Ideal leading pattern: more questions

[Ron Overs]

David, Bill and list,

>On Sat, 31 Mar 2001, "David Love" <davidlovepianos@hotmail.com> wrote
>
>>Without even looking at the belly rail felt I can tell that 
>>everything is to far in.  The position of the hammer #88 is well 
>>over 5 1/8" and any attempt to reposition to action brackets and 
>>reset that capstan line would move the hammers way out on the shank 
>>in the upper end of the piano.
>
>(Bill Ballard replied) The factory strayed from their own procedures 
>on this on. The reason for sliding the top action in/out on top of 
>the keyboard is to make a standard 5-1/8" shank length work with 
>whatever plate location the belly room may have given the piano.

Exactly Bill, they've cocked up in the procedure. Setting the action 
stack position to get a correct strike line, since the plate was 
poorly positioned, is just plain stupid production. I can't 
understand how factories can allow such sloppy practices to persist. 
Where was the jig to enable the plate to be set in the correct 
position relative to the case? If the plate was positioned correctly, 
the rest of the piano should fall into place, allowing the action to 
be set up in accordance with the original specification. Assembly 
line workers should not have to calculate work arounds for poor 
dimensional control. Of course, the reality is that they don't even 
when its necessary. So the pianos get sent out with any old action 
geometry set up, and they play like it.

For our third production piano (presently under construction), we 
have built a special assembly jig which is placed in the key bed of 
the piano before the pin block and plate is lowered into the case. 
The jig shows the correct position of the strike line in the case, 
with the first and last strike points for each string section marked. 
With the hitch pin and agraffe holes undrilled and the bridges yet to 
be positioned, the height of the plate and pin block is set relative 
to the key bed. The plate is then positioned with reference to the 
strike line on the jig. After positioning the plate, the agraffe and 
hitch pin hole groups are positioned for each section, using datum 
measurements taken from the CAD drawing. The datum lines run from 
specific strike points on strike line. Using this set up procedure, 
we can be sure that the strike ratios will be set as per the original 
design and the action can be assembled and installed to a standard 
specification. Futhermore, every piano will have the same action 
geometry and strike line standards. Product uniformity should result 
in pianos which are true to the original blueprint, and much more 
consistent in tone and touch.

>>(David L wrote) . . . .Given the plate location, I'm not sure how I 
>>would go about solving the problem anyway.  At least not without 
>>remaking the entire action, keys and all.  The best solution short 
>>of that, to my thinking, is to go to a spring assisted whippen to 
>>at least allow me to remove as much lead as possible.  I haven't 
>>yet tested that idea. Any comments?
>
>(Bill replied) These are two sure ways to lower FWs (read: remove 
>leads). Actually, if you know how to do it, bringing the capstan 
>line back towards the balance rail and (if necessary) relocating the 
>the rep heels . . .

Good suggestion Bill. If the action stack is incorrectly positioned 
relative to the key frame (to correct other anomalies), the capstan 
line can be repositioned to achieve the desired hammer/key leverage 
ratio (the hammer/key ratio will need to be checked at both ends of 
the action to determine a corrected capstan line). Don't consider the 
key ratio alone to be important. It doesn't matter what the key ratio 
is, as long as the hammer/key ratio is correct. Sure, when the 
capstan line is repositioned to correct for the overall hammer/key 
ratio, the wippen speed may vary a little, but it will be of little 
consequence to the player as long as the variation is not too great. 
If the wippen speed does vary considerably, it may effect the jack 
escapement speed during let-off. I have found that the jack tip/key 
ratio should be at least 1.8:1.

>(Bill continued) . . . Why though, if you have a perfectly 
>reasonable key ratio of 5.0 should you have to do any monkeying 
>around there. Have you bought, paid for and installed the shanks 
>already. I think you have alot more to gain by basing this action on 
>17mm shanks. What is this "best combination of 
>regulation/downweight" which hooked you up with 16.5mm shanks? Or 
>was it that 16.5 was what was in there and you're sticking with it.

If David were to reposition the capstans as Bill suggested, he may 
still be able to get the hammer/key ratios he's looking for without 
changing to 17 mm shanks. Relative to the 17s, the 16.5 mm shanks 
will require the capstan to be positioned a little closer to the 
balance pin (which will slow down the wippen speed - therefore, check 
the jack tip/key ratio also). I believe that attention to the 
hammer/key ratio should be the first consideration with any action 
set up. The use of excessive amounts of lead to get the required DW 
is a sure sign that there's something wrong with the basic geometry 
(assuming that all of the usual suspects, centre pin, bushing and 
balance pin friction have been checked).

Ron O
-- 
Overs Pianos
Sydney Australia
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Web site: http://www.overspianos.com.au
Email:     mailto:ron@overspianos.com.au
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