A Word of CAUTION

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its_virgil

its_virgil

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In my snake skin casting tutorial I showed a picture and explained how to make a lid the the HF paint tank from corian with a lexan window to observe the resin. That lid failed last nite with a loud boom and near heart failure from me as I was watching the resin bubble through the window. No injuries or damage as the pieces traveled toward the tank and stayed on top of it. I suppose that was a stupid thing to make the lid from, but it is working for another guy with no problems of which I'm aware. Any way, I'm going to change the lid for the vacuum process. Proceed with caution and be safe. Here is a picture of the lid afterwards.



2006925162020_Broken%20lid.jpg



Do a good turn daily!
Don
 
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Now take a look. It scared the liver out of me. I was looking in the window watching the resin bubble when it "boomed".[:D]
Do a good turn daily!
Don
Originally posted by wdcav1952
<br />
Originally posted by gerryr
<br />All you have left is a little red "X"?[:0][:0]
Click to expand...

Gerry, maybe that just marks the spot! [:D]
Click to expand...
 
Originally posted by its_virgil
<br />Now take a look. It scared the liver out of me. I was looking in the window watching the resin bubble when it "boomed".[:D]
Do a good turn daily!
Don
Click to expand...

Don, Glad you're ok. Now for priorities.........
new articles of underclothing first [:0]
new top for pot second [:D][:D]
 
Don, I've either read or some one told me to get a big glass pickle jar to draw a vacume in , have you thuoght of maybe trying that instead if the pot?
 
Wow!

Glad the only thing you had to change was your shorts Don.

That corian was probably just too brittle a material to use. You might want to look around for a thick piece of acrylic or Plexiglas for the next top. I use one for my vacuum setup but my vessel is probably only 6-7" in diameter so I don't know how it would do on a vessel the size of the paint pot. Another good idea would be to look for a thick piece of aluminum to make my next one out of.

You did prove a very important point though. Under vacuum the lid imploded and everything was drawn in. Same thing would happen to the glass vessels that were spoken of in an earlier stabilizing thread.

http://www.penturners.org/forum/topic.asp?TOPIC_ID=16066
 
I hooked the vacuum pump and turned it on. The guage was reading in the 25 inHG range. I should have done the calculations. That much vacuum was producing a load of 1200 lbs on the lid. Evidently too much for the corian. I will either find a smaller vessel or use a metal lid. I have a friend who is giving me a piece of high tensil strength aluminum which should withstand that kind of pressure. A smaller vessel will reduce the force on the lid also. When we vote for the year's most studip penturning stunt I suppose I will win hands down.[:D]
Thanks for all of the concern. I've revised the turorial so this doesn't happen to someone else down the road. The revision will be posted as soon as Jeff gets it done.
Do a good turn daily!
Don
Originally posted by Russb
<br />How much vacuum were you pulling?
Click to expand...
 
Thanks Dario. Any news on yuour attendance at SWAT this weekend? What were the blanks you gave me in Dallas that were stabilized with plexiglass and acetone? There were golden and had blace ??spalt lines?? in them.
Do a good turn daily!
Don
Originally posted by Dario
<br />Glad you are safe Don.

Thanks for the warning.
Click to expand...
 
well just be glad it was under vacume instead of pressure. Vacumes implode instead of explode. But boy they sure go bang either which way. Glad that was all the damage that happened and that you didnt end up getting hurt.
 
If you are going to use a clear lid, use polycarbonate, not plexiglas. Plexi is way too brittle and will shatter like glass. Poly will bend and not break and is used for bullet proofing as well. Polycarbonate always amazes me. You can put poly in a sheet metal brake and pull a cold bend over 90 degrees. You can even take a curl with a hand plane. It just looks too much like glass to be able to do that. When I first learned of vacuum veneering, I attended a seminar by Darryl Keil from Maine. He starts his show by putting a piece of 3/4" particle board across some 2x2's inside the vacuum bag. He pulls a vacuum and you watch the particle board bow and then WHAM[:0] the sheet breaks in half. A very graphic way to show the weight of our atmosphere.
Glad you are okay Don. Thanks for that tutorial as well.
Rich
 
Hi
The amount of psi generated by the vacuum and the size and shape of the vessel are critical here. Had the experience industrially in a lab of making a vacuum vessel froma 55 gal drum. Big mistake. The first time the pump was turned on the vessel caved in at the flat ends with a LOUD bang. We had to make one of heavy steel with DOMED ends. The dome shape resists the pressure much better. Such a cover could easily be made of wood, tho it might have to be reinforced with fiberglass and epoxy. A heavy plexiglas or polycarbonate window could be inserted. (Polycarbonate (Lexan) has the unfortunate property of stress cracking in contact with some solvents, especially acetone, and will just cumble away.) I would NOT use a glass vessel, such as a pickle jar, which has a flat end on it. I think that is a recipe for disaster, since the glass will implode, especially as with use it picks up scratches and so on which will weaken it. Just a couple of comments from experience.
 
Since I have been successfully using a vacuum for over 2 years with no major mishaps I didn't look at your tutorial.(If it aint broke, don't fix it)
What I found interesting is the shape in whish your corian broke.
They look like perfect pie shaped pieces.
How do the fractures represent the sections that you cut for the window?
I am guessing a window would work if it were round rather than sqaure.
 
I was intrigued by the shape of the sections also. There were five almost identical pie shapped sections as you mentioned. The hole for the window was round and centered. The lexan pane was square and epoxied to the top. After doing the calculations the 11 inch diameter paint pot and the 26 inHg I was pulling equals close to a 1200 lb load on the lid. I should have done the calculations first...I suppose corian is too brittle for that much load. Finding a smaller vacuum vessel will reduce the load on the lid and I'm in the process of making a lid from high tensil strenght aluminum which should work out fine.

BTW, the tutorial was not just on vacuum casting, but on casting snake skin blanks and the vacuum was only one small part of the turorial which has now been revised to omit the use of corian or similar material for the vacuum vessel lid.

Do a good turn daily!
Don
Originally posted by ctEaglesc
<br />Since I have been successfully using a vacuum for over 2 years with no major mishaps I didn't look at your tutorial.(If it aint broke, don't fix it)
What I found interesting is the shape in whish your corian broke.
They look like perfect pie shaped pieces.
How do the fractures represent the sections that you cut for the window?
I am guessing a window would work if it were round rather than sqaure.
Click to expand...
 
Originally posted by its_virgil
<br />Thanks Dario. Any news on yuour attendance at SWAT this weekend? What were the blanks you gave me in Dallas that were stabilized with plexiglass and acetone? There were golden and had blace ??spalt lines?? in them.
Do a good turn daily!
Don
Click to expand...

Don,

Those are spalted alder. Though those were stabilized with plexi-acetone...the solution didn't really penetrate deep enough so please plan accordingly. I usually drill with smaller bit, soak the hole with thin CA then re-drill.

I am afraid SWAT meeting is totally out for me, my family emergency is not yet over.

I am sure you will all have a good time...wish I can join you but maybe next time.

The weather also seems to be improving a lot [:)]...helps when there are lots of men around [;)][}:)]
 
Originally posted by DocRon
<br /> I would NOT use a glass vessel, such as a pickle jar, which has a flat end on it. I think that is a recipe for disaster, since the glass will implode, especially as with use it picks up scratches and so on which will weaken it. Just a couple of comments from experience.
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This has been argued before:

http://www.penturners.org/forum/topic.asp?TOPIC_ID=16066

I have been using pickle jars and bell jars for over 10 years and have not had many problems. I checked out logs and found that in 16 years we have had 11 "catastrophic failures" (implosions) 7 have been pickle jars and 4 have been bell jars. I have witnessed or seen the aftermath of 7 of these failures. GLASS DOES NOT FLY ALL OVER THE PLACE. Once the failure begins the pressure is relieved so fast that there is not enough inertia in the glass to go anywhere, it basically falls into a pile on the bench.

As I have said before, we use a cage of ¼†screen mesh as an implosion guard and I have never seen or heard of the glass making it to the guard which is 3†bigger in diameter that our vacuum vessels. I am much more likely to be hurt cleaning up the broken glass that I would be during the implosion.

At any given time we have at least 10 vessels under vacuum in the lab and when we have large orders all 20 vessels are being used. Quite often we leave the vessels under vacuum all weekend so I would estimate they are used 320-350 days a year.
 
Originally posted by DocRon
<br />Hi
The amount of psi generated by the vacuum and the size and shape of the vessel are critical here. Had the experience industrially in a lab of making a vacuum vessel froma 55 gal drum. Big mistake. The first time the pump was turned on the vessel caved in at the flat ends with a LOUD bang. We had to make one of heavy steel with DOMED ends. The dome shape resists the pressure much better. Such a cover could easily be made of wood, tho it might have to be reinforced with fiberglass and epoxy. A heavy plexiglas or polycarbonate window could be inserted. (Polycarbonate (Lexan) has the unfortunate property of stress cracking in contact with some solvents, especially acetone, and will just cumble away.) I would NOT use a glass vessel, such as a pickle jar, which has a flat end on it. I think that is a recipe for disaster, since the glass will implode, especially as with use it picks up scratches and so on which will weaken it. Just a couple of comments from experience.
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What experience have you had with pickle jars?
Your track record for 55 gallon drums speaks volumes.

I question the intelligence of anyone who thought they could pull a vaccum of any kind on a 55 gallon drum without a mishap.
I have been using pickle jars for two years using a vacuum that will pull 25 inches and had only one "break", nothing happened, I lost the vacuum.
 
Oh, I had battle scares but no battle scars. [:D][}:)]The pot is ok, just the corian lid is trash. Back to the drawing board.
Do a good turn daily!
Don
Originally posted by PenWorks
<br />Okay, you got my vote [:D]
Glad all that broke was the pot and you escaped without any battle scares. [:)]
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I've never built a vacuum chamber. I have been reading the posts about paint cans and pickle jars.

It seems like a very strong, and safe, vacuum chamber could be made from steel pipe about six inches in diameter, about a foot long, and threaded on each end.

A cap would be tightly and permanetly fastened to the bottom. The top cap would screw on, using a thread sealent, and tight enough so that it wouldn't leak.

The same type of vacuum chamber could be made from plastic water pipe, but it might not be strong enough, although some of this plastic pipe is rated for an internal pressure of about 150 PSI.

Of course, you would not be able to watch what was going on in the chamber.

The steel pipe would be available (I think) from a company that installs water mains.

Bonefish
 
A pickle jar is perfect for a small vacuum chamber. By the time you bought the pipe, cut it, threaded it, bought the caps you could have bought a jar of pickles cheaper. Some restaurants will save the jars for you if you ask.
 
Originally posted by bonefish
<br />

The same type of vacuum chamber could be made from plastic water pipe, but it might not be strong enough, although some of this plastic pipe is rated for an internal pressure of about 150 PSI.
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About half way down the page:

http://www.paragoncode.com/shop/vacuum_pump/
 
Don;

Here are some pics of my vacuum vessel. It is nothing more than a 3/16" glass vase I bought at Michaels.
Polycarbonate top with a piece of 1/8" rubber glued to it.


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Thanks a lot Scott. I hope to get it redesigned next week.
Do a good turn daily!
Don
Originally posted by Mudder
<br />Don;

Here are some pics of my vacuum vessel. It is nothing more than a 3'16" glass vase I bought at Michaels.
Polycarbonate top with a piece of 1/8" rubber glued to it.
Click to expand...
 
Steel pipe wouldn't explode or implode.

If I'm not mistaken, we are talking about a vacuum chamber that would not present any danger.

A pickle jar is for pickles. A steel water pipe is to hold pressure in, but it can also be used to hold it out. Go figure.

I can't imagine a steel pipe exploding or imploding and getting killed or worse. I can imigine a pickle jar imploding or exploding and getting killed or worse.

My recommendition is to use the pickle jar to store pickles in for using to make pickles in.

Whether this is rocket science or not, I don't think a rocket scientist would build a vacuum chamber out of a pickle jar. I wouldn't.

Bonefish

Bonefish
 
Originally posted by bonefish
<br />Steel pipe wouldn't explode or implode.

If I'm not mistaken, we are talking about a vacuum chamber that would not present any danger.

A pickle jar is for pickles. A steel water pipe is to hold pressure in, but it can also be used to hold it out. Go figure.

I can't imagine a steel pipe exploding or imploding and getting killed or worse. I can imigine a pickle jar imploding or exploding and getting killed or worse.

My recommendition is to use the pickle jar to store pickles in for using to make pickles in.

Whether this is rocket science or not, I don't think a rocket scientist would build a vacuum chamber out of a pickle jar. I wouldn't.

Bonefish

Bonefish
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Have you heard about pipe bombs?
Your post is confusing.The only statement I understood is that you believe the only way to safely make a vacuum chamber is one that would not allow you to observe what is happening inside the chamber while a vacuum is being pulled.
Pulling a maximum vacuum with the solution inside is usually a messy situation.(For those who do not knoiw what they are talking about I said messy, not dangerous)
Before you post your innacurate beliefs about something you know nothing about, try making the chamber the way you describe and post your results.( threaded steel pipe)
I'll be anxiously awaiting the report.
It still aint rocket science, but they have invented the wheel and the earth is not flat.
 
Originally posted by bonefish
<br />Steel pipe wouldn't explode or implode.

If I'm not mistaken, we are talking about a vacuum chamber that would not present any danger.

A pickle jar is for pickles. A steel water pipe is to hold pressure in, but it can also be used to hold it out. Go figure.

I can't imagine a steel pipe exploding or imploding and getting killed or worse. I can imigine a pickle jar imploding or exploding and getting killed or worse.

My recommendition is to use the pickle jar to store pickles in for using to make pickles in.

Whether this is rocket science or not, I don't think a rocket scientist would build a vacuum chamber out of a pickle jar. I wouldn't.

Bonefish

Bonefish
Click to expand...

If you want to make your vacuum chamber out of pipe, go ahead, thats your choice. I will continue to use pickle jars and as long as I don't knock it off the table or hit it with a hammer I will be safe.
 
It's all about the square inches. Something long and cylindrical like mudder has is fairly strong because of the tight curvature of the walls. The flat bottom is the weak point of the design, but it look pretty beefy in this case. The lid works from a thick piece of acrylic only because the square inches are down. If it were the size of a pressure cooker, it would probably collapse the lid (and floor for that matter) if it were made of the same glass and plastic.
 
Correct and an important difference. Each square inch reduction in area of the lid is a reduction of about 14 lbs to the load on the lid, depending of course on how many inHg the pump is pulling. The 11 in diameter paint pot produces a load of arount 1400 lbs at 30 inHg, but reducing the diameter to 6 reduces the load to about 416 lbs. ... a 1000 lb difference.

But, as eagle mentioned, degassing a liquid with vacuum can be a real messy chore with the liquid bubbling as the gas is removed. It get even messier when the liquid is a thick resin about the consistency of honey. Being able to look in to control the bubbling's vigor by controlling the vacuum strength is important.

After watching the resin's behavior for the last 3 months I have an idea of how vigorous the bubbling is. I've done two castings since the mishap putting 8 oz of resin in qt jar and placing the jar inside the paint tank. I used the paint tank lid and left the vacuum pump running for 10 minutes and no spillage. I may not need a smaller tank or a lid with windows.

do a good turn daily!
Don

Originally posted by Dario
<br />I think the big difference between the 2 is that the glass vase Mudder used has a much smaller diameter.
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Originally posted by ctEaglesc
<br />
Originally posted by DocRon
<br />Hi
What experience have you had with pickle jars?
Your track record for 55 gallon drums speaks volumes.

I question the intelligence of anyone who thought they could pull a vaccum of any kind on a 55 gallon drum without a mishap.
I have been using pickle jars for two years using a vacuum that will pull 25 inches and had only one "break", nothing happened, I lost the vacuum.
Click to expand...

Hi
Yeah, the 55 gal drum incident was a case of serious 'brain fart" all right. Should have had an engineer calculate the stresses for us instead of us chemists just forging ahead.

Have had no experience with the pickle jar vessel, just concerned that the flat base would not be strong enough. Encaseing the apparatus in a wire screen is a very good idea, as mentioned by Mudder elsewhere in this thread.
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We have been told over and over by several persons who use pickle jars for vacuum chambers with almost zero mishaps and when they do the impolsions leaves the glass in a pile on top of the jar's footprint. Even putting a wire cage around the jar was not necessary, but it was safe.

Scott Hettle, aka Mudder, has told us of this numerous times, given reports numerous times, and even posted pictures of how he does it...every day in his real job, numerous vessels online at the same time, often over nite or even over the weekend with a very very low percentage of failures. Just be careful cleaning up if one of the jars does break.[:D]

Obviously, Scott knows his business and I can trust his report and recomendations. Vacuum on! Besides, I love pickles and the aroma of pickles in the shop is better than the aroma of the resin. Say Scott, will 'bread and butter' jars work...my favorite. [:D][}:)]

Do a good turn daily!
Don

<br /> I can imigine a pickle jar imploding or exploding and getting killed or worse.
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Hey Aanthony,
You're the only vote so far. I guess others know something else and are saving their votes, or are wainting until someone else (or me) does something more less intelligent.[:D]
Do a good turn daily!
Don
Originally posted by PenWorks
<br />Okay, you got my vote [:D]
Glad all that broke was the pot and you escaped without any battle scares. [:)]
Click to expand...
 
I work for an engineering firm and I just talked with our chief stress engineer. He said that flat surfaces are highly prone to failure under vacuum. He said the reason a canning jar lid works is that it is dome shaped to begin with. He also said that design for vacuum is totally different than design for pressure, and that just because something is designed for high pressure does not make it a good candidate to withstand vacuum.
 
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Originally posted by gerryr
<br />I work for an engineering firm and I just talked with our chief stress engineer. He said that flat surfaces are highly prone to failure under vacuum. He said the reason a canning jar lid works is that it is dome shaped to begin with. He also said that design for vacuum is totally different than design for pressure, and that just because something is designed for high pressure does not make it a good candidate to withstand vacuum.
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I use FLAT plexi glass with a rubber gasket a la Mudder AND I use regular pickle jar lids with replacement valve stems a la Smoky Tom.
Neither of these iitems are domed.
Yes I understand a domed shape is stronger but what I have been using for 2 y ears works.
The worse that can happen is the seal weakens and won't hold a vacuum.
In that case I make another lid.
I replace lids because the "gasket" weakens or gets hard but don't have to replace the "chamber.
The search function on this site will bring up VOLUMES of threads on stabilizing with a vacuum and the first mention of plexiglass and acetone mix was in August of 2004.
HAppy reading.( search the archives)
 
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