repairing the hammer butt bulkskin

[jcalves]

Hello,

I'm starting to repair a German full upright, Sachter & Co (can't find any info about this builder). Major work will be to substitute some of the felts that were just eaten away, loosen some of the flange pins that are too tight due to humidity...and regulate. I'm using as a reference the book "Piano Servicing..." from A. Reblitz. The book is very complete, but I didn't find there the answer to three questions I hope someone in this forum can help:
1 - how to shape the bulkskin in the hammer butt (most of those felts under the bulkskin just disapeard)?
2 - if the let-off button does not release the jack, will it keep pusing the hammer until it strikes the strings?
2 - how to gauge the tension of the hammer return spring?
This action has the configuration of fig. 2.56, pag 45 in that book, with the jack being mounted directly in the wippen, without flange, and the hammer return spring mounted in the hammer butt with a retaining cord.

best regards,

josé
Porto - Portugal

[Barrie Heaton]

Hello,

I'm starting to repair a German full upright, Sachter & Co (can't find any info about this builder). Major work will be to substitute some of the felts that were just eaten away, loosen some of the flange pins that are too tight due to humidity...and regulate. I'm using as a reference the book "Piano Servicing..." from A. Reblitz. The book is very complete, but I didn't find there the answer to three questions I hope someone in this forum can help:

Not so complete if you have to ask questions

1 - how to shape the bulkskin in the hammer butt (most of those felts under the bulkskin just disapeard)?

Are we taking Notch pads or Notch cushions ?

If it is the Notch pads and you intend keeping the leather (bulkskin) you can thread thick bushing cloth under the leather that will give you some shape back. But if it was me I would replace the lot it is quicker and the leather has probably got groves cut into it by now

2 - if the let-off button does not release the jack, will it keep pusing the hammer until it strikes the strings?

Yes it will just block the string and in the UK it is called set off

2 - how to gauge the tension of the hammer return spring?
This action has the configuration of fig. 2.56, pag 45 in that book, with the jack being mounted directly in the wippen, without flange, and the hammer return spring mounted in the hammer butt with a retaining cord.

best regards,

josé
Porto - Portugal

Very seldom do you have to alter the tension of the butt springs if you have replaced them with the same size they should be fine

Barrie,