3D Chain Link

1 : Start by creating a single Torus with the dimensions of the type of chain link
you want for you scene. Obviously this can be any shape you would like.

2 : Next we will give the link physical properties. (By doing it now,      it will also set the attributes to the links we will be cloning shortly). 3 : Make sure the link is selected. Once selected go to      menu – Reactor > open property editor. 4 : The Rigid Body Properties window will open.      For this tutorial I will be using the settings      Mass: 6000.0 (how dense your “link” will be)      Friction: 1.0 (How “smooth” the link will be when rubbing against another link)      Elasticity: 0 (How “stretchy” your link will be) Make Sure to choose concave mesh or this will not work properly.

5 : Now you will want to “clone” your link (what ever axis you want).  You can do this by holding shift and moving the link in your chosen direction.  Make sure that when you do this that you only move the copying link far enough  to keep the old link and the new one connected. 6 : You will get this pop up. (I chose to make 15 copies) Click OK

7 : This is what your scene should look like now.

8 : Now select every other link. And rotate them 90 degree’s. Like so.

9 : Now select all of the links. Then go to 
     menu - Reactor > create object > Rigid body collection.

10 : Now choose the very first link you created. In this case chain_link, and go to
      menu – Reactor > open property editor. Make ONLY this links mass 0, and check
     off Unyielding. (This makes the object stay where it is, and allows it to be animated)

11 : We are just about done. Now give all of your links a material         (optional of course) BUT IT LOOKS BETTER! 12 : Now go to the Utilities sub menu (menu to the far right).

13 : Expand the Preview & Animation pull down menu.         Now chose either create animation, or preview in window.         Since this is our first go I think we should preview in window Now just click on Simulation > play/pause.

Go back and make any setting changes that you wish. 
Make it more realistic, or more cartoonish. It’s up to you. 
When you’re ready to go just choose Create animation in 
the reactor pull down instead of preview in window. 
This will automatically add the keys.

Source: "http://www.3dtotal.com/team/Tutorials/working_chain/chain_01.php"