Do you want to switch to SI units? 8

[ZeroExperience]

As title asks.

 

[drawoh]

Oops. When I typed "conforming metric units" I actually meant to type "non-conforming metric units", as a little arithmetic will reveal.

JHG

 

[ornerynorsk]

Caneit, I'm fairly old and I cannot visualize metric, as well, and I use it more than imperial measurements for about the last 8 years.

The imperial measurements are just old hat, as that what was ingrained so deeply into the grey matter in my youth. They are not odd or quirky at all, if that's what one is programmed for and familiar with, like you said.

I have a WWI era Russian infantry rifle that has the rear sights graduated in Arshins. It's very hard to gauge the target impact, especially after 4 or 5 kosushka's of cheap vodka! Seriously though, I never drink at the rifle range.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[KENAT]

While it may get exaggerated as to how useful it is, many of the Imperial/US customary dimension are based approximately on body ratios.

I wonder if that's part of the reason why they can be easier to visualize.

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[zdas04]

The interesting thing about this discussion is that anyone cares. Any system of measurement is arbitrary. If we say that a meter is so many multiples of the wave length of 6500K light or some such, it may feel "physical" but both the number of multiples and the light temperature are totally arbitrary. Why do we keep getting exorcised over whose arbitrary number we use? I often have a problem with people assuming that the system of units they use are universal and need not be communicated, but I've had that problem just as often with "Imperial" units as "metric" units. It is all arbitrary and if I know the units I can do my job.

I have a mish mash of "preferred" units in my head. I have no problem thinking of pipe length in meters, but calling nominal 1-inch pipe 25.4 mm is tough. MSCF is a pretty stupid unit, except that life is easier when you use it (the heat content of methane is about 1.0 MMBTU/MCF, much easier than 7900 kcal/SCM). I can do psi or bar, but kPa and MPa might as well be Urdu. I was looking at something with a design pressure of 10.2 MPa today and had to get UCONEER out to see if that was a big number or a small number.

I don't do kgf/m^2 at all.

David

 

[berkshire]

we now have 43 replies on a self perpetuating thread.
Has anybody heard from ZeroExperience?
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[drawoh]

While it may get exaggerated as to how useful it is, many of the Imperial/US customary dimension are based approximately on body ratios.

If only people were of a standard size. Here in Toronto, Canada, I figure people are somewhere between five feet and six and a half feet tall. People's body proportions are not that consistent either. This rules out body proportions for any rational system of units.

Part of the problem with the metric system in construction, is that people think in centimetres. If they thought in millimetres, all the decimals and fractions would disappear. Carpenters and welders would see a clear benefit to the metric system.

We all need to learn to stare blankly and stupidly at people who say "centimetres" to us.

JHG

 

[KENAT]

Actually drawoh, to make the most benefit of SI wouldn't we keep to meters and just use appropriate exponents?

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[JohnRBaker]

In a CAD system it makes sense to use something like a 'meter' as the base unit since that places the decimal place where you won't be wasting a lot of significant figureson the Left-hand side of the decimal place thus allowing for more precision on the Right. This is why the actual database unit of measure for our major CAD products, NX and Solid Edge, both use meters, despite the fact that when using the software you're generally working in either Metric units (millimeters) or Imperial units (inches) but that's just a convention so as to make it easy to understand and to comply with normal design and manufacturing standards, but deep inside, all the numbers are stored as meters. What this allows is being able to assure dimensional accuracy and precision down to the tightest manufacturing tolerances in general use today even for models so large as to just fitting into a cubic volume of space, one kilometer on a side.

John R. Baker, P.E.
Product 'Evangelist'
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[KENAT]

What about those of us spending time in the nanometer realm John - where's the love.;-)

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[patprimmer]

Fuel consumption calculations for a long haul jet would also get some clumsy numbers.

The advantage of metric is that in general it is real easy to adjust for magnitude by changing the prefix and moving a few decimal points.

The only real disadvantage is that a few units are non-intuitive (pascal for instance) and in some places they disturb the status quo.

To further improve, the counting system needs to changer from base 10 to base 8 or 16 for easy halving and re-halving. To bad for thirds as no matter what base that quickly becomes awkward with to the decimal repeated.

Regards
Pat
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[JohnRBaker]

But what would a system based on base 8 or 16 do for "moving a few decimal places"?

Now if our minds were taught to think like a computer we could just adopt a scheme based 2 raised to a power and be done with it ;-)

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

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[beej67]

As an occasional adjunct professor, yes dear god yes.

As a practicing civil engineer, not only no, but hell no.


Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[Hurricanes]

The whole Imperial measurements being easier to visualise is rubbish. It's all about what you were brought up with.

All I have ever known is metric. As such, I visualise length in metres, mass in kg, pressure in kPa etc. Pounds, feet, psi, I have no idea what a unit of those looks like until I have converted it into its metric equivalent.

 

[berkshire]

Pat

"""Fuel consumption calculations for a long haul jet would also get some clumsy numbers."""

Some years ago they did that in Canada and turned a 757 into a glider.
B.E

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[patprimmer]

They did to. I saw the show on TV, so it must be true.

I also saw one where they had a leaky tank, so they kept transfering fuel from the good tank until they ran out. Can't remember whether they glided in or crashed

Regards
Pat
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[Longinthetooth]

Berkshire- That was the "Gimli Glider". They landed on an old airstip in Gimli, Manitoba. Luckily the copilot was a glider pilot in his spare time and He landed then plane after having no power for several miles. Mid ninties I think.

 

[CANPRO]

beej67....just out of curiosity, why the big difference in unit preference from teaching to practicing?

 

[owg]

Conversion could be confusing some. A spokesman from Southampton for Total, commenting on the current gas leak in the North Sea yesterday on CBC radio, estimated the gas leak at 50 cubic tons. I don't think he mentioned per hour or per day. Thank God time isn't going SI.

HAZOP at

http://www.curryhydrocarbons.ca

 

[patprimmer]

I now wonder what the difference is between a cubic ton and a square tonne. Is there a linear tun.

Regards
Pat
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[SomptingGuy]

50 cubic tons?

Not only is it total nonsense, the numbers don't even add up.

I read that it's leaking at an estimated 200000 cubic metres/day. Not sure what the reference pressure or temperature is, but assuming atmospheric, methane has a density of about 0.66 kg/m3, giving ~132 tonnes/day.


- Steve