True, but I don't 0" should be understood as 14 psi since I know of no zero measurement for board feet, etc. Since any identifying mark would be larger than zero. Or maybe I am just used to say 0" as meaning no vacuum in my old trade.
If you don't say it's 0" vacuum, then it isn't a complete specification. Granted, if one is working within an environment where vacuum is the norm it'll become a shorthand and will be understood _in_that_environment_. But, it's still a shorthand and isn't precise without the qualifier.
If you say so, "0" is neither pressure nor vacuum.
So, we can extend that out to making sure one specifies PSIA or PSIG in all instances, and as there is no absolutes in vacuums it will need to be specified in PSI? or PSI? if you know what I mean.
An interesting time wasting discussion. Along these lines I have thought about the possibility of creating a near impossible large diameter pipe. With the right diameter inside, and if it was created with and interlock say 100 ft from its base. And a large door at its base, one could put something inside, open the interlock and open another door lower than the object and launch the object into space with no energy consumed.
The only drawback would be if someone opened the door and left it open all of the earths atmosphere would be sucked into space.
So that will be the last of my craziness for now. :)
Of interesting note for this topic, I found an addon for sketchup which works with both Pro and Make.
It is like some add on libraries for AutoCAD and my understanding is that it is free. There is an offline version, for downloading.
It has softwood libraries with the "finished " sizes, S4S, it has HVAC and ductwork fittings and stuff.
It has various piping fittings for plastic, steel, copper, etc.
Multi language
The wood sizing list is to me a bit on the weak side, but at least on designs if you were to say a 4x4 it would give you the real s4s measurements.
Could be valuable for vacuum piping design.
Right. Context is everything. One has to mentally add (or subtract) the absolute reference if the context requires it.
No, it is not. Your tire gauge will read 0PSI when the absolute pressure is 14PSI. The tire gauge is a *relative* measurement but this is understood by its context.
All irrelevant.
...either relative or absolute.
Nonsense.
OK, but the sky is blue.
What *are* you jabbering about now?
Smiling,
The tire pressure gauge reads 0 PSIg "g" is for gauge pressure. Not absolute.
Look at a low side refer gauge sometime. "0" on it is the divide between PSIg and hg
Well I was making a pitiful comment about wood to try and bring this around, back to wood, then I unfortunately through in the comment about microns used to gauge vacuum below a certain point for the purposes of ridding systems of H20 and other properties. Which I knew you would be clueless about. That was stupid of me and I am sorry.
So, please forgive me, and lets get back to WW'ing or should we be going to some gym and duke it out? LOL
On 02/27/2016 1:24 PM, OFWW wrote: ...
Yes, apparently you are. That, as noted above, would be a shorthand within that context that would be understood but is incomplete and potentially misunderstood if translated to another context wherein the missing reference units would not be automagically inferred.
...
0 "Hg Vacuum _is_ 14.7 psia by definition. It has to be else't the weather measurements for barometric pressure would have to 0" plus/minus instead of 30" plus/minus with fluctuations...and that isn't so.Or another way to say it which I know you know innately is that no vacuum is one atmosphere pressure.
You conflate two things of different relative measurements by comparing to bd-ft (and yes, I know you were trying to somehow get it back to w-working and that's a noble attempt) but there can be 0 bd-ft; you just don't have any wood. But the difference is that you can't have negative board-feet but you can have negative pressure or temperature or any of several other physical measurements. It is simply what the definition of the units reference point is.
Consider temperature, there are at multiple common scales, one of which is absolute and the two other of most familiarity each have positive and negative values but their zeros are at different absolute temperatures. For pressure, simply for convenience, units were developed historically from a mean atmospheric pressure and hence, are positive and negative around that value. That was purely convenience as it's nice when doing the ordinary things like tire pressure, etc., to not have to worry about that background 14.7 psi. Similarly for vacuum work, it was/is convenient to define a new zero at that point and measure how far away from that point one is and in fact "inches of vacuum" throws away the negative sign and speaks of less as more...kinda' like scoring in golf! :)
So, currently barometric pressure is heading up and is about 30" Hg, _not_ 15!!! :)
-MIKE- wrote in news:nakqfk$2th$ snipped-for-privacy@dont-email.me:
SWMBO has a friend who completely refuses to drive on interstate highways because they terrify her, and instead drives only on secondary roads -- where of course the risk of fatality is an order of magnitude higher.
Doesn't make sense to me.
On 02/28/2016 9:41 AM, dpb wrote: ....
...
Woops, dropped back into psi, not "Hg...
... barometric pressure is ... about 30" Hg, _not_ 0!!!
Logic does not apply. I know someone like that too. Even with someone else driving she does not like the highways. This is an otherwise intelligent, educated person.
Married to one of those ... me either.
Like you say Zero board feet is none existent. You cannot measure what is not there. However,...
LOL, There is a negative board foot and no doubt you have seen it many times. Ever pick up a piece of wood to use only to find out it is a
1/2 " too short, or 6" to short?Barometric pressure is relative, and a far different usage. It is also useful for altitude measurement.
Then here you now go into Temperature? There are a couple scales alright, degF and degC then there is a scale from absolute 0 wherein there is no molecular movement. But what is the point?
1 atmosphere equals 29.92 " hg positive pressure, not a vacuum..000024583 atmosphere equals .010 "hg positive pressure, not a vacuum.
As I have been saying, a vacuum is relative. There is in reality no such thing as less than O PSI absolute.
You can never achieve 30" HG barometric pressure unless you use a cheap gauge 29.92 is the best you can do, and it is not a vacuum.
but it was nice of you to explain why and how a vacuum is relative in your next to last paragraph. So can we consider this subtopic closed?
And not a vacuum either. ;)
On 02/28/2016 1:38 PM, OFWW wrote: ...
Precisely, what I've been saying all along. Thank you.
As I under stood you to say it was a vacuum. You said the formula, for sure, but that 29.92" was positive pressure.
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