Aluminum Plates

[Alexander Galembo]

In seventies, we compared four vertical (120 cm high) instruments of the
same model, made using the same technology, with two cast iron and two
aluminum plates. The results were:
- Tuning changes of the  "Aluminum" instruments with temperature was about
2.5 times  larger than for the "cast iron" instruments (that simly follows
the difference in temperature coefficient for Aluminum and cast iron).
- After the temperature coming back to the norm, the "iron" instruments
return back to the initial tuning better than the "aluminum" instruments
- Basses were deeper and richer in the iron instruments
- In extreme treble, the color and the intensity of the hammer-string
"knock" were sistematically different for different material of the frames.

Alex



At 12:37 AM 7/21/98 -0600, you wrote:
>I am curious to hear opinions regarding aluminum plates.  I have come
>across a few of these from time to time, and even recently sold such
>piano. I felt it was of high enough quality that I even invested a
>considerable amount of time and money into it with some new action
>parts, hammers, some case work, etc.  It was really quite a nice
>sounding piano when I finished it, not to mention a pleasure to move
>being at least a couple hundred pounds lighter then it's cast iron
>equal.
>
>I have heard many techs argue that these plates are not capable of
>holding a good tune do to flexing. Others have claimed that it changes
>the accustics to some kind of undesireable degree. Yet I have not
>personally found this to be the case. This recent piano turned out to be
>one honey of an instrument.
>
>My personal theory, (perhaps someone can support or rebute this), is
>that it may have simply been proven to be too expensive to manufacture.
>Aluminum is a rather expensive metal compared to the relative cheapness
>of gray cast iron. In fact, I could have probably made a nice piece of
>change extracting the plate and turning it in for cash for recycling.
>
>So, is there really an inferiority to aluminum or are there some valid
>technical points against it? Just curious.
>
>Rob Goodale, RPT
>
>

Alexander Galembo, Ph. D.
Acoustics lab, Dept. of Psychology, Queen's University
Kingston ON  K7L3N6 
Canada

Tel. (613) 5456000, ext. 5754
Fax (613) 5452499
E-mail: galembo@pavlov.psyc.queensu.ca
URL   :  http://www.geocities.com/CapeCanaveral/Lab/8779/