back check, a magical mystery tour.

[Richard Brekne]

Stephen Birkett wrote:

> Ric wrote:
>
>> As far as how often checks need adjusting.  Hmm... you'd be suprised 
>> how varied back check height is off the factory line... even in 
>> pianos like Yamaha where <<precision machines>> are specially made to 
>> do the job.  Then there is the hammer change job done by the tech 
>> down the street...... grin..  In short...  it happens often enough 
>> that they need addressing.
>
>
> What I meant actually was:  when some change is determined 
> advantageous how often do they have to be raised vs lowered. In other 
> words, is it mostly a case of lowering? or raising? checks to achieve 
> the 2mm space?
>
Not sure I really understand that first sentence. But backcheck height 
is a fairly stable adjustment.  I personally find as many sets that come 
in above the 2mm spec as below, so I think that bit is a bit random... 
as perhaps it should be given the way most of these are installed in the 
first place.

> The chalk thing would, of course, need a little cleverness, so the 
> hammer is caught somehow before it reaches the check position. 
> Otherwise, you couldn't interpret the presence of chalk transfer as 
> having occurred before the impact. Maybe not feasible, but, even if it 
> affected the impact (e.g. remove the string and have the hammer fly 
> upward and over), the experiment would achieve the desired result, 
> since the proposal is to see if the hammer tail catches the check 
> *before impact, under certain circumstances and configurations. High 
> speed imaging would work for sure, but may not be necessary to answer 
> the question.

Not a problem really... lots of ways of catching the hammer on the 
upward swing really.  A little imagination is all thats needed. And 
there are other ways of forcing the action into compression to see only 
the upward arc of the hammer. 

>
> For curiosity, is the dud problem more often associated with actions 
> that have softer whippen cushions?


Hadnt thought about that in this connection.... but I think I see where 
you are going.

>
> Stephen

Cheers
RicB