feedthrough to inner grid connection
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Vikram Singh
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feedthrough to inner grid connection
so below are some pictures of my hv feedthrough and i was wondering i just solder on the inner grid right and this is for star mode and what kind of the material is the easiest to find locally for the grid i was thinking of mig welding wire ? any suggestions and i know for the other side of the feedthrough that hooks up with the nst i am using a wire clamp and do i need some kind of insulator on the feedthorugh to prevent arching? kind of a noob to the whole feedthrough( however i was successfully able to wire nst and variac and diodes
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Richard Hull
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Re: feedthrough to inner grid connection
It is better to mechanically mount the inner grid. I would use a tiny collet with micro set screws to attach the grid. Simple soldering would melt and silver soldering (brazed) would be OK provided you used pure silver.
Richard
Richard
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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Vikram Singh
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Re: feedthrough to inner grid connection
so for the inner grid is it okay that i use 308 stainless steel and i have 45% silver brazing alloy for the solder. I can solder together the grid right?
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David D Speck MD
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Re: feedthrough to inner grid connection
Vikram,
The grids of a fusor often run at a red heat. As Richard pointed out, most grids are assembled by mechanical means with set screws. Other fusioneers will spot weld their grids together.
If you really want to use a soldering / brazing process, you will need a very high temp brazing material, or the grid will come apart when the fusor is energized.
Richard suggested you could assemble the grid with pure silver, which melts at 962 C. It might be difficult to get a good braze joint at this temp, but it would withstand a pretty high operating temperature. Ordinary brazing materials melt at around 400 C.
Dave
The grids of a fusor often run at a red heat. As Richard pointed out, most grids are assembled by mechanical means with set screws. Other fusioneers will spot weld their grids together.
If you really want to use a soldering / brazing process, you will need a very high temp brazing material, or the grid will come apart when the fusor is energized.
Richard suggested you could assemble the grid with pure silver, which melts at 962 C. It might be difficult to get a good braze joint at this temp, but it would withstand a pretty high operating temperature. Ordinary brazing materials melt at around 400 C.
Dave
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Vikram Singh
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Re: feedthrough to inner grid connection
So I am building a demo fusor with max voltage at 7 kv and so 400 C is not enough?
what temperature does the inner grid get to?
http://www.harrisproductsgroup.com/en/P ... v-45T.aspx
this is the stuff i have i believe it is rated at like 650K
what temperature does the inner grid get to?
http://www.harrisproductsgroup.com/en/P ... v-45T.aspx
this is the stuff i have i believe it is rated at like 650K
Re: feedthrough to inner grid connection
For a demo fusor at 7kV you should be fine with solder. We have used regular soldering (melting point around 370 C) up to 400W and it worked fine. You just can't run the fusor for a long time successively.
If you let the grid warm up to much it might sag a little. But with 7kV (and low current) you should have no problems.
A mechanical mount might be a better idea though, I believe the outgassing from soldering isn't very good either.
edit:
Am I correct to assume that you only want to solder the grid to the feedtrough, and that you bend the actual grid from 1 piece of wire?
Because if you want to make a grid from multiple pieces of wire and solder them together, that might not be a good idea. We tried that too, but it fell in pieces after a while.
If you let the grid warm up to much it might sag a little. But with 7kV (and low current) you should have no problems.
A mechanical mount might be a better idea though, I believe the outgassing from soldering isn't very good either.
edit:
Am I correct to assume that you only want to solder the grid to the feedtrough, and that you bend the actual grid from 1 piece of wire?
Because if you want to make a grid from multiple pieces of wire and solder them together, that might not be a good idea. We tried that too, but it fell in pieces after a while.
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Vikram Singh
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Re: feedthrough to inner grid connection
thank you for this feed back yes we are using a spiral grid so no soldering there and i will definitely use the solder because i am having difficulty finding the mechanical mount.
Furthermore how did you attach the wire to the other side of the feed through
Furthermore how did you attach the wire to the other side of the feed through
Re: feedthrough to inner grid connection
The outside of our feedtrough is different from yours (we use a special spark plug) but I guess you could solder it. Just make sure you put very good insulation around all exposed HV surfaces.
Also make sure that the wire is not held in place only by the soldering, so that in the case of melting the soldering the wire won't swing around freely.
Also make sure that the wire is not held in place only by the soldering, so that in the case of melting the soldering the wire won't swing around freely.