Leverage and Dip

[Richard Brekne]

Bill Ballard wrote:

>
> But if I may guess at your thinking, you wanted to know how the three
> portions of the key's stroke (at rest to the onset of escapement,
> escapement itself, and aftertouch) would work (and maintain proper
> proportion), for a specified total dip, and over some range of action
> ratio? IOW, is there some range of action ratio through which a
> specified 10mm total dip would be the basis of a successful action
> regulation? And at what point in a decreasing action ratio, would
> this specified dip have to be abandoned?
>

Yes... this was exactly what I was asking. I got to wondering about the problem
with too low a ratio, relative to the after touch/letoff condition. You can
fudge easily enough with a bit of extra dip, or a bit shorter striking distance
for sure, but if you wanted a 10 mm dip (for whatever reasons), just what range
there was for choosing a ratio ?

If I am not mistaken another aspect of this ratio is the speed of hammer travel
to key travel as well.... or what?  Implications ?

I think I am musing along the lines that there are obvious touchweight
differences that may be preferable for different conditions or people that are
more or less directly related to the ratio alone. So assuming you want to press
the overall action ratio as low as possible... just what can you get away with
in terms of strike distance ? I think we can aggree that 2mm is about as far a
letoff you can get away with.. or what ?

On the  side.... I tend to agree with David about the distance / weight ratio
correlation. I just cant see how it can be any other way. The ratio is simply
the ratio. I take a few samples and insert extra punchings under the keys to
insure an exact 5 mm key travel, and measure hammer travel to find it. Nice
thing about doing this is that it becomes more or less a constant. Using the
balance equation then you can insert this ratio, your known SW's and FWs and
WBW which you have also physically measured, and solve for BW. If, when you
begin to actually measure BW you find variances, you know these have to do with
friction related issues, or small variances governing leverage (i.e. knuckle
angel and the like). Doing this allows you to further even out the resulting
touch quite a bit really.

I appreciate your thoughts and replies muchly.  :)


Cheers !
RicB









--
Richard Brekne
RPT, N.P.T.F.
UiB, Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html