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  1. #81
    Steve Smith's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    yes, the brits took metric and imperial and created the worst of both morlds, highly confusing yo any driver. tank liters. go for miles,and mesure fuel efficiency in liters /100km.. go figureou the british empire!
    My car measures fuel efficiency in miles per gallon on a little display below the speedometer which measures in in miles per hour. (it is French though!).


    Steve.

  2. #82

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    Quote Originally Posted by ambaker View Post
    Ha! Eons ago, one of our tasks for practicing the conversion of units, was to convert the speed of light from miles per second, to furlongs per fortnight.

    Thanks for the reminder of old times.

    I've never quite understood the big deal about using metric or US measurements. For precise work, you grab a measuring device calibrated in the right units. For photography, unless you are focusing by a scale on a lens for close work, does it really matter? Metric infinity is pretty much the same as imperial infinity. It just has that strange Euro look to the colors... ;-)
    My favorite obscure measurement for velocity is attoparsecs per microfortnight. An attoparsec per microfortnight works out to be about 4% faster than an inch per second.
    ME Super

    Shoot more film.
    There are eight ways to put a slide into a projector tray. Seven of them are wrong.

  3. #83
    Worker 11811's Avatar
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    How about arcseconds per second?
    Randy S.

    In girum imus nocte et consumimur igni.

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  4. #84

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    That would work for angular velocity but not linear. On the surface of the Earth, at sea level, an arcsecond is about 100 feet. If you're higher up, an arcsecond will be more; in Death Valley it will be slightly less.
    ME Super

    Shoot more film.
    There are eight ways to put a slide into a projector tray. Seven of them are wrong.

  5. #85
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    Quote Originally Posted by Worker 11811 View Post
    How about arcseconds per second?
    1.

  6. #86

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    andy

    i usually don't think in terms of meters and feet
    but chains and links.
    i think to myself, there are 100 links in a chain, and a chain is 4 poles
    and 4 poles is the same as 25 links and 25 links is about .2meters,

    so lets say i am looking at something which is not far away,
    i say, that is about 5 links. ... and i look my holga
    and it has the 3 bodies ... which translates 5 links as 9 feet or 3 meters.

    its pretty easy

  7. #87
    Leigh B's Avatar
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    Quote Originally Posted by Steve Smith View Post
    Seems to be a pre-war standardisation but it is likely old equipment was still in use during wartime.
    Most of the machine tools (mills, lathes, etc) used to make equipment during WWII were made before WWII,
    with many being made before the "industrial inch" standard became commonly used.

    In fact, many machine tools made before WWII are still in service today, working just fine and still meeting original accuracy specs.
    Of course, they were made at a time when we expected machines to last a century or more, not a month or more.

    - Leigh
    “Wise men talk because they have something to say; fools, because they have to say something.” - Plato

  8. #88
    Steve Smith's Avatar
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    True. And as with most machine tools, they are probably set up with separate measuring instruments rather than the machine's own graduated scales.

    With non CNC lathes and mills, I have only ever used the machines' scales to get close. I have always used a vernier caliper or micrometer to do the final measurements.


    Steve.

  9. #89
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    Hi Steve,

    All of my traverse-type macines (mills, lathes, etc) have DROs with resolutions of .0001" or .0002". I never rely on the engraved scales.

    (I have a full commercial machine shop with all manual machines, no CNC at all.)

    - Leigh
    “Wise men talk because they have something to say; fools, because they have to say something.” - Plato

  10. #90
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    Quote Originally Posted by ME Super View Post
    That would work for angular velocity but not linear. On the surface of the Earth, at sea level, an arcsecond is about 100 feet. If you're higher up, an arcsecond will be more; in Death Valley it will be slightly less.
    Right. It does change but it's not arbitrary. If you are measuring over the surface of the earth we assume that it's ≈100 ft, but if measuring in space you have to consider the distance. Since most people would measure over the earth it's not necessary to consider distance.

    The neatest thing is that people often use the shorthand term "second" when they refer to arcsecond. Therefore, one might be able to say they traveled at a speed of 0.01467 seconds per second and that would mean the same as 60 miles per hour.
    Randy S.

    In girum imus nocte et consumimur igni.

    -----

    http://www.flickr.com/photos/randystankey/

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