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Old 08-11-2014, 13:15   #1
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Convenience of the metric system

A example where you see the advantage of the SI system.

Lewmars windlasses V1 have according to the datasheet:
The motor has a max power of 700 W.
Working load 113 kg.
To lift 1 kg you need a force of 9.8 N or about 10 N.
The force the windlass pulls with is then 1130 N.
Maximum chain speed is 19 m/min.
That corresponds with 0.317 m/s.
The power on the gypsy is then
1130 N * 0.317 m/s = 358 Nm/s = 358 W
The efficiency of the windlass is then 358 W / 700 W = 51%. That’s not much but its what you can expect for a worm gear.

I remember that there is 12 inch on 1 foot, but I don’t see the logic in that.
I never remember how many yards there is on one mile, and even less the logic in that.
There is 1000 m (meter) on 1 km (kilometre) is very logic since kilo means thousand.
It’s the same that there is 1000 mm (millimetres) on 1 m (meter), because milli means thousandth.
A cube with a side length of 0.1 m (meter) have a volyme of 1.0 l (liter).
1.0 l (liter) of watter have a wight og 1.0 kg (kilogram).


Approximate conversion between the two systems

1 m (meter) is 40 inches (39.37). 1.6% wrong.
1 m (meter) is 3 foot (3.281). 8.6% wrong.
4 l (liter) is 1 gallon (1.057). 5.7% wrong.
1 kg (kilogram) is 2 pound (2.205). 10.3% wrong.
1 m/s (meter per second) is 2 mph (2,237). 11.8% wrong.
1 m/s (meter per second) is 2 knots (1.944). 2.8% wrong.
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Old 08-11-2014, 13:41   #2
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Re: Convenience of the metric system

Uuuuhh !! O-o-k-a-y.
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Old 08-11-2014, 13:41   #3
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Re: Convenience of the metric system

"1.0 l (liter) of watter have a wight og 1.0 kg (kilogram)."

You must have a metric spellchecker.

The imperial system was not based on logic, so it needed none to understand it. You just had to learn the tables.

Even today if you tell me somebodies height and weight in metric I would have no idea if he was a fat midget or a skinny giant. I learnt the imperial system and it still works for me because I can judge something in inches/feet/yards by eye and do not even try to convert. It is simply what you feel most comfortable with really, nothing to do with being better or worse than the other.

Coops.
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Old 08-11-2014, 13:55   #4
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Re: Convenience of the metric system

Oh, Coops, No, no, no!

Metric makes the most sense....except it is largely opaque if you learned Imperial as a child.

The problem is getting all those Yanks to change what they do. We came close to metrification, a while back, but as far as I can see, little progress has been made. And we get by okay, as you suggest, because you learn it when you're little and it becomes part of your whole language acquisition skills and it's ruddy well stuck in there!

Cheers,

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Old 08-11-2014, 13:56   #5
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Re: Convenience of the metric system

The problem with the metric system is based on 10. Why 10, what a stupid number to base a number system on, what is that? Because we have 10 fingers!!! Dumb.
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Old 08-11-2014, 14:02   #6
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Re: Convenience of the metric system

In my spares kit I have BSF,BSW,AF and Metric mm capscrews in 1.25, 1.50, and 1.75 thread pitches. Makes it interesting. On early Mitsubishi cars, you could find all of them on the same vehicle.
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Old 08-11-2014, 14:04   #7
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Re: Convenience of the metric system

Quote:
Originally Posted by nimblemotors View Post
The problem with the metric system is based on 10. Why 10, what a stupid number to base a number system on, what is that? Because we have 10 fingers!!! Dumb.
Could have based on 20. fingers + toes, but insurance won't let me work with barefeet in engine rooms.
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Old 08-11-2014, 14:14   #8
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Re: Convenience of the metric system

In the UK they "almost" converted to Metric, the problem now for example Copper Tube, you can buy Metric and Imperial. Although close they don't fit together.

They also still drive on the wrong site of the road...
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Old 08-11-2014, 14:24   #9
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Re: Convenience of the metric system

My only problem with the metric system is it needs something between a meter and a Cm. If you say to me something is 2 ft long I get it. If you say 60cm... My brain has to convert it... If it made sense that things must be described in multiples of ten... well then wouldnt it make sense to only build things in exact multiples of ten?
How about time? should we break it into tens?
How about the naturally occurring number Pi? We'd better round that down to 3.000..
:>)
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Old 08-11-2014, 14:31   #10
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Re: Convenience of the metric system

Quote:
Originally Posted by Cheechako View Post
My only problem with the metric system is it needs something between a meter and a Cm. If you say to me something is 2 ft long I get it. If you say 60cm... My brain has to convert it... If it made sense that things must be described in multiples of ten... well then wouldnt it make sense to only build things in exact multiples of ten?
How about time? should we break it into tens?
How about the naturally occurring number Pi? We'd better round that down to 3.000..

:>)
They are "even in Metric" logics by it self...
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Old 08-11-2014, 14:33   #11
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Re: Convenience of the metric system

Quote:
Originally Posted by Lars_L View Post
I remember that there is 12 inch on 1 foot, but I don’t see the logic in that.
I never remember how many yards there is on one mile, and even less the logic in that.
There is 1000 m (meter) on 1 km (kilometre) is very logic since kilo means thousand.
It’s the same that there is 1000 mm (millimetres) on 1 m (meter), because milli means thousandth.
A cube with a side length of 0.1 m (meter) have a volyme of 1.0 l (liter).
1.0 l (liter) of watter have a wight og 1.0 kg (kilogram).


Approximate conversion between the two systems

1 m (meter) is 40 inches (39.37). 1.6% wrong.
1 m (meter) is 3 foot (3.281). 8.6% wrong.
4 l (liter) is 1 gallon (1.057). 5.7% wrong.
1 kg (kilogram) is 2 pound (2.205). 10.3% wrong.
1 m/s (meter per second) is 2 mph (2,237). 11.8% wrong.
1 m/s (meter per second) is 2 knots (1.944). 2.8% wrong.
Taking last things first:

May I suggest some better rules of thumb.

Not 1m = 3', which is way off, but 3m = 10 feet -- which is pretty close, and plenty close enough for a rule of thumb -- as soon as you need more precision, just go to 1" = 25.4mm and take it from there.

Not 1kg = 2 pounds, but 1kg = 2.2 pounds, which is exact.

Not 1 m/s = 2 mph, but 1 m/s = 2 knots.

And just memorize:

1 statute mile = 1.62 km, so 100 km/h = 62 mph and so forth.

1 inch = 2.54 cm

With just those bits, you shouldn't have any problem with the metric system.



Now, as to 12 inches in a foot -- what is so inevitable about Base 10? 12 is a much better subdivision than 10 -- can be divided more ways. Actually, Base 12 is really powerful, and there is an actual movement to replace Base 10 with it, see: Why We Should Switch To A Base-12 Counting System
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Old 08-11-2014, 14:35   #12
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Re: Convenience of the metric system

My car gets 40 rods to the hogshead and that's the way I likes it!!!
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Old 08-11-2014, 14:38   #13
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Re: Convenience of the metric system

Both require a functioning memory

The metric system quickly becomes unusable if one forgets value of the multiplier of the micro, milli, deci, centi, kilo, mega, giga, hecto; and that is only the common ones, not the esoteric ones. I see many metric trained people unable to quickly comprehend even simple measurements when say given in millimetres but they were expecting centimetres.

When working in fractions, 12 is a far better base than 10.

Metric is certainly more arithmetic friendly.

Having said that, I really do prefer to be "ambidextrous" and use what is most simple for the job.

Personally I will use thousandths of an inch rather than microns; hectopascals instead of inches of Hg.; PSI instead of Bar; miles or kilometres depending on circumstance. The list is long but I'm sure you get the drift.
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Old 08-11-2014, 14:40   #14
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Re: Convenience of the metric system

Quote:
Originally Posted by Dockhead View Post
Taking last things first:

May I suggest some better rules of thumb.

Not 1m = 3', which is way off, but 3m = 10 feet -- which is pretty close, and plenty close enough for a rule of thumb -- as soon as you need more precision, just go to 1" = 25.4mm and take it from there.

Not 1kg = 2 pounds, but 1kg = 2.2 pounds, which is exact.

Not 1 m/s = 2 mph, but 1 m/s = 2 knots.

And just memorize:

1 statute mile = 1.62 km, so 100 km/h = 62 mph and so forth.

1 inch = 2.54 cm

With just those bits, you shouldn't have any problem with the metric system.



Now, as to 12 inches in a foot -- what is so inevitable about Base 10? 12 is a much better subdivision than 10 -- can be divided more ways. Actually, Base 12 is really powerful, and there is an actual movement to replace Base 10 with it, see: Why We Should Switch To A Base-12 Counting System
Very logical............................

Stupid system that only Englishman and Americans understand.

BTW. why you accept the Metrical system for Currency??? The old English system made more sence for me
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Old 08-11-2014, 14:42   #15
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Re: Convenience of the metric system

In land surveying, a Chain is both a measurement, and the tool to determine it. It is 22 yards, the length of a Cricket Pitch wicket. ther ya go.
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