Is this a good place to ask if my own mechanical inventions are stupid?

Question

I have a book of inventions mostly mechanical. Since I'll never be in a position to patent and produce them maybe I can see if they are a good design here?

Answer 1

... maybe I can see if they are a good design here?

This type of design question would (should) be closed as "Too Broad." StackExchange isn't set up to handle bigger questions like the ones you're proposing. If it would take more than 3 - 5 paragraphs to provide a reasonable answer to the question, then it's not a good fit for the site.

Even if you scoped your questions to say "only give a high level answer," then we still have the same problem but in a different way. The question will then receive non-answers of "it's brilliant" or "definitely not the greatest" in reply. The challenge here is that you don't find out why the design was reviewed as such.

Since I'll never be in a position to patent and produce them ...

This actually gets to the heart of your problem. You need to attempt to build these designs and then refine based upon what you find. Dyson famously went through thousands of prototypes before settling on his final commercial design.

Don't worry about fake internet points and the opinions of strangers on the internet regarding your designs. Go build them. See if they have a hope of working. And if your designs are too big to fabricate, then learn how to scale them down and prototype.

That said, the tl;dr is "no, that sort of question is off-topic for the site."

Answer 2

That's iffy at best. Given your particular history, the answer is a solid NO.

We have a category called naive design questions. The users here have generally decided that such questions are not wanted. Yours tend to be worse in that they are founded on nonsense physics babble.

It is pretty much impossible to supply a concrete answer to such questions, and the end result is usually the OP arguing about it, or coming here to meta wanting to know why their brilliant idea that we were all supposed to marvel at was closed and downvoted to oblivion.

Such questions can be acceptable if the idea is based on reasonable physics and engineering with maybe a single mistake, and the question is more along the lines of "I know it can't work this way else everyone would be doing it, but what exactly makes xxx impossible or impractical?".

Again, though, your "ideas" have a history of being based on nonsense physics, have no regard for engineering, and are described by illiterate babble. The option in the previous paragraph is therefore not for you.

Don't. Just don't.