In MMD 23.3.27 Don Taig from Australia asks for some advice on how to
restore the hammers for a 48-note Racca Piano Melodico.

Don, I hope I can give you some help for your ongoing work. I have some
different Piano Melodico in my collection (30, 48, 51 (!) and 73 notes).
All these instruments I restored and on about a dozen others I helped
the owners during the restoration process.

As a first step to help you, I suggest you to go to

https://www.lulu.com/shop 

enter in the search field
C.F.C. Greinacher
and some publications of mine and of my wife will show up.
One of these publications is called
Restaurierungsbericht Nummer 2: Piano Melodico.

https://www.lulu.com/shop/cfc-greinacher/restaurierungsbericht-nummer-2-piano-melodico/ebook/product-1wzm748p.html?q=c.f.c.+greinacher&page=1&pageSize=4 

You could download it as Ebook or order it as Paperback. The text is
German language but I guess you can work through it with the help of
the drawings. Unfortunately some figures are not clearly printed. If
you will have problems, I will send you an email with original drawings.

The restoration report deals with a 30-note Piano Melodico, i.e.,
the dimensions of the hammers are different but the material and the
tricky design will be exactly the same for your 48 note Piano Melodico.

One most important advice: When you turn the crank handle of the
Piano Melodico about once per minute, the hammers will swing with
the frequency of about 10 Hz. Be aware of the fact that the system
"hammer spring plus hammer head" is an oscillating system -- the
natural frequency of it depends of the stiffness of the spring and
the mass of the hammer-head.

If this natural frequency comes near the "hammer frequency" the
hammers run out of control and you will get a mess of chaotic sounds!
In other words, the hammer springs have to have a stiffness so that
the natural frequency of "hammer spring plus hammer head" is up to
ten times higher than the "hammer frequency" or somewhere around 80
to 100 Hz., i.e., the hammer springs have to be relatively stiff. You
can control this stiffness by the cross-section area of the spring.

Now I hope that I could help you, and maybe some others, with this
answer to your recent posting. And if you are interested in some more
information about these most interesting machines called "Piano
Melodico," you could look in the Internet for my publication:

C.F.C. Greinacher: Piano Melodico, A family of mechanical music
instruments, in "The Carousel Organ", The Journal of the Carousel
Organ Association of America, Nr. 14, January 2003; pages 14 to 22.

Do not hesitate to email me if you have any more questions.

Regards from
Christian Greinacher
Röttenbach, Bavaria, Germany

 [ Christian's MMD articles (since 1998!) are indexed at
 [ https://www.mmdigest.com/Archives/Authors/Aut1250.html 
 [ -- Robbie