26-09-2018, 08:35 PM
12
Re: Measurement units
Originally Posted by Besoeker
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They are not comparable. They are measures of different things.
26-09-2018, 08:44 PM
13
Re: Measurement units
Originally Posted by Longdogs
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Well, I have no desire to be an expert on such things. All I know is, buying a bulb was once easy.
27-09-2018, 08:52 PM
16
Re: Measurement units
Originally Posted by Purwell
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In lots of ways the duodecimal system was easier, we can all halve linear measurements very accurately by eye.
But I do accept that duodecimal did have some merits.
You can do fractions like 1/2, 1/3, 1/4, 1/6, and 1/12 in your head. And that's fine for pennies and shillings or feet and inches. Not so good for links, chains and furlongs, miles, leagues....
With SI, it is all in metres - m, km, mm etc.
27-09-2018, 09:12 PM
17
Re: Measurement units
Originally Posted by Besoeker
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Surely if you are doing it by eye measurement units are irrelevant since you are not doing any measuring?But I do accept that duodecimal did have some merits.
You can do fractions like 1/2, 1/3, 1/4, 1/6, and 1/12 in your head. And that's fine for pennies and shillings or feet and inches. Not so good for links, chains and furlongs, miles, leagues....
With SI, it is all in metres - m, km, mm etc.
Unless accuracy is important, the distal section of my thumb is about one inch, the width of my hand is about four inches, the span of my hand (if I don't stretch too much) is about nine inches, and my nose to the end of my outstretched arm is about a yard.
Then, two steps (a pace) is a little over a yard as well, and a thousand paces (mille passim) amounts to about a mile.
It's obvious where the old Imperial measures originated! Not the British Empire, I should add; the Roman Empire.
27-09-2018, 09:43 PM
18
Re: Measurement units
Originally Posted by JBR
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Trouble is, you don't always have a ruler to hand.
Originally Posted by JBR
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Unless accuracy is important, the distal section of my thumb is about one inch, the width of my hand is about four inches, the span of my hand (if I don't stretch too much) is about nine inches, and my nose to the end of my outstretched arm is about a yard.Then, two steps (a pace) is a little over a yard as well, and a thousand paces (mille passim) amounts to about a mile.
It's obvious where the old Imperial measures originated! Not the British Empire, I should add; the Roman Empire.
Another example from my field. We used to define output power of electric motors in horse power, an Imperial unit. But you want to calculate what it will draw from your supply. That's in SI units, Amps, Volts and, where applicable power factor.
So the first thing you need to convert HP to kW. A factor of 0.746 is used. Now, if you gave the nameplate output in kW as it is in most of the world, that's one conversion you wouldn't have to do.
27-09-2018, 09:57 PM
19
Re: Measurement units
Originally Posted by Besoeker
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No great disagreement with any of that. Just that SI is so much simpler. You don't need all the conversion factors.
As I said earlier, I much prefer to use mm for fine detail. Far easier than 3/32nds or 15/64ths of an inch!
27-09-2018, 10:06 PM
20
Re: Measurement units
Originally Posted by JBR
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Oh yes, of course I agree with that.As I said earlier, I much prefer to use mm for fine detail. Far easier than 3/32nds or 15/64ths of an inch!
We buy our fuel in litres, measure our fuel consumption in mpg. The engine capacity is given in litres, the power output in BHP. Tyres are in mixed dimensions for diameter and tread width.
Get a drink for yourself and your wife in a pub - beer in pints, wine in ml.
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