I got 14 links of 5/16" (8.8 mm thick) zinc coated chain.  It is 18.25" long.  They weigh 533 grams.  Link's outer dimensions are about 28x48 mm.  It was US $2.97 per foot @ homedepot.  

I also bought 1 lb of 20 AWG magnet wire for around $16 US on Amazon.  1 lb of wire should be about 323 ft and I am hoping to use it for 3 breaks.  At about 1 Ohm each.  I need 14 total for 7 DOF.  $5/brake $75 total.  Each brake will be about 190 g.  2646 g (5.8 lbs) total.

This is getting heavy and expensive... (OR not https://temcoindustrial.com/20-awg-copper-magnet-wire-5-lb-mw0027-magnetic-coil-red-soderon155.html  OR https://temcoindustrial.com/20-awg-copper-magnet-wire-5-lb-mw0167-magnetic-coil-gpmr200.html)  I was hoping to make the whole robot for under $100.

Next thing to do is to anneal it in sand using a torch to improve its magnetic qualities.  This should also strip the zinc coating.  For this reason I bought zinc coated and not galvanized chain.  It is harmful to inhale zinc vapors.  Do it outside !!!

After annealing I will cut a slot in each link and try to separate the chain by bending them open.  Close the links back and leave about 3 mm gaps for disks to spin through.

Looking at a 1 lb spool of wire it seems big.  I hope I will be able to wind 107 ft (32.6 m)  around the link.  It will take some time :)

I don't  know how much current a 20 AWG wire will take.  Reference materials on the web state anywhere from 1.5 A wound (http://www.magnetwire.biz/magnet_wire_current.html ) to 18 A for a single conductor in air.  The brakes will not be operated at 100% duty cycle.  I am guessing 25% max.  This might need to be enforced in software.  Spinning disks can be equipped with blades for air cooling the brakes.  Therefore, I am hoping to be able to operate the brakes at 12 V through  IRFZ44  mosfets or MCP14A1202 or even MCP14A09?  Anyone has a schematic to recover the conductor EMF energy after it is turned off?