[ Ref. 151003 MMDigest, Seek Ampico Equaliser Springs ]
Hi Peter, I think your best option is to make the springs from
scratch. Chances are, any original springs you might buy will be
the wrong length. Use these dimensions:
wire size: 0.048 inches
coil size: 0.990 inches
The length is highly variable, from about 0.75 inch to 2.5 or
more inches (coil fully collapsed, not counting connection loops).
Except for upright pianos, these springs are variable in length due
to space limitations. On grands, the two springs are almost always
Once the minimum stack pressures are known for reliable soft playing,
the spring length should be adjusted to just barely allow the equalizer
to fully collapse at that pressure. When a transient pressure drop
occurs, the equalizer is pulled open immediately to counter-act the
drop in stack vacuum. It takes several tries to get the balance
perfect. The equalizers are always fully collapsed at intensities
above the minimum 1st intensity setting.
Let me know if you need any other information.
Now Robbie has to figure out how to archive this topic: English
spelling or U. S. spelling.
[ Hereafter I'll observe the (American) spelling found
[ in the Ampico Inspectors Reference Booklet of 1923. ;-)
[ MMDigest articles on this topic are indexed at
[ -- Robbie