By Craig Brougher
|When a player piano bobbles its hammer, that means the hammer assembly is bouncing between the jack and the string, and so the back check can't catch it and hold it. Sometimes on uprights, even when the jack is sufficiently clear, a poorly regulated hammer will bobble between the check and the string.
This is more of a problem on uprights because of the poor control afforded the hammer by the check. There are several things you can do. First, you can be sure you have taken out most of the lost motion between the player strikers and the action whippens. You also have to regulate them by adjusting the striker travel as well as the rest point of each striker. Too much travel and the hammer blocks the string. Too little and it bobbles.
If the hammer bobbles when the key is played by hand and when the player plays it, the problem is in the action alone. If the hammer bobbles only when the player plays it, then regulate that note to strike with the same depth as the key does it, and it usually fixes the problem, but not always! At that point, you may have to tip the back check forward on its wire a little.
Bobbling hammers can be a really tricky problem to fix, and anybody who has the problem also has my sympathy. It's very difficult, short of an action restoration, to cure it completely on some pianos.
(Message sent Tue 3 Dec 1996, 16:12:16 GMT, from time zone GMT.)