Copper Disks:

It would be nice to replace aluminum HD platelets with some copper ones to increase efficiency.  Maybe make them smaller and spin them faster? Should I make them copper rings to reduce the amount of copper used and weight?  On the other hand disks have larger thermal capacity than rings.  Aluminum disks with copper rings attached on both sides?
 I need about 10x10 cm of copper sheet to make a disk.  Where do I get cheap copper?

Plan B for getting an eddy current brake to work:

Buy a short length of steel "coil" chain.  Anneal it to improve magnetic properties.  Cut it into individual links with a grinder or a hack saw or a sawzall.  Individual links will form cores for the eddy breaks.  Disks will spin in the groove made by the cut.  Wind an insulated copper wire around the link to form an electromagnet.  Should I get 1/4" or 5/16" or 3/8" or 1/2" chain? Would it be better to use short pieces of 3/16" thick  1 1/4 square tubing instead?  I wish I could find a source of soft iron.  Steel stays magnetized.

Now where do I get some cheap copper wire? I don't have any transformers laying around... Scrap metal stores?  Aliexpress sells it for about $50/Kg shipped - WTF?  Amazon for $32/Kg shipped.  Current market price of copper is USD $5.65/Kg.  Time to start melting pennies and making my own wire lol...  Can I make a copper disk by soldering copper pennies together?

What diameter of wire do I need?  What length of wire will fit onto one coil of chain?  How heavy is it going to be?  If I want to use 12V, I need 106 ft (32 m) of 22 AWG (0.64 mm) wire to get 7A.  Alternatively I can use 133 ft (40.5 m) of 24 AWG (0.51 mm) to get 3.5A  How much current do I need to create enough eddy current?  What amount of impedance will it provide?  Is this why people get EE degrees???  Does this whole thing make any sense?  Am I just designing my own motors here???  HELP!!!  I am lost!!!