If you're lucky, you have fond memories of your grandpa. Everyone's family is different, but my grandpa was absolutely a guy who liked to build things. He was a curious person, and a tinkerer, and a consummate DIY-er (probably long before that phrase was a thing). It was just who he was; a trait that was baked into every fiber of his being.
While I do remember my grandma teaching me to sew on the vintage Singer sewing machine that my grandpa had electrified for her (see?), and while I also remember him fixing up a bicycle for me that someone had abandoned on their land, I don't remember him ever turning a Singer sewing machine into a minibike.
