## PSN-L Email List Message

Subject: Re: Folded Pendulum
From: tchannel1@............
Date: Wed, 27 Jun 2007 18:16:43 -0600

```Hi Chris,   Thanks, that answered several questions.

>What happens as you trim the mass closer to the balance point? Do you =
have a trim mass set by a screw thread?

I got about 12 second, with just a block for a mass,  When I do it for =
real I will use a threaded rod and moveable mass.
Thanks, TEd

----- Original Message -----=20
From: ChrisAtUpw@..........
To: psn-l@.................
Sent: Wednesday, June 27, 2007 4:39 PM
Subject: Re: Folded Pendulum

In a message dated 2007/06/27, tchannel1@............ writes:

I have seen a few descriptions of the "Folded Pendulum" sensor =
concept.  Here is one http://jclahr.com/science/psn/youden/  from this =
one and others I get the general idea.

I made a mock up using two pendulums 16" long and a cross member of =
about 15"  By moving the mass L and R on the cross member beam, I could =
get up to 12 seconds period.

Hi Ted,

A 16" pendulum has a period of 1.28 seconds. A factor of x10 =
increase in period should be quite easy. We can get >30 sec from a 1.4 =
sec Lehman, no problems. The limitation is likely to be in your =
suspension system.

The Australians managed to get a period of 90 sec from a 1 sec =
folded pendulum without feedback, if my memory is correct.=20

I guess the longer the pendulums the longer the period, so If I use =
24" It could be more than 12 secs.  This design by David H. Youden, uses =
6.47" pendulums, and I did not see what period it produced.  The overall =
dim of it, is 10.27" tall....So perhaps it has a shorter period.

Dave Youden's pendulums are 0.8 seconds. Since it is a feedback =
instrument, the period will depend on the electronics. It looks as if =
this corresponds to about 6 seconds. However, the SG pendulums can be =
extended to ~50 seconds.

What happens as you trim the mass closer to the balance point? =
Do you have a trim mass set by a screw thread?

Regards,

Hi Chris,   Thanks, that =
questions.

>What happens as you trim the mass =
closer to the=20
balance point? Do you have a trim mass set by a screw =

I got about 12 second, with just a =
block for a=20
mass,  When I do it for real I will use a threaded rod and moveable =

mass.
Thanks, TEd

----- Original Message -----
From:=20
ChrisAtUpw@.......
To: psn-l@..............
Sent: Wednesday, June 27, 2007 =
4:39=20
PM
Subject: Re: Folded =
Pendulum
In a=20
message dated 2007/06/27, tchannel1@............=20
writes:
I have seen a few descriptions of the "Folded Pendulum" =
sensor=20
concept.  Here is one http://jclahr.com/science/=
psn/youden/ =20
from this one and others I get the general idea.I made a mock up =
using two=20
pendulums 16" long and a cross member of about 15"  By moving =
the mass=20
L and R on the cross member beam, I could get up to 12 seconds=20
period.Hi=20
Ted,       A 16" pendulum has a =
period=20
of 1.28 seconds. A factor of x10 increase in period should be quite =
easy. We=20
can get >30 sec from a 1.4 sec Lehman, no problems. The limitation =
is=20
likely to be in your suspension=20
system.       The Australians =
managed to=20
get a period of 90 sec from a 1 sec folded pendulum without feedback, =
if my=20
memory is correct.
I guess=20
the longer the pendulums the longer the period, so If I use 24" It =
could be=20
more than 12 secs.  This design by David H. Youden, uses 6.47"=20
pendulums, and I did not see what period it produced.  The =
overall dim=20
of it, is 10.27" tall....So perhaps it has a shorter =
period.       Dave =
Youden's=20
pendulums are 0.8 seconds. Since it is a feedback instrument, the =
period will=20
depend on the electronics. It looks as if this corresponds to about 6 =
seconds.=20
However, the SG pendulums can be extended to ~50=20
seconds.       What happens as =
you trim=20
the mass closer to the balance point? Do you have a trim mass set by a =
screw=20