Vacuum Chamber Prototype

[James Combs]

I have a lot of spalted maple, some I have used to make several items, for example these:
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(Hmm... note to self. Self you have gotten better at the lighting:D...)

Anyway as I was saying I have a lot of this spalted maple and it is very, very, very punky. I pretty much have to soak it with CA every time I try to turn it. It is getting too expensive to use CA so I am thinking I will try stabilizing it with a resin that is pulled into it with a vacuum. Probably will use Mesquite Man's Cactus Juice. What ever I use I need a vacuum chamber and a fairly large one.

The following is a prototype that I tried out today. (Continued in next post due to number of photos.)

[James Combs]

I am using a 10" sewer pipe coupling. I found it at a pipe supply that had them in stock by accident with no other components to go with it. It is normally about $30, the counter guy asked me for $15, I told him I would go $10, he took it.

It had two rubber seals, one at each end molded into the PVC. I cut those out with a razor knife.
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I found a 1/4"npt x 3/8" barb fitting, turned off the barb and threaded it at 3/8-24 added a couple rubber washers, flat washers, a lock washer and a nut, drilled a hole high on the side of the PVC fitting and install a QD fitting along with the threaded barb.
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I cut a couple of appropriate size circles from an old laminate door and used them as a bottom and a top. (these are prototypes for the 3/8" clear polycarbonate sheets that I ordered, due the 21st)
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I set the coupler on one of the circles and put the other on top. I hooked up my vacuum pump and got a piddly 6-7" of hg:confused:. Hmm.. maybe a little weight on the top.
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Much better now I get 27" of Hg plus the next time I tried it I didn't need a weight.
BTW when I saw the vacuum start to climb I moved to the other end of the shop in case of... well use your imagination.;)
I ran it up and down from no vacuum to the 27" maximum that I could get several times. I never heard any creaking or moaning. Each time I got a little braver and a little closer to it. When I was finally confident enough that it wasn't going to implode I look it over real good, didn't see any swaying or any indications of collapsing walls or any other signs that it wasn't strong enough. I shut the valve off to the pump turned off the pumb and it held vacuum for about 90 seconds.
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When I get the polycarb I will epoxy the bottom sheet on, double stick tape a handle to the top sheet and be ready to drown my punky wood in resin.:D

[David E Keller]

Now that's a good idea(assuming it doesn't implode at some point)! I'll be watching for your test results. Best wishes on a successful maiden voyage.

[Paul Maue]

The setup looks great. Are you going to impregnate the entire block or are you going to rough out the general shape. I would think that you would get better penetration. In a previous career I had to check the porosity and density of ceramics using kerosene. We would pull a vacuum for 30minutes with nothing in the vessel except the test pieces then while still under vacuum, bleed in the liquid and hold that for an hour. After that we then pressurized the vessel to force the liquid to prenetrate the test piece. Something to consider. We also used a simple 2gallon paint pressure pot from Sears.

[James Combs]

Now that's a good idea(assuming it doesn't implode at some point)! I'll be watching for your test results. Best wishes on a successful maiden voyage.

David, as I noted above (I was probably editing while you were posting) It seems to hold up pretty good. I will be trying a small piece of wood tomorrow.



The setup looks great. Are you going to impregnate the entire block or are you going to rough out the general shape. I would think that you would get better penetration. In a previous career I had to check the porosity and density of ceramics using kerosene. We would pull a vacuum for 30minutes with nothing in the vessel except the test pieces then while still under vacuum, bleed in the liquid and hold that for an hour. After that we then pressurized the vessel to force the liquid to penetrate the test piece. Something to consider. We also used a simple 2gallon paint pressure pot from Sears.

Paul, I will definitely be treating only rough-outs. Cactus juice may be cheaper then CA but it ain't cheep. I don't think I will be needing to hold a vacuum much longer then a few minutes, just long enough to vacuum out most of the air. The spalted stuff is very dry so I am not worried about having to vacuum enough to get moisture out. Like I mentioned to David I will be trying the first piece tomorrow, probably a roughed out birdhouse roof.

[Roland Martin]

Pretty neat James. Looking forward to reading about test your results. Really nice spalting and great turnings.

[Tim Rinehart]

Very creative James... I think about this (and a million other things) and can feel the concern and waiting for something to implode. Looks pretty beefy and I suspect the sides are not going to implode, but the top/bottom are the weak points. To see if they are moving more than an 'acceptable' amount, put a straightedge along the top while pulling vacuum. If nothing else, the deflection may make it harder to keep a good seal. You could beef it up with some gussets if you think its deflecting too much.

Can't wait to hear how this goes, I too struggle with some punky wood that I don't want to pitch, but don't get the results I want with Polycryl and similar products by just brushing on or soaking for smaller pieces.

[Faust M. Ruggiero]

Jim,
First of all, that the spalted maple pieces is spectacular and worth saving. I also marvel at your engineering imagination. I'm curious as to how you actually apply the stabilizing agent and what keeps the "juice' itself from being sicked into the vacuum or at least into your dust filter. I'm probably imagining it differently that you are actually doing it. Do you just coat the piece with a liberal amount of agent then stick it into the vacuum chamber or do you put the wood into a bath of the stuff and put it in there?
faust

[Michael James]

James, good luck with this! I admire your inventive spirit and suspect it will all take you to better places in your turning.
Sitting and watching in NM,
mj

[James Combs]

Pretty neat James. Looking forward to reading about test your results. Really nice spalting and great turnings.

Thanks Roland, I am having an unexpected but welcome visit from my Sister out of the Dallas/Fortworth TX area so I will be putting off testing for a few days. Maybe by then I will have a clear top for it and be able to watch what is happening. Watching is pretty much a necessity for the process I plan on using.


Very creative James... I think about this (and a million other things) and can feel the concern and waiting for something to implode. Looks pretty beefy and I suspect the sides are not going to implode, but the top/bottom are the weak points. To see if they are moving more than an 'acceptable' amount, put a straightedge along the top while pulling vacuum. If nothing else, the deflection may make it harder to keep a good seal. You could beef it up with some gussets if you think its deflecting too much.
Can't wait to hear how this goes, I too struggle with some punky wood that I don't want to pitch, but don't get the results I want with Polycryl and similar products by just brushing on or soaking for smaller pieces.

Tim I was definitely feeling a little tightness where I sit:rolleyes: when she pumped down the first time to 27. I like your idea of checking the top/bottom for deflection with a straight edge. I also like the idea of gussets. I will try to engineer a way of doing that so as not to compromise the integrity of the clear polycarb top & bottom ie no holes drilled. My first thought when I read your gusset comment was maybe use 3/4" aluminum angle iron across the full width (12") of the cover and use double stick tape to hold it on, what do you think?:confused:



Jim,
First of all, that the spalted maple pieces is spectacular and worth saving. I also marvel at your engineering imagination. I'm curious as to how you actually apply the stabilizing agent and what keeps the "juice' itself from being sicked into the vacuum or at least into your dust filter. I'm probably imagining it differently that you are actually doing it. Do you just coat the piece with a liberal amount of agent then stick it into the vacuum chamber or do you put the wood into a bath of the stuff and put it in there?
faust

Faust, I plan on using a heat activated resin. Two reasons, 1 - No mixing and 2 - You can pour any unused resin back into the original container. Using that as given here is a "mockup" of the process steps.

I purchased this set of plastic bowls some time ago and they have been very handy but I think their nesting feature will make them even handier.
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Lets pretend that this bowl I borrowed from the wife's kitchen (shhhh don't tell her) is a roughed out bowl.
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I will place some kind of spacer into the bottom of one of the plastic bowl that the roughed out bowl "just" fits into. Perhaps some nuts like these.
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Then the rough out sits on these "spacers". The rough out should not have a concave bottom using this process. Some more spacers will be placed into the rough out.
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Then another plastic bowl is selected that "just" fits inside the rough out. Some kind of weights are placed into this bowl as simulated by the rocks. I will probably use chunks of steel. It doesn't really matter as long as the last plastic bowl doesn't float. Then it is just a matter of pouring the resin into the cavity between the two plastic bowls making sure the rough out is completely covered in resin. This arrangement of course is being built up inside the vacuum chamber. It is shown outside the chamber here for clarity. All that is left is to pull a vacuum on the setup for a while and then release it causing the resin to be sucked into the wood. The main reason for using the nesting of the two external plastic bowls to sandwich the rough out is to limit the amount of resin that is required and to prevent it from contaminating the inside of the vacuum chamber (my assumptions)
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After removing the rough out from the chamber, drained real good, pouring any excess resin back into its container, the rough out is wrapped in aluminum foil and cooked per the resin manufactures instructions. (about 45 mins at 225* - the reason for the foil is that the resin would run out al over everything without the foil before it cured.)
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Of course so far this all "plan" and I have never done it before so there may have to be some changes to this scenario but it will be the first round.
As far as your concern about pulling the resin into the vacuum pump, note that the vacuum fitting is fairly high up on the chamber at about 12". The PVC fitting (chamber) is about 12" OD and 14" high. The use of the clear cover will also help. The resin will tend to bubble (look like it is boiling) from the air that is being extracted from the wood so the vacuum has to be applied slowly to limit the "boiling". If it is done correctly there shouldn't be any spillage into the chamber itself nor anything being sucked into the vacuum line.

Here's crossing my fingers.;)


James, good luck with this! I admire your inventive spirit and suspect it will all take you to better places in your turning.
Sitting and watching in NM,
mj

Thanks MJ, wish me luck.:)

[Andrew Kertesz]

I would almost think you would want a pressure pot versus a vacuum chamber.

[James Combs]

I would almost think you would want a pressure pot versus a vacuum chamber.

Pressure has it's proponents but I think at this point, never having used either, I would prefer Vacuum. The actual mechanics are essentially the same anyway. After you vacuum it which is typically of much shorter duration then applying pressure you release the vacuum and now what you have is atmospheric pressure ~14lbs/sq inch or there abouts, depending on altitude, pressurizing the item "from now on". Yeah you can apply pressure but in the case of impregnating the resin into the wood as soon as you release the pressure any compressed air inside the wood will push the resin back out of the wood so therefore you have to use catalyzed resin and allow it to harden while under pressure. Now you have hardened all of the resin including in over-pour which to me is a waste of money. In my vacuum scenario I am using heat activated resin so therefore I can limit the hardening to only that resin which is inside the wood. Should be much more economical as well as efficient. I won't have to turn/cut away the excess over-pour resin. I guess I have done enough rambling but those are my thoughts.

[Faust M. Ruggiero]

Jim,
You dazzle me. Let us know how it works. By the way, we promise not tell your wife about her tupperware.
faust

[Doug Wolf]

James, Sucking the liquid resin into your system is not going to be the problem as you said:

"As far as your concern about pulling the resin into the vacuum pump, note that the vacuum fitting is fairly high up on the chamber at about 12". The PVC fitting (chamber) is about 12" OD and 14" high."

But, when you lower the atmospheric pressure on a liquid, ie resin, it will "boil" at some point and the vapor is what could get in your vacuum system. You should be alright with the clear cover to keep an eye on it, just watch for the vapor mist. Good luck, we're all cheering for you.

[Jerry Marcantel]

James, you are right about the pressure verses vaccum.
I think you're heading the right direction on you vac chamber, but one thing you might want to rethink.
A history lesson first. I have a Vigor Inva-Cast vaccum casting table for casting jewelry and other stuff.... One side of the table is used for removing bubbles in the investment media. What this side of the table consists of is a clear plastic dome (looks like acrylic?sp) 8" tall x 8" ID with a machined foot/flange 7/16" thick. The dome wall is just under 3/16" thick. The vaccum port rises out of the machine through a spring loaded metal plate (for vibratiory action to remove bubbles on the surface) with a piece of rubber (don't know what kind) and the dome is placed on the rubber. Turn on the pump, and within 45-60 seconds, it reaches 27+ inches. If I don't get maximum vaccum, I usualy spronkle a litte water around the contact between the rubber and dome base. My mentor also said to reach max vaccum, release the vaccum, repeat several times, release vaccum and then turn off pump. Remove the investment ring, and let it set up.
Now, to the part about rethinking your design. My thoughts are you don't need a bottom if you can find a good piece of solid rubber (not pourous). Make your chamber with the clear top (no bottom), and then you won't have to work from the top into your chamber. You just set your stuff onto the rubber base, and after you've done the set up of the juice, double bowls and wood bowl, just set the chamber over the stuff and pull your vaccum untill you think you've done what you set out to do.
Side note: a while back I did a little experiment with coffee grounds and resin. I mixed exactly 1 ounce of resin with 1 ounce of grounds and let it cure. I mixed another batch, and then vaccumed it. The batch that set up without vaccuming is exactly 1" tall. The batch that was vaccumed is 7/8" tall. By vaccuming the grounds, I lost 1/8" of height in volume, and there are no bubbles to be seen as apposed the the batch that was not vaccumed....... If you want to see pictures, just ask..
When you get your chamber made, vaccum a cup of water for about 5 minutes and let me know what it tastes like...... ......... .......Jerry (in Tucson)

[James Combs]

... Now, to the part about rethinking your design. My thoughts are you don't need a bottom if you can find a good piece of solid rubber (not pourous). Make your chamber with the clear top (no bottom), and then you won't have to work from the top into your chamber. You just set your stuff onto the rubber base, and after you've done the set up of the juice, double bowls and wood bowl, just set the chamber over the stuff and pull your vaccum untill you think you've done what you set out to do...

When you get your chamber made, vaccum a cup of water for about 5 minutes and let me know what it tastes like...... ......... .......Jerry (in Tucson)

Jerry, great idea, I will see if I can work that into the design. Worse case (no rubber found) I will glue the top piece of polycarb on and leave the bottom loose. I was thinking last night on how I could make a good seal whether I use a loose top or a loose bottom. I am thinking that if I mask off the every thing except the top surface of the PVC (chamber) ring and spray that surface with 2-3 coats of a good spray type contact cement which is basically liquid neoprene, allow it to dry completely that I would end up with a good "rubber" seal. I have successfully used the same stuff as a spray-on liner for a water wheel reservoir so I know that when it drys completely it looses all of its tackiness. I am going to try that today on a scrap piece of 6 inch PVC and some 1/8" Lexan. I'll let you know how it works.

BTW I will try your water/taste experiment too. The water will probably taste pretty flat.

[Bernie Weishapl]

Pretty cool James. Looking forward to the test results.

[Curtis O. Seebeck]

James,

You are exactly correct in your analysis of vacuum vs. pressure for stabilizing. Vacuum lowers the pressure inside the chamber and causes the air inside the wood to expand. When it expands, it comes out of the wood and is evacuated by the vac pump. When the air stops coming out of the wood, release the vacuum and atmospheric pressure forces the resin into the wood to displace where the air used to be and atmospheric pressure holds the resin in place. If you use pressure, you are just compressing the air inside the wood and when you release the pressure, the air re-expands and pushes the resin back out. You may pick up a little extra resin with pressure and it may help with some woods but in my opinion, is not worth the extra step.

I did some pretty extensive testing when I first got Cactus Juice and I found that 80 psi for 24 hours after vacuum only marginally to the weight of the finished blank. Here is a graph of some of my results. Also notice that my testing was only done at 24" Hg since I did not have a big vac pump at the time. The pump I have now will go much higher so maybe I need to re-do my testing and see what happens.
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