Hi Folks,  http://www.phy.mtu.edu/~suits/PH3110/pendulums.html  This is =
a description of different long period pendulums.   My goal in building =
sensors is to obtain the long period, like 20 seconds,  In most cases I =
have found this hard to do.   I know it can be done, but even with the =
Lehman the setup to get to 20 second is, for me difficult.   I usually =
give up at about 15 seconds.

I was pointed to this wed site long ago, and tried my hand at some of =
the ideas.   I made some prototypes, spending very little time, and had =
little success.
After thinking about the "Rocking Chair Pendulum" recently discussed, I =
saw a similarity between it and one of these Long period pendulums, so I =
went back to the shop and made another mock up of the "Nearly Balanced =
Pendulum"    This time I took a little more time.  Using a 48" dowel, I =
drilled a pivot hole in the center, inserted a finishing nail into the =
pivot hole, attached the nail to a table top, so the dowel would spin =
like a propeller.   Next I threaded a 1/2" machine bolt, nut onto one =
end of the dowel.   I timed the period at 2.5 seconds.   I threaded =
another nut on to the opposite end of the dowel, this time  one half the =
distance, from the end to the pivot.   I timed the period at about 3.5 =
seconds.   I keep moving the second nut closer to the end of dowel, to =
match the first nut which remained at the opposite end of the  dowel.   =
As I move the nut the period got longer and longer.  When I reached the =
end of the dowel, I got a 20 second period, with very little effort.

All this may be old news to some of you, but I found it to be amassing.  =
 Now I need to build another sensor, using this approach.

I think I will do another mock up, this time taking great care as to the =
pivot and finer adjustments, to see how long a period I can achieve.

Thanks,







Hi Folks,  http://www.p=
hy.mtu.edu/~suits/PH3110/pendulums.html =20
This is a description of different long period pendulums.   My =
goal in=20
building sensors is to obtain the long period, like 20 seconds,  In =
most=20
cases I have found this hard to do.   I know it can be done, =
but even=20
with the Lehman the setup to get to 20 second is, for me =
difficult.  =20
I usually give up at about 15 seconds.
 
I was pointed to this wed site long =
ago, and tried=20
my hand at some of the ideas.   I made some prototypes, =
spending very=20
little time, and had little success.
After thinking about the "Rocking Chair =
Pendulum"=20
recently discussed, I saw a similarity between it and one of these =
Long=20
period pendulums, so I went back to the shop and made another mock up of =
the=20
"Nearly Balanced Pendulum"    This time I took a little =
more=20
time.  Using a 48" dowel, I drilled a pivot hole in the center, =
inserted a=20
finishing nail into the pivot hole, attached the nail to a table top, so =
the=20
dowel would spin like a propeller.   Next I threaded a 1/2" =
machine=20
bolt, nut onto one end of the dowel.   I timed the period at =
2.5=20
seconds.   I threaded another nut on to the opposite end of =
the dowel,=20
this time  one half the distance, from the end to the =
pivot.   I=20
timed the period at about 3.5 seconds.   I keep moving the =
second nut=20
closer to the end of dowel, to match the first nut which remained at the =

opposite end of the  dowel.   As I move the nut the =
period got=20
longer and longer.  When I reached the end of the dowel, I got a 20 =
second=20
period, with very little effort.
 
All this may be old news to some of =
you, but I=20
found it to be amassing.   Now I need to build another sensor, =
using=20
this approach.
 
I think I will do another mock up, this =
time taking=20
great care as to the pivot and finer adjustments, to see how long a =
period I can=20
achieve.
 
Thanks,
Ted