Tonight, I finished all the staging point throw bars. This followed the same springing scheme I explored with a proof of concept a couple of weeks ago. As I was finishing the last one, I thought to myself that not only was I in danger of almost knowing what I was doing, but that perhaps the design isn’t as good as I’d thought after all.
Andrew and I had concluded that the design should be an improvement over the bent wire spring because the wire spring would bear against the sides of the holes, and eventually wear them out. Well, as I was playing with the last one, I noticed that this design rubs a little brass wire against a piece of phosphor bronze. So, they should get softer with time too.
Well, anyway, here is what I learned over the course of six of these sprung throw bars:
- To solder the point to the throw bar, it is best to place a little dab of flux, and a tiny piece of solder against the foot of the point. Then, heat the area with the soldering iron, rather than the resistance soldering unit. The RSU seems challenged with getting current through the narrow head of the point.
- Test the points again after they are soldered to the throw bar. The diverging point, in particular, seemed to want to bend away at the tip for some reason. Heating them again with the soldering iron while they were against their stock rail seemed to take some tension out, and the fell back in line.
- Once the throw bar is working nicely, push the sprung headblock up against it and test it. There was always enough friction to hold them in place, and this seemed to be about the right amount of tension. Too much tension seemed to distort the points.
- I held the spring headblocks in place by hand, applied a little flux and solder and zapped ’em with the RSU. A couple took a second try to get the tension right, but that was okay by me.
I also added a few more extra-wide ties and cut all the gaps. Well, I believe I cut all the gaps. I’ll run around with the meter after the flux rinse is dry and check. Once that is assured, I’ll trace the various PC board pieces and pop all the track up so I can route out reliefs for them.