Here is a cutaway view of the spindle showing housing, bearings, draw bar and collet system. At the top you can see the pulleys for the drive and the belleville washers which hold the tool in place by pulling up the R8 collet
I to am following this with interest. Have you decided on the size and number of the bellevilles? Also could you give more details on the drive arrangement for the PDB as I am making one for my mill but using an intensifier (small jack) to give a 7:1 advantage with 12 belleville washers. From a post on the Zone by SDM