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| Building a vacuum fixture... http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=9617 |
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| Author: | John Elshaw [ Fri Dec 01, 2006 4:01 pm ] |
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I've seen plenty of info about how to build your own vacuum clamping system, however there is very little about building the vacuum fixtures. Does anybody have a good reference for building a fixture? Specifically I'd like info on how to ensure you get a proper seal with the neoprene sheeting, and how to properly seal the edges, etc. I'd like to build a fixture to set my dishes in for clamping braces, however I'm sure there are some things I need to watch out for. Thanks! John |
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| Author: | LanceK [ Sat Dec 02, 2006 3:49 am ] |
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Bump, This is a good question for Don Williams... |
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| Author: | crazymanmichael [ Sat Dec 02, 2006 4:19 am ] |
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if you sand and seal the wood of your frame well the membrane will seal itself, though you need to use a lot of screws as can be seen from any of the various photos of one. any good finish works, but i used polycrylic. the base of the fixture is flat, and the dish can just sit on it. i use a dish cut to a rough guitar shape so as not to have to make the fixture bigger than necessary. i use a seal on the base and a second seal on the lid. |
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| Author: | Don Williams [ Sat Dec 02, 2006 4:59 am ] |
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John, I built one for myself as shown on my website here. I have since been building them with an aluminum/wood frame. It's more work, but it is a bit cheaper to do, and you can get a really good seal without having to coat the whole unit with poly as Michael said. Here are a couple pictures of one I recently made for Bill Greene: 
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| Author: | Bill Greene [ Sat Dec 02, 2006 1:14 pm ] |
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John: If these aren't enough photos for you, I'd be happy to take a few others and send them to you. You can get me via PM. I check in here often. Make sure to give me your regular email address. Don's dish is great - as is everything Don makes. Works like a dream. Bill |
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| Author: | John Elshaw [ Sun Dec 03, 2006 2:49 am ] |
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Hi Fellas, Thanks for the great info. I'm going to try and build a fixture like Don has. The only problem is I've never actually seen a fixture in person, so I can't visualize everything that is going on. I may be e-mailing you guys as I begin the process. One of the things I'm unsure about is all the bolts/screws in the top cover? Also, is the membrane only on top? I was thinking it's almost like a bag where it covers the entire mold, top and bottom, but after looking at Don's pictures, I'm thinking maybe not. Thanks again guys for your help! John |
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| Author: | crazymanmichael [ Sun Dec 03, 2006 5:11 am ] |
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the membrane is only on the top. the top is sealed to the base by closed cell tape. i just use closed cell weather striping ftom the borg, but you can of course use specialist vacuum tape. the dish sits on the base. place plate and braces on base, close and lock top, turn on vacuum source, membrane is molded over the plate and braces clamping them in place. open after 10 min or so and clean up squeeze out, close and release vacuum again for an hour or so. it is best to use a plexiglass or laxan sheet over the membrane for protection, and to seal the membrane to the top frame as shown in the phtos above. the sheet has to have holes in it as shown of course. the multitude of screws are simply to give a tight even seal of the membrane around the frame. the photos above are very self explanatory. |
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| Author: | j.Brown [ Sun Dec 03, 2006 6:18 am ] |
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What material is the membrane? |
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| Author: | crazymanmichael [ Sun Dec 03, 2006 6:34 am ] |
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there are a number of materials that can be used, e.g. latex, silicon rubber, vinyl. i currently use silicon rubber. latex is probably the softest, and thus conforms very well, but tendes to deteriorate fairly rapidly. the silicon rubber tends to be a bit harder, but still conforms very well, and lasts very well. i've never used the clear vinyl. |
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| Author: | Don Williams [ Sun Dec 03, 2006 6:51 am ] |
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What Michael said, except that I've had latex rubber in mine for about 6 years now with no signs of drying out yet. I too use the weatherseal material from Agent Orange, but have tried a fatter marine closed cell tape that also works well. You just need to adjust the hinge and sash locks appropriately for the thicker material. |
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