Sine bar protractor

[BadDog]

Sorry about that, I started just in fun, then it got out of hand. Sad thing is, in my hasty replies, I made so many stupid oversights as to be rather silly. Forgot to include the radius in the formula, forgot to include the pin diameter, didn't notice/include the base pin being offset. Sheesh, sometimes it does not pay to post...

Edit: Or to put it more simply, "Better to remain silent and be thought a fool..."

[toastydeath]

I certainly thought it was all in good fun and vigorous discussion!

I apologize if anyone took it in a different way.

[BadDog]

Not at all. I knew what Marv meant (as indicated in my post), I was just poking fun too. But the following discussion was very intertesting, even if I did forget to put my brain in gear for a few points.

[madman]

Clear??

No not really. I just uze my protractor (MZB) with xtra long arm for well extra long work. Or my sine bars and joe blocks. Never trusted verniers much. They wear all over the place the jaws that is ect.

[NickH]

Edited as I had obviously "lost the plot"

[BadDog]

"Height" is not measured, distance between the pins is measured. Check out the picture Marv posted, it describes how it works very well.

[Evan]

Marv,

Check out this page. It describes the double arm drive principle that I used to design and build an astronomical tracking device. It seems to me that the same principle could be used to make a protractor that would be settable by a strictly linear measurement over a good part of the travel. I don't have time to play with this idea now, I have much too much else to do.

http://hometown.aol.com/davetrott/page17.htm

[John Garner]

Marv --

Great minds really do think alike . . . Moore Special Tool used (uses?) the same concept for their sine plate, which can be used to generate an angle up to 90 degrees without the accuracy degradation exhibited by the conventional-design sine plate.

It's been long enough that I don't remember for sure, but I have a hazy memory that the "separating rolls" on the Moore plate are coaxial when the top and bottom plates are parallel. If so, the thickness of the gage block stack needed to set any given angle would simplify to twice the sine of the half angle times the plate constant less the roll diameter.

John

[toastydeath]

Oops, didn't mean to reply here. Post removed.

[toastydeath]

Marv --

Great minds really do think alike . . . Moore Special Tool used (uses?) the same concept for their sine plate, which can be used to generate an angle up to 90 degrees without the accuracy degradation exhibited by the conventional-design sine plate.

It's been long enough that I don't remember for sure, but I have a hazy memory that the "separating rolls" on the Moore plate are coaxial when the top and bottom plates are parallel. If so, the thickness of the gage block stack needed to set any given angle would simplify to twice the sine of the half angle times the plate constant less the roll diameter.

John

Moore still makes the microsine table, which is what you're referring to.

However, last time I saw one for sale, the person wanted $14,000 for it.

Better than the Moore Master Index table, which is $30k and up.

[mklotz]

Marv --

Great minds really do think alike . . . Moore Special Tool used (uses?) the same concept for their sine plate, which can be used to generate an angle up to 90 degrees without the accuracy degradation exhibited by the conventional-design sine plate.

Ah well, there goes my chance to make a million bucks. In a world where the majority of the people can't read a ruler, a device that requires inverse sine functions to find an angle probably never had a chance anyway.

[mklotz]

Oldtiffie,

Thanks for the kind words.

I try to make all my programs as user-adaptable as possible. When only a few inputs are required, as in PROTRAC, I have the program query for them directly.

Where large data sets are required, as in CHANGE, the program reads these inputs from a standard ASCII text file modifiable by the reader using any text editor.
This ensures that the user, once having entered the data specific to his situation, can make future reruns of the program without the tedium of reentering his data.

Lots of folks like to go on about measuring to tenths (0.0001") and arc seconds. Such accuracy is gross overkill in most HSM projects and, furthermore, is probably realistically unachievable in the average HSM shop.
For instance, one arc second is about 5 microradians. That translates to a 0.3" error at a distance of one mile.

5E-6 * 5280 ft/mile * 12 in/ft = 0.3 in

"Yeah - I am "metricated" and my rotabs and verniers are calibrated in "deg/min" and not "decimal degree""

Frankly, I would think that the metric countries would use fractional degrees rather than the absurd sexagesimal system inherited from the Babylonians. Ah well, at least you Aussies haven't adopted the French grad. (I may be wrong but I think *only* the French use the grad.)

[mklotz]

If you examine the equations, you'll see that d and delta have to be known separately in order to solve for either the angle or the separation. Of course, once a protractor is built, the user could hard wire the values of these variables into the code and thus avoid the need to reenter them with each use.

All the calculations are easily done on any scientific calculator. I've never seen a scientific calculator that doesn't have inverse trig functions implemented.

In 30+ years of working on military (both US and foreign) contracts, I have never had occasion to see an angle quoted in grads nor had a need to convert an angle to grads. It was a French idea and seems to have gone the same way that the post-revolutionary "metric" clocks went.

[John Garner]

Beware the angular unit "grad", which we "murkins think is "1/400 of a circle" or "1/100 of a right angle", because our German brothers think that a grad is "1/360 of a circle" or "1/90 of a right angle" . . . the unit we call "degree".

In an attempt to rectify this dichotomy, the International Federation of Surveyors (FIG, from the French "Federation Internationale des Geometres") about 20-some years ago declared the 1/400 of a circle unit to be officially renamed the GON. The companies making survey equipment went along with the renaming, but the calculator makers haven't.

Then there's the French. I've worked with English-speaking French engineers who use the word "degree" to mean either 1/360 circle or 1 /400 circle . . . the former being a "sexagesimal degree" and the latter a "centesimal degree".

Incidentally, the centesimal degree can be divided into 100 centesimal minutes (abbreviated "c"), each of which can be subdivided into 100 centesimal seconds (abbreviated "cc"). I don't know if there is an "official" way of notating an angle measured in centesimal degrees, centesimal minutes, centisimal seconds, but I've seen them recorded in a number of ways, using slashes, commas, or dots as unit separators. In any case, as long as two digits are recorded for the centesimal minute and centesimal second values the "notational conversion" to decimal division of the centesimal degree is trivial: replace the centesimal degree - centesimal minute separator with a decimal point (or, in European practice, a comma) and delete the centesimal minute - centesimal second separator.

An example to illustrate?

An angle of 123 centesimal degree, 45 centesimal minute, 67 centesimal second may be recorded 123,45c,67cc or 123.45.67 or 123,45,67 or 123/45/67, which is 123.4567 centesimal degree.

John

[lynnl]

I'm sorry I read that!