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<DIV><FONT size=2 face=Arial>I shrank, then later annealed mine in an industrial
oven at a neighboring shop. It had a pretty good digital thermostat and
circulating air. It took quite a long time, with many trips next door to
keep bringing down the temp, but I had no problem. </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I don't know what the pros do, but I placed my
acrylic on glass sheets that I lightly dusted with talcum powder to prevent
sticking. There were a few dots of talc that were bumped up and
they left tiny impressions. That leads me to believe that if I
just tried doing it without the flat glass, my viewports wouldn't be flat
when I was finished. I think if I placed them directly on the
rack, they would have had stripes imbedded in them. </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Dan H.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<BLOCKQUOTE
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dir=ltr>
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=hanker_20032000@yahoo.ca href="mailto:hanker_20032000@yahoo.ca">hank
pronk</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=personal_submersibles@psubs.org
href="mailto:personal_submersibles@psubs.org">Personal Submersibles General
Discussion</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, April 02, 2014 8:30
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [PSUBS-MAILIST] annealing
acrylic</DIV>
<DIV><BR></DIV>
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style="BACKGROUND-COLOR: #fff; FONT-FAMILY: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; COLOR: #000; FONT-SIZE: 12pt">
<DIV><SPAN>At one time I was going to go down this road, I researched the hell
out of it. I recall that a circulation fan with a given air speed was
absolutely essential. I would research the ovens that the pro's
use. </SPAN></DIV>
<DIV
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<DIV style="DISPLAY: block" class=yahoo_quoted>
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<DIV dir=ltr><FONT size=2 face=Arial>On Tuesday, April 1, 2014 8:09:05 PM,
Brian Cox <<A
href="mailto:brian@ojaivalleybeefarm.com">brian@ojaivalleybeefarm.com</A>>
wrote:<BR></FONT></DIV>
<DIV class=y_msg_container>
<DIV id=yiv4244535910>
<DIV style="FONT-FAMILY: Arial, sans-serif; FONT-SIZE: 10pt">Well at least I
have a piece of acrylic that can serve as a temperature block now !<BR><BR>---
cast55@telus.net wrote:<BR><BR>From: "Sean T. Stevenson"
<cast55@telus.net><BR>To: Personal Submersibles General Discussion
<personal_submersibles@psubs.org><BR>Subject: Re: [PSUBS-MAILIST]
annealing acrylic<BR>Date: Tue, 01 Apr 2014 19:57:59 -0600<BR><BR>
<DIV dir=ltr>To be clear on terminology, additional thermal mass does not
decrease stability, but rather increases the time constant of the system
response. Controllers simply need to be tuned in accordance with the system
characteristics, and there are control algorithms which can account for the
long delays typical of thermal control loops.</DIV></DIV>
<DIV dir=ltr>An unstable, or underdamped system with oscillation, is more
typical of a controller with too much gain, or a highly non-linear control
element which is not accurately modeled in the control algorithm. </DIV>
<DIV dir=ltr>As far as the oven goes, a simple solution might be to add a
convection fan to even out the oven air temperature, and measure the surface
temperature of the acrylic for the control variable as opposed to the oven air
temperature. </DIV>
<DIV dir=ltr>Sean<BR><BR><BR>
<DIV>On April 1, 2014 7:40:34 PM MDT, Marc de Piolenc
<piolenc@archivale.com> wrote:
<BLOCKQUOTE
style="BORDER-LEFT: rgb(204,204,204) 1px solid; MARGIN: 0pt 0pt 0pt 0.8ex; PADDING-LEFT: 1ex"><PRE>Adding thermal mass inside an oven actually destabilizes closed loop <BR>control, as you have just learned.<BR><BR>With open loop control it can help a bit by ironing out fluctuations.<BR><BR>Best,<BR>Marc<BR><BR>On 4/2/2014 2:02 AM, Alan wrote:<BR><BLOCKQUOTE style="BORDER-LEFT: rgb(114,159,207) 1px solid; MARGIN: 0pt 0pt 1ex 0.8ex; PADDING-LEFT: 1ex"> Brian,<BR> I was going to suggest earlier that you build a larger oven next to your<BR> small<BR> oven & use the small oven to heat it. That way the temperature fluctuations<BR> would be less dramatic. Possibly make it out of insulation batts &<BR> aluminium foil.<BR> you could still use the control unit I suggested.<BR> Alan<BR><BR> Sent from my iPad<BR><BR> On 2/04/2014, at 3:49 am, "Brian Cox" <brian@ojaivalleybeefarm.com<BR> <mailto:brian@ojaivalleybeefarm.com>> wrote:<BR><BR><BLOCKQUOTE style="BORDER-LEFT: rgb(173,127,168) 1px solid; PADDING-LEFT: 1ex"> Epic Fail ! my attempt to anneal a viewport did not go well. The<BR> temps swings were so great that it was impossible to regulate. The<BR> mass in the oven that I had hoped would moderate the swings made it so<BR> the lag time between the heating cycle and when the thermometer sensor<BR> saw the temperature change uncontrollable. And the heat was not even<BR> though out the oven as well.<BR> Brian<BR><BR> --- hanker_20032000@yahoo.ca <mailto:hanker_20032000@yahoo.ca> wrote:<BR><BR> From: hank pronk <hanker_20032000@yahoo.ca<BR> <mailto:hanker_20032000@yahoo.ca>><BR> To: Personal Submersibles General Discussion<BR> <personal_submersibles@psubs.org <mailto:personal_submersibles@psubs.org>><BR> Subject: Re: [PSUBS-MAILIST] annealing acrylic<BR> Date: Tue, 25 Mar 2014 05:35:51 -0700 (PDT)<BR><BR> Brian,<BR> I say when in doubt,
test. If your!
not
building a test chamber , you<BR> can make your sample window to fit my chamber and I will test it for you.<BR> Hank<BR><BR><BR> On Monday, March 24, 2014 7:23:18 PM, Brian Cox<BR> <brian@ojaivalleybeefarm.com <mailto:brian@ojaivalleybeefarm.com>> wrote:<BR> Hank,<BR> I have the book, that's where the annealing schedules are,<BR> they vary quite a bit, there is an absolute minimum time and then<BR> there is the original recommended time. The recommended time comes out<BR> to be around 51 hours where as the shortened time is maybe half that.<BR> I'm just doing one test piece to start off with. I was also using the<BR> same oven ( a toaster oven I got from Sears for $75 bucks) to heat the<BR> welding rod to 250 degrees F before we used the rod ( it had been<BR> sitting out for a few days). I was able to keep the temperature<BR> fairly even for the welding rod at 250.<BR> Brian<BR><BR> --- hanker_20032000@yahoo.ca
<mailto:hanker_20032000@yahoo.ca> wrote:<BR><BR> From: hank pronk <hanker_20032000@yahoo.ca<BR> <mailto:hanker_20032000@yahoo.ca>><BR> To: Personal Submersibles General Discussion<BR> <personal_submersibles@psubs.org <mailto:personal_submersibles@psubs.org>><BR> Subject: Re: [PSUBS-MAILIST] annealing acrylic<BR> Date: Mon, 24 Mar 2014 17:39:27 -0700 (PDT)<BR><BR> Brian,<BR> Do you have the Stachiw book of Acrylics, I can send you mine if you<BR> don't have a copy. There is some pretty important stuff in there.<BR> Hank<BR><BR><BR> On , hank pronk <hanker_20032000@yahoo.ca<BR> <mailto:hanker_20032000@yahoo.ca>> wrote:<BR> Brian,<BR> How thick is your acrylic? should take more than a night?<BR> Hank<BR><BR><BR> On Monday, March 24, 2014 6:33:09 PM, Brian Cox<BR> <brian@ojaivalleybeefarm.com <mailto:brian@ojaivalleybeefarm.com>> wrote:<BR> Yes, I have the annealing schedules.!
I have
an electric oven and two<BR> digital thermometers, one I'm going to put in a piece of acrylic and<BR> the other one I'm going to use to monitor the oven temperature itself<BR> . I'm worried that the thermometer in the acrylic won't register<BR> until it gets heated throughout, and so then the oven temp might go<BR> higher than it should. So between the two readouts I can heat it<BR> gradually up. It'll be a long night.<BR> Brian<BR><BR> --- hanker_20032000@yahoo.ca <mailto:hanker_20032000@yahoo.ca> wrote:<BR><BR> From: hank pronk <hanker_20032000@yahoo.ca<BR> <mailto:hanker_20032000@yahoo.ca>><BR> To: Personal Submersibles General Discussion<BR> <personal_submersibles@psubs.org <mailto:personal_submersibles@psubs.org>><BR> Subject: Re: [PSUBS-MAILIST] annealing acrylic<BR> Date: Mon, 24 Mar 2014 17:22:32 -0700 (PDT)<BR><BR> Brian,<BR> Are you going to anneal your windows yourself?<BR> Hank<BR><BR><B></B> On
Monday, March 24, 2014 6:03:10 PM, Brian Cox<BR> <brian@ojaivalleybeefarm.com <mailto:brian@ojaivalleybeefarm.com>> wrote:<BR> Used my polarized lenses on the newly cut piece and it appears clouded<BR> throughout the whole piece. Where as another piece I have, you can<BR> clearly see a stress area around where it has been drilled.<BR> Brian<BR><BR> --- emile@airesearch.nl <mailto:emile@airesearch.nl> wrote:<BR><BR> From: "Emile van Essen" <emile@airesearch.nl <mailto:emile@airesearch.nl>><BR> To: "'Personal Submersibles General Discussion'"<BR> <personal_submersibles@psubs.org <mailto:personal_submersibles@psubs.org>><BR> Subject: Re: [PSUBS-MAILIST] annealing acrylic<BR> Date: Mon, 24 Mar 2014 22:40:46 +0100<BR><BR> As far as I know it is only cast.<BR> Regards, Emile<BR> *Van:*Personal_Submersibles<BR> [mailto:personal_submersibles-bounces@psubs.org] *Namens *Brian Cox<BR> *Verzonden:* maandag!
24
maart 2014 20:37<BR> *Aan:* PSubs<BR> *Onderwerp:* [PSUBS-MAILIST] annealing acrylic<BR> I'm planning on annealing my viewports, does anyone know if the<BR> acrylic from the factory is pre-shrunk ?<BR> Brian</BLOCKQUOTE></BLOCKQUOTE></PRE></BLOCKQUOTE></DIV>
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