Ratio question

[Ed Sutton]

But wait.
Is that 1:1 metric?
ES
----- Original Message ----- 
From: "Farrell" <mfarrel2 at tampabay.rr.com>
To: "Pianotech List" <pianotech at ptg.org>
Sent: Monday, May 12, 2008 5:24 AM
Subject: Re: Ratio question


> Thanks Jon, you saved me the trouble....
>
> Terry Farrell
>
> ----- Original Message ----- 
>> If you don't measure the dip at the front of the key (where it is 1:1)
>> you have to consider the length of the key and the angle formed from
>> pivoting on the balance rail and how far back from the front you measure.
>>
>> For instance, my dip block measures 48 mm in length,
>> 9.9 mm (.390") at the front tapering to 8.4 mm.
>>
>> That's roughly .19 mm decrease for each 6 mm moved back.
>>
>> But it is much too complicated for the task involved. Not only do you
>> have to consider the angle of the key at dip, you have to consider
>> the rate of height change on the risen key since it is pivoted at the 
>> back rail.
>> So the height measured 6 mm back on that key will be ever so
>> minutely less than the +1mm due to the longer radius (probably half
>> the rate of change as the 'dipped' key due to twice the radius).
>>
>> Keep life simple, measure dip at the front, 1:1.
>>
>> The amount of dip is dependant on what is required for regulation
>> but that's a different topic.
>>
>> Jon Page
>>
>
>
>