Imperial versus metric

[wumpus]

1 hour ago, mikegarrison said:

In my experience, no one uses slugs. But maybe there are some engineering disciplines where they get used all the time. I wouldn't know, because I've been in my little airplane world my entire career.

I do know, from discussions with my dad (a civil engineer), that different disciplines use different things.

The electrical (US) world is blessed with metric.  Only issue is that often printed circuit boards (and components) are in inches and mils (.001 inches).  I've often been thankful that I don't have to deal with 12 1/2 Franklins to the Edison for current or such.

[kerbiloid]

14 minutes ago, wumpus said:

Franklins

1 Franklin is a money unit, equal to 100 USD.

At least here, when you have it .

Handy for household numismatics, so has its own name.

[Shpaget]

2 hours ago, wumpus said:

Only issue is that often printed circuit boards (and components) are in inches and mils (.001 inches). 

Yeah, and then you get to work with a component with pin pitch that is not 0,1'' but rather 2,5mm, but in the general dismay that yet again you have to work with imperial nonsense, you don't even notice, and have 100s of your boards made only to realize weeks later that the error compounds so much that you can't use the boards and have to make them again, only now you're near the deadline and need to place a rush order and DHL charges you an arm, both legs and your firstborn to get it to you a couple of days sooner.

[StrandedonEarth]

Off topic? Nope! 

Alt-txt:

Spoiler

Sorry, in SI units that's "there's a big football in there."

 

[JoeSchmuckatelli]

1 hour ago, StrandedonEarth said:

Off topic? Nope! 

Alt-txt:

  Hide contents

Sorry, in SI units that's "there's a big football in there."

 

That explains why it would float in water!

[kerbiloid]

When they were copying B-29 to create Tu-4, it appeared that the hull sheet is 1/16 " thick.

And 1/16 " = 1.5875 mm.

The standard 1.5 mm was too weak.
The standard 1.6 mm was too heavy.
The exact but non-standard 1.5875 needed accuracy unavailable for existing machines.

The morale of that: using Imperial, always think about them, who suffers converting it into Metric.

[darthgently]

10 minutes ago, kerbiloid said:

The morale of that: using Imperial, always think about them, who suffers converting it into Metric

They could have used the 1.5 mm and re-engineered the number, spacing, and size of the stringers, longerons, ribs, bulkheads, etc to compensate.

Or not copied and just designed their own bomber

Edited April 9, 2022 by darthgently
tpyos

[Deddly]

Or they could have used the 1.6 mm standard and added MOAR boosters

[Bej Kerman]

On 12/30/2013 at 2:07 AM, Themohawkninja said:

It's really not that complicated, since you just memorize a few numbers and that's it.

"a few numbers"

Yeah....

About that...

Literally all you have to remember in Metric is how to multiply and divide by 10 and 100, which really should be kindergarten level maths.

[JoeSchmuckatelli]

Roman mile missing 'pace'.  1000 paces = mile 

Pace is the measure derived from counting each time the left foot strikes the deck 

Edited April 9, 2022 by JoeSchmuckatelli

[benzman]

35 minutes ago, Bej Kerman said:

"a few numbers"

Yeah....

About that...

Literally all you have to remember in Metric is how to multiply and divide by 10 and 100, which really should be kindergarten level maths.

I have often thought that the British national sport is dreaming up freakishly weird standards of measurement! Brilliant graphic.  I could stare at it for hours, and it all makes sense. Well, kind of.

[darthgently]

48 minutes ago, benzman said:

I have often thought that the British national sport is dreaming up freakishly weird standards of measurement! Brilliant graphic.  I could stare at it for hours, and it all makes sense. Well, kind of.

A lot of those go back way before Britain I imagine.  I know "cubit" goes back to Sumeria or so.  The English language just likes to collect new terms like a hair brush collects hair

Edited April 9, 2022 by darthgently

[benzman]

I once read that the reason some British people dislike Metric is because it was invented by the French,  and they don't like the French.  And the reason some Americans dislike it is because it was invented by godless atheists.  Both reasons are equally stupid.

[mikegarrison]

41 minutes ago, benzman said:

I once read that the reason some British people dislike Metric is because it was invented by the French,  and they don't like the French.  And the reason some Americans dislike it is because it was invented by godless atheists.  Both reasons are equally stupid.

Thomas Jefferson helped design the metric system, and the early United States almost adopted it. In 1793, Jefferson sent to France to get some artifacts (specifically, a copy of the official kilogram) that the US could use for standardization, but the ship carrying it was captured by pirates.

US units are all now defined by SI units anyway, just with specified conversion factors.

Edited April 10, 2022 by mikegarrison

[kerbiloid]

7 hours ago, darthgently said:

They could have used the 1.5 mm and re-engineered the number, spacing, and size of the stringers, longerons, ribs, bulkheads, etc to compensate.

They have used sheets of varying thickness, from 0.8 to 1.8 mm, depending on local stress.

But the B-29 developers could be more courteous to the colleagues...

6 hours ago, Deddly said:

Or they could have used the 1.6 mm standard and added MOAR boosters

They did this, too, by using the locally upgraded engine based on the licensed Wright Cyclone.

[darthgently]

45 minutes ago, kerbiloid said:

But the B-29 developers could be more courteous to the colleagues...

I imagine that the original plans for the B-29 were drawn up around available materials and form factors within and for the USA.  I doubt that WWII USA had a lot of metric materials in the local supply chain, and this being prior to computer aided engineering it would have taken a team of slide-rule churning engineers quite a while to be that courteous.  It was probably assumed that engineers on the receiving end would take that on as required; the plans for a working bomber, even if the hull thickness might need tweaking, compared to starting from scratch was probably seen as quite the offering at the time. Given that some team of engineers would need to do the tweaking necessary and the first team had already done so much already it isn't a stretch that the receiving team, who were perfectly capable, could do the tweaking as needed for their part.  Maybe I'm missing something but it looks like everyone was just doing their job within the constraints they were expected to get the job done.   Both teams did a good job, there is no reason to see fault in the process that I can see

Edited April 10, 2022 by darthgently

[mikegarrison]

10 hours ago, darthgently said:

I imagine that the original plans for the B-29 were drawn up around available materials and form factors within and for the USA.  I doubt that WWII USA had a lot of metric materials in the local supply chain, and this being prior to computer aided engineering it would have taken a team of slide-rule churning engineers quite a while to be that courteous.  It was probably assumed that engineers on the receiving end would take that on as required; the plans for a working bomber, even if the hull thickness might need tweaking, compared to starting from scratch was probably seen as quite the offering at the time. Given that some team of engineers would need to do the tweaking necessary and the first team had already done so much already it isn't a stretch that the receiving team, who were perfectly capable, could do the tweaking as needed for their part.  Maybe I'm missing something but it looks like everyone was just doing their job within the constraints they were expected to get the job done.   Both teams did a good job, there is no reason to see fault in the process that I can see

What you apparently don't realize is that a lone B-29 landed in Russia in WW2. I don't remember offhand exactly why, but it wasn't an intentional gift from the US. The USSR kept the airplane, which was at the time the most powerful and sophisticated weapon in the US military arsenal other than maybe the atomic bomb. They made, as best they could, an exact duplicate of it and pretended that it had been designed by Tupolev. They called it the Tu-4, and it was the main Russian bomber for many years after the end of WW2.

Edit. Just checked. Not one, but rather four B-29s. They were airplanes that had been on bombing raids in Japan and for one reason or another ended up making emergency landings (or crashes) in the USSR. Due to the neutrality pact between the USSR and Japan that existed during most of the war, the USSR claimed that they could not return the planes to the US.

Tupolev was apparently quite annoyed that rather than being able to build his own design, he was firmly ordered to reverse engineer an exact copy of Boeing's airplane. Even when he came up with changes that were (or might have been) improvements, he was mostly instructed not to use them.

Edited April 10, 2022 by mikegarrison

[darthgently]

1 hour ago, mikegarrison said:

What you apparently don't realize is that a lone B-29 landed in Russia in WW2

Ok, that makes a lot more sense.  I'm not an expert, obviously, but was allowing that @kerbiloid knew something about the tenuous semi-alliance between the USA and USSR against the axis powers that I didn't know about.  My first hunch was that any alliance was not tight enough to share state of the art aircraft designs.  Thanks for the education, this is very interesting, and illuminating

Edited April 10, 2022 by darthgently

[kerbiloid]

1 hour ago, mikegarrison said:

What you apparently don't realize is that a lone B-29 landed in Russia in WW2.

Five ^*). In different circumstances, from storm to fire damage.

51 minutes ago, darthgently said:

@Kerbaloid

Who's that?

P.S.
^*) Usually, "four", but can't now find the link where five were described.

Edited April 10, 2022 by kerbiloid

[darthgently]

2 minutes ago, kerbiloid said:

Who's that?

Oops.  Not you, apparently.  I was typing from mis-memory apparently.  The name came up, so it must have been someone at some time.  I'll correct just because

[kerbiloid]

1 hour ago, mikegarrison said:

Tupolev was apparently quite annoyed that rather than being able to build his own design, he was firmly ordered to reverse engineer an exact copy of Boeing's airplane. Even when he came up with changes that were (or might have been) improvements, he was mostly instructed not to use them.

https://sachev-ru.translate.goog/tupolev_an_2/ne_kopiya_a_analog_o_samolete_tu-4.htm?_x_tr_sch=http&_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=ru

[darthgently]

4 minutes ago, kerbiloid said:

https://sachev-ru.translate.goog/tupolev_an_2/ne_kopiya_a_analog_o_samolete_tu-4.htm?_x_tr_sch=http&_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=ru

I'm out of "likes" for the day, but I like this, thanks

[JoeSchmuckatelli]

2 hours ago, kerbiloid said:

https://sachev-ru.translate.goog/tupolev_an_2/ne_kopiya_a_analog_o_samolete_tu-4.htm?_x_tr_sch=http&_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=ru

I read this both with interest and a sense of tragedy.  It's almost a testament to Tupolev's skill, not that he completed the project - but that he wasn't 'disappeared' along the way.  I'm not sure what sense of nostalgia Russians might feel for the years of Stalin... but from an outside perspective?  You poor stand-up guys! 

(The last may not translate well - but this may help translate US Marine to English:

 

EDIT: LOL at the 'swear translator' included on this forum.   "Stand up guys" indeed!)

Edited April 10, 2022 by JoeSchmuckatelli

[kerbiloid]

Soviet howitzer: 152.4 mm = 60 lines = 6 inch. Round inches, not round mm.
American howitzer: 155 mm = 61 line = 6.1 inch. Round mm, not round inches.

Where is logic?

Why make 6.1 when others make 6.0?

Or why round millimeters being fond of inches?

Edited April 25, 2022 by kerbiloid

[Deddly]

6 minutes ago, kerbiloid said:

Where is logic?

I don't know about that particular case, but a lot of manufacturing is done with the help of international contractors, so a standard has to be picked somewhere in the planning process according to available materials and machinery.

There are other oddities. For example, even in Europe, we use inches to describe the size of wheels on our cars, even if every other component is measured in metric.