I would have to see the testing device, the way you bulit the "test triangles", and a whole lot more before I would believe your story. No properly brazed silver joint will fail before the tube in an impact. Seen lots of them. Seen more broken joints (where tube did not break but braze joint did, which is just as wrong with brass as with silver) on brass brazed frames than with silver by quite a large margin. I've seen a good number of relavatively poorly brazed silver joints not fail after impact. It sounds to me like you tested a bunch of improperly brazed silver joints. Probably better to use brass in that situation, but properly silver brazed joints have at least equal strength to those of brass.
For those of you out there who do not or have not built a good number of frames; there is no way to really decide which information is closeset to the truth. Since I happen to know what I've seen and experienced, I know for sure I don't buy this particular story.
It is obvious that good bikes and excellent bikes can be made useing either method and that the primary factor in that is the ability of the builder and their intentions towards producing a quality product. But there is such a thing as reality. 700 frames a year is not the place for silver. Silver is for those individually producing handmade frames with traits and features that aren't part of low production work. It's a different world, different circumstances. Like I said, good that you did some testing and concluded that for your circumstances brass worked better for you. Silver works better for the type of work I do.
La Mesa, CA
Show me, talk is cheap.
I came into this thread late but I thought I would share a couple of tidbits. In the mid-80s, when we (Davidson Cycles) were building around 700 frames per year, we wanted some idea of what was going to happen to them in a crash, so borrowed a destructive testing device (I forget who had it. Bicycling Mag, maybe?) that simulated a front end crash. Made a bunch of front ends to test in it, with all different materials and methods but otherwise the same, and found, almost without exception, that the joint failed (came apart) when done with silver, and the tube failed behind the intact joint when brazed with brass. What does that tell you? Well, given a hard enough impact you will destroy a steel bike no matter, but the brass did make a stronger joint. Yes you can braze at a lower temperature with silver, but if you are burning the snot out of it getting it to move around then you will do a lot more harm. I think an experienced builder using brass will build a much superior bike to a rookie with silver.
It is not only the absolute temperature that is reached that degrades the steel, it is the length of time at that temperature. The longer it stays hot, the farther away from the joint the heat affected zone travels. It is that margin of the heat affected zone that is where a frame will usually fail in a crash. Keeping it closer to the lug, in the butted section, makes it more likely to withstand a crash. So brazing it quickly is the answer to making the strongest frame. We developed a way to braze them very quickly. We don't do a lot of lugged steel frames any more so I don't mine sharing the tricks. We made little rings of brass that were the shape of the inside of the joint, and assembled the frame with them in there. The joint is heated quickly and evenly with a large, broad flame until red hot. You can see the brass ring in there as a shadow. Once it is gone you know the brass has melted, we switch to a small torch and work the heat around until brass comes out all the edges evenly, and voila, you are done. Almost no cleanup involved afterwards. A few of our brazers would use the big torch in one hand and the small torch in the other. We had fork crowns made with a shelf that the steerer butted against, and stamped out washers of brass that fit right in there and did the same thing for the crown to steerer braze, and had rings inside the blade sockets too. Two guys could braze up 30 steerer, crown, blade assemblies an hour that way. Again with almost no cleanup. And it leaves a little fillet of brass on the inside of the joint too to further strengthen it. You would never get penetration that good by brazing from the outside only, and not nearly as fast.
Another tidbit, and all framebuilders know this, but 853 Reynolds is always brazed with brass. It doesn't get hot enough for the air-hardening to happen with silver.
Elliott Bay Bicycles
2116 Western Ave
Seattle, WA 98121
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