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Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Grenadier wrote ...
So next up is soldering. Not sure how I'm going to do that, may have to borrow a 100w solder gun from someone. I'm going to have to drill an aperture hole in this box, but it'd be useless without one. I also wonder how I'm going to drill a 1.5" hole in hard lead. Maybe I'll have my school's tech dept CNC one.
You could drill a hole large enough to get a rat's tail needle file in, and then work it up till you can get the next size file in, and/or drill a circle of holes, and join up the dots. Drill very slowly to avoid melting and keep the swarf in spirals.
Some angle irons inside and out would hold those corners nicely, as well as providing sound anchor points for grab handles, or mountings of some kind, and adding a bit more shielding.
Some folks might say you've gone a bit over the top, and could have used less Pb, but not me. It's important for peace of mind to be totally confident in your shielding, and if that means erring on the side of caution, so be it.
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
I never thought of using a file, thanks PM. A dremel with a cutoff wheel could work too. I can't cut anything until I solder this box togrther though, and I'll try to get that done next week. But I have a problem... Where will I get some 60/40 plumbing solder? All I can buy now is that crappy lead free stuff.
After I build the lead box, the woodworking will be the biggest job. I have no time to get into my school's woodtech dept though. Maybe before hours I could, provided a teacher would be willing to go to work at 5:30...
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Grenadier wrote ...
I never thought of using a file, thanks PM. A dremel with a cutoff wheel could work too. I can't cut anything until I solder this box togrther though, and I'll try to get that done next week. But I have a problem... Where will I get some 60/40 plumbing solder? All I can buy now is that crappy lead free stuff.
After I build the lead box, the woodworking will be the biggest job. I have no time to get into my school's woodtech dept though. Maybe before hours I could, provided a teacher would be willing to go to work at 5:30...
I think you may get into difficulties if you try to solder the corners of your slab cast box. Heat will be conducted away from the joint so fast that I doubt that even a 180W iron as used in stained glass etc would be able to make normal soldering possible. An iron which had the wattage to keep the solder mobile as you moved along the seem would probably start melting big holes in the work. There are folk on this forum that know more about brazing and such than I do, so hopefully one of them would share their thoughts with you. If you are going to use solder, it would be plumber's solder that you should be after, much thicker than the electronics grade.
Beyond using cornerless lead cyclinders as I suggested above, how would I tackle the box problem? Probably with the reinforcing angle irons I suggested above on the outside, and perhaps with lead sheet bonded with epoxy on the inside of the corners.
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
Hmm, I think I'll just get a pencil butane torch then. I had one but the butane tank cracked. :( I don't think it would melt holes in these plates, they have quite a lot of thermal mass.
Of course I meant plumbers solder. The problem is I can't buy 60/40 plubers stuff anywhere. There is lead electronics solder here aplenty, but it would take a whole lot of that to weld this together.
I could also just JB weld the hell out of the box too. That stuff is very strong, and oil-proof. Actually I'm going to do that. JB weld or liquid nails would make putting this together very easy and cheap. Then I could use lead sheet on the inside seams to prevent rays from getting out.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Well, the solder and like likely melt at the same temperature or thereabouts, so in order to get the solder to melt, the lead would have to be close to the same temperature. The large thermal mass only means that it is that much harder to get the lead up to temperature. Maybe it will work, i have never done such a thing .
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Grenadier wrote ...
Hmm, I think I'll just get a pencil butane torch then. I had one but the butane tank cracked. :( I don't think it would melt holes in these plates, they have quite a lot of thermal mass.
Of course I meant plumbers solder. The problem is I can't buy 60/40 plubers stuff anywhere. There is lead electronics solder here aplenty, but it would take a whole lot of that to weld this together.
I could also just JB weld the hell out of the box too. That stuff is very strong, and oil-proof. Actually I'm going to do that. JB weld or liquid nails would make putting this together very easy and cheap. Then I could use lead sheet on the inside seams to prevent rays from getting out.
I don't know the glues you mention, but will say that surface preparation is everything with adhesives if they are to perform well.
Of course, X-rays can degrade polymers much as solar UV can rot car tyres and discolour plastics in hot countries, but I can't see this being a problem at the doses likely to be absorbed by the adhesive on the reverse side of your lead corner overlays.
I've been trying to learn about the possible production of hazardous organolead compounds that might be liberated by a reaction between the different sorts of resins and lead shot/granules in the making of castable shielding, but as I know even less about chemistry than I do about electricity, I haven't come up with any very reliable-looking conclusions yet. The anti-knocking agent tetraethyl lead is the most famous organolead compound, and there's no keeping company with it, as we all know.
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
Well JB weld is a two part epoxy, and it's very strong when hardened. It's what I used to put together that light emitting antidiode.
Liquid nails is a cyanocarylate based adhesive, and it's crazy strong when hardened. It's often used in construction now when laying floors and ceiling tiles. Sometimes it's even used to hold down flashing and roofing shingles.
As for surface prep, a dremel + a 60 grit wheel would roughen things up quite nicely.
I would stay away from organolead compounds proud may as they are much more toxic than lead metal itself. Just like methyl mercury is much more toxic than mercury metal.
If you want to make castable sheilding, or even better yet a sheild made of a clay like material, why not try lead powder? It could easily be mixed with plasticine.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
The epoxy sounds right, and the lead internal corners should stiffen the box a bit too. I believe lead can be expected to deform under its own weight over time, so bracing the corners can only help.
As for lead toxicity, I feel confident about working with the metal when wearing gloves, but as you say, the organolead compounds should be avoided at all costs. It's a shame, because the big shielding companies are able to produce a clear water-white acrylic with 30% by weight of lead as a dissolved organolead compound, but there's no way that the little guy could reproduce the safety conditions essential in this kind of chemical process.
That's why I've turned to the idea of castable shielding using lead shot - not my idea, but one that lends itself to low risk small scale production. As a variation on this, I have several low power XRD tubes intended to operate inside an oil cooling jacket, and am looking at the oil flowing through lead shot inside the jacket, which will not only cool the tube, but increase the average density of the lead shot shield.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Grenadier wrote ... I also wonder how I'm going to drill a 1.5" hole in hard lead. Maybe I'll have my school's tech dept CNC one.
A bit late for this comment, but the easiest way would be to put a 1.5" round core in your mold before the slab is cast! Could be some plaster of Paris hardened in a drinking glass, or a metal pipe or stack of washers that could be knocked out with a hammer, or a tin can full of sand... With your open-face mold, consider buoyancy of the core.
Also you can use an ordinary hole saw. Keep it cool with a dribble of water while cutting.
As for joining: Did you make some spare slabs for bonding practice? I would put a test bond in a vise and break it on purpose. Bet that a solder bond would be MUCH stronger and more ductile than JB-weld on a lead surface, however prepared. I think you could do the job with tin/lead solder and a butane torch -- don't forget to use flux. Know your melting points.
Could also assemble the box with screws to carry the load -- then seal the seams with material of your choice.
Will your machine be restricted to horizontal or vertical x-ray beams?
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Grenadier's big thread of Röntgen related shenanigans
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