[pianotech] GH-1s

[Ron Nossaman]

On 12/20/2012 11:06 AM, David Love wrote:
> How many fixed end formulas are there?

Not many, but I've found I can't assume anything.


> Of course in actual practice

Yes, yes, yes.


>  Google it and look
> it up.

I have the formulas, but as I said, I've found I can't assume anything.


> But if we
> use those different formulas and all other parameters remain the same then
> the simple ends beam will be a much sturdier beam than the fixed ends one by
> a factor of 4.

This is where I was going. These calculations are done with full section 
simple beams. After feathering, a fair bit of strength is given up. I 
did some calculations and deflection tests years back that indicated 
around a 16% loss of strength. Calculated with simple ends, this loss is 
fairly closely cancelled by gluing the final rib form into the rim, and 
what small panel compression that exists also compensates. So my 
conclusion was and is that the simple end full section calculation ends 
up being pretty close to the reality after it's built. A fixed end 
calculation showing a beam of some specific dimensions to be four times 
stiffer (however you care to describe it) under a given load than a 
simple end formula produces a beam of 1/4 the stiffness of a simple end 
calculation to produce a given deflection under a given load. That means 
to me that, since I've verified to my satisfaction the similarity to the 
real world of the simple end calculations after feathering and assembly, 
that a fixed end calculation will produce a rib that, after feathering, 
will be considerably weaker than the calculations indicate. That is, 
unless there is some surprise secret windage compensation (perhaps a 
factor of four?) that hasn't been mentioned just yet. Include a low 
crown and a 1°+ bearing load on long ribs with no cutoff, and the 
numbers say it doesn't work and won't support that kind of load at those 
deflections without being stiffer than is claimed. So I'm wondering how 
this works.


> BTW re your other post on hybrid RC&S directed at Nick G's post., I took
> that to mean the hybrid versus RC&S positions.

I didn't care to make that assumption, so I asked.

Ron N