PSN-L Email List Message
Subject: Re: Folded Pendulum
From: ChrisAtUpw@.......
Date: Wed, 27 Jun 2007 18:39:50 EDT
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.
> 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,
Chris Chapman
In a me=
ssage dated 2007/06/27, tchannel1@............ writes:
I have seen a few descriptions=20=
of the "Folded Pendulum" sensor concept. Here is one http://jclahr.com/science/psn/youden/&n=
bsp; 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 1=
5" 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 sec=
onds. A factor of x10 increase in period should be quite easy. We can get &g=
t;30 sec from a 1.4 sec Lehman, no problems. The limitation is likely to be=20=
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 co=
rrect.
I guess the longer the pendul=
ums the longer the period, so If I use 24" It could be more than 12 secs.&nb=
sp; This design by David H. Youden, uses 6.47" pendulums, and I did not see=20=
what period it produced. The overall dim of it, is 10.27" tall....So p=
erhaps 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 electroni=
cs. It looks as if this corresponds to about 6 seconds. However, the SG pend=
ulums can be extended to ~50 seconds.
What happens as you trim the mass close=
r to the balance point? Do you have a trim mass set by a screw thread?
Regards,
Chris Chapman
[ Top ]
[ Back ]
[ Home Page ]