turbocad's custom dual/quad headlight mod

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I think your spiral wound should be ok. You could always put a 15lb weight on the hose, with a 1" contact area to give yourself a ballpark idea if it will crush or not.
 
15lb weight? from everything I've been reading I thought it's a whole lot more than that, I'm under the impression that it's equivalent to many tons of weight? I've heard that this much vacuum can completely crush your hand to a pulp
 
15psi (close to -14.7psi) = 15 lbs per square inch. In reality you would have a 15 lb weight sitting on every square inch of tubing. That's why I said ballpark - if the tube crushes or deforms with just one 15lb weight, it's not going to hold vacuum. It's not a for sure test, just an indicator to save you some time.

That's all assuming you are at 0psi absolute. If your pump will go beyond that into the negative range, you are right - it's much more than 15lbs. A vacuum wouldn't crush your hand, it allows your cell walls to rupture and the fluids/plasma escapes out due to gasses in solution under pressure. Heard of the bends for divers? Same deal - under pressure the nitrogen stays in solution in your blood. When you decrease pressure, the nitrogen bubbles out and travels as air in your bloodstream - which would be bad.
 
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It seems to me that Brad has a point here.. Just wish I was a rocket scientist to prove him wrong....lol :tongue::smile:

Goodness allot of smart people on IS...(Actually Dr2K and I were discussing this on Friday Night while playing pool).... these are the days I am happy to be part of this community..

Reasonable people willing to put in their 2 cents for the sake of making things work and not with the intent to criticize..

Just getting a kick of watching these posts John and Brad..
 
I have a vacuum sewer system up here at 6,000 ft and run this system with standard 2" ABS piping and clear 3/8" and 5/8 in vacuum hose. This system has 800cfm capacity at 23 in of Vacuum. At this altitude the maximum vacuum that can be obtained is 24 inches. If your interested in getting any of this clear vacuum hose you can get it from http://www.airvac.com/ ask for Becky. If you just need a little bit I could probably hook you up. I'm the vacuum system specialist for the County.
 
jumbosrule said:
15psi (close to -14.7psi) = 15 lbs per square inch. In reality you would have a 15 lb weight sitting on every square inch of tubing. That's why I said ballpark - if the tube crushes or deforms with just one 15lb weight, it's not going to hold vacuum. It's not a for sure test, just an indicator to save you some time.

That's all assuming you are at 0psi absolute. If your pump will go beyond that into the negative range, you are right - it's much more than 15lbs. A vacuum wouldn't crush your hand, it allows your cell walls to rupture and the fluids/plasma escapes out due to gasses in solution under pressure. Heard of the bends for divers? Same deal - under pressure the nitrogen stays in solution in your blood. When you decrease pressure, the nitrogen bubbles out and travels as air in your bloodstream - which would be bad.
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The worst case scenario here is not a crushed hand. It's the pot/plexi grenade imploding with an insane amount of force. Assuming your pot is 14" in diameter and 14" tall, each flat face would have a surface area of 153.8sq inches. 15psi x 153.8 = 2307lbs of force on your plexi lid. 2307 on the lid, 2307 on the bottom of the pot, and a combined 9231lbs on the curved shell.
Adding up those forces we see that you are dealing with (at a perfect 0psi vacuum) around 13,850lbs of pressure. I know your pot is slightly smaller than 14x14, but still its a pot for cooking, not a vacuum chamber. I would get someone to run calculations on that pot before you start pumping.
Also, when they tell you how much vacuum you can run with the pot, get a vacuum regulator in case your gauge malfunctions.
 
tchuck said:
The worst case scenario here is not a crushed hand. It's the pot/plexi grenade imploding with an insane amount of force. Assuming your pot is 14" in diameter and 14" tall, each flat face would have a surface area of 153.8sq inches. 15psi x 153.8 = 2307lbs of force on your plexi lid. 2307 on the lid, 2307 on the bottom of the pot, and a combined 9231lbs on the curved shell.
Adding up those forces we see that you are dealing with (at a perfect 0psi vacuum) around 13,850lbs of pressure. I know your pot is slightly smaller than 14x14, but still its a pot for cooking, not a vacuum chamber. I would get someone to run calculations on that pot before you start pumping.
Also, when they tell you how much vacuum you can run with the pot, get a vacuum regulator in case your gauge malfunctions.
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A perfect vacuum of 0 is only going to be acheived in sapce.
Because it is virtually impossible to remove all the air molecules from a container, a perfect vacuum cannot be achieved. Of course, as more air is removed, the pressure differential increases, and the potential vacuum force becomes greater.
The vacuum level is determined by the pressure differential between the evacuated volume and the surrounding atmosphere. Several units of measure can be used. Most refer to the height of a column of mercury - usually in.-Hg or mm-Hg. The common metric unit for vacuum measurement is the millibar, or mbar. Other pressure units sometimes used to express vacuum include the interrelated units of atmospheres, torr, and microns. One standard atmosphere equals 14.7 psi (29.92 in.-Hg). Any fraction of an atmosphere is a partial vacuum and equates with negative gage pressure. A torr is defined as 1/760 of an atmosphere and can also be thought of as 1 mm-Hg, where 760 mm-Hg equals 29.92 in.-Hg. Even smaller is the micron, defined as 0.001 torr. However, these units are used most often when dealing with near-perfect vacuums, usually under laboratory conditions, and seldom in industrial applications.
Atmospheric pressure is measured with a barometer. A barometer consists of an evacuated vertical tube with its top end closed and its bottom end resting in a container of mercury that is open to the atmosphere, Figure 1. The pressure exerted by the atmosphere acts on the exposed surface of the liquid to force mercury up into the tube. Sea level atmospheric pressure will support a mercury column generally not more than 29.92-in. high. Thus, the standard for atmospheric pressure at sea level is 29.92 in.-Hg, which translates to an absolute pressure of 14.69 psia.
The two basic reference points in all these measurements are standard atmospheric pressure and a perfect vacuum. At atmospheric pressure, the value 0 in.-Hg is equivalent to 14.7 psia. At the opposite reference point, 0 psia, - a perfect vacuum (if it could be attained) - would have a value equal to the other extreme of its range, 29.92 in.-Hg. However, calculating work forces or changes in volume in vacuum systems requires conversions to negative gage pressure (psig) or absolute pressure (psia).
Atmospheric pressure is assigned the value of zero on the dials of most pressure gages. Vacuum measurements must, therefore, be less than zero. Negative gage pressure generally is defined as the difference between a given system vacuum and atmospheric pressure.

---------- Post added at 08:45 AM ---------- Previous post was at 08:09 AM ----------

Max vacuum at sea level is 29.92in Hg =14.69533223463184lbs per sq in.
 
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Yeah, what MTN said. :tongue:

I was just trying to give John a quick and dirty indicator test to see if his current set-up would work.

In terms of the pressure exerted on the inside of the pot, it sounds a lot worse than it is. True, the pot could catastrophically implode, but it's much more likely to do what we call, "leak before burst". Meaning, it will crack, slightly deform or fail at a seal and never get to that "implosion".

The reality is that this current set-up should work for the purposes John is looking for. Even the food vacuum sealers don't suck nearly as much pressure as this one is capable of, but would probably work for setting these reflectors. You just need a differential so that the air wants to move from high pressure to low pressure. A perfect vacuum is not possible, but it's not necessary either.
 
from what I know, even in outer space a perfect vacuum is not possible, the only possibility of a perfect vacuum even in outer space would be a black hole... even outer space itself has some molecules & is not a total void...

& jumbo, I think your test of a 15lb weight is not good because it is only exerting pressure on one point & doing nothing to oppose that force where it would want to displace the pipe, where under vacuum the pressure would be evenly distributed all around the pipe making it support the pressure much better than just pressure at one point with no support opposing this pressure... the sides of this pressure point test would not be supported & could displace outward where under vacuum it would not because the pressure is evenly distributed & the sides would be also forced in as much as the top, would be more of a clamping force than a crushing force ...

like you said though, the aluminum pot can not catastrophically implode, it would buckle & crack thereby releasing the vacuum force... I have talked to a guy though that tried doing this with a very thick glass Mason jar & he had an implosion... was messy from what I hear...

anyway, I did receive the vacuum pump oil yesterday & I was able to finish this chamber up & test & use it last night... I'll add to this & explain my results in a bit when I get back in the office... who's taking bets as to weather the gas line crushed or not? :tonguey:
 
I've said it three times now - it's an indicator, not a definitive answer. Is the test perfect, no. But if the line crushes with 15 lbs, it won't hold vacuum with 15psi "evenly distributed" along the entire length of hose. Gotta see the forest through the trees here. I have a lot of experience with pressure systems - mostly the Active Thermal Control System (ATCS) of the International Space Station (ISS), which uses pressurized nitrogen to move ammonia through a complex loop of pumps, valves and lines. I personally designed and used pressurized set-ups to test components of the system, including vacuum and quickly reactive varying pressures. But that's cool, no skin off my back if you don't want to believe. Trial and error will work just as well - just might be more expensive...
 
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sorry bro, didn't mean to challenge you as much as explain my interpretation & understanding of things from what I've been just recently learning... I never ment to imply that you don't know what your talking about, up until a month or 2 ago I knew very little about the subject & all I know now is whatever goggle has tough me. don't mean to sound like a pro in this area, just meant to explain why I thought the test was not correct from my understanding of the principles here is all... I do appreciate your input & value it & sorry if I offended you :shy: I just stated why I thought the test was not "good" & explained why I thought that
 
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None taken, really. Just wanted to help out and maybe help you avoid a pitfall by using a really simple indicator. The older and more experienced I get, the more I understand I don't know everything. Still learning new things from new applications every day, which is what you have. If you were testing the ATCS components on the ISS, then I would talk like I know it all.:smile:
 
Wha?!? The last time I looked this quad headlight mod was a much simpler thing.. Wow.. John, when are you going into CF wrapping business with that pot of yours? :.smile:
 
haha, I see someone figured out one of the things I have in mind for this vacuum pump :wink: once I get through this project I plan on building a vacuum table, this pump is overkill for that but it'll also do the job nicely... & yeah, the simple days, when the inner projector was just dtrl based & the corners were not,.. well, not what they are now... I think i'm just a glutton for punishment :eeerr:
 
ok, so we got the pressure cooker to get that chili up & done quickly & then we can play some air hockey, you got the cornbread covered, who's bringing the wine? :tonguey:
 
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