Mason & Hamlin upright

[Keith Roberts]

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Re: Mason & Hamlin uprightI'll be working on it again towards the end of =
the week. I can take pictures and will see if I can't get them posted =
soon thereafter.=20
Basically it looks like a miniature of the flat steel spring used on the =
pedal trapwork. An eyeglass size screw and pin fastens it to about the =
middle of the jack. There is a 1/4 inch thick piece of felt glued on the =
back of the catcher covering the hole the bridle strap comes through. As =
the jack trips out at let off, the spring pushes against that felt on =
the catcher and forces the hammer back towards the strings. There is a =
slight backwards wink of the hammer before the hammer goes forward. It =
is my feeling that the amount of wink should be the same and it should =
be sufficient enough to achieve a proper checking distance. In this case =
I think the checking distance should be 1/2 inch because the spring adds =
to the acceleration on repetitive blows but any less distance weakens =
the force of the blow too much.=20
As I write this I'm getting the feeling I want to mess with the =
thickness of the felt instead of the spring or I'll end up with one of =
those actions with all those pieces removed. (broken). Is it worth it? =
When this action is working at it's optimum, it probably performs quite =
well. If I am not going to bring it back to spec I can see a possibility =
that hammers could block as regulation goes out.=20
Does anybody know any different from what I'm assuming here? Checking =
distance, etc.
Keith Roberts
  ----- Original Message -----=20
  From: Keith McGavern=20
  To: Pianotech=20
  Sent: Sunday, March 07, 2004 7:58 AM
  Subject: Re: Mason & Hamlin upright


  At 11:08 PM -0800 3/6/04, Keith Roberts wrote:
    I'm working on one of those  M&H uprights with those flat brass =
springs between the jack and the hammer butt catcher. Is there an =
adjustment for those? ...


  Keith,


  Any chance you could get a pic of that device? I don't recall ever =
seeing that arrangement.


  Keith
--=20

  Keith McGavern                                    Texas State =
Association
  Registered Piano Technician                 SOONER SPRING SEMINAR
  Oklahoma Chapter 731                            March 11-14, 2004
  Piano Technicians Guild                        http://www.ptg.org/tsa/
  USA



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