Over the years, I've come to realize that the analytical psychology of programming has spilled over into other forms of engineering disciplines. It seems whenever I have the time, money, and energy I wind up taking on pet projects that typically solves problems but more often are motivated by wanting to learn.
Not long after getting my driver's license, I quickly got hooked on the modified sports car hobby. It's been a while now, and like software development, I've stuck to it. For example, I've recently completed a full 5-speed transmission rebuild with upgraded parts. This, IMO, required a some engineering skills, a great deal of motivation to learn, the right tools, and ability to figure out mechanical problems from not-so-obvious symptoms.
I could've sent it to a shop for about $1000 to have it done professionally, but that would've been a failure in my eyes. I made mistakes and probably spent as much doing it myself, but was fully rewarding knowing I did it and I'm now driving it.
Where has your technical knowhow taken you outside of software? Provide some examples.