Follow-ups to the questions:
Fixturing it so the joiner is vertically oriented does make it easier to braze, but it’s not necessary if you have everything else just right. I don’t have any thin silver braze material, so making a loop preform isn’t happening. So, I clean meticulously, then flux everything, then heat the joint and dab the end of the thick brazing rod. It is easy to overdo the amount of material and make a messy job. This one turned out fine. There is a nice even fillet on both sides. Using a close-fit hole in the arm (+.003ish) helps control the capillary braze flow and the effects of gravity. And, if everything is really, really clean you can get the heat on it and watch for the top fillet formation. Then get the heat off immediately. Chances are good that the bottom fillet is complete at that point. The added picture shows the fillet on the opposite side.
The hole thru the fixture block is a firm push-fit for the joiner wire. The collar was used as a precision stop, and only needed because I already had all of the airplane structures built, and I needed to get the arm in exactly the right spot or I would have to start making changes to the elevators. The collar was not intended as a heat sink, nor was it needed.
The horn I showed is a replacement for a defective unit on an SV-11 ARC. It is quite short, but I will use formed brass stock to wrap around it and insert into the stab TE. No tubes required. I used 1/8” music wire for this one. I locally heated the wire where I wanted the bends and formed them hot, then allowed to slowly air-cool. Even annealed, the wire is robust. Since you are actually brazing and not soldering, you will have already heated the center portion of the joiner to the point where it is likely annealed. Be aware that some of the silver brazing rods have a melting point of essentially the annealing temperature of the parts, including A2. Note that the condition for the A2 drill rod you are likely to buy is fully annealed. So compare the annealed strength of the music wire that of the A2. Finally, remember that the stiffness of the wire is not changed by temper, just the yield point. A2 looks higher according to my table.
If you are in hurry to build or finish a plane, then paying someone else for a completed piece like a horn is usually worth it. If you can’t get exactly what you need, then making one is often your only choice. Of course, if your shop is already filled with tools and materials you have collected over the years and just waiting around to be used for something, then making your own parts may be also be cost effective--as long as you enjoy doing it. If you don’t, then by all means order the parts from Brodak!
Dave
Topic: Brodak prices (Read 11689 times)