"A lot of these guys don't use plans. They do TLAR (that looks about right), or maybe a sketch or two, and figure stuff out as they go." - TLAR - I love it!
Describes how I usually operate because I'm usually working with what I have or can scrounge not what I really want. Needs must as needs be.
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Gummymonster, there are a LOT of plans here but sometimes you need to adjust for personal circumstances, materials, tools, size etc. The interweb is a great resource as well. You could look for old Popular Mechanics designs,(thousands of them),and also look at sites that do things you may not have thought about, hot rods, motorcycles, farming. Every Trade , hobby and occupation has machines and tools specif to them but there is a lot of cross-over in usage.
Try using different search engines as well if looking for something specific as each work slightly differently.
Good luck.