bobble heads

[Daniel Dover]

Wim,

If the bobbling is a result of poor checking, please consider the following. I
solved the same problem permanently in a very problematic 'D' awhile back. 

As you probably know, string heights (measured off the keybed) in Steinways vary
considerably-- from piano to piano, section to section, and from one end to
another of the same section. I've measured variances of as much as 6mm (1/4")
within the same piano. The biggest variance can often be in the area you first
described.

If you put a set of hammers with a standard bore distance into such a piano, the
hammers will be over-striking by quite a bit in some sections. And to set a
reasonable blow distance, the hammers will need to be raised much higher than
normal above the backchecks. 

If those same hammers also have a short tail (under 1"),then the hammer tails
will be sitting impossibly high above the backchecks. With the key depressed,
hammer not in check, the bottom of the tail should be within 1/8" of the
backcheck to work properly.

Loose hammer flange pinning, strong rep springs, and tail geometry can further
complicate this mess. But when I replaced the old parts with custom-bored,
long-tailed (1 1/8") hammers, the bobbling disappeared forever.

Hope this helps.

Danny Dover
Dartmouth College
Hanover, NH