Steinway B Scale Conversion

[Ron Nossaman]

> I am interested to know where you got your list of breaking strains 
> which differs so greatly from mine and Paulello's.  

One from Mapes, and one from Roslau, neither of which you will 
find credible, as you have already indicated.

For scaling work, I use Al Sanderson's generic formula of 
Tension/(2528*diameter(inches)^2), which corresponds 
reasonably well with the Roslau numbers. I keep core tensions 
under 55% by this formula. For your #21 core example, your 70% 
limit would be 283lbs by your tensile strength number, while 
my 55% by Sanderson's formula would be 307lbs. That would be 
76% by your figures, while your 70% would be 51% by mine. Not 
that far apart. The point is to retain a reasonable safety 
factor, whatever the numbers used.

There are a number of commercial scales, including Yamaha and 
NY Steinway, having core tensions well above 60%, and in cases 
above 70% by Sanderson's formula, and showing little to no 
tendency to self destruct.

For what it's worth,
Ron N