I hate imperial units

[Spehro Pefhany]

Units of thermal conductivity: BTU*in/(ft^2*h*°F)

ugh

http://www.gordonengland.co.uk/conversion/thermcon.htm

Steel alloy (4140 like) is around 200, or around 30 in the more
sensible metric system units: W/(m*K)


Best regards,
Spehro Pefhany

 

[Fred Bartoli]

Spehro Pefhany a écrit :

Units of thermal conductivity: BTU*in/(ft^2*h*°F)

ugh

http://www.gordonengland.co.uk/conversion/thermcon.htm

Steel alloy (4140 like) is around 200, or around 30 in the more
sensible metric system units: W/(m*K)

Tell this to JL

 

[Genome]

Units of thermal conductivity: BTU*in/(ft^2*h*°F)

ugh

http://www.gordonengland.co.uk/conversion/thermcon.htm

Steel alloy (4140 like) is around 200, or around 30 in the more
sensible metric system units: W/(m*K)


Best regards,
Spehro Pefhany
--

L is, of course, our inductance. B is the flux density and H is the
magnetising force. All of these sums use something called the SI system of
units which was worked out by the French because the British Imperial system
is shit. Unfortunately the British landed the Americans with Imperial units
so all their data sheets are messed up. The British noticed that the French
system was better but could not admit it so they had to join the European
Community. Then the Belgians forced them to use it and, after a lot of
complaining, the British gave up and said OK neatly avoiding having to give
the French credit for anything, and we still get to buy our potatoes in
pounds and ounces. Politics ay?

The other parts of the sums are the number of turns of wire on the inductor,
N, and the current in that wire, I. Then there is the special one, Uo, which
is the permeability of free space. That one works with inductors, there is
another one used with capacitors called Eo which is the permittivity of free
space. These 'normalise' everything so the units work. As it happens the
speed of light is given by 1/SQRT(Uo.Eo) which is why Einsteins equations
have lots of square roots in them. You can not travel faster than the speed
of light in free space (outer space) because then all the electerons fall
off the back of your rocket and it dissapears in a flash of light. If you
watch Star Trek then you will know about this effect.

Uo is 4.pi.E-7 which looks a bit suspicious, I mean 'What are the chances of
that!'? That was done to confuse the Russians. What you have to realise is
that Eo is 8.85E-12 which is a pretty meaningless number and back in those
days the Russians had comparatively slow calculators with which to try and
factorise such a number to find out if there was some hidden meaning. Of
course when the Russians join the EU we'll tell them about that one and
everyone can drink lots of Good Vodka and roll about laughing.

DNA

 

[John Larkin]

Spehro Pefhany a écrit :

Tell this to JL

Me? I do all my thermal stuff in SI units. What I hate is the way
people randomly use calories and joules/watts when specifying thermal
conductivity.

This is neat: you can use Spice to model thermal dynamics. Just
equate...

1 K/w == 1 ohm

1 K == 1 volt

1 gram aluminum == 1 farad

1 second == 1 second.

Works to about 5%

John

 

[Spehro Pefhany]

Me? I do all my thermal stuff in SI units. What I hate is the way
people randomly use calories and joules/watts when specifying thermal
conductivity.

This is neat: you can use Spice to model thermal dynamics. Just
equate...

1 K/w == 1 ohm

1 K == 1 volt

1 gram aluminum == 1 farad

1 second == 1 second.

Works to about 5%

John

Cool. Diffeq's is diffeq's.


Best regards,
Spehro Pefhany

 

[Joel Kolstad]

Cool. Diffeq's is diffeq's.

If you're really intent on it you can use SPICE to solve mechanical systems as
well... I remember spending one class years back going through the equations,
and somewhere around here I have the conversion charts.

I do remember being told that the main problem with simulating mechanical
systems like this is that real viscious dampers are horribly non-linear, even
springs aren't great, etc.

 

[Bob Eld]

Units of thermal conductivity: BTU*in/(ft^2*h*°F)

ugh

http://www.gordonengland.co.uk/conversion/thermcon.htm

Steel alloy (4140 like) is around 200, or around 30 in the more
sensible metric system units: W/(m*K)


Best regards,
Spehro Pefhany

http://www.speff.com

It's all a bunch of baloney! It doesn't make any difference what the units
are, the math is the same. The metric system, more specifically SI, is fine
for school kids and ingenues who need their ten fingers to count and figure
things but it is a red herring elswhere. A decimal inch micrometer works
just as well as a mm one. It makes no difference. Much of the imperial
system was/is binary making calculation even easier than base ten. For
example take 1/2 cup, 1/4 cup, 1/8 cup, etc. These are powers of two as are
the fractional inch numbers. It's all a matter of what you are use to.
Furthermore, the metric system has some curious anomalities in it as does
the imperial system. Did you know that a cubic centimeter equals 0.00099997
liters? So, things arn't as simple as you have been taught. I personally
don't care what the units are and don't undersand why a technical person
would be befuddled by one particular set vs. another. So, as an exercise for
the class: figure the speed of light in furlongs per fortnight. When you are
done, you will find that it is just a number as meaningles to a human as
2.99776*10^8.

 

[Joerg]

Units of thermal conductivity: BTU*in/(ft^2*h*°F)

ugh

http://www.gordonengland.co.uk/conversion/thermcon.htm

Steel alloy (4140 like) is around 200, or around 30 in the more
sensible metric system units: W/(m*K)

I got used to non-metric units, except maybe when I lay tile where I
still use centimeters a lot for tiles with really complicated cuts.

When I see a tree I sometimes think out loud "Oh, that one would be
about 20,000,000 BTUs". Drives people crazy.

 

[Adrian Tuddenham]

When I see a tree I sometimes think out loud "Oh, that one would be
about 20,000,000 BTUs". Drives people crazy.

It depends when you said it.

A BTU was a Board of Trade Unit = I kWh = 3.6 Megajoules
A BThU was a British Thermal Unit = 1.05 Kilojoules

Then some nincompoop decided to abolish the BTU and rename the BThU to
BTU. So a "BTU" could mean either of the above, depending on when it
was said.

What a mess!

 

[Le Chaud Lapin]

L is, of course, our inductance. B is the flux density and H is the
magnetising force. All of these sums use something called the SI system of
units which was worked out by the French because the British Imperial system
is shit. Unfortunately the British landed the Americans with Imperial units
so all their data sheets are messed up. The British noticed that the French
system was better but could not admit it so they had to join the European
Community. Then the Belgians forced them to use it and, after a lot of
complaining, the British gave up and said OK neatly avoiding having to give
the French credit for anything, and we still get to buy our potatoes in
pounds and ounces. Politics ay?

I have often wondered about the intransigence of Americans and Britons
when it comes to SI. If an alien race invaded Earth, they would see
immediately that we are a lazy race. We have spent millions on
publicity campaigns to convert, and nothing has changed really.

Declaring a law that all printed matter on government-approved
consumables will use solely SI unit might force the transition, and
perhaps the idea came up in the governments, but their are probably
people in the House of Lords and the Senate who like football too much.
"Let's see...would the 50-yard-line become the 50-meter-line? And what
would happen to all those football statistics. And so what if we
confuse ourselves every now and then and lose a $125 million
spacecraft?"

http://www.cnn.com/TECH/space/9909/30/mars.metric/

-Le Chaud Lapin-

 

[Spehro Pefhany]

It's all a bunch of baloney! It doesn't make any difference what the units
are, the math is the same. The metric system, more specifically SI, is fine
for school kids and ingenues who need their ten fingers to count and figure
things but it is a red herring elswhere. A decimal inch micrometer works
just as well as a mm one.

If you need inches. If you need mm, it avoids a conversion and a
possible source of errors, especially when the numbers are oddball
sequences of digits and humans are involved.

It makes no difference. Much of the imperial
system was/is binary making calculation even easier than base ten. For
example take 1/2 cup, 1/4 cup, 1/8 cup, etc. These are powers of two as are
the fractional inch numbers. It's all a matter of what you are use to.

Yes, and if you use gills, be sure to specify US or British gills.

Furthermore, the metric system has some curious anomalities in it as does
the imperial system. Did you know that a cubic centimeter equals 0.00099997
liters? So, things arn't as simple as you have been taught.

How do you know what we've been taught or have taught others? The
liter is defined as 1 dm^3 = 0.001m^3 *exactly*. It has been since
1964 (!). This just in... be sure to check out the 'new' definition(s)
of the inch from around that period (both US and British inches
changed, in the opposite directions to converge at the 2.54mm
definition).

I personally
don't care what the units are and don't undersand why a technical person
would be befuddled by one particular set vs. another.

Hmm.. well, let's us take those units out of the particular problem
domain they were designed for and try to figure out how many watts it
takes to maintain temperature difference of 10°C (18°F) across a 0.5"
(12.7mm) piece of P20 steel 3/8" (9.52mm) thick. Convert between W and
BTU, between in or mm and square feet etc. Lots of unnecessary work
and possible places for errors.

So, as an exercise for
the class: figure the speed of light in furlongs per fortnight. When you are
done, you will find that it is just a number as meaningles to a human as
2.99776*10^8.

Au contraire, at least if you consider EEs to be human. You ever think
about how long it takes a signal to get across a PCB (or along the
clock lines on a chip, for that matter). A 10E-9 second is a long time
in some problem domains..



Best regards,
Spehro Pefhany

 

[[email protected]]

http://www.speff.com

It's all a bunch of baloney! It doesn't make any difference what the units
are, the math is the same. The metric system, more specifically SI, is fine
for school kids and ingenues who need their ten fingers to count and figure
things but it is a red herring elswhere. A decimal inch micrometer works
just as well as a mm one. It makes no difference. Much of the imperial
system was/is binary making calculation even easier than base ten. For
example take 1/2 cup, 1/4 cup, 1/8 cup, etc. These are powers of two as are
the fractional inch numbers. It's all a matter of what you are use to.
Furthermore, the metric system has some curious anomalities in it as does
the imperial system. Did you know that a cubic centimeter equals 0.00099997
liters?

Did you mean to say a cc of water = 0.00099997 kg?

The volume a gram of water occupies is temperature dependent, but I
think it's defined as 1 g water = 1 cc at 4 degrees C. Plus or minus
at different temperatures...

http://en.wikipedia.org/wiki/Water_(molecule)#Density_of_water_and_ice

Michael

 

[Jim Thompson]

I got used to non-metric units, except maybe when I lay tile where I
still use centimeters a lot for tiles with really complicated cuts.

You don't own one of those sliding pins thingies ? Wonderful for
transferring a door facing shape to a tile cut.

When I see a tree I sometimes think out loud "Oh, that one would be
about 20,000,000 BTUs". Drives people crazy.

Really ?

...Jim Thompson

 

[Joerg]

You don't own one of those sliding pins thingies ? Wonderful for
transferring a door facing shape to a tile cut.

Thought about it but then I always figured that after finishing this one
more room I'd be done tiling for the next 20-30 years. Wrong! I am
married, so...

What works really nicely is to cut several odd vellum templates. Those
can be angled at will and then fastened to each other with some masking
tape. The tape comes off with ease and you can re-use the templates for
all the other odd tiles to come. Until a splotch of mortar accidentally
lands on it, that is. However, every time it almost broke my heart not
having used that sheet for a nice high-tech super-gizmo schematic.

[ ... ]

 

[Bob Eld]

I got used to non-metric units, except maybe when I lay tile where I
still use centimeters a lot for tiles with really complicated cuts.

When I see a tree I sometimes think out loud "Oh, that one would be
about 20,000,000 BTUs". Drives people crazy.

My Great Grandfather was a member of the Britsh Thermal Unit in World War
One. They fought many heated battles!

 

[Jim Thompson]

You don't own one of those sliding pins thingies ? Wonderful for
transferring a door facing shape to a tile cut.

Thought about it but then I always figured that after finishing this one
more room I'd be done tiling for the next 20-30 years. Wrong! I am
married, so...

What works really nicely is to cut several odd vellum templates. Those
can be angled at will and then fastened to each other with some masking
tape. The tape comes off with ease and you can re-use the templates for
all the other odd tiles to come. Until a splotch of mortar accidentally
lands on it, that is. However, every time it almost broke my heart not
having used that sheet for a nice high-tech super-gizmo schematic.

[ ... ]

I have been known to accurately measure the WHOLE house, then lay down
a hexagonal placement grid on the plan and slide it around for best
fit, with mostly near-1/2-tile cuts, and best look to the eye... with
fudging to accommodate a long hallway with almost an inch of TAPER :-(

I generally transfer the pin gauge info to full page label paper, cut
out and stick to the tile, where it stays while I wet saw ;-)

...Jim Thompson

 

[Joerg]

Jim Thompson wrote:

On Tue, 12 Dec 2006 17:37:34 GMT, Joerg



Spehro Pefhany wrote:



Units of thermal conductivity: BTU*in/(ft^2*h*°F)

ugh

http://www.gordonengland.co.uk/conversion/thermcon.htm

Steel alloy (4140 like) is around 200, or around 30 in the more
sensible metric system units: W/(m*K)



I got used to non-metric units, except maybe when I lay tile where I
still use centimeters a lot for tiles with really complicated cuts.


You don't own one of those sliding pins thingies ? Wonderful for
transferring a door facing shape to a tile cut.

Thought about it but then I always figured that after finishing this one
more room I'd be done tiling for the next 20-30 years. Wrong! I am
married, so...

What works really nicely is to cut several odd vellum templates. Those
can be angled at will and then fastened to each other with some masking
tape. The tape comes off with ease and you can re-use the templates for
all the other odd tiles to come. Until a splotch of mortar accidentally
lands on it, that is. However, every time it almost broke my heart not
having used that sheet for a nice high-tech super-gizmo schematic.

[ ... ]

I have been known to accurately measure the WHOLE house, then lay down
a hexagonal placement grid on the plan and slide it around for best
fit, with mostly near-1/2-tile cuts, and best look to the eye... with
fudging to accommodate a long hallway with almost an inch of TAPER :-(

Our neighbor is a civil engineer. Before he even thinks about firing up
the saw he does the whole project on AutoCad. Even if it's just the
guest bath. That drives his wife crazy because it can take a long time.

If it's any consolation I also had to fudge the hallway. Did the kitchen
first and calculated it all so the 1/2-tile symmetries came out nicely.
I had no choice but to either compromise the kitchen or fudge the (long)
hallway because its end is almost 1/2" off track. Opted for making the
kitchen perfect because that's where everybody always hangs out.

I generally transfer the pin gauge info to full page label paper, cut
out and stick to the tile, where it stays while I wet saw ;-)

I did it the Sharpie way

 

[Bob Eld]

.

Hmm.. well, let's us take those units out of the particular problem
domain they were designed for and try to figure out how many watts it
takes to maintain temperature difference of 10°C (18°F) across a 0.5"
(12.7mm) piece of P20 steel 3/8" (9.52mm) thick. Convert between W and
BTU, between in or mm and square feet etc. Lots of unnecessary work
and possible places for errors.

Watts don't convert to BTU's one is power the other is energy, Right? Don't
you need some time in the conversion somewhere? It seems to me that's a
much bigger issue than how many sq feet there are in a sq meter, or
whatever. The unit conversions are trivial but physical relationships, not
so much.

Au contraire, at least if you consider EEs to be human. You ever think
about how long it takes a signal to get across a PCB (or along the
clock lines on a chip, for that matter). A 10E-9 second is a long time
in some problem domains..

A nano second is how long it takes light to go one foot a very convenient
way to think about it. Right now my wife is 12 nanoseconds away and, of
course, I see her in the past the way she was nanoseconds ago. To know how
long it takes a signal to go across a PCB you'd have to know something of
the dielectric constant, Right?
Bob

Best regards,
Spehro Pefhany

http://www.speff.com

 

[Jim Thompson]

Jim Thompson wrote:


On Tue, 12 Dec 2006 17:37:34 GMT, Joerg



Spehro Pefhany wrote:



Units of thermal conductivity: BTU*in/(ft^2*h*°F)

ugh

http://www.gordonengland.co.uk/conversion/thermcon.htm

Steel alloy (4140 like) is around 200, or around 30 in the more
sensible metric system units: W/(m*K)



I got used to non-metric units, except maybe when I lay tile where I
still use centimeters a lot for tiles with really complicated cuts.


You don't own one of those sliding pins thingies ? Wonderful for
transferring a door facing shape to a tile cut.


Thought about it but then I always figured that after finishing this one
more room I'd be done tiling for the next 20-30 years. Wrong! I am
married, so...

What works really nicely is to cut several odd vellum templates. Those
can be angled at will and then fastened to each other with some masking
tape. The tape comes off with ease and you can re-use the templates for
all the other odd tiles to come. Until a splotch of mortar accidentally
lands on it, that is. However, every time it almost broke my heart not
having used that sheet for a nice high-tech super-gizmo schematic.

[ ... ]

I have been known to accurately measure the WHOLE house, then lay down
a hexagonal placement grid on the plan and slide it around for best
fit, with mostly near-1/2-tile cuts, and best look to the eye... with
fudging to accommodate a long hallway with almost an inch of TAPER :-(

Our neighbor is a civil engineer. Before he even thinks about firing up
the saw he does the whole project on AutoCad. Even if it's just the
guest bath. That drives his wife crazy because it can take a long time.

If it's any consolation I also had to fudge the hallway. Did the kitchen
first and calculated it all so the 1/2-tile symmetries came out nicely.
I had no choice but to either compromise the kitchen or fudge the (long)
hallway because its end is almost 1/2" off track. Opted for making the
kitchen perfect because that's where everybody always hangs out.

I generally transfer the pin gauge info to full page label paper, cut
out and stick to the tile, where it stays while I wet saw ;-)

I did it the Sharpie way

Sharpie washes off in the wet saw :-(

...Jim Thompson

 

[Joerg]

Jim Thompson wrote:

On Tue, 12 Dec 2006 20:05:38 GMT, Joerg



Jim Thompson wrote:



On Tue, 12 Dec 2006 17:37:34 GMT, Joerg




Spehro Pefhany wrote:




Units of thermal conductivity: BTU*in/(ft^2*h*°F)

ugh

http://www.gordonengland.co.uk/conversion/thermcon.htm

Steel alloy (4140 like) is around 200, or around 30 in the more
sensible metric system units: W/(m*K)



I got used to non-metric units, except maybe when I lay tile where I
still use centimeters a lot for tiles with really complicated cuts.


You don't own one of those sliding pins thingies ? Wonderful for
transferring a door facing shape to a tile cut.


Thought about it but then I always figured that after finishing this one
more room I'd be done tiling for the next 20-30 years. Wrong! I am
married, so...

What works really nicely is to cut several odd vellum templates. Those
can be angled at will and then fastened to each other with some masking
tape. The tape comes off with ease and you can re-use the templates for
all the other odd tiles to come. Until a splotch of mortar accidentally
lands on it, that is. However, every time it almost broke my heart not
having used that sheet for a nice high-tech super-gizmo schematic.

[ ... ]


I have been known to accurately measure the WHOLE house, then lay down
a hexagonal placement grid on the plan and slide it around for best
fit, with mostly near-1/2-tile cuts, and best look to the eye... with
fudging to accommodate a long hallway with almost an inch of TAPER :-(

Our neighbor is a civil engineer. Before he even thinks about firing up
the saw he does the whole project on AutoCad. Even if it's just the
guest bath. That drives his wife crazy because it can take a long time.

If it's any consolation I also had to fudge the hallway. Did the kitchen
first and calculated it all so the 1/2-tile symmetries came out nicely.
I had no choice but to either compromise the kitchen or fudge the (long)
hallway because its end is almost 1/2" off track. Opted for making the
kitchen perfect because that's where everybody always hangs out.

I generally transfer the pin gauge info to full page label paper, cut
out and stick to the tile, where it stays while I wet saw ;-)

I did it the Sharpie way

Sharpie washes off in the wet saw :-(

Usually but if you let it dry a minute or two it's just perfect. Then it
holds almost until the end of the cut. Problem with my saw is that I
wore it out pretty good so it doesn't cut very straight anymore. It also
doesn't want to cut ferrite too well anymore and that's a real drag.

Drilling a 3/8" hole into porcelain tile to mount a toilet etc. is a
whole 'nother matter.