Hi Chris,

Thank you for the re-education on the temperature stable metals. I remember
using Invar back in my microwave vacuum tube days. Invar and similar metals
hardly expand with increasing temperature. They are very different. I'm
looking into Ni-SpanC 902. Just to see what's available.

Gary

 

 

 

 

 

 

From: psn-l-request@.............. [mailto:psn-l-request@............... On
Behalf Of ChrisAtUpw@.......
Sent: Monday, September 01, 2008 9:59 PM
To: psn-l@..............
Subject: Re: A test curtain rod bracket/s vertical

 

In a message dated 2008/09/02, gel@................. writes:




You and others have mentioned temperature affects. What is it that we need
to worry about? Is it the spring constant or just simple
expansion/contraction that we need to worry about. Are there ways we can use
that will nullify the affects, maybe bimetal springs? 



Hi Gary,

       It is the Temperature Coefficient of Young's Modulus of Steel which
is the problem. It is a whacking -2.4 x 10^-4 per C Degree. This large value
makes it very difficult indeed to compensate for it's effects, when you need
ppm accuracy.
       However alloys like Elinvar and Ni-SpanC were developed from the mid
1930's onwards which have near zero temperature coefficients. So seismometer
manufacturers just use these alloys. However, since they are relatively
expensive, they are not widely available for DIY constructors.

       Regards,

       Chris Chapman. 














Hi Chris,

Thank you for the re-education on the temperature stable =
metals.
I remember using Invar back in my microwave vacuum tube days. Invar and =
similar
metals hardly expand with increasing temperature. They are very =
different. I’m
looking into Ni-SpanC 902. Just to see what’s =
available.

Gary

 

 

 

 

 

 



From:=

psn-l-request@.............. [mailto:psn-l-request@............... On =
Behalf
Of ChrisAtUpw@.......

Sent: Monday, September 01, 2008 9:59 PM

To: psn-l@..............

Subject: Re: A test curtain rod bracket/s =
vertical



 

In
a message dated 2008/09/02, gel@................. writes:







You
and others have mentioned temperature affects. What is it that we need =
to worry
about? Is it the spring constant or just simple expansion/contraction =
that we
need to worry about. Are there ways we can use that will nullify the =
affects,
maybe bimetal springs? 





Hi Gary,



       It is the Temperature Coefficient =
of
Young's Modulus of Steel which is the problem. It is a whacking -2.4 x =
10^-4
per C Degree. This large value makes it very difficult indeed to =
compensate for
it's effects, when you need ppm accuracy.

       However alloys like Elinvar and =
Ni-SpanC
were developed from the mid 1930's onwards which have near zero =
temperature
coefficients. So seismometer manufacturers just use these alloys. =
However,
since they are relatively expensive, they are not widely available for =
DIY constructors.



       Regards,



       Chris Chapman.