Vacuum Chamber Purchase/Size

[gamempire]

Tyler,

Please see this thread, where an active discussion is ongoing about laser cut grids: viewtopic.php?f=6&t=2914#p17937

I posted a technical drawing of my grid. Its not made of wire like most. Instead, it is lasercut. I'm not sure if you're in university, but if you are, you should be able to get your engineering school's machine shop to fabricate something for you on the cheap (most likely for free). I have the AutoCAD files if thats the route you'd like to go.

You can also get some good stainless steel wire from smallparts.com (search around the forum for proper thickness).

-Josh

[Tyler Christensen]

Stupid question, but are two grids used or just one? There are two designs in the "simplest fuser" document, one with one and another with two.

I believe I need to use two grids especially without a spherical vacuum chamber. Are there approximately 1" and 6" identical grids one inside the other with opposite charges?

[Andrew Seltzman]

The $1100 quote from Sharon Vacuum does seem about right.

I don't know exactly about their cost breakdown, but for the chamber for my fusor (6" hemispheres, 8" CF flanges, and 10 2.75" CF ports) they charged $350 for TIG welding and a leak check (I machined all of my own parts and has it sent to Sharon for welding).

Here is my vacuum chamber:
http://www.rtftechnologies.org/physics/ ... sphere.htm

That probably breaks down to about 3 hours at $100/hour which for a professional TIG welder is about on average, if not on the low side. They do an extremely nice welding job though so it is well worth the cost any you probably wont find anywhere less expensive.

For my vacuum chamber I spent:

For parts($200):
$50 for each of the two 8" rotatable CF flange
$30 for each of the two 6" hemispheres
$5 for each of the 8 of 2.75" CF nipples which were cut apart to make half nipples (8 non rotating, 2 rotating)

For tooling($155):
$80 for a boring head
$30 for boring bars
$20 for step drills to rough out the ports
$15 for sandpaper (200 through 2000 grit)
$10 for center drills

For welding from Sharon vacuum:
$350 for TIG weld and leak chack

Total:
About $700
It also took about 30 hours to build, and I had access to a lathe, mill, indexing head, and a reasonably well stocked machine shop (I still had to buy some tooling).

So for $300 max, you could conceivably do a 6" if you were really good at scrounging(Parts only cost me $200) and welding, or had someone to weld it for free. Most of the cost will come from the welding if you send it out to be done, but for something that complex to weld, I would recommend that it be professionally done.

Andrew Seltzman
www.rtftechnologies.org

[Tyler Christensen]

Where did you get your flanges for $50 a piece? Best I can find is $121, which is what your word document says on your documentation page. Was the $50 a typo in the post or is there a cheaper source?

[Andrew Seltzman]

$50 was from e-bay/salvage etc. One of them I got new from e-bay with a lot of vacuum parts for about $55, the other I got for slightly less, but it had already been welded to a pipe which had been cut off. I cut that off on the lathe and used the flange on the fusor.

$50 or less is the expected price if you find a used flange.

Andrew Seltzman
www.rtftechnologies.org