×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Question about metric
6

Question about metric

Question about metric

(OP)
Hi guys,

we are a company (ACE-Hellas SA) that has a software for static and dynamic analysis plus design of structures.

The question though is the following:

Currently we are looking for partners to promote our software all over the world.
Our software supports only metric and not imperial units.
I see that in US there are a lot of talks about adopting officially the metric system.
For us to support imperial units is not so easy - as we have to recreate all forms and calculations, so it will take a lot of time.

Do engineers in US work with metric or imperial units for the static and dynamic analysis?

We want to see if we should try to promote the software in the US as well.

Thanks!

RE: Question about metric

"For us to support imperial units is not so easy - as we have to recreate all forms and calculations, so it will take a lot of time."

Seriously? Almost any program that supports units defaults all calculations to one consistent system. They convert any other unit inputs into their internal representation and present results converted back to the user input unit convention. Mathcad is a good example of that. It supports arbitrary dimensional units for input, but internal representation is always SI. In fact Mathcad supports mixed units as well.

"Do engineers in US work with metric or imperial units for the static and dynamic analysis?"

Yes, but, if anything, they probably do most things in imperial units.

TTFN
FAQ731-376: Eng-Tips.com Forum Policies

Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers

RE: Question about metric

(OP)
Thanks for your reply and your feedback IRstuff.

For us accuracy is everything.
We have done some tests internally with converting but you get to loose always with decimals conversions.

For example 2.5 meters = 98.4251969 inches, so you see it is a matter of precision mostly for us and you know that there are a lot of mathematical calculations going on till the end result.

Our software is used to calculate skyscrapers and bridges. All numbers matters when we are talking about human lives.

I perfectly understand your point but we have chosen for the above reasons not to go down this road.
We prefer to not have it, than to have wrong results, or results that won't make sense and discredit the software.

RE: Question about metric

If you are considering making a business decision based on this topic you would do well to understand that the US will NOT likely switch to the metric system anytime soon. Be very skeptical of any reports that it will; the debate over whether or not to so has been going on since the country's founding, literally.

Whether or not that's a good thing is a different question. I happen to be among the minority of my associates in my belief that the Imperial system is superior for engineering applications. That might earn me a heap of scorn but that's ok. But if this thread turn into a metric vs. imperial debate don't let it detract from the answer to the question you originally asked: the US will NOT likely switch to the metric system anytime soon so make your business decisions accordingly.

RE: Question about metric

(OP)
Thank you Archie.

No need for this to be a debate.

I hear you guys loud and clear :)

RE: Question about metric

Quote (Original poster)

so you see it is a matter of precision mostly for us and you know that there are a lot of mathematical calculations going on till the end result.

Scary to read. Using Double Precision (double) should not be a problem.
Fire your programmer. Serious FEA Software should be able to use consistant unit. Your client should be able to switch Length or/and Force unit as they wish ! Ex : (kN / m or kN/mm or kip / in or kip / ft, etc...)

RE: Question about metric

(OP)
Hey Pico,

it is not only the calculation part - let's say we use double and let's assume that all goes well.

Still we have to recreate all the forms to be feet/inches, so two boxes - one for feet and one for inches.
Currently there is only one for cm for example.
Except if you tell me that using only inches (so only one box) is acceptable.
Then things are easy, I agree. We just change everything from cm to inches and do internal conversion.

Truly we never looked at imperial implementations as our target market was always EU.

RE: Question about metric

Wouldn't the bigger issue than units be code equations used... lets say all your steel is designed with EuroCode, But i want AISC in the states. Now steel may be small difference but i bet Concrete would a different beast.
-
Or am i showing my ignorance of other country's engineering?
-
As for the two inputs, many programs only accept feet, ie 4.58' is about 4'-7"

RE: Question about metric

Impose a format, use a single textbox and parse the string.

Convert internally
8'-5" -> 8.416667 ft
8'-5 3/32" -> 8.424479 ft

RE: Question about metric

(OP)
EngineeringEric - yes we currently use EuroCode but every country in Europe has their own "extensions" which in some cases they might be required by local country laws.
So yes AISC would still be something we would need to do after we offer imperial.

Pico - thanks for your feedback. I will forward it to the development team.

RE: Question about metric

For my calculations... I normally only use about 6 significant digits <G>... for programming, or even Excel, I usually use double precision even for conversion since many programming languages execute double precision faster than single precision... I generally tone down the output to maybe 'sliderule' accuracy...

Dik

RE: Question about metric

The conversion accuracy question is a bit of a red herring. Once you get past the initial input parameters, your calculations should be double precision, so it's mostly irrelevant what the inputs are, and given double precision, the accuracy loss is minor, at best.

Moreover, the imperial to metric conversion factor is EXACTLY 1 inch = 2.54 cm, so there is no precision or accuracy loss going in. The only loss would be on the other end of the calculation, and with double precision math, it's completely negligible.

TTFN
FAQ731-376: Eng-Tips.com Forum Policies

Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers

RE: Question about metric

The problems would not be in unit conversion so much, but in using different codes, different methods mandated by different codes, different standard member sizes, etc.

RE: Question about metric

Canada converted to SI in the early 1970's but we do not use the same units as some metric countries. In engineering drawings and calculations we use metres with prefixes representing 10 raised to a power that is a multiple of 3. Thus we do not use centimetres but we do use millimetres (the editor is indicating a spelling error in all the above words containing "metres"...the editor thinks it should be meters, but that is not the case in Canada).

There are still a large number of engineers in Canada who refuse to use the SI system, instead clinging rigorously to the Imperial system. I became intimately familiar with both systems over the years and feel comfortable working in either system but I do not like mixing the two. Better to work in one system, then convert at the end if required.

BA

RE: Question about metric

Well BA - you can call it bere but we here in the States prefer beer.

RE: Question about metric

Doesn't matter as much in the US that the design might be in metric.
But the parts and pieces will be bought in ANSI units, and built all-to-often by newly-arrived-unskilled poor-language labor using inches and (maybe) fractions correctly. Tools and jigs and steel and pipe and xonrete and boards are NOT metric. But they are NOT "pure ANSI" feet-inch-fraction-decimal either!

You will need specific and different pipe tables, steel tables, nut-and-bolt tables, wood size tables, and stair heights and sheet rock wall thickness and plywood sizes and rebar sizes. Plate dimensions, rail sizes, tube sizes, weld spec's, etc. Nails? Screws? Rill bit Diamters? Wheels? Bearings?

Today is NOT an easy world in construction.

RE: Question about metric

Whether or not your program handles different units, I won't use it if it mentions centimetres in any way.

RE: Question about metric

Quote (hokie66)

I won't use it if it mentions centimetres in any way.

ooo I hate those things.

Then again, at least they're not as bad as "hectopascals".

RE: Question about metric

Sounds like your programmers need to investigate "significant figures"

RE: Question about metric

Hokie66, you've piqued my interest. What's wrong with centimetres, specifically? Just curious.

RE: Question about metric

The US has been converting to the SI system for the past 30 yrs. However, given that the SI system is, essentially, a system derived from original French standards, it's unlikely to garner much support from those that consider the French to be a socialist country and see SI units as a part of the new world order conspiracy.

TTFN
FAQ731-376: Eng-Tips.com Forum Policies

Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers

RE: Question about metric

IRstuff,

I don't think that's the reason behind the resistance to change. Rather, I think, it's that in the US systems are in place as racookpe1978 noted.

I remember years ago I mentioned to my boss that a particular project was required to be designed in metric. His response was, "They can do that if they want but there is no one in town who would be able to build it."

That's assuming real metric design, of course. Some that I've seen have been laughable, i.e., "place 2.54 cm of non-shrink grout under base plate..."

RE: Question about metric

BA... about 90% of the work I do is still Imperial... in Canada, still... appears only Alberta has taken SI seriously...

Dik

RE: Question about metric

Certainly, the inertia is a big issue, but it's an issue because the conversion is fully voluntary. Until seat belts became mandatory, not much was ever done. Likewise, until SI is mandatory, nothing much will come of it; there is no political support for it, particularly from the right.

TTFN
FAQ731-376: Eng-Tips.com Forum Policies

Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers

RE: Question about metric

Good. I don't like being told what to do.pipe

RE: Question about metric

IRStuff
Its not just the right- its all politicians. A congressman (Democrat by the way) once told me that the reason we still have daylight savings time is because there are no votes to be gained by eliminating it. No politician is willing to spend political capital on something that won't benefit them in any way. Same goes for Metric conversion.

RE: Question about metric

In the building arena the reason SI didn't catch on was that there was so much physical infrastructure involved in construction that converting to "hard" metric was just economically a disaster. One example was that every steel mill and rebar mill facility in the country would have to totally re-tool to begin producing SI bars.

For the early 1990's the US Federal government started mandating that the US convert...only to be pushed back by most every industry in the construction world. We were already starting to do bridge in SI for the state DOT's but they then reversed course. Nothing to do with left or right.

RE: Question about metric

Murdof,

To get back to your original question - you would absolutely need to handle imperial units to have success in the US market. I would also say that you shouldn't either force feet or inches, but have both options (along with lbs, kips etc.) if you are going to compete with the other software out there. Download some trial versions of the popular software used in the US (Etabs, Ram, Midas, Risa etc.) to see what they offer - all of them allow you to switch easily between units at any time.

RE: Question about metric

Not directly related to the above ...

Even in Europe, we are not consistent in using the SI system. I have seen stresses expressed in (metric) tonne / cm squared.

RE: Question about metric

JAE - I have on my desk a 1995 DOT fully metric specbook. I think it was used for a matter of months before reverting to Imperial.

RE: Question about metric

murdof,

I am in Canada. I just today walked up to the counter of a fastener and tool store and asked for a 90° countersink. They stared at me blankly and told me that countersinks are 82°.

In the USA and Canada, you need to cope with English units.

--
JHG

RE: Question about metric

(OP)
Thanks for your replies all,

there is still a lot more to do for Europe as I mentioned, so I just wanted to see if US would be a market we could target soonish.

We already discussed the feedback you guys gave and we have decided to focus in Europe/South Africa/Australia for now.

I would love though to get some feedback from guys in Europe about our software and what they think about it.
We have free version available (http://www.scadapro.eu), plus manuals and we are making more youtube videos with examples.

RE: Question about metric

>>>I just today walked up to the counter of a fastener and tool store and asked for a 90° countersink. They stared at me blankly and told me that countersinks are 82°. <<<

Metric affects angles?

RE: Question about metric

Ya Archie, didn't you hear what they're teaching kids in math these days... get with the times!readingbigsmile

RE: Question about metric

All they need to do now is make sure reality is aware of these latest developments.bigsmile

RE: Question about metric

After a bunch of beer after work at the office in Edmonton about 25 years ago, was with a group. I was surprised that SI had taken such a foothold. I called AGT (Alberta Telephones) and asked when they were converting the phone system to metric... and the poor little lady didn't know... so, I asked her to find out and call me back... after about 15 minutes or so, I got a call back and she stated, "At the present time, AGT has no intentions of converting the phone system to metric." I thanked her for her reply...

Dik

RE: Question about metric

@dik,

I have noticed that a few engineers in BC are still using Imperial, but I thought that most of Canada had converted to metric. Our codes are written in metric, so I don't know why people are so slow to comply.

In Alberta, all government projects must be detailed in metric. Many of the steel fabricators are detailing strictly in metric, even in projects in which the EOR details in Imperial. This is not a very good situation and has led to errors in the past.

Unfortunately, the lumber industry has not generally converted to metric. We are still using plywood and OSB which are 48"x96" which means that our studs and joists are spaced at 16" or 24" (406mm or 610mm on government projects which is a total pain in the butt). We can specify 1200 x 2400 plywood, but we pay extra for it because they take a 4' x 8' sheet of plywood and cut it down to size which means we pay for the cutting and end up with less material. It is not likely to change any time soon because the lion's share of the market is in the USA.

BA

RE: Question about metric

Personally I would welcome a project in metric. While it would be hard to get a "feel" for the units I know about how much force a newton is, about how long a meter is, and our soda are in liters so I have no problem there. :P

Maine EIT, Civil/Structural.

RE: Question about metric

Quote (Archie264)

Hokie66, you've piqued my interest. What's wrong with centimetres, specifically? Just curious.

Our weatherman uses centimetres to describe rainfall or snowfall. For that purpose, they are fine but they do not mix readily with metric units in the SI system which Canada has adopted. For example, 1 kiloNewton per meter is the same as 1 Newton per millimetre (1 kN/m = 1 N/mm). But 1 kN/m = 10 N/cm and there is a chance of making an order of magnitude error.

Or another example, 1 MPa (1 MegaPascal) is 1 MegaNewton per square metre which is the same as 1 Newton per square millimetre. That is, 1 MPa = 1 MN/m2 = 1 N/mm2.

Incorporating decimetres or centimetres is a recipe for disaster when carrying out engineering calculations. I came across one Mexican contractor who reported concrete strengths in kilograms per square centimetre (kg/cm2). That was a total pain to convert to usable units.

So I agree with hokie on this point. I would not want anything to do with a program which used centimetres unless it offered a conversion into more acceptable units.

BA

RE: Question about metric

BA,

Thanks for the explanation. I suppose it might be inevitable that this turn into a SI vs Imperial debate but suffice it to say you've hit on two of my annoyances with SI for structural engineering applications: (1) a slipped digit doesn't easily reveal itself and (2) people incorrectly using kilograms as a unit of "force". My third quarrel with it is that I find SI dimensions to be difficult to read quickly. For example, I've seen dimensions such as this: "60000". Quickly, is that 6 meters, 60 meters or 600 meters? I guess those who work with it regularly have no problem but discretely different units such as feet and inches are much easier to read quickly...for me.

I'm now wearing my flame-resistant suit...bigsmile

RE: Question about metric

PS: I think for certain scientific applications metric is superior but that's when dealing predominately with units of mass, not force. Just my opinion.

RE: Question about metric

2thumbsup

RE: Question about metric

Archie,
BA has done a good job of answering your question to me (while I was asleep). I don't even like centimetres for rainfall or dressmaking, but I can't do anything about it. In structural engineering in Australia, we only use multiples of 1000, which is really what metric is about. Dimensions are all in mm. Europeans, particularly the French, use cm, but they do a disservice to the concept.

RE: Question about metric

Hokie66,

Thanks. I know the bulk of the world uses SI so it can't be all bad.bigsmile

RE: Question about metric

The metric system was sanction by the US Congress in the 1860's or 1870's....seems like implementation is going a bit slowly.

RE: Question about metric

...any day now...bigsmile

RE: Question about metric

I quite clearly stipulate that shop drawings must be prepared in the units of the project... I have no difficulty designing in either... I like the Imperial system because of the different units... less likely to make an error due to the unusual units... with SI, it's easier to slip a decimal place... other than government projects, few projects I've been involved with are SI. Mostly alterations to larger facilities, where the original facilities are in Imperial...


Dik

RE: Question about metric

Archie264,

Most English flat head screws have 82° heads. Some English flat head screws have 100° heads.

Metric flat head screws have 90° heads.

--
JHG

RE: Question about metric

On metric drawings, we are encouraged not to use decimal points or commas to delineate numbers. Instead we are encouraged to use a space where required. The number 60000 should not appear on a metric drawing. Instead, it should should read 60 000.

On structural or architectural drawings, it is not usual to dimension anything to a precision of less than one millimetre. Where smaller dimensions are needed, micrometres or nanometres should be used, but I have never seen either used on structural drawings.

BA

RE: Question about metric

It seems ironic to me that mainland Europe, including France, commonly uses such peculiar units as kgf/cm^2 for stress, but the countries following the UK tradition use "proper" SI units as a matter of course.

To be fair, the Eurocodes do use SI units, but even they adopt the peculiar practice of designating millistrain as 0/00, which at the moment makes no sense at all to me.

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

RE: Question about metric

Quote (hokie66)

in Australia, we only use multiples of 1000, which is really what metric is about.

Do you know why they teach centimetres in school?

I've never been able to figure that out.

RE: Question about metric

Tomfh,
No, I don't know how that started or why it can't be changed.

BA,
Do you have a reference for that? Where would you start? You mentioned 1200 x 2400 above, but don't like 60000. I see the point, but it is just the number of zeroes that is the problem? Is it 24000 or 24 000?

RE: Question about metric

hokie,
To be consistent, I probably should have said 1 200mm x 2 400mm but felt there was no danger of misreading 1200mm x 2400mm as there are only two zeros involved. Similarly, 24000 is easier to read than 20000. So, yes it is really the number of zeros which causes the reader problems. The whole object is to dimension in such a way that it cannot easily be misinterpreted by the reader.

I did have a reference years ago, but have not been able to find it tonight. The comma and decimal point are discouraged because they have different meanings in different parts of the world. The folowing discussion is of some interest but is not necessarily authoritative:

http://forums.autodesk.com/t5/Drafting-Techniques/...

BA

RE: Question about metric

I found the following reference from NIST (National Institute of Standards and Technology). They are using a space and a decimal point in Item #16. The decimal point is not required on structural drawings as one millimetre is precise enough for most applications.

http://physics.nist.gov/cuu/pdf/checklist.pdf

BA

RE: Question about metric

I haven't seen the space convention used, perhaps because it is seldom needed to prevent misinterpretation. Grated, it is easy to read, say 60240, but not as easy to read 60000. I will continue to leave out the space. Writing 'mm' is redundant if that is the only unit used.

RE: Question about metric

I agree that writing "mm" is redundant.

BA

RE: Question about metric

Learning centimetres in school is essential for those aspiring to become dressmakers or pizza chefs.

RE: Question about metric

The worst aspect by far as mentioned above somewhere is when nominal measurements are then converted exactly into the other unit (seems to be more imperial to metric), hence 1" becomes 25.4 instead of 25 or 30. Drive me mad every time I see a very precise number for something I know is a nominal figure and if I convert it back you can see it's just 6 foot or something like that. Not that the US will ever change IMO, but if it does by small degree, this is a key point to watch out for. Lots of people I know still use imperial for timber (2 x 4, 3 x 3 etc, even though what they are buying is actually 50 x 100 and 75 x 75...) Ok for building, but not precise drawings..

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

RE: Question about metric

But Little Inch, a 2 x 4 is not that size either, it is just lingo.

In countries like Australia, where the SI system has been in place for many years, soft conversions are uncommon. We don't have 8' or 9' ceilings, they are 2400 or 2700. And the walls are built with 70 x 35, 90 x 45, etc. studs.

RE: Question about metric

Sorry to be an @ss here, but the US do not use Imperial units- they use US customary units. Their gallon is smaller (3.785 L) than the Imperial gallon (4.54 L, such that 1 imperial gallon of water weighs and even 10 pounds- at least making some tiny bit of sense). Any useful piece of engineering software is going to have a unit conversion system on there, and will need it for a long time.

In Canada the transition to SI is anything but total, despite happening forty years ago. Sure, all the official weights and measures stuff is in metric, and people talk about km/hr and km distances rather than miles, temperatures are in degrees C, milk comes in litres etc. But we share so much across the border that we still work in all three systems- US customary, Imperial and SI/metric units. Plywood is still sold in the store by its inch dimensions even though it's made to even mm thicknesses. Pipe here is all inch NPS dimensions, and tubing in OD inch dimensions. And nobody uses metric fasteners, other than in automotive- they're still in the specialty part of the hardware store, in the tiny little bins with an enormous cost per item.

Fortunately, Bob Villa seems to have taught the Americans the virtues of the Robertson (square drive) woodscrew, but that's about all we can claim to have spread from our side of the border! In years past, I had to send a set of Robertson screwdrivers with each plant we built because as much as we tried to have "bisexual" fasteners everywhere with at least a slot to resort to in a pinch, some Robertson-only screws would sneak onto the plant somewhere and we'd have a hell of a time on site with them. Now you can find square drive screwdrivers in any Home Depot south of the border.

RE: Question about metric

LittleInch - I fight that translation over-precision in ASTM all the time. My favorite was "Approximately 1 pint (473.18mL) of gravel (250-300 stones.)"

Each stone is ~1-2ml, yet they went the extra distance to require precision to the hundredth of a ml.

RE: Question about metric

A 2 x 4 was a 2 inch by 4 inch, but is now something marginally different. I couldn't believe someone would actually cut down a piece of 4' x 8' plywood to the exact 1200 x 2400 though - that's really crazy. The UK went metric officially in the early 1970's, but managed to keep miles and mph and pints in official weights and measures, but precious little else. However fuel consumption in cars is still spoken of in mpg, despite it being impossible to buy a gallon of anything for about 25 years...

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

RE: Question about metric

It seems ironic to me that mainland Europe, including France, commonly uses such peculiar units as kgf/cm^2 for stress, but the countries following the UK tradition use "proper" SI units as a matter of course.
no we don't. the default unit for stress is MPa everywhere i know. prehaps the british are doing it differently.
there are some other units in use sometimes, like BTU, but i am not aware how much (outside britain).

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources