Mechanical parts, clearance, thickness? input on first project(extender)

I have no previous experience with 3d modeling or 3d printing at all.
This is my first project and I would like to have some input as I know for sure this isn't as good as it can be.
I tried to make the walls as thick as I could without making the prop too "fat" but I have my doubts on certain parts on it.

It's inspired by the hidden blade from assassins creed and I tried making it as functional as possible, without the lethality of course.
The thing I am most worried about is the wheel locking mechanism, I whipped up something quickly as I couldnt figure out a clever way to do it at the point of writing this.

Can you spot any glaring mechanical errors?

Some parts will have either springs or rubberbands between them so what you see if not all there is to it.

Would appreciate some feedback, also ideas on how to improve the design are welcome.

https://www.shapeways.com/support/faq
Explicit sexual content and weaponry look products are not accepted on Shapeways, neither private, nor public. Any file containing such content will be removed without further notice. We are allowed to make an exception for miniature weaponry (maximum size 10cm).

Beyond that restriction, your gears are not properly formed. You need to deal with "inverted normals", and it appears that the mechanism doesn't have enough clearance to actually move. What material were you wanting to try to print this in? It'll never work in steel.

I wanted to print it in WSF, just plain plastic, I don't think going through all this trouble to create a weapon is worth it, I mean if I wanted a knife I would just go to the kitchen.

And for the clearance for the mechanism, how much room do I need? I read through the shapeways guidelines and tips but they never actually gave me an example of how much room you need.

Would my gear not work? I mean, it looks weird but as long as the pin can stop the gear from going backwards that's fine by me.

This page is good in general tutorials, and this one is better specifically for the clearance issue Designing Mechanical parts for 3D Printing

There is also a parts database which might have been useful if the page actually worked: https://www.shapeways.com/themes/3dparts

I did read through all of the 3d parts guide but it didn't explicitly state how much clearance for need, it only stated that a 3mm hole would not fit a 3mm peg. I don't want to make my parts to delicate, also because of the design I have limited room to work with. Currently I have left a headroom of 0.10mm - 0.30 mm most parts. But as smith stated that's not enough, so I will have to increase that to maybe 0,5mm or even 1,0mm

Well, I can only say that in the Designing for Mechanical Parts link I gave you above, the first paragraph is (my bold):

But the way they say it, don't they mean that if you want to say create a haircomb, you would want to keep a clearance of atleast 0,6mm between the pins. But my parts will be printed separate, so that's not relevant to me or is it?

Lets take the worst scenare, as parts can have a deviation of 0,2mm. Say I make a hole with 3mm diameter, it might turn out to be 2,8mm diameter.
And the peg I make was meant to be 2.9mm, but turned out 3.1mm.

By that logic I should try to keep a clearance of ~ 0,4mm.

The 0.6mm clearance guideline is for printing details very close to each other so that they don't fuse.

I could be wrong though