If you are making a crane, I find it hard to believe you would give the crane itself away for free, since you have to recoup your costs. So that point you are selling cranes and engaging in commerce, so they have jurisdiction to regulate you.

If you make and publish designs for a crane, or you speculate on how cranes ought to be built, it's your right to free speech. Think about it, even an engineering textbook must describe how to design an unsafe bridge to teach you how to build a safe one. It will show you examples of famous collapsed bridges, perhaps with full blueprints and design instructions.