[Fred T]

I would say that you probably have a balance issue which is contributing to the problem. I don't like the sheet metal parts. Upgrade to the stronger support if you keep the 2 piece shaft. I agree with your shaft man on keeping the 2 piece. Whatever you do have it balanced, factory shafts, many times, are lousy on this.

I have two problems with the part you made. First is the tube should be thicker for two reasons. One is welding to the thicker ring. The other is it lacks the stiffness of the formed sheet. That's why the ridges are pressed in.

My other issue is welding a part subject to vibration. Welding starts cracks and introduces impurities, both of which contribute to failure from vibration. It's hard to tell from the pics, but it doesn't appear to have good penetration. Also, TIG welding is preferred, you get a cleaner weld than gas, stick or MIG.

The part you made should be good for a while, I just wouldn't depend on it for the long term.