Brass Swingarm

I Can't Weld; I Can Solder.

This isn't my best work.


I had looked into TIG welding, the cost of the equipment, the time it would likely take to learn how to do it and considered the fact that I really had no place that I could set up a TIG welder even if I committed to the money and time.

The cost of the brass tubing for this test piece was far more than the cost of the 4130 steel for the actual part; working with brass opened up the ability to connect relatively strong tubing with a rather weak method. This would let me test my thoughts on stress points much in the same way that my habit of playing with wood or Styrofoam models had in the past.

I hadn't designed the final version of this part yet for a simple reason: without having computer modeling as an available option I was taking it on faith that I would be able to figure out how to route this part around the components of the frame that I had designed and had made. As it turns out you can likely see what I hope will be considered another tribute to another frame builder's approach to connecting tubing. This worked quite well for maximum strength; it meant mitring requirements went from good and rotationally variable to ludicrously precise and definite but I couldn't go back to the idea of simply fish-mouth mitering and butt-welding the tubing once I saw this as the option. I figured this out the way I've solved a few of the issues I've run up against. I took a bath.

I was using some modeling clay and a test piece of Titanium round bar to try to figure out how to mitre two intersecting tubes at a compound angle... seeing an empty toilet paper roll gave me the idea of encasing them in a cross brace. It was then that I saw the similarity to some of the industries most recognised tube mitering style*.

I built the swingarm on the bike to make sure everything lined up. I tested the approach that I was going to use to make the Titanium parts**. Once I had everything figured out I soldered it together using fine flux core electrical Sn-Pb solder and a propane torch in my bath tub... uh... welding studio.


*Please be understanding in court.

**Titanium was still the plan.