Results 1 to 15 of 32

Thread: Metric and English Conversion

Hybrid View

Previous Post Previous Post   Next Post Next Post
  1. #1
    Join Date
    Apr 2008
    Location
    Brooklyn, NYC
    Posts
    510
    I may be alone on this but I think the Imperial system has advantages for working with middle sized numbers. For very large (for example measuring space) or very small (measuring a molecule), base ten units make computing easy since we use a base ten numbers system. BUT for some things a base 16 system is really nice. For example, I often need to find the center points of various measurements. When a fraction is involved it is often easier to divide a base 16 number than a base 10. Half of one is 1/2, half of 1/2 is 1/4 half of 1/4 is 1/8 half of 1/8 is 1/16. With a base ten system you quickly run into undesirably lone numbers, .5, .025, .0125, .0625. Maybe the best would be to adopt a base 16 numbers system first. Then the "decimal" would align with the "fractional".

  2. #2
    Join Date
    Jan 2007
    Location
    central PA
    Posts
    1,774
    Quote Originally Posted by Harlan Barnhart View Post
    I may be alone on this but I think the Imperial system has advantages for working with middle sized numbers. For very large (for example measuring space) or very small (measuring a molecule), base ten units make computing easy since we use a base ten numbers system. BUT for some things a base 16 system is really nice. For example, I often need to find the center points of various measurements. When a fraction is involved it is often easier to divide a base 16 number than a base 10. Half of one is 1/2, half of 1/2 is 1/4 half of 1/4 is 1/8 half of 1/8 is 1/16. With a base ten system you quickly run into undesirably lone numbers, .5, .025, .0125, .0625. Maybe the best would be to adopt a base 16 numbers system first. Then the "decimal" would align with the "fractional".
    I have not used metric to this point, but I suspect if you were building using the metric system you wouldn't build to "fractions", you would build base ten dimensions. Yes 1/2 of 37cm is 18.5cm or 185mm, but that's still easier than adding or subtracting 16ths and 32nds! Make something with that in mind like you would now.
    ex: I want a pc. 3' tall so I can have my shelves about 1' equally spaced. In metric maybe make something 90cm tall with each shelf 30cm. I'm sure our Canadian/European/Aussie.....friends can give better examples.
    I feel blessed to have been born in this country, but I find it almost embarassing that we still use such an antiquated system of weights and measures.

  3. #3
    Join Date
    Jan 2008
    Location
    Crystal Lake, IL
    Posts
    87
    Just how "new" do you folks think the metric system is? I may be a little off, but as I recall it was first defined and used in the 18th century. It wasn't widely adopted until the 1960s, but it certainly isn't a recent invention. There's nothing antiquated about the imperial system -- it's just a different system that uses a different set of standards. The standards for both systems are somewhat arbitrary and only apply to everyday life once your brain learns to associate them with something. If you really think the metric system makes sense, ask your favorite european how many Newtons he/she weighs...

  4. #4
    Join Date
    Dec 2006
    Location
    Toronto Ontario
    Posts
    11,294
    Quote Originally Posted by Dan Schocke View Post
    . If you really think the metric system makes sense, ask your favorite european how many Newtons he/she weighs...
    Well Dan, since the Newton isn't a unit of mass he/she may not know.

    However if they know their mass in Kg, they could multiply it by 9.8 m/s to obtain the force they exert on the floor.

    It would be similar to asking someone in North America what their weight is in poundals.

    regards, Rod.
    Last edited by Rod Sheridan; 12-13-2010 at 1:26 PM.

  5. #5
    Join Date
    Jan 2009
    Location
    Niagara, Ontario
    Posts
    657
    Quote Originally Posted by Rod Sheridan View Post
    Really? Cubic meters seems like such a big unit. For instance, yesterday I bought a board that's 7" by 8' by 1" thick. That's five board feet. If I'm doing my conversion correctly, it would also be .0083 cubic feet. Liters would be a unit more like the usual size of boards. That board would be 8.3 liters. Of course, we'd all be confused when we buy lumber and Coke with the same unit.
    Jamie, and how many board feet do you buy when you buy firewood? Or do you buy them by the cord in the US?
    Similarly, when you're buying a single board of the dimensions you stated you'd buy it as a board with the dimensions you stated. The price would likely be calculated in cubic meters because that's how wood is traded, however small the number would be. To you it would still be a board 8 feet long, or 1000 8 feet long boards.

    Liters is used for volume (mostly fluid) but is actually not a part of the official SI system. Instead cubic decimeter is used and it is equivalent to 1 liter (1/1000 of a cubic meter). If the unit level is too small or too big you can use one higher or smaller. Similarly, you know that a distance from Berlin to Paris is not expressed in light years or millimeters.

    When you buy wood in quantities other than a size of a match then you will definitely buy it by cubic meters. That's how cabinet makers and builders buy. So 100bf a hobbyist would buy is roughly 0.25 cu meters. I think it's quite a manageable number. Also, using the number such as .0083 cubic meters is an attempt to transplant the SAE standard to metric realities, and if correct, the number no more ridiculous than 4.67 b/f
    To understand recursion, one must first understand recursion

  6. #6
    Join Date
    Mar 2003
    Location
    San Francisco, CA
    Posts
    10,333
    Quote Originally Posted by Darius Ferlas View Post
    ...
    Liters is used for volume (mostly fluid) but is actually not a part of the official SI system. Instead cubic decimeter is used and it is equivalent to 1 liter (1/1000 of a cubic meter)....
    I think you're making my point for me. While cubic decimeter may be an official SI unit, people use liter. They use it because it is a convenient size. Cubic meters is a convenient unit if you're buying some things -- for instance concrete -- but not so convenient if you're buying others -- for instance Coke. Cubic decimeters, while an ideologically pure unit, is too much bother to write out. So folks use liters, whether or not it is official.

  7. #7
    Join Date
    Jan 2009
    Location
    Niagara, Ontario
    Posts
    657
    Quote Originally Posted by Jamie Buxton View Post
    I think you're making my point for me. While cubic decimeter may be an official SI unit, people use liter. They use it because it is a convenient size. Cubic meters is a convenient unit if you're buying some things -- for instance concrete -- but not so convenient if you're buying others -- for instance Coke. Cubic decimeters, while an ideologically pure unit, is too much bother to write out.
    Some do, some don't. I'm actually one of those "people". I didn't know what an inch was until the age of 26.

    A lot depends on the context, material, country and tradition, even though Europeans will easily switch from one metric unit, or its representation, to another. My point was not the actual usage of the decimeter and I agree, it is not used as frequently in the context of volume as liter, but the usage is certainly not unknown (example below).

    Decimeter is not as hard to write out either. How hard can it be to write dm3 for volume (where 3 is a superscript), or simply dm for length. A liter is not any more convenient than dm since both are exactly the same when it comes to volume.

    Some practical examples of usage: if you or I buy a bottle of coke it will be either 335 ml, 1L or 2L. In some EU countries you can buy a quart/quarter of some fluid, i.e. 0.25 of a liter (a capacity of a standard glass/mug). That's for personal consumption. A major bar (I mean really major) may buy a few thousands of liters, or a few hectoliters (hl). When I had a Summer job in a winery and distillery all containers were marked in hectoliters. But when you buy a shot of vodka it's often in grams rather than milliliters (50 grams please) even if volume measuring cup is used instead of scales. The two are not 100% equivalent but close enough and after a few those fifties (1.7 fl.oz. straight as ice and such are for sissies) few could tell the difference anyway.

    Concrete, even in the fluid form will be sold by cubic meters (m3) just like lumber. But when you buy a single board you will buy a single board of dimensions specified but your vendor bought it in cubic meters as a part of a larger shipment. However weird it may sound, from the point of view of your vendor he will sell you (as an example) 0.0039 m3 of wood, not 3.9 liters, or 3.9 decimeters or whatever the unit the buyer might consider more convenient.

    In dry form, concrete and sand will be sold by kilograms (if bought as individual bags) or by tonnes (even if you order a truckload of individual bags). The water you add to it will be in liters or hectoliters and that will depend on the size of your job. If you pour concrete into forms to create cubes of 10x10x10cm you'll get 1 dm3 cubes (1 cubic decimeter), not 1 liter cubes, even though you use 1 liter of wet concrete.
    To understand recursion, one must first understand recursion

  8. #8
    Join Date
    Jan 2008
    Location
    Crystal Lake, IL
    Posts
    87
    Rod, you hit my point exactly... Kilograms are units of mass, not weight. Weight is mass multiplied by local acceleration due to gravity, and the unit for that in the metric system is Newtons. Pounds, on the other hand, are units of weight, not mass. As human beings cannot sense mass, the kg is somewhat useless as a unit of measure in everyday life.

    The poundal is a unit that was really invented to make force calculations simpler in the English system of units, so not sure how that applies here.

  9. #9
    Join Date
    Dec 2006
    Location
    Toronto Ontario
    Posts
    11,294
    Quote Originally Posted by Dan Schocke View Post
    Rod, you hit my point exactly... Kilograms are units of mass, not weight. Weight is mass multiplied by local acceleration due to gravity, and the unit for that in the metric system is Newtons. Pounds, on the other hand, are units of weight, not mass. As human beings cannot sense mass, the kg is somewhat useless as a unit of measure in everyday life.

    The poundal is a unit that was really invented to make force calculations simpler in the English system of units, so not sure how that applies here.
    Dan, you're correct, it's been so long since I've used the BE system I forgot that. However I don't think I've ever seen Kg used for anything other than mass.

    As for not being able to sense mass, I'm not sure I would agree with that, we only sense force however we can sense mass in both instances where there is gravity and no gravity. If there's no gravity, theres no weight, however we can sense mass by pushing on the object with our finger.

    Mass tells us how much matter is in the object, so does weight if we know what the gravitational acceleration is. (fortunately for me I only work on earth so I don't have to worry about that ).

    I think in both systems that the average person doesn't understand the units, any quick quiz will demonstrate that, however the metric system is a lot eaier to use.


    regards, Rod.

    P.S. I was surprised to find that the difference between the Imperial system and the American system was due to updates happening in the Imperial system after the Revolutionary War. I had always assumed that the US had modified their system after the break from England.
    Last edited by Rod Sheridan; 12-13-2010 at 3:09 PM.

  10. #10
    Join Date
    Jul 2007
    Location
    Forest Grove, OR
    Posts
    1,167
    Quote Originally Posted by Rick Moyer View Post
    I have not used metric to this point, but I suspect if you were building using the metric system you wouldn't build to "fractions", you would build base ten dimensions. Yes 1/2 of 37cm is 18.5cm or 185mm, but that's still easier than adding or subtracting 16ths and 32nds! Make something with that in mind like you would now.
    ex: I want a pc. 3' tall so I can have my shelves about 1' equally spaced. In metric maybe make something 90cm tall with each shelf 30cm. I'm sure our Canadian/European/Aussie.....friends can give better examples.
    I feel blessed to have been born in this country, but I find it almost embarassing that we still use such an antiquated system of weights and measures.
    Its really easier to just work in tenths or 100ths of a mm, just like machinists do. (Machinists work in 100ths of inches as well as SI units).

    I'm an electronics engineer, we work in mils and um (micro meters). Circuit boards are in mils, IC's in um, generally. It can cause confusion, but at least it avoids fractions.

  11. #11
    Join Date
    Nov 2009
    Location
    Canon City, Colorado
    Posts
    299
    Lets further complicate the question.

    If I buy a 2 X 4 I get a piece thaty is nominally 1 1/2" X 3 1/2".
    If the metric equivalenty is 100mm X 50mm (1.968" x 3.937") would I get 100mm X 50mm or would I get a nominal size that is equivalent to the 1 1/2" X 3 1/2" American?

  12. #12
    Inching Forewards casts some light on the history of both systems of measurement. Also, check out the links in Pat Naughtin's comment at the foot of the page.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •