Contraversial basic regulating

[David Boyce]

"On the contrary, the jack top does have friction-related resistance to
moving across the hammer butt leather on an upright. You can especially feel
it while pressing the key down very slowly - it is not nearly as prominent
as on a grand, but it is there".

Surely the factor here is "pressing the key down very slowly" - so slowly in 
fact that the hammer will not travel to the string.  Because insufficient 
momentum is imparted to the hammer to enable it to continue to travel 
forward to the string after letoff.  With such slow depression of the key, 
the hammer butt remains "linked" to the tip of the jack by its own weight, 
until letoff *forces* the jack tip back and out, scraping against the 
buckskin as it does so.  The hammer doesn't continue to travel forward, as 
it has no momentum to do so.

In normal playing, however soft, the intention is to get the hammer to 
strike the string, and to do that, it has to have enough momentum to keep 
moving forward without continuing propulsion.  When it has enough momentum 
to do that, as in normal playing, that means that the hammer is already 
moving forward by virtue of the imparted momentum at the point of letoff, 
and it simply travels off the jack tip of its own momentum, so that there is 
no friction involved.  Such movement as there is of jack tip against leather 
will surely be of a pivoting nature, not involving any traverse of the 
buckskin surface.

Certainly, in the very slow key depression and letoff described above, on 
older actions it's very easy to feel (and sometimes hear) the "scrooping" of 
the jack tip against the buckskin on the hammer butt.

I suppose an analogy would be to imagine an ice hockey puck on the ice. If 
you put a finger on its edge and shove it along very slowly, it will remain 
in contact with your finger, but if you shove it with some force, it will 
leave your finger and continue to travel forward without being in contact 
with you in any way.  Similarly, if you have a football sitting on your open 
palm, it will not leave your palm if you simply lift your hand gently. But 
if you lift your hand quickly with sudden velocity, the ball will leave 
contact with your palm and travel up by itself.

Am I wittering?

P.S. I could harly bear to put "contraversial".

Best regards,

David.