PSN-L Email List Message

Subject: Re: Different types of Pendulums
From: tchannel1@............
Date: Sat, 27 Oct 2007 16:58:42 -0600

```Hi Chris,  What you described below, I think, was one of the =
illustration,  Let me describe it this way...........
Lets say a 36" horz rod.............from the balance point 18" connect a =
short 2" x 4"  (L) shape rod, the 2" leg is welded to the balance point =
of the horz rod.
Now the 4" leg is inserted into some sort of bearing, and the whole =
thing swings back and forth from this 4" axle.   You have two equal =
masses, one on the left and one on the right of the 36" horz. rod.   NOW =
CAN  one extend the period of the device by relocating one or other of =
the masses?

Thanks, Ted
----- Original Message -----=20
From: ChrisAtUpw@..........
To: psn-l@.................
Sent: Saturday, October 27, 2007 3:44 PM
Subject: Re: Different types of Pendulums

In a message dated 27/10/2007 22:23:56 GMT Daylight Time, =
tchannel1@............ writes:
Hi Folks, Sometime in the past I saw a web site describing different =
types of pendulums used in sensors.  I don't remember their names, but

1.  one was a long vertical rod, with a center pivot, it contained a =
mass at the top of the rod and a mass at the bottom of the rod.

My question has to do with 1.  I thought this pendulum (positioned =
like an airplane propeller) was able to adjust it's period by moving the =
top and or bottom mass, up or down the rod?
I made a simply mock up of this illustration, but was not successful =
in any way. Can one adjust this arrangement to result in an extended =
period? Does anyone know of this web site or one similar?
Hi Ted,

There are several possible systems, but you need to suspend the =
pendulum near the middle, a small height above the centre of gravity. =
This gives a high moment of inertia due to the masses at the ends and =
the small restoring force due to 2x mass operating just below the =
suspension axis. It should work fine. You can also vary the position of =
one of the masses.=20

Regards,

Hi Chris,  What you described below, I think, was one of the=20
illustration,  Let me describe it this way...........
Lets say a 36" horz rod.............from the balance point 18" =
connect a=20
short 2" x 4"  (L) shape rod, the 2" leg is welded to the balance =
point of=20
the horz rod.
Now the 4" leg is inserted into some sort of bearing, and the whole =
thing=20
swings back and forth from this 4" axle.   You have two equal =
masses,=20
one on the left and one on the right of the 36" horz. rod.   =
NOW=20
CAN  one extend the period of the device by relocating one or other =
of the=20
masses?

Thanks, Ted

----- Original Message -----
From:=20
ChrisAtUpw@.......
To: psn-l@..............
Sent: Saturday, October 27, =
2007 3:44=20
PM
Subject: Re: Different types of =

Pendulums

In a message dated 27/10/2007 22:23:56 GMT Daylight Time, tchannel1@............ =
writes:

Hi Folks, Sometime in the past I =
saw a web site=20
describing different types of pendulums used in sensors.  I =
don't=20
remember their names, but

1.  one was a long =
vertical rod, with=20
a center pivot, it contained a mass at the top of the rod and a mass =
at the=20
bottom of the rod.

My question has to do with 1.  =
I thought=20
this pendulum (positioned like an airplane propeller) was able to =
it's period by moving the top and or bottom mass, up or down the=20
rod?
I made a simply mock up of this =
illustration,=20
but was not successful in any way. Can one=20
adjust this arrangement to result in an extended period? Does anyone =
know of=20
this web site or one similar?

Hi Ted,

There are several possible systems, but =
you need=20
to suspend the pendulum near the middle, a small height above the =
centre=20
of gravity. This gives a high moment of inertia due to the =
masses at=20
the ends and the small restoring force due to 2x mass operating just =
below the=20
suspension axis. It should work fine. You can also vary the =
position of=20
one of the masses.

Regards,

Chris=20
Chapman
```