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Re: Easy Inner Grid Fab

Posted: Mon Dec 11, 2017 1:23 am
by Silviu Tamasdan
Was searching for something else and came across this old thread. And an idea came to me. It would be useful only to those with big fusor chambers (I'm looking at a small grid, probably 2cm across only for my small chamber so I wouldn't be able to use this method).

Ping-pong balls.

They're AFAIK still made of celluloid. Which is nitrocellulose with a low degree of nitration. It doesn't explode, but it burns very very quickly, and leaves no residue. And it's rigid enough to withstand some pressure.

Wrap the grid wire over a ping-pong ball, then set it on fire. Done.

Re: Easy Inner Grid Fab

Posted: Mon Dec 11, 2017 9:40 am
by Dennis P Brown
My grid, like most people's, is made from very thick steel wire that is more like a small diameter rod. Bending it into shape requires very large forces. I used an Al cylinder and wrapped it with the rod using four turns ( the cylinder held in a vice horizontally.) I removed the "coil" that was formed and placed one of the single turns in the vice. Then using vice grips, bent the other three loop's these (with a lot of force) into a 'spherical' set of loops. Took less than ten minutes and no welding.

The final product can be seen here in this recent post: viewtopic.php?f=6&t=12025

Re: Easy Inner Grid Fab

Posted: Mon Dec 11, 2017 2:42 pm
by Silviu Tamasdan
Why SS and not tungsten? There is excellent tungsten wire available fairly cheaply. I personally am making my grid from "surplus" 0.0275" tungsten wire which I bought from the "orphan bin" at Midwest Tungsten

In particular I use the OB-18 on that page. It consists of 9 wires braided, 12 inches long. They can be very easily unraveled, and you get 9 lengths of 0.7mm tungsten wire for $1.80 (granted they have a $40 minimum order - used to be $25 when I bought it a number of years ago; but they have other interesting items there, such as molybdenum sheet, tungsten rods, thicker wire etc; the selection varies over time, but the OB-18 is present constantly and has been for 12 years) The OB-57 may be interesting too for making a cylindrical grid without too much trouble - I have a few of those too.

This wire is quite ductile and doesn't break easily. After unraveling it's wavy and needs to be straightened but that's easy to do. Last evening I wound one of these by hand (look ma, no tools) on a 2cm cylinder and there was no breakage at all. I then straightened it and wound it again on a 1cm cylinder, again no breakage. The ends of the wire are a bit fragile and can exhibit some minor chipping if you try to give them a sharp turn.