H Chris,

I don=E2=80=99t think we need to worry too much about the steel =
corroding here in California. The air is very dry even in the basement =
where the seismometer will be located. I purchased the SS pins from =
Small Parts. They seem pretty smooth, but by my finger nail test says =
they are not as hard as the steel dowel pins. Now 415 matensitic SS, I =
have not come across this one. I=E2=80=99ll have to look into that. =
Could that be an EU term? The .017 music wire is nickel plated.

Thank you for the comments, they are most useful.

Gary

=20

From: psn-l-request@.............. [mailto:psn-l-request@............... =
On Behalf Of ChrisAtUpw@.......
Sent: Monday, June 09, 2008 4:27 AM
To: psn-l@..............
Subject: Re: My First Lehman

=20

In a message dated 2008/06/09, gel@................. writes:




I have some pictures for the first Lehman. At this point I=E2=80=99m =
just getting familiar with it and learning how to set it up. I have 2 =
sets of crossbars, one set is 1/8=E2=80=9D SS dowel pins and the other =
is 1/8=E2=80=9D hardened steel dowel pins.=20



Hi Gary,

       Ordinary steel will corrode in the damp air during rolling =
contact. They are OK for trying out, but they won't last long. Are the =
SS dowel pins hardened, ground and polished? Can you get them in =
something like type 415 martensitic SS? Incidentally, you can buy =
martesitic SS rod quite easily, but you would have to harden it.

So far I think I like the hardened steel better. The upper mounting uses =
the idea=20



from Ted, he suggested using a =C2=BC-20 acorn nut. This worked perfect, =
I drilled a .020=E2=80=9D hole in the center to receive the =
..017=E2=80=9D dia. music wire. A nice snug fit.=20



       If this works, fine! I use thinner nickel plated music wire, 8 to =
12 thou OD. I fit an L bracket at the top of the column with a =
horizontal hole in it. I fit a bolt with a hole bored through the centre =
and clamp the wire between flat washers. This seems to work OK.

       Then I use a =C2=BC=E2=80=9D dia. Si3N4 ball bearing. The ball =
bearing grade is 5, so it is very=20



smooth and very hard, much harder than steel. So far I have been able to =
achieve just under 30 sec.resonant period. I=E2=80=99ll be using the =
Chapman magnet system for both the sensor and damping. The Lehman is =
shown here http://gelindgren.googlepages.com/lehman_6_8_08.jpg    The =
bearing detail:  =
http://gelindgren.googlepages.com/lehman_bearing_6_8_08.jpg  The upper =
mounting: =
http://gelindgren.googlepages.com/lehman_upper_mount_6_8_08.jpg  and =
lower mounting: =
http://gelindgren.googlepages.com/lehman_lower_mount_6_8_08.jpg =20



       If you are getting 30 seconds, that is great.=20

       Regards,

       Chris Chapman=20














H Chris,

I don=E2=80=99t think we need to worry too much about the =
steel
corroding here in California. The air is very dry even in the basement =
where
the seismometer will be located. I purchased the SS pins from Small =
Parts. They
seem pretty smooth, but by my finger nail test says they are not as hard =
as the
steel dowel pins. Now 415 matensitic SS, I have not come across this =
one. I=E2=80=99ll have
to look into that. Could that be an EU term? The .017 music wire is =
nickel plated.

Thank you for the comments, they are most =
useful.

Gary

 



From:=

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

Sent: Monday, June 09, 2008 4:27 AM

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

Subject: Re: My First Lehman



 

In
a message dated 2008/06/09, gel@................. writes:







I
have some pictures for the first Lehman. At this point I=E2=80=99m just =
getting
familiar with it and learning how to set it up. I have 2 sets of =
crossbars, one
set is 1/8=E2=80=9D SS dowel pins and the other is 1/8=E2=80=9D hardened =
steel dowel pins. 





Hi Gary,



       Ordinary steel will corrode in the =
damp
air during rolling contact. They are OK for trying out, but they won't =
last
long. Are the SS dowel pins hardened, ground and polished? Can you get =
them in
something like type 415 martensitic SS? Incidentally, you can buy =
martesitic SS
rod quite easily, but you would have to harden it.



So far I think I like the hardened steel better. The upper mounting uses =
the
idea 





from Ted, he suggested using a =C2=BC-20 =
acorn nut.
This worked perfect, I drilled a .020=E2=80=9D hole in the center to =
receive the .017=E2=80=9D
dia. music wire. A nice snug fit. 





       If this works, fine! I use thinner =
nickel
plated music wire, 8 to 12 thou OD. I fit an L bracket at the top of the =
column
with a horizontal hole in it. I fit a bolt with a hole bored through the =
centre
and clamp the wire between flat washers. This seems to work OK.



       Then I use a =C2=BC=E2=80=9D dia. =
Si3N4 ball bearing.
The ball bearing grade is 5, so it is very 





smooth and very hard, much harder than =
steel. So
far I have been able to achieve just under 30 sec.resonant period. =
I=E2=80=99ll be
using the Chapman magnet system for both the sensor and damping. =
The
Lehman is shown here http://gelin=
dgren.googlepages.com/lehman_6_8_08.jpg   
The bearing detail:  http=
://gelindgren.googlepages.com/lehman_bearing_6_8_08.jpg 
The upper mounting: =
http://gelindgren.googlepages.com/lehman_upper_mount_6_8_08.jpg =

and lower mounting: =
http://gelindgren.googlepages.com/lehman_lower_mount_6_8_08.jpg =







       If you are getting 30 seconds, that =
is
great. 



       Regards,



       Chris Chapman