Hi Folks,  I am pursuing, the concept of a "Inverted T torsion spring"  =
I just want to experiment with a mock up, in the shop, to study the =
idea.

I started with a 3/8" discarded band saw blade, cut it into a ribbon and =
hung it from the shop ceiling.  It measured about 78" top to bottom.
I Secured the top of the band to a beam in the ceiling, and to the =
bottom of the band, I attached a 5/8" wood dowel, 40" long centered, 20" =
on either side.

This formed and inverted T, which if twisted would return to the same =
spot, as the flat band of steel untwisted.
I will call this spot, the center line.

To the bottom of the wood dowel, centered, in line with the band saw =
blade, I placed a small finishing nail, pointing down.  This nail fits =
into a small hole in the bottom of a coffee can,  The nail and coffee =
can act as a retainer so the band can only rotate.  The band can no =
longer swing like a pendulum.  The coffee can is waited so it can't =
move.  There is a very small space between the nail and the coffee can =
hole, so it does not rub.

I balanced two 1 1/4 # weights on the wood dowel, one on each side, at =
14" from the center of the dowel.

This first thing I noticed, was the length of time the torsion spring =
would cycle, once moved, (twisted) about 8" from the center line, and =
released.
It rotated back and forth, for 5 hours, from 3:58 pm until 9:00pm, and =
you could still see some movement.

The two masses 14" from center, arrangement resulted in a cycle of 27 =
seconds, and at 16"  the cycle was 32 seconds.

I add a pair of magnets and an Aluminum plate as a damper, on one end of =
the dowel, and a pick up coil and magnet to the other end of the dowel.

It is all connected and ready to record.   I covered most of the sensor =
with a makeshift tent of old blankets to keep draft away.   A small hole =
in the top of the tent allows the band saw blade, to pass.

It all seems to be working.   I hope to leave it set up and record a few =
earthquakes, before I must remove it, so I can continue my other shop =
work.

When and if I get some recordings,  I will post them on PSN under the =
name TCIDTS   for Torsion Spring.

This is all very interesting to me.   With very little effort I could =
get a 32 second period, by adding more mass or a longer dowel, I could =
get even longer.

Thanks, Ted............Ps.......I did take the time to cut all the teeth =
off the band saw blade, so now it looks like a ribbon of steel about =
3/8" x 78".  and the finial period is about 30 seconds.










Hi Folks,  I am pursuing, the =
concept of a=20
"Inverted T torsion spring"  I just want to experiment with a mock =
up, in=20
the shop, to study the idea.
 
I started with a 3/8" discarded band =
saw blade, cut=20
it into a ribbon and hung it from the shop ceiling.  It measured =
about 78"=20
top to bottom.
I Secured the top of the band to a beam =
in the=20
ceiling, and to the bottom of the band, I attached a 5/8" wood dowel, =
40"=20
long centered, 20" on either side.
 
This formed and inverted T, which if =
twisted would=20
return to the same spot, as the flat band of steel =
untwisted.
I will call this spot, the =
center=20
line.
 
To the bottom of the wood dowel, =
centered, in line=20
with the band saw blade, I placed a small finishing nail, pointing=20
down.  This nail fits into a small hole in the bottom of a coffee=20
can,  The nail and coffee can act as a retainer so the band can =
only=20
rotate.  The band can no longer swing like a pendulum.  The =
coffee can=20
is waited so it can't move.  There is a very small space between =
the nail=20
and the coffee can hole, so it does not rub.
 
I balanced two 1 1/4 # weights on the =
wood dowel,=20
one on each side, at 14" from the center of the dowel.
 
This first thing I noticed, was the =
length of time=20
the torsion spring would cycle, once moved, (twisted) about 8" from =
the=20
center line, and released.
It rotated back and forth, for 5 hours, =
from 3:58=20
pm until 9:00pm, and you could still see some movement.
 
The two masses 14" from center, =
arrangement=20
resulted in a cycle of 27 seconds, and at 16"  the cycle was 32=20
seconds.
 
I add a pair of magnets and an Aluminum =
plate as a=20
damper, on one end of the dowel, and a pick up coil and magnet to the =
other end=20
of the dowel.
 
It is all connected and ready to=20
record.   I covered most of the sensor with a makeshift tent =
of old=20
blankets to keep draft away.   A small hole in the top of the =
tent=20
allows the band saw blade, to pass.
 
It all seems to be working.   =
I hope to=20
leave it set up and record a few earthquakes, before I must remove it, =
so I can=20
continue my other shop work.
 
When and if I get some recordings, =
 I will=20
post them on PSN under the name TCIDTS   for Torsion=20
Spring.
 
This is all very interesting to=20
me.   With very little effort I could get a 32 second =
period, by=20
adding more mass or a longer dowel, I could get even =
longer.
 
Thanks, Ted............Ps.......I did =
take the time=20
to cut all the teeth off the band saw blade, so now it looks like a =
ribbon of=20
steel about 3/8" x 78".  and the finial period is about 30=20
seconds.