Filmwasters
Which Board? => Main Forum => : Kai-san September 13, 2022, 05:54:48 PM
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Haven't done this before, but there's a first for everything. Today I dropped the lid of a stainless steel tank on the floor, and it split apart. The light trap separated from the lid, it had been spot welded in three places. I will try to find somebody who can do spot welding, but there is hardly anyone here that will accept a private client. I'll have to try one of my contacts from my previous professional life to see if I can get in the back door. Luckily I have two other tanks that I can borrow the lid from. Let this be a warning, don't drop the lid on the floor. :)
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You could make your own spot welder...
https://www.instructables.com/DIY-Battery-Spot-Welder/
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Or you could either take it to an auto body shop.
And then, there's the François solution: JB Weld Epoxy 😁
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Thanks Pete and Francois! I could have built the spot welder without problems, but not just for this purpose. Plus I don't know what thickness of plates it can do. The auto body shop is a good idea, need to look into that. I'm more sceptical about the epoxy.... ;D
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Drill out the weld spots, pop rivet the pieces back together. Put a little bit of epoxy between the two pieces to help strengthen the connection and deal with any stray light leaks. The dimpled metal will guide the drill bit perfectly, so no worries about getting the two pieces positioned correctly.
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Drill out the weld spots, pop rivet the pieces back together. Put a little bit of epoxy between the two pieces to help strengthen the connection and deal with any stray light leaks. The dimpled metal will guide the drill bit perfectly, so no worries about getting the two pieces positioned correctly.
Yes; that's the first thought I had, and I have the tools to do it. It's the light leaks that worries me. On the other hand, if I get it spot velded it might as well happen again. I doubt that the pop rivets will break, so this might be the best solution.
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Drill out the weld spots, pop rivet the pieces back together. Put a little bit of epoxy between the two pieces to help strengthen the connection and deal with any stray light leaks. The dimpled metal will guide the drill bit perfectly, so no worries about getting the two pieces positioned correctly.
Yes; that's the first thought I had, and I have the tools to do it. It's the light leaks that worries me. On the other hand, if I get it spot velded it might as well happen again. I doubt that the pop rivets will break, so this might be the best solution.
There's enough surface area to put a layer of epoxy all the way around the area and seal up any light leaks. Use one that has a slightly thinner consistency to it (no putty), so it can flow into gaps. The rivets will just pull it together tightly and provide a mechanical connection in addition to the bond of the epoxy. It's a low stress application - it will be fine.
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Just checked my glue inventory, no epoxy. I'll avoid those who set in one minute, that's too fast. 5 minutes should do, the alternative is one hour. I don't know which is thinner, but it's not putty.
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Drill out the weld spots, pop rivet the pieces back together.
Just one word of warning though: Pop rivets are not light tight!
I used them in a pinhole camera and I had light leaks galore as the light makes it's way through the tube even with the pop bead fully in place.
I had to tape them up... not fun.
Though there is one thing to consider. JB Weld makes an epoxy putty called WaterWeld. You could just rough the surface near the spot welds and put a few beads of the putty there. The stuff is surprisingly good.
Also, you could look for a place that repairs pots and pans. Most of them will be able to weld stainless steel.
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There's enough surface area to put a layer of epoxy all the way around the area and seal up any light leaks.
Isn't that going to block the exit path of the chems? Isn't there supposed to be a gap between these two parts? Isn't that why the original welds were on raised points?
Epoxy normally dries clear(ish) so won't act as a light block. I would be tempted to put a a small amount of milliput black epoxy putty on each point before bringing the two parts together so it just surrounds the rivet. Then put some on the outside over the rivet head.
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There's enough surface area to put a layer of epoxy all the way around the area and seal up any light leaks.
Isn't that going to block the exit path of the chems? Isn't there supposed to be a gap between these two parts? Isn't that why the original welds were on raised points?
Epoxy normally dries clear(ish) so won't act as a light block. I would be tempted to put a a small amount of milliput black epoxy putty on each point before bringing the two parts together so it just surrounds the rivet. Then put some on the outside over the rivet head.
Drilling one millimeter holes are not going to obliterate the raised points, there will still be room for the chems to exit. But the real problem is on top of the lid where the weld points are very close to the collar for the small top cap. The collars on the rivets will block the cap from getting fully seated, so there will be leakage galore. Doesn't look good..........
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Drilling one millimeter holes are not going to obliterate the raised points, there will still be room for the chems to exit. But the real problem is on top of the lid where the weld points are very close to the collar for the small top cap. The collars on the rivets will block the cap from getting fully seated, so there will be leakage galore. Doesn't look good..........
I was thinking putting loads of epoxy everywhere would block the space.
How about drilling some new holes further away from the edge, using some extra long pop rivets and fitting a stack of washers onto the rivet between the two surfaces to keep them apart.
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Drilling one millimeter holes are not going to obliterate the raised points, there will still be room for the chems to exit. But the real problem is on top of the lid where the weld points are very close to the collar for the small top cap. The collars on the rivets will block the cap from getting fully seated, so there will be leakage galore. Doesn't look good..........
I was thinking putting loads of epoxy everywhere would block the space.
How about drilling some new holes further away from the edge, using some extra long pop rivets and fitting a stack of washers onto the rivet between the two surfaces to keep them apart.
I've been thinking the same, but I dont think I'll need the washers; the raised points will keep them apart as before. I assume the force of the pop gun is not enough to buckle the metal, it seems pretty sturdy. The challenge will be to get the holes drilled through both parts in alignment. I suppose I will have to find a way to clamp the two parts together so they dont move.
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Yeah, the space is required for the chems to flow through.
But I'd really avoid drilling holes as it's just asking for a light leak.
Some epoxies are opaque. Epoxy steel is gray, so is epoxy putty (though this one cures closer to white).
The best solution really would be to weld the cover again.
Hot riveting would be an option, but I know that it's well beyond my own skill set, so I'm aware that it's also beyond the skills of 99% of the population.
The good thing about epoxy is that it's a somewhat reversible process. If the lid breaks again, you can dremel out the old epoxy and go to plan B.
You could glue a small washer on each dimple and then glue the washers to the top, using a piece of cardboard as a centering spacer. That would be just as solid as the original and no drilling is required.
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You could solder the rivets to block light.
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I'm thinking of using Liquid Silicone Gasket to stop light leaks, it's pitch black and non-translucent. It can withstand temperatures up to 350C and is resistant to oil, glykol etc. I checked the data sheets for both silicone gasket and epoxy; both can react to acids and alkalines, no difference. Fixer is PH 5 (slightly acidic), stop bath is PH 7 (neutral) and developer PH 9 (slightly alkalic), these are approximate figures. I don't see a big problem with either. The pop rivets that I've got and which are readily available are made from aluminum. Aluminum can be soldered, but you need an iron that can provide heat in the 280C to 380C range and a solder with flux core. That's an option if the silicone gasket fails. Pop rivets can easily be drilled out if need be.
Any good advice on aligning the drill holes?
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Clamp the two pieces together, check alignment, then drill.
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The thing with aluminum and steel is that you will get electrolytic corrosion between both elements.
Even stainless will corrode with aluminum. What's most likely is that over time you will get a bunch of brittle aluminum oxide around the rivets.
Also, you don't want to have a spot where chemicals could leave a trace that would contaminate other solutions...
While drilling would make alignment fairly easy in a way, I really don't feel like it's a wise thing to do.
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If you don't like aluminum rivets, screw them pieces together with stainless steel hardware. A drop of blue Loctite, or lock washers, will keep them together.
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So I had to do some more research today. As for corrosion of aluminum from chemicals there is little risk; a PH level between 4 and 9 is ideal, and most photographic chemicals are within that range. Then there is galvanic corrosion between metals. Some metals have a positive electrode potential (cathode) and some a negative potential (anode). Positively charged particles move from the cathode to the anode, and the anode gets the major share of corrosion. The larger the potential difference is, the more corrosion. Both aluminum and stainless steel have a negative potential and there is little difference in potential, hence little corrosion. The aluminum has the larger negative potential of the two, so if there is corrosion it's the aluminum that gets eaten. I checked online with a manufacturer of fasteners who says that stainless steel fasteners are increasingly used for aluminum.
Now I understand the worries about drilling holes in the lid, but I think the problems of getting this thing welded is underestimated. The laws and regulations here are such that mechanical workshops can only sell their services to registered companies. Independent car body shops are almost non-existent, and they are not cheap. I haven't seen anybody repair pots and pans since the early seventies and that was done by travelling gypsies. They have been marginalised and harassed by the state.
As I said yesterday I will use Liquid Silicone Gasket and try to minimise contact between the two metals. If the aluminum rivets gets eaten, they can be replaced. The biggest worry is space for the rivets, the margins are small on both sides.
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I must admit that space is at a premium on those parts.
I'll have to try and think of something else...
Custom 3D printed insert maybe?