Tuesday, 31 May 2011
I wasn't 100 percent happy with the fit-up of the seat tube socket on the bottom bracket of Ben's bike. The casting was just a bit more sloppy than what I'm used to using with 56% silver.
The issue here is that 56% silver is not at all forgiving of gaps. It flows like water (which is a good thing, as I can get really good penetration when everything is just so), but has practically no ability to fill.
So I asked for advice on the framebuilder's list, and was pointed in the direction of System 48 filler and flux, by Wade Barocsi of Cycle Designs. This stuff is still a silver filler, but is formulated so it's got an ability to fill a little. Like 56%, it's revoltingly expensive. I do wish people wouldn't speculate on silver and push the prices up.
In use it's clearly more viscous than 56%. You've gotta give it encouragement to draw it through the lug. It does though, and the result is really strong, without having to go to higher temperature fillers like LFB. The cable guide on the other side is held on with 56%, and I didn't reflow this join.
The picture shows the result, immediately after soaking the flux off and prior to any clean-up, so it still looks ghastly. You can see it's penetrated 100%, and also that I was a little on the generous side.
Another thing you can see here are pins. I pinned this join, and soldered it out of the jig. I'm quite happy with the result - it's a hell of a lot easier to get access.
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