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

      =20 Regards,

       Chris = Chapman=20

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