Vacuum Chamber Construction

For posts specifically relating to fusor design, construction, and operation.
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Dennis P Brown
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Re: Vacuum Chamber Construction

Post by Dennis P Brown » Sun Jun 07, 2020 5:19 pm

Very pleased to hear it all worked out - both literally and figuratively.

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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause » Thu Jul 09, 2020 4:42 am

Just a quick update. I've got the chamber all assembled, and sitting on its frame. While I'm sure in the future I'll like having so many ports, at the moment it's mostly a lot of tedium anytime I try and put it all together. This is the second time putting it together today as earlier I was nearly done, but ran into some problems again with bolts biting into threads on the top port. Rather than fuss about with it, I disassembled the top half and drilled out the threads on every hole up top. Don't have to worry about that problem again! Tomorrow I plan on tightening up all the bolts, and pressurizing the chamber with a bike pump I have handy. I'll use a soap and water solution on the joints to check for any major leaks.
IMG_1104[1].JPG

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Dennis P Brown
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Re: Vacuum Chamber Construction

Post by Dennis P Brown » Thu Jul 09, 2020 11:14 am

Your system looks absolutely professional and you've obviously become an expert machinist, as well. I'd find it hard to believe that you'll see any leakage using pressure/soap because that system is too well made to exhibit any significant leaks. Look forward to your further posts.

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Richard Hull
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Re: Vacuum Chamber Construction

Post by Richard Hull » Thu Jul 09, 2020 1:22 pm

I'm glad you took my advice on just drilling out those threads to make it thru-hole. Threads are great and even demanded in tight or ill-designed conflat mountings, but plain holes with clearance warrants that a bolt that is snapped off in no problem. A messed up nut just be cut off without having the hassles you have had with stripped or damaged threaded flange holes. In addition, thru-holed flanges are cheaper.

My motto is design with clearances so you can use common hardware bolts, if you can, and use thru-hole flanges.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Rich Feldman
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Re: Vacuum Chamber Construction

Post by Rich Feldman » Thu Jul 09, 2020 2:05 pm

Anybody here using nut plates instead of single nuts, to use fewer wrenches and lockwashers?
CF-Flange-Plate-Nuts.png
CF-Flange-Plate-Nuts.png (75.69 KiB) Viewed 288 times
https://apexvacuum.com/product/conflat- ... late-nuts/
All models are wrong; some models are useful. -- George Box

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Frank Sanns
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Re: Vacuum Chamber Construction

Post by Frank Sanns » Thu Jul 09, 2020 3:00 pm

I use those on my 2.75" flanges. They work great especially since I have so many connections of that size.

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Richard Hull
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Re: Vacuum Chamber Construction

Post by Richard Hull » Thu Jul 09, 2020 7:03 pm

I use them on all my 2.75 conflats just like Frank. They are a real time saver, but at $6 or more per set of 3, I have never bought any as regular nuts are just fine. All that I have came off a number of surplus system disassembly efforts in the past. I guess I have about 4 full sets on hand. I used them on the abortive fusor V alpha. Now dismantled, I have them all at my disposal once again. I have 100's of nuts on hand. These plate nuts are handy for through hole flanges where a wrench to be placed on a nut for tightening is almost impossible to get to. They do serve a glorious purpose at times. To conserve the few I have, I have been known to use one in tight spaces and 4 regular bolts and nuts on the easier to reach parts of a flange. There are no vacuum police to regulate how they are used.

As far as I think, based on what I have and need in future, I'll probably never have to actually purchase any plate nuts.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause » Thu Jul 09, 2020 11:31 pm

Dennis I appreciate the kind words, but reality is a harsh mistress. Looks like I'm going to be redoing some of the welds!
IMG_1106[1].JPG

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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause » Fri Jul 10, 2020 12:41 am

I was concerned about missing leaks on the underside of the chamber since a lot of the soap solution had dripped off, so I just completed a second leak test in the bathtub. Virtually all of the leaks appear to be coming from one of the main rings on the hemisphere. I'm unable to see any other bubbles from the underside to that's nice, there were also a couple of small leaks from some conflat seals I evidently hadn't tightened enough.
IMG_1107[1].JPG

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Rich Feldman
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Re: Vacuum Chamber Construction

Post by Rich Feldman » Fri Jul 10, 2020 12:54 am

Good clean toes. :-)
Assuming the main ring welds aren't leaking ...
Is it possible that a thick steel ring was rendered non-flat, beyond tolerance, by the welding operations?
I guess that could be checked by assembling without Cu gasket, all bolts finger tight, and check the joint all the way around with thin feeler gauge.

Would an elastomeric seal tolerate more non-flatness than traditional copper ring?
All models are wrong; some models are useful. -- George Box

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