In earlier post, I talked a little bit about the benefits of different joining methods. I've talked to various frame builders as well as metal fabricators in the area, and have come to some interesting conclusions regarding strength and endurance of different joints. Traditional thought would suggest that TIG welding is the strongest joining method; whereas with brazing there is simply a different metal compound that more or less 'glues' the two pieces of metal together, welding actually joins the two pieces into one.
True Temper, a well know fabricator of high quality golf clubs (and lesser known, bicycle tubing) engaged in a test of the 3 different joining methods: TIG, fillet, and lug. Each tests examined the strength of all the different joints without changing the quality of the joint (i.e. having a fixed frame builder for all 3 methods equally experiences in all techniques) or the forces of the test. Fillet and lug brazing both out lasted TIG in True Temper's test. A few conclusions were reached:
1. The greater temperature that TIG inflicts on the steel compromised the strength of the welds to a noticeable degree.
2. Though strong against blunt trauma, TIG as a long standing process did not hold out as long against constant applied pressure.
3. Silver brazing rod was far superior to brass brazing rod in both fillet and lugged joints. Being better at penetrating the grooves between miters and lugs, the surface area covered by silver was a significant improvement over brass of the same quality.
Though TIG was weaker as a lasting joining method, it was not by a considerable margin. All 3 joints proved to withstand the pressures that the average cyclist inflicts on them, leading to some other frame failure before joint failure.
Beyond strength, there are other benefits. With TIG and fillet, there is more freedom with different sizing and customization of the frame geometry due to the precision of the miters. With lugging, each tube is easier to replace if damaged. Aside from this, joining methods often boils down to aesthetic choice.
Finishing details on the frame drawing (or at least the first one.) Will post pictures when completed.