Sostenuto regulation

[Horace Greeley]

Keith, et al,

At 08:53 AM 2/7/2001 -0600, you wrote:
> >...   If the underlevers are allowed unlimited upward travel, a strong
> >blow can
> >send them over the top of the engaged sostenuto rod.  This doesn't happpen
> >with the unsprung sos. tabs, but the later models will allow the underlever
> >tab to go above, and when it does, it stays up there!
> >Regards,
> >Ed Foote RPTs
>
>Ed, Conrad, List,
>
>Thank you for this additional information.
>
>For my benefit, let me be certain I understand your comments.
>
>With the damper and sostenuto system properly regulated, with the sostenuto
>pedal purposely engaged, and for some reason the damper stop rail is not
>regulated properly, but is set at its highest point, then any piano playing
>during this time that has strong blows can cause other notes to hang up on
>the engaged blade, that is, on the models that don't have the tabs with the
>springs.
>
>This is what you are saying, yes?

Not exactly.  With the earlier, unsprung tabs, the tab itself absorbed the 
impact, and bent (over time, breaking) in these conditions - but did not go 
past the sostenuto.  With the sprung tabs, however, a sufficiently hard 
blow will force the tab past the edge of the rod even when the tab is 
already fully depressed.  Thus, in a properly regulated machine, the 
placement of the upstop rail makes a difference that it does not in one 
which is really sloppy but, somehow, "works" anyway.

I think that what happened for Patrick is that, in correcting one thing, he 
got caught in a loop which began with improper original installation and 
regulation - one which did not come to light until he started getting 
things more to where they "should" be.  The tip-off was the length of the 
trichords, and what he had to do to compensate for it.

Best.

Horace