Yamaha Hammer Spring Cord Repair..from the archives

[Jon Page]

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Yamaha Hammer Spring Cord Repair
Problem:
   Hammer return spring cords have become fragile and are breaking.

Symptoms:
   Cords have turned a brownish color.
   Random breakage is occuring.
   Touchweight is affected on some notes where the spring is contacting the=
=20
damper lever.
   Hammer sometimes falls audibly into strings on slow release before being=
=20
pulled back by bridle tape.

Solutions:
   Replace hammer flanges
   Replace cords

Condition of action:
   If condition of the hammers, pinning, and travelling/mating to strings=20
is all good, replace cords.
   If pinning is poor then flange replacement may be a better option.
   Beware of earlier type action without butt plates - the following method=
=20
would not work in this case.

Cord Replacement Procedure:
   1.    Place action in cradle; remove hammer rest rail and treble bracket.
   2.    Reverse action so that hammers and dampers are facing you.
   3.    Loosen hammer butt plate screws.
   4.    Remove hammer assemblies from flanges and let hang from bridle=20
wires; keep them in order to avoid tangling.
   5.    Straighten any bent return springs.
   6.    Tighten all wippen flange screws.
   7.    Tilt action toward you 90=B0 so that the hammer flange cord slots=
=20
face upward.
   8.    Tighten remaining flange screws.
   9.    Using specially adapted shimming chisel or other suitable tool,=20
clean slots (no solvent) and vacuum up debris.
10.    Wrap 90+ turns on dowel with new cord and cut turns with a razor.
11.    Glue one end of each piece to one slot on each flange.
12.    Return to first flange and glue the other ends to remaining slots;=20
check with gauge.
13.    Lubricate damper spring slots.
14.    Replace hammers; tighten butt plate screws; hook springs under=20
flange cords as you go.
15.    Replace hammer rest rail bracket and reinstall rest rail.
16.    Final check: jack springs engaged with jacks, spring cords in crook=
=20
of hammer return springs, bridal tapes not twisted.


Tools and Materials:
   __flange, thin-bladed, and Phillips screwdrivers
   __spray lube and spring hook (for damper springs)
   __shimming chisel modified to clean flange slots, or other suitable tool
   __glue applicator (syringe) filled with Tightbond & damp rag
   __action cradle
   __replacement cord, e.g., braided Dacron of suitable diameter (kite=20
string, parachute cord) or silk cord (Pianotek)
   __9/16" dowel [turned down from 5/8" dowel] or suitable width piece of=20
cardboard
   __blunted scriber (or use small screwdriver, to help place cords in=
 slots)
   __gauge (dowel, sized to fit intact flange cord, with end rounded off,=20
to check loop size)
   __razor
   __forceps

Many different types of cord will work. White braided Dacron looks the best=
=20
and will last forever. Joe Goss suggests Spider Wire which I've bought but=
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haven't tried yet. It's a similar color to the stuff you're replacing so=20
that tends to go against using it. I used to use squidding line but the=20
kind you'll likely find in fishing supply places is waterproofed and=20
wouldn't take well to Tightbond. Probably the easiest (and possibly=20
cheapest) is to order the silk action cord from Pianotek ($3.95 for a=20
30-yard roll).

Cleaning out the slots is not critical and you could even give the flanges=
=20
a quickie scrub and vacuum treatment and commence with step 10.

This method is taken from Tom Driscoll who posted it to the list in May,=20
2002 (Yamaha Upright Hammer Flanges). =20
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