This is the procedure I use. The hammer flanges are not removed from the rail, but in order to give clearance enough to swing the hammer butts out of the way, the dampers are removed. This takes about an hour longer than it would to replace the loop cord on flanges with butt plates, where the hammer butts can be removed. Any suggestions would be appreciated. Sorry for the lack of photos.
1. Detach bridle straps
2. Remove hammer rest rail
3. Remove damper stop rail
4. Number dampers
5. Remove dampers. Loosen but do not remove the screws from the flanges. Grab 4 or 5 at a time and hang them from the outside edges of a suitable box with the lid removed.
6. Rotate the action cradle so hammer flanges are facing up, hammers hanging down with enough angle to depress the whippens thus pushing the jacks out of the way.
7. Apply acetone to the remnants of the old cord in the flange to soften it, about a dozen at a time (since the acetone evaporates rapidly), then scrape out the grooves in the hammer flange. For this I use a small pick that has the end bent at 90 degrees, with the edge sharpened to a rounded chisel point. Use adequate ventilation. Use a suede brush to clean up and blow it out with air compressor.
8. Cut 90 pieces of loop cord 50 mm in length. I use .9 millimeter lift cord which I you can get from any mini blind supplier. It has a similar appearance and diameter as the original polyester cord but is much stronger and more durable. To make the tool for this take a 5/8" soft wood dowel and plane down 2 opposing sides until the circumference measures that length. Drill a small hole at one end and fasten the cord with a nail head button. Loop it around 90 times and then cut down the middle of one flattened side with a razor blade.
9. Glue in all cords on the left side only of the flange as you face it. (I'm right handed.) For this you will need a glue bottle with a small diameter opening. I use titebond for this. A very small drop of glue will suffice. Ideally you don't want the glue to wick all the way up the channel to the top. You will notice that old cords which are glued fast at the top always seem to break at this point as they wear due to the back and forth motion. Allow the cords to dry thoroughly .
10. Orient the action cradle so hammers will stand in up position, canted just enough forward to hold them upright.
11. Doing 4 or 5 at a time, apply a small dab of glue to the right hand channel. Move the hammers up and glue in the cord. This takes some dexterity, but you'll so get the hang of it when you've done a few. I use small 6 " tweezers in left hand to maneuver the cord into position and the bent pick in the other, using the side of the pick to press the cord in the groove. As long as no strain is put on the cord, you can wipe it into place. When the glue is dry check then install springs.
12. Before reassembling, do some misc. housekeeping: Lube damper lift rod and spoons, jacks; tighten action screws. Straighten any bent hammer butt springs. If the bridle tape ends are delaminating, paint with PVC-E sizing and let dry before reinstalling. When reinstalling dampers, be careful to counter-rotate until you hear the screw seat itself before tightening. Aluminum rails have many advantages, but the ease with which you can strip screw holes is not one of them.