In theory the next step should be adding a little filler and cleaning up all the joints before painting. Oh if life were only that simple!which was because I already knew what happened next...
It turns out that when I originally soldered the cab back on, I'd not done it very well. Having trial fitted the chassis into the model I noticed that the back wall was no longer vertical. While trying to correct this it fell off and for some reason the floor came loose too. I took the photo after cleaning up all the parts ready ro reassemble everything.
Rather than trying, and probably failing, to solder the rear wall on again I instead opted to use some two part expoxy. I started by using the epoxy to fix the floor into the right place as this gave a much bigger contact patch to then make sure the rear wall was fully attached. I also decided to change the approach to couplings and so cut off the Greenwich couplings while the model was in pieces.
Once everything was back together it was time to start applying some filler and that brings us up to date. It's been about a month since I added the filler and I've still not got around to sanding it back as I've been distracted by other things. Hopefully I'll get back to it soon and then I can move on to painting it.
This is something that shouldn't happen. I think it may be down to using modern solder. Try and get some old lead based solder, clean and tin the parts first then using the best flux you can find gently heat the parts with a small blowlamp. One of those that chefs use for caramelising sugar should be overkill. I wouldn't attempt to use a soldering iron for anything this small. Half the problem is the safety elves who set standards for things they have no experience of then make products so innocuous that they are useless.
ReplyDeletePS. Flux is important Bakers is good but Fluxite paste is better, comes in a green tin and lasts for ever. You may find some on E-Bay or carboot sales. You have to get rid of all the old solder as it oxidises and don't play the flame on the solder but on the metal adjacent you should see the solder flash along the joint. You will need a fixture of some sort to hold the pieces.
DeleteLead based solder is readily available, but if you are using lead free, the trick is that the initial melting point and point where it's properly liquid are further apart than the traditional material. It works, you just need a slightly different technique. However, there is no suggestion in the post that lead-free solder, so I suspect dirt in the joint that made it weaker. It happens to all of us, just clean up and re-solder.
ReplyDeleteNot sure I'd want to wave a blowlamp around there either. That whitemetal boiler could get a bit molten if the flame hits it. A 25w iron should be more then enough for these tiny joints. I have a 45w and it will cope with O gauge materials most of the time, I only resort to a gas flame for really big bits.
For flux, try Copalux from the DIY store which needs minimal cleaning or Powerflow from the same place that really does. Bakers will work, but needs even more scrubbing afterwards.
The solder I was using does have lead in it according to the label. Specifically I was using Carr's 179 No Clean Solder Cream which usually works really well. It even gives the element ratio as Sn62:Pb36:Ag2 so over a third lead in there.
ReplyDeleteMy guess is that I simply didn't use enough and probably didn't get it hot enough. If you remember back to when I fitted this part (see here) I did mention that the holder was acting as a giant heat sink. Couple that with the fact I was conscious of the lack of clearance for the chassis and didn't want a large solder seam so used as little solder as I thought I could get away and I think we can blame my construction technique rather then the solder.
I do have a small soldering torch but I've not actually tried using it yet. I should probably fill it and have a little practice session. Mind you as Phil says, I'm not going anywhere near the castings with a torch.
I forget how small these bits are. You shouldn't need to build up the joint if it flashes then it will be good. I wipe away flux whilst the joint is hot but then I'm usually patching old petrol tanks for vintage tractors, motorbikes and such like. I do purge them first and for about twenty minutes after I found that five minutes isn't always enough.
DeleteI've never really got on with solder cream, some swear by it, I swear at it. Give me a decent 25w iron, some 145 or 188 in wire form, and some 12% phosphoric acid and I'm a happy man.
ReplyDeleteI must admit that sometimes it works better than others. For example, I find it really useful when building track as I can add it between sleeper and rail, then hold the rail down tight while I apply the heat and it leaves a lovely join that needs almost no cleanup. In instances like this though where there is less contact area and it's hard to apply pressure while heating the join I do find it less effective, and I really should have known better than to rely on it in this case. Ah well, lessons learnt, which is as important as anything.
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