My pops and my grandpops built a lot of exercise equipment when my dad was younger and thats what I started working out on...they didnt design it really but they copied the designs from magazines and built their own equipment off pictures.
had a power rack that you could attach a leverage device to one side and do leg presses, squats, shoulder presses, bench presses etc...dipping bars, pull down machine, and Honestly to this day the bar none best preacher curl machine Ive ever used.
he gave most of it away when they moved a couple yrs ago but I took that damn preacher curl machine its pretty damn cool.
they also built a model A(old timey car) which he still has