Is There Any Logic To Body Tube Designations

[MetricRocketeer]

Of course the Metric system is more logical. Every child knows that a metre is the distance travelled by light in vacuum in 1/299 792 458 second. Or that it used to be 1/10 000 000 of the meridian through Paris between the North Pole and the Equator.

Hi @Cape Byron,

On this matter you are not correct.

The distance from the North Pole to the Equator is 10,000,000 metres (or 10,000 kilometres). So the circumference of the Earth is 40,000,000 metres (or 40,000 kilometres). This is an extraordinarily close approximation, from which one can easily calculate all the parameters of a globe.

Stanley

 

[Grant_Edwards]

I congratulate you on your maximum-altitude flight measuring 26,240 feet. How many miles was that? Let's get out the calculator to divide 26,240 feet by 5280.

I thought in rocketry nautical miles were used. Or is that just for distance downrange? Only when launched over the ocean?

 

[MetricRocketeer]

Hi @Grant_Edwards and everyone else,

If if were up to metric advocates, metres and kilometres would be used to measure distances on the Earth, in the air, and on the sea.

Stanley

 

[Grant_Edwards]

I'd be perfectly happy doing everything in metric, as long as sawmills switched over so that common finished board sizes made sense in metric.

 

[Cape Byron]

Hi @Cape Byron,

On this matter you are not correct.

The distance from the North Pole to the Equator is 10,000,000 metres (or 10,000 kilometres). So the circumference of the Earth is 40,000,000 metres (or 40,000 kilometres). This is an extraordinarily close approximation, from which one can easily calculate all the parameters of a globe.

Stanley

I pretended I was a student in the 2020s and just used Wikipedia.

'(1793): 1/10 000 000 of the meridian through Paris between the North Pole and the Equator.'

FWIW I use Metric and I like Metric.

I also like a laugh.

 

[MetricRocketeer]

Hi @Cape Byron,

We don't have a dispute, do we? A meridian is a line of longitude, and the line of longitude -- or the meridian -- we are discussing is the one passing from the North Pole, through Paris, to the Equator. Actually, however, the length of any meridian from the North Pole to the Equator -- or indeed, any quarter of a great circle of the Earth -- measures 10,000 kilometres.

One more point, please. I am glad that you use the metric system and that you like it. You come from Australia, which is a great example of a major country of the world that has almost thoroughly metricated. If the United States were as metric as Australia is, I would consider my metric mission to be just about fully accomplished.

Stanley

 

[Cape Byron]

We don't have a dispute, do we?

Nope. I'm too old for disputes and as far as grudges go I'm over hiding the bodies.

 

[OzHybrid]

So to summarise it.

Body tube sizes were numbers chosen for sizes where the larger the number(generally) the larger the tube. The sizes used were based on available supplies and mandrels at the time.
The numbers left some space between them so that if a different smaller size or larger size were made it could be accommodated as a new number in the body tube system of numbering. Other than that, there is no logic or linear size progression from it.
Looking back on it, the creators of the system regret the dinosaur they created.
The dinosaur they created still exists and it's extremely unlikely it will change.
Global warming will probably make cardboard tubes redundant as they will be too soggy to maintain shape or strength.
Metric would be a better system to use if we were all starting again from scratch, but we're not.
When converting from inches specified to 3DP ( Decimal Places) to mm you only need to use 2 1/4 DP(approx) for the same accuracy.
A size is not properly specified unless it is toleranced or the size without a specified tolerance matches the ISO implied tolerance.

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[lakeroadster]

I'm a huge fan of Dinosaurs, as well as Rockets.

I love it when a plan comes together.

 

[kuririn]

Apogee Components tried to use a metric classification for body tubes a while back.
They found out you can't fight city hall.
Everybody knows what a BT-60 tube is.
Few know what a BT-41.6 tube is.
(It's the same thing under Apogee's system).
BT-70 was BT-56.
BT-80 was BT-66.
You get the idea.

 

[6inchmonster]

What the heck would you prefix with "BT" if you wanted different.. ah nevermind, apogee does what apogee does

 

[OzHybrid]

I'd be perfectly happy doing everything in metric, as long as sawmills switched over so that common finished board sizes made sense in metric.

I'm uncertain that allowing your sawmill to dictate your measurement standards is the best idea. They quote the size of wood in rough sawn dimensions. So a rough 4x2 is 4x2 but a finished 4x2 is 3 3/4 x 1 3/4....... So a finished tube would be 1/4 less on the outside and also be 1/4 larger on the inside. This could cause a massive hole in the space time continuum............... We could have negative wall thicknesses. If we now convert from an imperial time system to our new metric time system, using the rounding errors we could create small positive and negative time differentials from rounding the actual time. Amplify those and build a box from 1/8" rough sawn timber and finish it once its constructed and we could create a box that's larger on the inside and can move forward and backward in time. Sort of a Time And Relative Dimensions In Space working prototype.............

 

[user 35280]

http://www.ninfinger.org/rockets/body_tubes.html

 

[prfesser]

I'd be perfectly happy doing everything in metric, as long as sawmills switched over so that common finished board sizes made sense in metric.

I don't know about studs, rafters, etc....but my understanding is that some metric countries (or maybe it's contractors) use 1.2 metres as a sort of "base" dimension, just as US plywood is sold in 4' widths. 1.2 metres subdivides into 60, 40, 30, and 20 cm. I may be full of old bootlaces and sardine juice, though.

 

[MetricRocketeer]

I don't know about studs, rafters, etc....but my understanding is that some metric countries (or maybe it's contractors) use 1.2 metres as a sort of "base" dimension, just as US plywood is sold in 4' widths. 1.2 metres subdivides into 60, 40, 30, and 20 cm. I may be full of old bootlaces and sardine juice, though.

Hi everyone,

I would like very much to know if that is correct. A length of 1.2 metres is just about 4 feet, and 120 cm so conveniently divides into 60 cm, 40 cm, 30 cm, and 20 cm.

Could anyone kindly jump in, please. Is @prfesser understanding correct?

Thank you.

Stanley

 

[Cape Byron]

Hi everyone,

I would like very much to know if that is correct. A length of 1.2 metres is just about 4 feet, and 120 cm so conveniently divides into 60 cm, 40 cm, 30 cm, and 20 cm.

Could anyone kindly jump in, please. Is @prfesser understanding correct?

Thank you.

Stanley

Yup. 1.2 metres is very much a standard timber length in DAR (dressed all round) and rough sawn timber supplies. So is 1.8 and 2.4 for the reasons already stated.

 

[MetricRocketeer]

Yup. 1.2 metres is very much a standard timber length in DAR (dressed all round) and rough sawn timber supplies. So is 1.8 and 2.4 for the reasons already stated.

Hi @Cape Byron and everyone else,

Wow! That information has been tremendously enlightening for me. I am so glad to have learned it.

And then one followup question, please. What is the standard timber thickness?

Stanley

 

[Cape Byron]

Hi @Cape Byron and everyone else,

Wow! That information has been tremendously enlightening for me. I am so glad to have learned it.

And then one followup question, please. What is the standard timber thickness?

Stanley

Oh, logical stuff like 12 mm (really 12.7 so 1/2"), 19 mm (really 19.05 so 1/4"), 25 mm (really 25.4 so 1")...

Sort of Imperial disguised as Metric.

The timber industry is, in reality, about as metric as a pre-war English motorcycle.

 

[OzHybrid]

Oh, logical stuff like 12 mm (really 12.7 so 1/2"), 19 mm (really 19.05 so 1/4"), 25 mm (really 25.4 so 1")...

Sort of Imperial disguised as Metric.

The timber industry is, in reality, about as metric as a pre-war English motorcycle.

19.05 3/4”. Ahhhh impetric. I lived through the change over to metric/ impetric In the UK. You’d get floorboards 8x4 and 2400x1200 at the same time as the stocks changed over. Lots of fun now the swearing has stopped ringing in my ears……

 

[Cape Byron]

19.05 3/4”. Ahhhh impetric.

Yeah, well I'm a farmer not a mathermaticolorian thing...

 

[OzHybrid]

Yeah, well I'm a farmer not a mathermaticolorian thing...

Don’t you get lippy now or that 304.8mm ruler will be straight across the back of your knuckles young sir.

 

[Cape Byron]

Don’t you get lippy now or that 304.8mm ruler will be straight across the back of your knuckles young sir.

Yeah, give some of you guys 25.4 mm and they take 1609.4 metres.

Hmmm. Doesn't work as well as the Imperial version...

 

[MetricRocketeer]

Yeah, give some of you guys 25.4 mm and they take 1609.4 metres.

Hmmm. Doesn't work as well as the Imperial version...

"Give the person a centimetre, and they take a kilometre."

What's wrong with that?

 

[Antares JS]

"Give the person a centimetre, and they take a kilometre."

What's wrong with that?

Too mouthy. "Inch" and "mile" are monosyllabic words that let the phrase sound much snappier.

 

[MetricRocketeer]

Too mouthy. "Inch" and "mile" are monosyllabic words that let the phrase sound much snappier.

A valid critique.

 

[Cape Byron]

Too mouthy. "Inch" and "mile" are monosyllabic words that let the phrase sound much snappier.

"Give them an inch and they think they're a ruler."

 

[MetricRocketeer]

Hi @Antares JS and everyone else,

I have come across interesting metric terminology pertaining to this issue.

My wife is involved with fiber arts. At a recent conference that she attended, a presenter from India referred to kilograms as kay-gee. This impressed me most favorably. Metric advocates always point out that kilograms should be called just that — kilograms — and not kilos, a term widely used. Kilos is not correct, because that term is a prefix and not a unit of measurement in itself. Nevertheless, even in countries where the metric system is universally used, people often use the word kilo — no doubt because this two-syllable term is quicker to say than the four-syllable word kilogram.

Actually, I find the designation kay-gee to be revolutionary. Constituting only two syllables, it nonetheless references both the prefix kilo and the unit gram. Indeed, the very term kay-gee transforms itself into the acronym meaning kg, which is the abbreviation for kilogram.

Then, at another conference related to fiber arts, a participant also from South Asia referred to millimetres as mm — so the term was pronounced as em-em. At the same conference, another participant used the term cm to refer to centimetres.

Well, this is interesting. Perhaps then we have established quite succinct and totally unambiguous terminology to use for metric measurements. Adding to mm, cm, and kg, we could also use km for kilometres.

Hence, in response to @Cape Byron's post #82, I suggest "Give the person a cm, and they take a km."

Stanley

 

[jqavins]

In my experience, there's nothing new here. I've often heard kay-em, kay-gee, em-em, see-em, and see-see. They are all just reading out the letters of an abbreviation, which bothers me, only a little, since one would not read out "ee-tee-see" for etc., "el -ee" for lb, and so on. And, hypocritically, "see-see" for CC doesn't bother me at all, because it's so well established.

no doubt because this two-syllable term is quicker to say than the four-syllable word kilogram.

You might want to count those syllables again.

Actually, I find the designation kay-gee to be... unambiguous terminology...

But, I thought a kay-gee was 9806.6 m/s².

 

[Tobor]

This is a every funny thread. It seems to go on for miles.......

 

[kuririn]

This is a every funny thread. It seems to go on for miles.......kilometers.

Fixed it for ya.