[pianotech] was GH-1s

[David Love]

Read more carefully, I said the dimension was 21 by 21.4 not 21 by 24.  But
don't let me stop you from making up your own facts.  Straw men are in vogue
this holiday season.  

I said the preset bearing was 1.5 degrees, the board deflects by half so you
think that half the load has simply disappeared?  Interesting.

I have no idea what you are talking about in the last paragraph, nor do I
care to try and decipher it.  

As the song says, "you go your and I'll go mine, it's better that we do".

Happy Holidays.  


David Love
www.davidlovepianos.com

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Ron Nossaman
Sent: Friday, December 21, 2012 11:58 AM
To: pianotech at ptg.org
Subject: Re: [pianotech] was GH-1s

On 12/21/2012 12:11 PM, David Love wrote:
> The premise of my load distribution is irrelevant in this case but it 
> is not false.  I believe your individually calculating the load of 
> each rib based on how the unisons fall is incorrect, that the bridge 
> does distribute the load.  How much bearing you set at one end or the 
> other of the piano can, of course, influence the load on each rib.  
> But you push the bridge down on rib number 6 and rib number 4 
> deflects.  It doesn't do that just to be respectful to rib number 6.

Which is why I said I smooth the load, and it's no where near uniform
distribution. The treble is hugely more heavily loaded than the bass.



>The issue, however, is how we're designing them
> and the criteria we are using.  If I anticipated the same load that you
did,
> 25 lbs, that's how I'd build it.  The premise of a rib in a piano that has
> 900 lbs of downbearing carrying only 25 lbs is a false premise unless you
> have a whole lot of ribs or not much downbearing.

I didn't say anything about 900 lbs of bearing, that's your figure. My 
rib loading was based on individual unison loads being carried by the 
rib. Total bearing, which was irrelevant, was under 600 lbs.


> You want something more similar that's real world.  Here's a rib in a
piano
> I built, Steinway A, with a small cut-off bar.  The rib is close in length
> to your sample at 810mm in length.  The dimensions were calculated with a
> load of 65 lbs.  The dimensions were 810 mm in length, 21mm w x 21.4 mm h.

At last! The first hint of real information.

So let's see what we have. A 900lb bearing (guessed at or calculated?) 
and wildly erroneously assumed uniform weight distribution means 14 ribs 
for that 65lb load. But we're just interested in this one. Using a fixed 
end formula that reads four times stiffer than the free end, which as I 
indicated works out pretty closely to reality in bench tests after it's 
feathered and glued in to a rim, it's sized at 21x24, deflecting 4.3mm, 
but that was twice the real deflection, because what you really wanted 
was 0.75° bearing instead of the 1.5° you've been repeatedly pounding, 
but the load is calculated to about twice what it actually is anyway, 
and is halved again as it's strung and loaded so it all ends up just 
perfect. I have to admit, I'm impressed. I never would have thought of 
that. I'm not sure I want to know how you treat rib #1 with about a 20lb 
load and rib #14 with over 60lb as if they both have the same load. I 
think I'll pass on that one. It'll take too long to unravel.

But then the rib dimension is pretty close to what I started out doing 
before I determined by trying it that I liked a little stiffer rib 
scale, as it gave me a broader range of hammer choice. I have a hunch, 
just a guess really, that you might disagree.
Ron N