Gram weighing of parts

[David C. Stanwood]

Hi Joe,

When one studies piano friction weights (D-U)/2  they find that, with 
uniform flange frictions, on average the friction weight drops by about 4g 
from bass to treble.   This of course is due to the fact that hammers are 
heavier in the bass and push the parts together with more force causing 
more friction in the bass end.

Many of us sort friction with high in the bass and low in the treble and 
this exaggerates this natural tapering of friction even more.  So what 
you've done is to make friction weight even less tapered than normal by 
putting the lower friction hammer flanges in the bass.

One finds that a change of one gram of rotational friction measured at a 
32mm radius on the hammer flange a gram will create a difference in the 
friction weight of about one gram which means a change of 1g in both down 
and up weight.

So if your sort yields say one gram rotational in the bass to say 5 grams 
in the treble then your offsetting the natural decrease of friction bass to 
treble of 4g with an increase bass to treble of 4g giving a more or less 
uniform friction weight bass to treble so if the down weights are weighed 
off to be a uniform level bass to treble the up weights will be uniform as 
well.

If, in this case, you sorted with high friction in the bass to low in the 
treble the up weights in the bass would be much much slower than in the 
treble, with a uniform down weight.

If your going to sort by friction I think it makes more sense doing what 
you've done because it creates a more consistent friction weight bass to 
treble which in turn creates the possibility to weigh off to a more 
consistent down weight and up weight bass to treble.  I'm sure that many 
pianists would notice and like that kind of set up.

I actually prefer, in the case of shanks, to sort by shank strike weight 
then working the flange frictions to be as uniform as can be from bass to 
treble, with special attention given to key bushing friction 
control.  Friction comes and goes but weight is pretty constant by 
comparison...

Whew!

David Stanwood


>Forever, I've been gram weighing all new parts and marking therein. 
>Repinning where necessary and installing the greatest friction parts to 
>the bass end and graduating to the lowest, (within specs.), in the treble. 
>The last grand action I did, I decided to put the lowest in the bass and 
>graduate to the highest in the treble. The action felt/played just fine. 
>!!?? My thinking, (if you could call it that.), was that in order to get 
>the hammer moving, in the bass, less "action friction" would get the big 
>uns moving faster, thus off-setting the size of the hammers. In terms of 
>UW/DW, I found that the action was more consistant from bottom to top. Hmmm?
>Have I stumbled onto something here, or is it "olde-timer's disease" 
>kicking in?!! OR, am I just messed up in my rationale?
>Would like to know your thinking on this.
>Regards,
>
>Joe Garrett, R.P.T. (Oregon)
>Captain, Tool Police
>Squares R I