Jebus... you may be my long lost twin.
I made my living as a Steamfitter (known in some places as a Pipefitter) until I was forced into early retirement by a broken neck and a destroyed shoulder.
For 30 years, guys bitched about the stock location of the oil filter on Harley-Davidsons as it's a huge pita. I laid awake nights for years trying to solve it, with no intentions of going into any kind of business. I just wanted to make my life easier. Once I did, guys started asking me to do their bikes and then other guys asked me to do theirs, etc.
Then guys with other models of Harley asked could I do something with their bikes, and I could.
Then the chopper and custom crowd asked if I could do various parts for them, and I could.
Now I do oil coolers as well that are unlike others for bikes. And it all started with my knowledge of fluid dynamics and heat transfer from my former life. I was also a certified pipe welder but my vision isn't good enough anymore. I can still stick 2 pieces of mild steel plate together with good penetration and a respectable bead, but that's about the extent of what I can do. I now leave the difficult welding to people still good enough to do it right. That was a pretty tough pill to swallow but once I finally swallowed it, it stayed down okay. A man's got to know his limitations.