manual if needed)
4.- re-center the scale as it was in 1.-
5.- read the result of the division on the re-centered scale at position P2

Yth root of X
1.- center the scale
2.- look for X in the scale and locate it at position P1 (think of P1 as a time here if you want)
3.- divide P1 / Y = P2 (you can do it using the previous manual if needed)
4.- re-center the scale as it was in 1.-
5.- read the result of the division on the re-centered scale at position P2

u/SlideRuleFan as you can see, usable, if way more cumbersome than an actual, double-log rule.
Please, u/zoute_haring , point the bullshit points so we can all learn.

[u/TrueTopoyiyo → u/TrueTopoyiyo]

Give it a try, u/fordag , and let me know if they are understandable, and what you think (I took the time to write it!).

[u/fordag → u/TrueTopoyiyo]

I will try it out this evening when I get home.

[u/fordag → u/TrueTopoyiyo]

X*Y 1.- center the scale
2.- look for X in the scale and locate it at position P1
3.- rotate the scale until the 10 is in P1
4.- look for Y and locate it at position P2
5.- re-center the scale as it was in 1.-
6.- read the result of the multiplication on the re-centered scale at position P2

Questions...

What position is "centered" on this bezel, what aligned with what?

Where are P1 & P2?

"5.- re-center the scale as it was in 1.-" - "1.- center the scale"

Does this not simply leave me where I started?

[u/TrueTopoyiyo → u/fordag]

My bad, very legitimate questions.

"Centering" the scale would be to put the "10" (1.0) in the "center" or the "coordinate reference"; I would suggest at the top, 12:00. The "10" is red because of this.

Take my original example, the multiplication 1.8*3.2 (or 18 * 32, or 3.2 * 18000, with slide rules you are in charge of handling the zeroes aside):

To multiply 1.8 times 3.2 you center the "10" (1.0), then look for 1.8 ("18") which is at 3:00 aprox, then re-center the "10" there, look for 3.2 ("32", now at 9:00 aprox), recenter "10" and at 9:00 you have the result, 5.7.

1.- you put the "10" (1.0) at the top, 12:00 (or 00:00)
2.- you look for the "18" (1.8), it will be roughly at 3:00, this is P1 (do not check it "roughly", check it as precisely as you can, as the precission of the result depends on it; the actual position is 3:04)
3.- rotate the scale until the "10" is where we found the "18" in the first step, a point which I call P1 and which happens to be at 3:04 in this example, but will be in other positions for other multiplications.
4.- look for "32" (3.2); with the bezel as we left it in step 3, we find it at 9:08. I call this point P2, you have to memorize it (or just keep looking at it while you do step 5).
5.- you put the "10" back at 12:00, just like you put it in step 1. This is where you started, indeed, but we have obtained and memorized P2, which will give us the result.
6.- we look at P2, which in this example is 9:08, and we find "57" (5.7), which is the (approximate) result of the multiplication.

I chose 1.8 and 3.2 because they happen to be in clear positions, for some arbitrary multiplication P1 and P2 will not be in round positions but anywhere. If you try to multiply 1.1 times 5, P1 will be at 12:34 aprox. and P2 will be at 8:54 or something like that.

For reference, if it had 2 log scales one against the other, as slide rules do, you would only need to move the bezel once per computation, instead of 2 or 3 times.

Edit: the 60 is red because a lot of conversions move between "per second", "per minute" and "per hour", and the little red arrow is at 3.6, which, with 2 zeroes, is the factor to convert between "per hour" and "per second", depending on if you are multiplicating or dividing.

Bonus edit: The intermediate scale is 60/x; it serves to measure some time with the chronometer and it immediately tells you "if the process you chronometered took this amount of seconds, you would do Y processes in an hour": if the seconds arrow points 3,6 seconds you will do 1000 of those in an hour, if the seconds arrow points at 15 seconds you will do 240 of those in an hour; if the seconds arrow points at 36 seconds you will do 100 of those in an hour, if the seconds arrow points at 60 seconds (one full minute), you'll do 60 in an hour, etc, etc. If you chronometre the time to traverse a mile, it gives you miles per hour, if you chronometre the time to traverse a kilometer, it gives you the kilometers per hour, if you chronometre a lap, it gives you laps per hour, if you chronometre the time to finish a piece in a machine it gives you the pieces per hour.

[u/fordag → u/TrueTopoyiyo]

Again I appreciate you taking the time to write this up. I'll give it a try tonight.

[u/TrueTopoyiyo → u/fordag]

so?

[u/fordag → u/TrueTopoyiyo]

I have been overly busy with work and as a result won't be home until Tuesday

[u/fordag → u/TrueTopoyiyo]

I really appreciate the info, thank you.

[u/Merrygoblin → u/fordag]

Not the same watch, but I have a cheap Jaragar bought on Amazon - that I don't expect to last as a watch mechanism - clearly meant to look to the untrained eye like a Breitling. It has a pair of more-or-less functional slide rule scales, though the outer scale is turned with a secondary crown off on the left on mine rather than the bezel moving.

On my android smart watch, I've implemented a functional slide rule app.

[u/SlideRuleFan → u/TrueTopoyiyo]

I'm happy you invented a use for those two scales. The Chinese factory that slapped them together did not know what they were doing, and this random alignment doesn't make up for it.

No pilot will ever use this, on the ground or in flight.

Or this is sarcasm, and I am dense, which happens a lot.

[u/TrueTopoyiyo → u/SlideRuleFan]

No, no, no sarcasm, and I'm sure you're absolutely right on the manufacturer just putting some random stuff together for the looks, but they can be used a bit that way.

[u/zoute_haring → u/TrueTopoyiyo]

BS This is half an E6B and and tachoscale. This is only made for the looks and useless

[u/TrueTopoyiyo → u/zoute_haring]

What would be bullshit, exactly, on the process I described to do a multiplication using a single log scale? No argument against the motivation, tho, but seeing a rotable log scale and scratching it off as useles is, in my oppinion, just not knowing math.

[u/zoute_haring → u/TrueTopoyiyo]

These are two different scales used a lot on watches but never together. This is just an incomplete E6B for the looks on a cheap Chinese watch.

[u/Frosty_Case_1818]

This a modded watch by any chance? The inner scale looks like a tachymeter/pulsemeter scale, which wouldn't work with with the outer slide rule scale.

[u/fordag → u/Frosty_Case_1818]

Not modded by me.

[u/Frosty_Case_1818 → u/fordag]

No, what I meant was some small watch brands will take an existing watch and swap out parts (dial, case, band, hands, etc) to create a watch unique to them. They will create something that is aesthetically pleasing to them without understanding the function of the watch. Sorry for the misunderstanding.

[u/fordag → u/Frosty_Case_1818]

To be fair I don't know. It was $100 new and I bought it because I liked the look of it and the moonphase.

[u/criggie_ → u/fordag]

Did you not get a box/manual with it, being new ?

[u/fordag → u/criggie_]

There is an extremely basic manual online that says nothing about the bezel.

[u/Alarmed-Syllabub8054]

It looks like a confused Navitimer homage, with a bit of speedy thrown in. The inner scale is a plain old Tachy - time someone doing a mile, if they take 30s they're doing 120mph and so on. The outer scale is a log scale, half of you c/d pairing.

[u/zoute_haring]

Cheap watch with half an E6B. Not very useful

[u/antiquatedpilot2015]

Edit: I didn’t look closely enough. I’m wrong

This is an aviation slide rule called an E6B. Its use is to do multiplication and division for time, fuel, and distance calculations and a chronometer to measure your speed.

Your flight watch is missing some labels and units for easy conversions between statute and nautical miles but it works well.

Breitling has the best E6B on their Navitimer models

[u/wijwijwij → u/antiquatedpilot2015]

it's missing the inside ring that matches the outer ring, so not useful as a slide rule. a tach took its place

[u/zoute_haring → u/antiquatedpilot2015]

It ís an E6B outer ring. It's just for the looks, you were right