Key Leads and Inertia

[John Hartman]

David Love wrote:
> Thanks John.  The pictures are very descriptive.  Perhaps I should have
> asked the first question first.  How does excessive flex manifest itself as
> a problem.  For example, does it limit the upper end of power or is the
> problem literally the delay in response when the key is accelerated too
> quickly, lack of control, all of the above or something else?  

Yes all of this. It limits the dynamic range. I can't sense the time 
delay but Del said he could.

If one were
> hiring someone to make new keys for a piano, let's say a small company in
> Oregon, what would you specify in terms of either the type of wood used,
> thickness, reinforcement or anything else to get the type of performance
> you want?  On the flip side, is there any problem with having a key that
> has insufficient flex?
> 
> David Love

The key sticks are made from pine, spruce or basswood.

Pine is the weakest and basswood is the strongest.

I have used basswood on Masson and Hamlin grand key sets were the keys 
have an aggressive side shift. In this case the keys become narrower and 
the basswood compensates.

Short keys that are reasonable straight are not usually a problem, I 
just use maple buttons and make sure there is a external basswood shoe.

Some times you can extend the shoe to add stiffness. If you use top 
plates you have to be careful they don't interfere with the fall board.

Del made some comments on the problems with too little action 
compliance. Making the key stiffer is not going to get rid all the 
compliance so I am not too worried about making the key too stiff. Just 
be careful not to make the key too heavy. I use the weight to test the 
flex and if it is not over the line I don't worry about it.

John Hartman RPT

John Hartman Pianos
[link redacted at request of site owner - Jul 25, 2015]
Rebuilding Steinway and Mason & Hamlin
Grand Pianos Since 1979

Piano Technicians Journal
Journal Illustrator/Contributing Editor
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