consistent downbearing measurements

[David Skolnik]

Hi Greg and Dale -

Dale said:

>     Gregg
>   I made some of John Hartmans stick bearing gauges & am just getting 
> around to using them. They don't lie. He posted picture a month or so back.

Before I loose them, here are the image links:

[link redacted at request of site owner - Jul 25, 2015]
>
[link redacted at request of site owner - Jul 25, 2015]


Dale - As you say, these gauges don't lie, but neither do they provide 
specific information about the front or rear bearing.  For a number of 
reasons, these were not of concern to John.

Greg -
You've got a couple of different issues going.  The mechanics for one, the 
purpose being another.


>I'm having some difficulties achieving consistent downbearing 
>measurements. I'm struggling with the Lowell gauge and each time I move it 
>and then attempt a repeat I start with a completely different reading that 
>I zeroed in before.

In discussions like this, it's better to avoid descriptions like 
"completely different".  Like, how completely different WERE the 
measurements?  Dale is right when, in an earlier post, he said that a light 
tough works best, but even here, there are two separate issues.  I suspect 
that the inconsistency you observe occurs when trying to zero the gauge on 
the bridge segment.  As an experiment, try taking numerous measurements on 
the sounding length.  With the touch Dale described, you should get the 
same basic results.  Try getting the gauge to stand, almost by 
itself.  Zeroing on the bridge segment is more difficult, because the same 
gap that you need to leave so that the gauge is not binding between the 
bridge pins will allow SOME amount of variation, depending upon whether you 
are favoring the position of the gauge towards the front or rear pin.

>  The little "V"'s in the bottom of the feet don't seem to sit very well 
> upon the string in any segment. I think it's because the tool isn't heavy 
> enough so it rocks too easily. Are there any better tools available and 
> if not has anyone modified theirs to give less trouble? I'd like to 
> modify the Lowell gauge to use rare earth magnets as it's feet if there's 
> nothing else available. Any idea's on how to accomplish that?

I had one gauge where the 'V"s in the feet were not quite aligned.  I don't 
recall whether I replaced it or filed it.  The channels can by filed a bit 
deeper, using a jeweler's file, but you have  to be careful, as if is cut 
too deep, the tips of the "V" can contact the top of the bridge, thus 
distorting your reading.  As for magnets, I have also thought about 
adapting the feet to be magnetic, but haven't figured out how to do it, 
yet.  The gauge did originally come with an alternate magnetic base, which 
can be used to compare front and rear segments (net bearing), but not 
isolate front and rear bearing.

I think you are right that the tool would benefit from some redesign, 
especially the weight distribution.  I have adjusted to its shortcomings, 
for the most part.  The way I use it in evaluating a strung piano, would be 
challenging for you until you develop the "light touch".  I had described 
it in some previous discussions about downbearing.  It requires keeping the 
feet as CLOSE together as possible while reading the bridge segment.

David Skolnik
Hastings on Hudson, NY