Repetition Revisited

[Roger Jolly]

Hi Terry,
             I think we devoted a full chapter to this subject, complete
with drawings and photo's so all will become very clear when you get that
issue in about Oct. Heck I don't have July yet.
 
>Lance Lafargue, RPT wrote:
>"How do you decide what height new backchecks should be installed?"
>
>Roger Jolly responded:
>
>"A rule of thumb for checking height."
>(Do you mean backcheck installation height or hammer checking height?)

Intallation of check height

>
>"A Jollyisum,  Divide the check length into thirds"
>(The backcheck tall dimension?)

The overall length of the check minus the wire.
>
>", with the hammer at the desired height"
>(The desired hammer checking height?)

The hammer blow distance at rest.  about the thickness of a hammer shank
off the rest rail on  a Steinway.
>
>", the centre line of the shank should line up with the top one third point
>of the check."
>(Do you mean 1/3 of the way down from the top of the backcheck?)

Yes, this will align the shank with the bulbous part of the check at rest.

Another check for Lance. Check the height of the checks, by using a
straight edge across the tops of the shank's. This will rule out the
obvious. Pun intended.

Another question for Lance,  Is it a sharp or natural that is causing you
grief?  Another long winded explaination in the series covering sharp after
touch and height.  But a clue for you, ALL back checks should line up like
toy soldiers for correct operation.  If sharp height is incorrect WRT the
naturals, this will not be the case. This can be checked by placing a
straight edge across the backs of the checks.
Do it at the bottom and top of the wooden backs, and check for consistent
rake.

If all checks are correctly aligned, checks are not the problem, but a
symptom of some other malady.

Sliding friction inconsistencies at the rep spring slot can cause some
strange problems, due to timing.
Take one wippen off, burnish the slot,  polish the spring, and lub, to
eliminate as a source of problems.
On a performance piano with high checking, this can be critical.

Centre pinning, is a very critical parameter, both for consistent
adjustment and tone.  Terry, you saw the demonstration of 4 vs 6 swings,
food for thought.  How fast is the loose pinned flange going into check?

I better quit, or there will be another 40 pages.  <grin>

We finished the last chapter, but you will have to wait untill exmas.
After a break then start on the mystries of dampers.

Regards Roger


Roger Jolly
Saskatoon, Canada.
306-665-0213
Fax 652-0505