Youngs Modulus for Piano wire

[John Delacour]

At 7:47 pm +0200 27/8/06, Stéphane Collin wrote:

>Hi John.
>
>I once had a university professor test for me the breaking strength 
>of a sample 1mm diameter Röslau wire and a sample of 1mm diameter 
>original Bechstein wire from a 1871 piano, see how they compare. 
>Both samples had the same breaking strength, that is sure.

Surprise, surprise!  And that was just at the beginning of the 
stupendous rise of MORITZ POEHLMANN

1. Official Test by the Jury of the World's Exhibition, Paris 1867:
   MORITZ POEHLMANN's wire
     No 17 broke at 312 lbs
     No 18 broke at 348 lbs
     (Pleyel Wolff's testing machine)

2.  Official Test by the Jury of the World's Exhibition, Vienna 1873:
   MORITZ POEHLMANN's wire
     No 17 broke at 322 lbs
     No 18 broke at 336 lbs

3.  Official Test by the Jury of the World's Exhibition, Philadelphia 1876:
   MORITZ POEHLMANN's wire
     No 17 broke at 342 lbs
     No 18 broke at 386 lbs
     (Steinway's testing machine)

4.  Official Test by Max Schiedmayer and George Steck
     The World's Fair, Chicago 1893:
   MORITZ POEHLMANN's wire
     No 17 broke at 415 lbs

[ Alfred Dolge -- Pianos and their Makers ]



>   Now the guy reported me the breaking strength was 1500 N/mm?, 
>which is much less than what Röslau claims.

That makes 337 lbs. for a No. 20 wire.  I work with a figure of 371 
lbs. for mwg. 20 and never exceed 70% of that in string-making; in 
other words I never make a string with a 20 core that will require 
more than 260lbs. tension.  If I were to design it for 290 lbs. it is 
certain it would break. I have seen strings made with Poehlmann wire 
still alive and kicking after 100 years with tensions far higher than 
that.  The top singles on the old Blüthners have a No 20 core at a 
tremendous tension.  After 100 years they do break.  If I replace 
them with the same design made with Röslau wire, the stringer will 
break them before they are even up to pitch.  That's how good the 
wire is now.

>The guy told me that the way you clamp the wire in the testing 
>machine has a tremendous effect on the measurements results.

Yes.  I keep meaning to build a machine to do this.  It's cheap and 
easy enough but it's quite involved.

>Now, what are we measuring ?  And what do the results mean ?
>How would you do the measurement of Young's modulus ?

No more clues yet.  I'm waiting for Ric to come indoors from his experiment :-)

JD