About this 3D model

After making the Block and Tackle Pulleys by SteveWall I was left curious about these things, so I started researching them and found many variations. My favorite one was in a boating catalog, it used 3 sheaves and made a type of spiral with the rope. It also had a lock which would make it more useful. I used the hook from SteveWall's with a couple of variations and drew the rest of the parts. I'm not sure how strong the ABS axles for the sheaves will be. I think that screws might work best as axles for heavy work. Also all I had was a rather slick nylon rope so that the lock is not locking properly. I'm in search of a cotton rope for a test, if it fails I'll have to re-work the lock.