In the "keep alive" thread Doug posted about his latest work on HV feed-through. This post was intended as a reply to that (hence the intro stuff) but that thread is locked and most of this probably fits better in this section.
Reference to that post: viewtopic.php?f=42&t=980#p5839
___________________________
Doug,
Sorry to hear you had some health issues but very good to learn you are OK now.
You mentioned missing recent posts. Maybe you know this, but on the BBS main page, near the top, you can click on "View active topics" to see all the recent posts. Default period is the last week but you can adjust it up to a year if one hasn't visited the forum in a while. That's the method I always use when checking a phpBB forum.
It was good to see the description of your latest HV feed-through. I'm very slowly working toward building a fusor. The chamber I plan to use is cylindrical, so I plan to employ a lot of the techniques you developed: grid style, and feed-through being the biggies, so far.
I wonder if I might trouble you with a few more detailed question about this feed-through.
-- You said the Cu rod was 14" x 12.75". I assume that was a typo and should have been 1/4" x 12.75".
-- On the aluminum end cap, about how long did you make the section that fits inside the glass tube?
-- I think the BN rod extends past the end of the glass tube. If so, about how far past the end of the pyrex?
-- (You did mention the Cu rod extending past the BN by 1/4". Just noting that I saw that.)
-- I'm curious if you did anything on the Cu / aluminum connection to allow for venting to aid any slow virtual leaks when evacuated? Maybe that's just not really somthing worth worrying about.
-- When you have the feed-through in its operating position, about how far does the glass project into the chamber beyond the inside wall? And, accordingly, about how much glass between the coupler and the aluminum end cap on the outside?
I had already been planning to make a feed-through based on your earlier work. I decided to go with 1.25" OD borosilicate tubing to keep the BN diameter requirement to 1". The ID of the glass is on the order of 0.93". So I got the tubing and a CF/compression fitting for 1.25". I haven't had the guts to order BN yet.
Being reminded, I just checked McMaster's BN page again. The 1" dia x 12" rod is $368 but I see they have 1" square x 12" for $302 -- $66 less. They both require lathe work. The effort and scaryness of knocking the corners off is probably justified at $66 worth. (I'm not paying myself per hour.)
-- I've never tried to cut big thick pyrex tubing and the pieces I've got need to be cut. Do you do that in a lathe with a diamond wheel? Any tips on technique?
Thanks for all the sharing you have been doing over the years. As you can see, I'm planning to steal extensively from your work.