Boeing and metrcication question

At Standard Temperature and Pressure STP only. Water changes if not on the mark.

Mart> >

I use decimals. Using metric is like using wire drills or letter sizes.

I still prefer Imperial threads. It tells you the major diameter and the threads per unit.

What the heck does M8x30 mean?

Mart> For myself, I calculate in metric in Physics and Engineering.

Shoulda told him that an 11/16" was a damn near perfect fit!

I left Commercial over a year ago. The 787 I don't know much about, but ISTR in my limited work with some tiny projects for it, it's still imperial. Nobody I've talked to has mentioned metric in any way, and believe me, they'd say something. Boeing isn't about to make the switch to metric unless there's a serious need, and I have a hard time seeing it. They're not resisting metric just because they want to conform to some silly notion of conformity, but trying to change all that to metric is economic suicide for any company heavily tied to engineering designs.

That's fine if you're doing calculations involving joules and motor output, Mark. But for every design engineer doing conversions there are ten people who have to figure things such as, say, how much of the 500-kg load they just put in their trailer should be shifted so that roughly 10% of the load is on the tongue. Do you seriously think they should convert the load to Newtons, and then gauge the tongue weight by estimating it in Newtons? I don't think so.

My point is that the traditional, non-SI units more often are based on measures that relate to our senses, without conversion. Even if they result in inelegant units, they often are more practical for ordinary measurements.

Even where metrics stand up well in those every-day measurements, the SI usually has little or no advantage. Sometimes, like with tongue weights and converting kilgrams of force to Newtons and back, the SI results in a confounding complication.

Again, on the whole, I wouldn't claim that the inch, or Imperial, or CGS metric systems are superior to the SI. I'm just saying that the supposed advantages of the SI don't apply in practical uses by most people, and that sometimes they can actually be a disadvantage.

Not many people would care, either. d8-)

You're talking about design engineering. We started this discussion talking about manufacturing, where it matters little, and I've tried to point out that most people who measure things are interested in neither scientific nor engineering calculations. I also have mentioned that, where metrics are preferred, we use metrics in the US. We even use the freakin' froggie SI. d8-)

Virtually all of our scientific calculations are done in metrics. Like scientists in various specialties everywhere, we don't always prefer the SI to CGS. Medical science still uses calories, for example, pretty much worldwide.

None of this has had an influence on our exports or imports. Nor has it seemed to retard our capabilities to invent and innovate. So, what is your point, in the end?

Well, the news here last week reported that the EU has decided to let your pubs continue to use the pint measure. I didn't realize the EU had that authority, but it was damned sporting of them, don't you think? d8-)

Perhaps they read Huxley's _Brave New World_, which addresses this very issue.

-- Ed Huntress

I hope not!

Nick

No, the point is different. You have to distinguish between force and mass. For some simple minded people (pun intended or not?) it is the same, but it ain't.

It works even greater in practice!

Have no insight into medicine at all.

The coherent system (why do you always say "theoretical", it *is* coherent) has a lot of advantages as soon as you start to make calculations.

A simple and cyclic example: Your did some math and the result's unit is [kg * m / s^2] Now what's that? It is force, so the unit is [N]. And how do you know? By the formula f = m * a. If you do the check with units it is: [N] = [kg] * [m/s^2]

That system is really great as soon as your calculations are a single step behind adding. Do a check with the units and you see whether you made some nonsense or not.

If you do have a problem "converting" mass to force, simply multiply the kg by 10 and you do have Newton.

Are you supposing to do the calculations in SI and then convert them to imperial? Don't ask for the famous prove what the result is.

Hmm ... I mean is someone is failing to understand the difference between mass and force and isn't able to calculate the resulting force, will he be able to properly dimension the legs (Euler's buckling resistance)? I bet no. Or the other way round: Does it help Joe Bar in calculating the stress of some odd-shaped column when he is using odd units? As soon as that Joe Bar wants to find out whether a screw is strong enough to keep his trailer together, it doesn't help to work in pounds when he considers the torque the screw is tightend with and the resulting stress and clamping forces (that was a longish German sentence :-))

Then it's OK! But wait ...

I remember a discussion about a year ago. It was such a mess that I had to bail out. And again "he pound, both as a unit of force and as a unit of mass, is quite handy" is just quite confusing and will only result in errors.

Yes, I can! ;-)

So, I do have to be annoying again: | Units of force, for example: the Newton equals roughly 0.101 972 | kilograms of force (kgf). That's what you wrote!

I have several answers: a) There is no such thing like kgf b) did you mean kp? c) kp was left behind 1960 and replaced with N e) from the factor 0.101972 I see that we live on the same planet (1 / 0.101972 = 9.806..) but I doubt that this is true everywhere. f) from e) I feel that you didn't fully understand the difference between force and mass.

Sorry! I do *not* want to kick your ass, I'm just a bit pi**ed when people are confusing things. And I see it so many times here that people write MM when they meant mm (what would MegaMega mean?) or write S when they meant s (I don't know what Siemens (the inverse of Ohm) has to do with time) etc.

But!!!: If you reduce the discussion to inch vs. metre (or meter) it is not worth continuing. There is just a factor to convert between them. Neither meter nor inch is more precise. The discussion starts when you look around and see things like feet, AWG, steel gage for sheet metal, drills by numbers and letters, etc. No such thing in the metric system.

Nick

AMEN.... amen.... amen...

Thank you so much. You have given me a true spiritual uplift in that for once I can see management as being on the right side of the equation and not the kinds of upes we see at GM. I admire Boeing, in spite of the problems, as one of the US's greatest example of overall excellence. Look at them... standing alone against a European consortium of socialistic money and against every US labor regulation and insane environmental and OSHA rules still staying on top of the pyramid.

Thanks!

Wayne

I can give you another uplift as well, Im with Boeing, as a desiner, maker and marketer of my own products, direct to the user. Like Boeing, I stand or fall by my own efforts, competing in my busines field with other co.s similar to my work. My customers choose my products not on wether they are made in metric units or imperial units but on my overall competitive value. Im in the UK which has standardised on the Metric system except where it conflictswith old tradition , like a pint of beer our road distances are still in miles of 1760 yds with 36 ins in a yard. we can still buy a pound of bananas tho the weight is given in both lbs and kilos. I use the imperial system just like Boeing, because all my machinery is set to work this way. my lathe is imperial. I can make everything in metric but it costs more, just like it would from Boeing. As for the Newton, well, its a vague name so could mean anything , but lbs per sq in . says what it is. and thats why folk prefer it, and will continue to do so.

Pressure is in Pascal. :-))

Nick

Standing alone with the aid of $2Billion per year in government subsidies! Your tax dollars at work, a triumph of free market lobbying :-)

And with all that money they still can't manage to convert to the measurement systems that the rest of the industrialised world uses. Quite sad really.

Mark Rand RTFM

Its not that simple unfortunately, Its not about conversion to what every one else in the industrial world uses. Its about all the suppliers of everything to Boeing, for example, all the US nut and bolt makers, screw makers wire and plug makers etc that supply the majority of US customers. It would need for the whole of whats left of the US manufacturing base to change all their manufacturing machinery and cnc programmes to suit who?s requirements? They dont need to at the moment. It will never happen.

Why should they bother? Heck, you can't even convert your pints of beer.

But "why should they bother" really is a serious question, Mark. Please, tell us.

-- Ed Huntress

London, Kentucky?

No, that third world, union run country that still has it's royal family. Gerry :-)} London, Canada

Until as recent as a few years back, the international measurment standard was a platinum bar with 2 X's engraved on it, preserved in Paris. The X's are 1000mm apart. This bar is the standard that all measurements were defined from, with the Inch being defined as

It is interesting to note that while people may argue against metrification, in reality the Imperial system is now derived from the Metric system.

This year the BSPF and BSPT thread standards have now been given a new "Metric" Designation ISO Rc Series (Taper) and ISO G Parallel Series. They are still designated with fractions and TPI, but have been incorporated into SI standards. This is a good example of "Inchification". Hope this makes some of you Yankees feel a bit better.

Cheers from Down Under

Dominic.

There are a number of other things to consider when it comes to aviation and metric. Flight levels... in feet. Runway distances and aircraft performance figures in the US are all in feet. All the aircraft instruments are in feet, inches or lbs/sq. in. When you have a working system you stay with it unless there is a vast improvment with a new system. It's the same as some countries using 50 cycle ac power when

John

Not likely as those standards are British and not US. US thread standards differ from British in TPI for most sizes and the included angle of the thread.

I've been asked to modify some software to accept N/mm^2 instead of MPascals but they are the same thing, it's a display thing as different parts of the world are used to different unit designations.

Nick, out of interest with this software, what is the German abbreviation for seconds, sek (sekond), or sec.