Metric Fuel Consumption

Metric Fuel Consumption

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InitialDave

11,856 posts

118 months

Friday 24th November 2017
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LimaDelta said:
Try general aviation in the UK...

Altitude - ft
Distance - nm
Runway length - m
Speed - Kts
Fuel - lbs
Fuel flow - GpH
Air pressure - Hpa (mb)
Manifold pressure - inHG
Power - hp
Engine oil - quarts
Air temp - DegC
Oil temp - DegF
Oil pressure - PSI

And probably others I've forgotten to mention.
Haha, yes. You soon get used to switching between metric and imperial with certain aerospace stuff.

E.g. you get drawings for a bolt with a 1" UNF thread on it, but the dimensions are in metric, so the shank diameter is given as 25,4mm.

It's a minor irritation that makes you think "oh, just call it a bloody inch and be done with it", but not really a problem. You just get used to it.

Same with MPG really. I "think" in MPG rather than L/100k, but simply out of habit. I don't think either is "better", other than I'd rather stick to what I'm used to.

I have no issue switching between metric and imperial for my bodyweight or gym weights either, generally I'll use whatever the person I'm talking to is working in.

Though you should always lift weights working in pounds because the numbers are bigger! biggrin

TooMany2cvs

29,008 posts

125 months

Friday 24th November 2017
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Crosswise said:
Someone mentioned Canada earlier, and although it is definitely Km and Liters when it comes to driving, it is probably even more confused in many other regards. It is officially metric, however, as a lot of equipment comes from the US, it is far more common to use imperial. Today, in my job alone, we have set up 2 identical high pressure pumps, both control panels have the flow in gpm and pressure in psi, one has the motor temperature in Fahrenheit, one in centigrade. We've installed metric sized junction boxes in imperial housings using a combination of metric and imperial fixings. At least once a week I deal with the results of metric bolts being forced into imperial fittings or the other way round.

The UK is far from unique.
No, the US is the other country that's not metric - and even they don't do the half-arsed mix-and-match that we do.

The fact that Canada has to buy Dibnah stuff from the neighbours doesn't mean Canada shouldn't be metric, though. I'm surprised that the fitters aren't aware of the issue.

saaby93

32,038 posts

177 months

Friday 24th November 2017
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Horsetan said:
saaby93 said:
snt it because they thought there were about 360 days in a year
To change that to metric you'd need to do something significant
...like the 1789 French Revolution, which really did impose ten-day weeks, each day split into ten hours of 100 minutes each.... They still kept to twelve months in a year, though....
Also in France you can still buy a 'pound' of some things when it's a convenient size

Isnt Metric length arbitrary - defined by a metre long bar of platinum somewhere
Whats the betting they started out with an inch being 25mm but decided it was too obvious so made it 25.4


TooMany2cvs

29,008 posts

125 months

Friday 24th November 2017
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saaby93 said:
Also in France you can still buy a 'pound' of some things when it's a convenient size
When is 454g ever more "convenient" than 500g?

saaby93 said:
Isnt Metric length arbitrary - defined by a metre long bar of platinum somewhere
Whats the betting they started out with an inch being 25mm but decided it was too obvious so made it 25.4
Originally defined in 1793 as 1/10,000,000th of the distance from equator to North Pole.

The foot, btw, has been officially defined as 304.8mm since the 1950s - the first time there was ever a single international standard for it.

It always makes me chuckle that so much "not metric" sentiment in the UK seems to come down to "not invented here" - ignoring the minor detail that it was... It all started from work done in the 17th century by John Wilkins, Bishop of Chester, Master of Trinity College (Cambridge), Warden of Wadham College (Oxford).

Toltec

7,159 posts

222 months

Friday 24th November 2017
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No, a metre is defined as how far light travels in one 299792458th of a second in a vacuum.

Mass is the last SI unit still using a physical object and that will not be for long


InitialDave

11,856 posts

118 months

Friday 24th November 2017
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Toltec said:
No, a metre is defined as how far light travels in one 299792458th of a second in a vacuum.
Are you replying to TM2CVs? He did say "originally".
TooMany2cvs said:
Originally defined in 1793 as 1/10,000,000th of the distance from equator to North Pole.

saaby93

32,038 posts

177 months

Friday 24th November 2017
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TooMany2cvs said:
Originally defined in 1793 as 1/10,000,000th of the distance from equator to North Pole.
on the surface? at high tide or low tide, which side is the moon?
id they come up with 1/10,000,000 because it meant that 25mm was about an inch?
Why not from north pole to south pole?
Somewhere the decision was abitrary

A foot is a foot because....

TooMany2cvs

29,008 posts

125 months

Friday 24th November 2017
quotequote all
saaby93 said:
TooMany2cvs said:
Originally defined in 1793 as 1/10,000,000th of the distance from equator to North Pole.
on the surface? at high tide or low tide, which side is the moon?
id they come up with 1/10,000,000 because it meant that 25mm was about an inch?
Why not from north pole to south pole?
Somewhere the decision was abitrary
Yes, it was. Of course it was. That was the best-available standard over 200 years ago - as Toltec points out, the standard has been refined over the years for greater consistency and accuracy as science has enabled it.

Why not to the South Pole? Simple. Because nobody had been anywhere near it.

saaby93 said:
A foot is a foot because....
Go on...

What size of human foot? Come to that, which standard of foot unit of measurement? Remember, until it was set as a specific fraction of the international standard metre, there was no single definition of a foot... Over history, it's varied from about 250mm to about 350mm. Several of the standards around the 10th century were based on multiples of the size of a grain of barley, while Henry I is rumoured to have set the British standard to be based on the length of his arm.

Even if we go with the human foot, and ignore the natural variance there, isn't that an arbitrary choice, too? Why not a hand-span, or a lower leg length? The ancient Egyptians had a measurement of about 300mm - which was four palm-widths, or 16 digits.

captain_cynic

11,873 posts

94 months

Friday 24th November 2017
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TooMany2cvs said:
An American cup is.
A metric cup is 250ml.
An imperial cup is 284ml.
A Canadian cup is 224ml.
A Japanese cup is 200ml.
A Latin American cup is either 200ml or 250ml.

I do apologise - there is a second common definition of a teaspoon - the US teaspoon is not exactly 5ml, it's 4.9289ml.
This is why we need metric, it's standardised everything.
A metric teaspoon is 5mL
A metric tablespoon is 15mL
A metric cup is 250mL

Like many of us, I've got a Pyrex measuring jug at home, its got metric measurements on it as well as imperial, I never use the imperial side. I've also got a set of teaspoon/cup measures... they're all in metric. Few recopies these days call for imperial measurements, very few list measurements in imperial only+. liquids are in cups and mL, powders in tbsp/tbs or grams and solids in grams.

+ I know what you're thinking, "What about the abundance of American recipe sites"? Well first off they often use metric as well as non-metric units like many British sites. Secondly the Imperial system was first defined in Weights and Measures act of 1824, nearly some 50 years after their little rebellion, so the US doesn't use the Imperial system, they're not even that advanced. The US uses US Customary Units which predates the Imperial system.

Shakermaker

11,317 posts

99 months

Friday 24th November 2017
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saaby93 said:
thegreenhell said:
The only reason that the decimal system is so prevalent is because most of us have 10 fingers, which makes for easy counting. If only we had an extra digit on each hand then we'd all be using the duodecimal system, and most of these odd units would make much more sense. 12, and multiples thereof, is much more readily divisible into useful fractions than 10, so using base-12 as our counting system would make life a lot easier.
Even during the times most people had 10 fingers it was still more common to have dozens for useful things which to some may have been gross.
Surely today 16 is the most used counting system even if it is largely hidden
Actually, go to lots of places around the world and despite how people still have 10 fingers and 10 toes, they don't use those in the same way for counting as we do...

Some use base 12, because on one hand you can use your thumb to count the 3 joints on each of the 4 fingers.

Some count the gaps in between fingers...

Some don't stop at fingers, they then use the palm, wrist, forearm, elbow, upper arm, shoulder, and go down the other side again.. totalling a base 27 system....


Toltec

7,159 posts

222 months

Friday 24th November 2017
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InitialDave said:
Toltec said:
No, a metre is defined as how far light travels in one 299792458th of a second in a vacuum.
Are you replying to TM2CVs? He did say "originally".
TooMany2cvs said:
Originally defined in 1793 as 1/10,000,000th of the distance from equator to North Pole.
Reply was to saaby93, didn't notice the quote got missed, sorry.

TooMany2cvs

29,008 posts

125 months

Friday 24th November 2017
quotequote all
captain_cynic said:
Secondly the Imperial system was first defined in Weights and Measures act of 1824, nearly some 50 years after their little rebellion, so the US doesn't use the Imperial system, they're not even that advanced.
TBF, they simply picked a different one of the three pre-1824 gallons to standardise on. The old story about some of the water in a measured gallon evaporating/being spilled on the Mayflower is just urban legend.

Corn Gallon - 4.4 litres
Wine Gallon - 3.8 litres
Ale Gallon - 4.6 litres

The UK went for something close to the Ale Gallon, the US had already settled on the Wine Gallon. The choice of the Ale Gallon was based on the weight-volume relationship (10lb of water), because the kilogram/litre were already doing a similar link...

captain_cynic

11,873 posts

94 months

Friday 24th November 2017
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Vanin said:
Good man! One of my favourite subjects!

You forgot to mention to all the metric freaks out there that a circle is divided into 360 degrees for navigation and then into minutes which leads nicely to the next topic which is time
24 hours in a day, 12 hours on most clock faces, sixty minutes in an hour and sixty seconds in a minute.

How does all that sit with the decimal mentality? What next 10 hour days with 100 minute hours and 100 second minutes?

100 degree circles?
SI units are designed for computationally convenient (which means easy to use in calculations) not Ideologically rigid. Things like distance, mass and volume are best in base 10 because we need to multiply and divide across orders of magnitude. When it comes to things like hours, minutes and compass directions, we need to divide it into more equal fractions as opposed to across orders of magnitude, so base 12 is better here because its easily divisible by 2, 3, 4 and 6.

Sorry, did is this answer too sensible?

Edited by captain_cynic on Friday 24th November 10:46

captain_cynic

11,873 posts

94 months

Friday 24th November 2017
quotequote all
.

TooMany2cvs

29,008 posts

125 months

Friday 24th November 2017
quotequote all
captain_cynic said:
SI units are designed for computationally convenient (which means easy to use in calculations). Things like distance, mass and volume are best in base 10 because we need to multiply and divide across orders of magnitude. When it comes to things like hours, minutes and compass directions, we need to divide it into more equal fractions as opposed to across orders of magnitude, so base 12 is better here because its easily divisible by 2, 3, 4 and 6.

Sorry, did is this answer too sensible?
The SI unit of angular measure is the radian, anyway, defined in 1714 by Roger Cotes, who worked closely with Isaac Newton. One radian is the portion of a circle where the circumference is the same as the radius. Nice, easy, natural division.

There's a couple of theories as to why there's 360deg in a circle - the Persian calendar had 360 days, and the Babylonians used base 60 for counting.

LimaDelta

6,507 posts

217 months

Friday 24th November 2017
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Another one for you...

The Earth's circumference is a complete circle[citation needed] of 360 degrees. there are 60 minutes in a degree so the Earth's circumference is 21,600 minutes

The Earth rotates every 24 hours and there are 60 minutes in an hour (1440 minutes in a day) so 1 minute of time = 15 minutes arc.

Or 1 minute = 900 seconds

Mr2Mike

20,143 posts

254 months

Friday 24th November 2017
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TooMany2cvs said:
If you'd read on a sentence or two, you'd have been reminded that that particular conversion is SLAP BANG IN FRONT OF YOU ON THE DASHBOARD...
No it's not. The conversion factor is, but unless your speedometer goes up to 300kmh, you don't have a direct conversion slap bang in front of you, it's still yet another step in the calculation that isn't needed with the existing units. You wrote a wall of text describing how to do a calculation that, using mpg, can be done in a fraction of second in your head with no conversion factors required. Explain again how it is just as simple?

TooMany2cvs said:
It's also one that's inherently pretty damn familiar with everybody who isn't so utterly insular as to never drive outside the UK.
Basing your argument around being well travelled, as opposed to making life simple isn't going to help.

Mr2Mike

20,143 posts

254 months

Friday 24th November 2017
quotequote all
TooMany2cvs said:
An American cup is.
A metric cup is 250ml.
An imperial cup is 284ml.
A Canadian cup is 224ml.
A Japanese cup is 200ml.
A Latin American cup is either 200ml or 250ml.

I do apologise - there is a second common definition of a teaspoon - the US teaspoon is not exactly 5ml, it's 4.9289ml.
The size of a cup is pretty irrelevant, it's only commonly used in recipes where high accuracy is rarely needed and it's most always a ratiometric measurement anyway i.e. add 2 cups of X, then 3 cups of Y.

TooMany2cvs

29,008 posts

125 months

Friday 24th November 2017
quotequote all
Mr2Mike said:
TooMany2cvs said:
If you'd read on a sentence or two, you'd have been reminded that that particular conversion is SLAP BANG IN FRONT OF YOU ON THE DASHBOARD...
No it's not. The conversion factor is, but unless your speedometer goes up to 300kmh, you don't have a direct conversion slap bang in front of you,
I assume you can cope with scaling from 30 ~= 50, 50 ~= 80, 100 ~= 60? Because, if not, then you're not going to get very far with anything involving maths...

Mr2Mike said:
it's still yet another step in the calculation that isn't needed with the existing units. You wrote a wall of text describing how to do a calculation that, using mpg, can be done in a fraction of second in your head with no conversion factors required. Explain again how it is just as simple?
Are you perhaps forgetting that we haven't bought fuel in this country by the gallon for more than a third of a century, so a conversion - 4.54 litres = 1 gallon - is required?

captain_cynic

11,873 posts

94 months

Friday 24th November 2017
quotequote all
TooMany2cvs said:
The SI unit of angular measure is the radian, anyway, defined in 1714 by Roger Cotes, who worked closely with Isaac Newton. One radian is the portion of a circle where the circumference is the same as the radius. Nice, easy, natural division.

There's a couple of theories as to why there's 360deg in a circle - the Persian calendar had 360 days, and the Babylonians used base 60 for counting.
60 is base 12, which is good for division, regardless of the reasons for it's original use we keep it because it's computationally convenient.