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Post by Ron Walker on Sept 18, 2022 17:58:33 GMT -7
Posted by: Ron Walker Jul 21 2013, 05:44 PM Every mechanical device (or any device for that matter) will in time fail and cause some kind of problem. While I believe that mercury is fairly safe and stable until heated into a gaseous state, it is probably not wise to have small "balls" of it laying around the base of your planetarium. Sooner or latter someone will find one, pick it up and eat it. It is better to avoid this problem altogether by preventing any leakage. While anything can and will eventually leak, one of the most common leaks is from the mercury weights on the horizon cut off devices on star projectors. I will talk mainly about my Minolta projector but I would imagine this same fix would work for Zeiss and Goto projectors as well. On all of these projectors there are 32 star projectors, 16 on each northern and southern star globes. Each projector has a horizon cut off shutter designed much like a doll's eyes closure control. The main difference is in a star projector, the device can be placed at virtually any angle and yet the horizon cut off must always be horizontal and parallel to the dome spring line. Thus the "doll eye" mechanism is placed in a ball bearing device weighted on the bottom to keep proper alignment. The weight is the long tube under the star projector. Now one might wonder why use mercury in the first place and it is really an ingenious design. As the projector slowly turns in daily motion, there are many instances where it might rotate into a setting position and the "doll eye" mechanism could be 180 degrees out of position. Also, it might be balanced enough to not rotate into proper position. The weight tube is placed at an angle purposely off from the horizon so that as the unit rotates, the mercury will shift in the weight tube and give the mechanism enough push to allow the weight to swing to the bottom and align with the horizon. This weight tube is adjustable via a thread on the outside to allow for perfect horizontal alignment of each weight tube. It also allows adjustment if there is too much or too little mercury in each weight. These weight tubes can be easily removed from the "doll eye" unit. Every part of these projectors is precision made and the weight tubes are no exception. They are made from thick tubing on which threads are cut to allow adjustment when mounted. You can see a lock ring used to hold the tube in position when balanced. At the lower end of the tube a cap is soldered into position with a small screw which allows the filling of the tube half full with mercury. The top end is caped as well and soldered into position. It is normal for this top end to spend virtually all of its life in a down facing position and the mercury to sit at the same end. This is where the trouble usually occurs. Not being a chemist I can not tell you why or for sure, but it appears that there is a reaction between the mercury and the solder material which allows the mercury to eventually eat a hole through and start migrating out. This could also be a result of age and a simple crack or separation of the solder but the result is the same. Looking at the above picture, it is easy to see the outer paint coat is cracking away and a leak will soon follow. I actually had one weight deteriorate to a point where small drops of mercury leaked out and I found them on my work bench. Luckily I had two protection caps that came on a piece of rod stock that fit the diameter of these weights exactly.
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Post by Ron Walker on Sept 18, 2022 17:58:45 GMT -7
One went on the leaking weight and the other on a weight that looked ready to leak any time. I noticed that there were several of these units that were starting to show paint chips missing and assumed more of these weights would start to leak sooner or later. My first idea was to find a supply of these end caps but no one seemed to sell in quantities of less then 10,000. Besides a waist of a lot of caps, this idea did not seem as permanent as it could be. What if someone removed a cap and tasted what was inside. One of my first thoughts was to use a hot glue gun material, and my first experiments looked promising. The problem was the hot glue became brittle after a while and could easily break off. Again, the mercury would be exposed for the tasting. I put this aside for a while as other projects took priority. In the course of building I came across this elastomeric compound for roofs and was planning experimenting with it as well. As the heat of summer tends to keep me away from exterior building projects, I came back to this. I was also trying to come up with a material that I could "paint over" a few of the electrical connections that would come within reach or prying hands and protect the inquisitive souls from electrocution. Normally the projector would be higher and out of reach, but my limitations require a lower projector.
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Post by Ron Walker on Sept 18, 2022 17:59:34 GMT -7
The web is a wonderful place and after looking for a time I found this stuff. It is for tools and comes in spray or liquid for dipping. It is form fitting and acts as an insulator to protect the user when working on powered circuits. You can dip it as many times as you want to make the coating as thick as you want. It is rubberized and stays flexible. Sounds perfect and worth the experiment. It is also available at The Home Depot for about $7 a can. First a made a simple box jig with some short wire ends to hold the weights for dipping into the material. It comes is all colors but I picked black for obvious reasons. The leaking unit had not leaked in over a year but I needed to remove the cap to be able to dip. It did a very good job of holding the mercury in the end but I could see the handwriting on the wall with respect to the other units. This fix was coming just in time. With this unit I used a Q-tip to paint a cap over the end and let it dry before the dipping process. Thus the mercury would not be pushing down as a layer dried.
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Post by Ron Walker on Sept 18, 2022 18:00:25 GMT -7
Posted by: Ron Walker Jul 21 2013, 06:17 PM Each unit was cleaned with alcohol to make sure there was no grease that would keep the material from sticking. Then they were dipped according to the instructions on the can and hung to dry. This is a fairly viscus material and the little nib that formed on the end did not drip but was rather absorbed back up. While they say one coat is enough, I did three to make sure there was a thick inert covering on the weight base. Another view of the before (left) and after (right). It is easy to see the thickness of the three coats and the small nib at the bottom.
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Post by Ron Walker on Sept 18, 2022 18:00:42 GMT -7
Posted by: Ron Walker Jul 21 2013, 06:26 PM I really didn't want to go any thicker for fear that a larger diameter would interfere with the rotation of the device. There are four screws that stick out and they must be cleared. The final step is to place the weights back into their respective rings (yes I did mark them when I removed them). Everything looks as good or better then new and there will be no leakage for many years to come. Best of all, the mercury didn't need to be removed or handled so the fix was both safe and cheap.
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Post by Ron Walker on Sept 18, 2022 18:01:03 GMT -7
Posted by: bjsullivan Jul 22 2013, 09:11 AM QUOTE(Ron Walker @ Jul 21 2013, 08:26 PM) * I really didn't want to go any thicker for fear that a larger diameter would interfere with the rotation of the device. There are four screws that stick out and they must be cleared.
The final step is to place the weights back into their respective rings (yes I did mark them when I removed them).
Everything looks as good or better then new and there will be no leakage for many years to come. Best of all, the mercury didn't need to be removed or handled so the fix was both safe and cheap. Excellent Fix !! Mine are leaking too. I can see small silver droplets forming at the ends that are hanging down. Getting replacement mercury is not nearly as easy as it used to be. I remember some time ago seeing flasks of the stuff on eBay, but not any more. The Feds have apparently been cracking down on the availability of this stuff.
I have a friend who's father owns a chemical store who is donating a supply to replace what has already leaked out. The Minolta at my house is coming along nicely. It is about 50 percent functional. Most recently got the starball cooling fans working and both hemispheres are now producing stars.
Sometimes I wonder how much mercury fumes I have inadvertently consumed when I look at all these projectors awaiting restoration. Most of them are loaded with mercury.
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Post by Ron Walker on Sept 18, 2022 18:01:26 GMT -7
Posted by: bjsullivan Jul 22 2013, 09:20 AM QUOTE(bjsullivan @ Jul 22 2013, 11:11 AM) * Excellent Fix !! Mine are leaking too. I can see small silver droplets forming at the ends that are hanging down. Getting replacement mercury is not nearly as easy as it used to be. I remember some time ago seeing flasks of the stuff on eBay, but not any more. The Feds have apparently been cracking down on the availability of this stuff.
I have a friend who's father owns a chemical store who is donating a supply to replace what has already leaked out. The Minolta at my house is coming along nicely. It is about 50 percent functional. Most recently got the starball cooling fans working and both hemispheres are now producing stars. The AVI Omniscan is also nearly restored, shown here, running shows from the ADAT using a 7 watt Argon medical laser. This water-cooled unit gives the front yard a good soaking from the drain hose.
The Minolta/Viewlex Series IIB from Indiana is parked in the living room and produces stars that form the backdrop of the laser shows. It is an awesome 3-D effect that adds alot of depth to the laser abstracts. The stars are crisp and realistic. Photo credit: Swamidog
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Post by Ron Walker on Sept 18, 2022 18:01:46 GMT -7
Posted by: Ron Walker Jul 22 2013, 01:34 PM Mr. Brent, take all of your weights out and mount them in the top of a cardboard box so they are upside down as the last picture in post #3. This way the mercury won't be putting pressure on the fine holes in the solder and no more will leak out. Units that are leaking will benefit from a dabbing by way of a Q-tip before the normal dunking process. I had one that was leaking as well as the two that you dropped off for experimentation were fixed this way.
Unless the mercury really gets extremely hot and turns into a vapor you should have no problems. Any mercury that has leaked out of the weights should collect as small drops of metal and can be herded together and pushed into a container. I would not mail or ship any of these units as if the package happened to open we would probably be in jail.
I have saved the mercury that has leaked out of the two units of yours that I have, but I don't really think you need to get any extra mercury. The little that leaked out can be compensated for by simply adjusting the position of the weight. Also I did save the material that leaked out of these but I'm not at all sure how one would get it back in the tubes.
When you take them off, use a pencil and write the number on the short fill end of the tubes as they will not be coated.
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Post by Ron Walker on Sept 18, 2022 18:02:41 GMT -7
Posted by: Ron Walker Jul 22 2013, 01:35 PM QUOTE(bjsullivan @ Jul 22 2013, 09:11 AM) * Excellent Fix !! Mine are leaking too. I can see small silver droplets forming at the ends that are hanging down. Getting replacement mercury is not nearly as easy as it used to be. I remember some time ago seeing flasks of the stuff on eBay, but not any more. The Feds have apparently been cracking down on the availability of this stuff.
I have a friend who's father owns a chemical store who is donating a supply to replace what has already leaked out. The Minolta at my house is coming along nicely. It is about 50 percent functional. Most recently got the starball cooling fans working and both hemispheres are now producing stars.
Sometimes I wonder how much mercury fumes I have inadvertently consumed when I look at all these projectors awaiting restoration. Most of them are loaded with mercury.
Looks like a blast furnace from middle Earth.
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Post by Ron Walker on Sept 18, 2022 18:03:03 GMT -7
Posted by: Ron Walker Jul 22 2013, 01:37 PM QUOTE(bjsullivan @ Jul 22 2013, 09:20 AM) * The AVI Omniscan is also nearly restored, shown here, running shows from the ADAT using a 7 watt Argon medical laser. This water-cooled unit gives the front yard a good soaking from the drain hose.
The Minolta/Viewlex Series IIB from Indiana is parked in the living room and produces stars that form the backdrop of the laser shows. It is an awesome 3-D effect that adds alot of depth to the laser abstracts. The stars are crisp and realistic. Photo credit: Swamidog
BEAUTIFUL SHOT!!! I can only hope to have something that looks half that good. Congrats Mr. Brent!
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Post by Ron Walker on Sept 18, 2022 18:03:23 GMT -7
Posted by: bjsullivan Jul 23 2013, 10:55 AM QUOTE(Ron Walker @ Jul 22 2013, 03:34 PM) * Mr. Brent, take all of your weights out and mount them in the top of a cardboard box so they are upside down as the last picture in post #3. This way the mercury won't be putting pressure on the fine holes in the solder and no more will leak out. Units that are leaking will benefit from a dabbing by way of a Q-tip before the normal dunking process. I had one that was leaking as well as the two that you dropped off for experimentation were fixed this way.
Unless the mercury really gets extremely hot and turns into a vapor you should have no problems. Any mercury that has leaked out of the weights should collect as small drops of metal and can be herded together and pushed into a container. I would not mail or ship any of these units as if the package happened to open we would probably be in jail.
I have saved the mercury that has leaked out of the two units of yours that I have, but I don't really think you need to get any extra mercury. The little that leaked out can be compensated for by simply adjusting the position of the weight. Also I did save the material that leaked out of these but I'm not at all sure how one would get it back in the tubes.
When you take them off, use a pencil and write the number on the short fill end of the tubes as they will not be coated.
Just to make sure I understand... it looks like these are hanging in a way that WOULD put pressure against the nib, in your post #3 ? And, when you pre-coat the leaky ones with Q-tips, are you doing that with paint or doing it with the plexi-seal material? And finally.. is that brand of coating material you used on yours the same brand that they sell at Home Depot ? I wouldn't want to risk using Brand X of a similar product only to discover that the viscosity is different in a bad way, that would be my luck. And finally, how many coats (dips) did you do on yours ? It occurs to me that I could probably go with hot yellow or orange, perhaps even blue but black most closely matches the original.
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Post by Ron Walker on Sept 18, 2022 18:04:06 GMT -7
We are placing them so that the longer section from the threads, the part that usually hangs down (and is the end that leaks) is pointing up. The short side from the threads is mounted down into the box. This is also the end that has the small filler screw and it will face down through the box. Without the constant weight of the mercury on the end cap, no more will leak out.
The material, Performix "PLASTI DIP" multi-purpose rubber coating is the material that Home Depot had, at least the store on Carefree Highway. It was also half the price of other stores on the web, $7 a can.
The pre-coat of the leaky ones was done with the same material. I did the entire end cap and then about 1/8 inch down the tube. I let this dry for about four hours and then with the non-leaky ones gave them a full dip to the threads. I let them dry about two hours between coats and did three coats. Then I let them dry completely overnight, about 10 to 12 hours before remounting them. The material is viscus enough that it self applies a fairly thick coating with each dip. I stopped at three coats because I didn't want the diameter of the weights to get so thick that it would hit the screws that hold each projector in place as it rotated.
All in all, with my 32 weights and the two experimental ones of yours, I still have half a can left. This is truly an inexpensive fix.
I thought about the other colors and would probably have experimented if they only had blue, but I really doubted if I would have liked yellow or orange on the projector. I'm actually very glad they had black as the machine looks original and the slight extra thickness blends right in as you can see in the pictures.
The material holds on really tight but it can be removed with a knife and some work. This is good as it will make a great insulator to cover some connections on the outside of the machine that will be reachable if an audience member reaches in and touches. Once connected up and operational, a simple coating of this material will prevent any chance of shock.
Another thing that I found is that a drop of light machine oil (3 in 1) on the threads allows for an easy job of replacing the weights in their mounting brackets.
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Post by Ron Walker on Sept 18, 2022 18:04:33 GMT -7
Posted by: moonmagic Jul 23 2013, 03:49 PM That IS a great fix for this problem Ron. Perhaps this same solution will work for the various mercury filled coordinate projectors on the Spitz A-4's/512's/etc. (The tips on those units are easily bumped and subject to breaking off with the loss of almost all their mercury at once. This may be an excellent way to re-seal those as well. (I'm sure BJS remembers how much those little "cut-offs" cost through Spitz!) Sooner or later I guess we need to grab a few old machines JUST for the parts. BTW....Wonderful to see a post from Mr. Brent. The picture of the Minolta Star field with the Laser imagery is fantastic! I think of all you guys often, always wishing we were all closer together. Reading about and seeing what you are doing remains a constant source of encouragement. In a similar vein, I saw a story on CBS recently about a gentlemen (perhaps living in Wisconsin) who many years ago rescued an old theatre pipe organ and re-assembled it in his basement. Later on, he obtained additional items from old ornate movie theatres and added them in his basement. He now gives regular concerts and has people from all over that attend. He is 87 years young and started the project (I believe the story said) when he was in his 30's. While I know it's not planetariums, the magnitude of his passion is certainly similar. I found the story inspirational, perhaps you will too. (The only negative I thought about, is that I hope I don't wait until I'm 87 to start!) I also wish I had a basement the size his must be! www.cbsnews.com/video/watch/?id=50151287nwww.timesfreepress.com/news/2013/jun/23/western-electric-plugs-into-rossville/?businesstnvalleyMeanwhile...another interesting thing crossed my eyes today. There was a story out of northwest Georgia that some guy bought from AT&T the "Western Electric" (name and logo) company. He is now manufacturing rare TUBES for classic audiophiles for stereo's, recording equipment and musical instruments. (I've always admired and even collected some vintage WE stuff, especially phone related things, so this naturally piqued (sp?) my interest too.) This also serves to illustrate one of my many problems....too many shiny objects. Why didn't I find "EVERYTHING" this interesting when I was in school. mm
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Post by Ron Walker on Sept 18, 2022 18:05:04 GMT -7
Yes, I think this stuff can be used to protect any and all of these fragile parts. I am going to look at the Milky Way projectors next as they have an interesting problem of their own. Yes, Mr. Brent's picture is indeed fantastic....someday....
The old pipe organ guy is indeed like us planetarium freaks, and we are indeed equally nuts. I wonder if I will ever be put on some kind of tour like his. Time will tell. I would be very happy to be as active at 87. Rather then all of those keys, I have knobs.
I'm always on the look out for some good 6L6 GC's. I have a feeling that his prices might be a bit out of my league.
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Post by Ron Walker on Sept 18, 2022 18:05:45 GMT -7
Posted by: bjsullivan Jul 24 2013, 01:43 PM QUOTE(moonmagic @ Jul 23 2013, 05:49 PM) * (I'm sure BJS remembers how much those little "cut-offs" cost through Spitz!) Sooner or later I guess we need to grab a few old machines JUST for the parts.
Yes, costly indeed. I would certainly take any opportunity to grab these machines for parts, even if they are too far gone to restore. Many of these parts are impossible to get at any price. I have turned the den into a spaceport. I will use Ron's technique to seal up the mercury weights on this machine, as several are leaking. One of the tall racks houses the AVI Omniscan laser projector, a sphere mounted on a motorized, telescoping pole emerges from the top.
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