PSN-L Email List Message

Subject: How Pivotal is the pivotal relationship?
From: "Paul Cianciolo" Paulc@........
Date: Fri, 15 Jun 2007 12:19:46 -0400


Hello Folks,

Now that I have my instrument somewhat operational, there are another few
"improvement"

Here is the deal.

When constructing my first experimental Lehman units I used a piece of steel
channel iron mounted in a vice at the vertical member.
The idea being it would for an experimental platform for different pendulum
lengths, weights, suspension wires, bearing surfaces, material  etc. etc.

The first bearing surface was the head of  # 5 bolt polished, and mounted
into a holed drilled into the vertical member. The arm had a similar bolt
mounted in the end of an aluminum tube. This bolt had a hole in the center
of the head and a hard stainless ball glued into it.

The suspension was a .020 piano wire and the mass was a 5 Lbs roll of copper
wire slide over the end of the aluminum pipe.
The top of the suspension wire was simply drooped over the top of the
vertical member and  "C" clamped to it in order to made the pendulum as
close as possible to horizontal.

By moving the pivots laterally I could see the effect, and cause the mass to
stop where ever I wanted within reason.

OK  comes the problem.  After putting guitar tensioner on the top of the
vertical member, so I could adjust the pendulum level, I could no longer
cause the mass to stop anywhere.
It seemed that no combination of level the pendulum, changing the mass
position moving the bottom pivot would allow the pendulum to stop.

After a couple hours of messing around, I reverted back to the original
setup and Bingo... perfect balance.

So... blah. blah, blah,

Finally I realized that the adjustment apparatus had moved the top wire
suspension point back slightly so that it was a bit behind the vertical
member.
No longer directly vertical of the bottom pivot.

I find that I need to have the top pivot just slightly forward of the bottom
pivot to get any pendulum I build to balance.

Is there some rule of thumb...  It seems the closer to 90 degrees the angle
between pendulum and vertical becomes the easier the pendulum will shift off
balance.

Currently my bottom pivot is crossed hard cylinders, and I want to do the
top this way, but I would like to know more about the "Pivotal Relationship"
before I construct the bearing.

Phew!!!.. I hope this makes sense to someone.
Thank you

PauLC
W1VLF






Hello Folks,
 
Now that I have my instrument = somewhat=20 operational, there are another few "improvement"
 
Here is the deal.
 
When constructing my first = experimental=20 Lehman units I used a piece of steel channel iron mounted in a vice at = the=20 vertical member.
The idea being it would for an = experimental=20 platform for different pendulum lengths, weights, suspension wires, = bearing=20 surfaces, material  etc. etc.
 
The first bearing surface was the = head=20 of  # 5 bolt polished, and mounted into a holed drilled into the=20 vertical member. The arm had a similar bolt mounted in = the end of=20 an aluminum tube. This bolt had a hole in the center of the head and = a hard=20 stainless ball glued into it.
 
The suspension was a .020 piano = wire and the=20 mass was a 5 Lbs roll of copper wire slide over the end of the aluminum=20 pipe.
The top of the suspension wire was = simply=20 drooped over the top of the vertical member and  "C" clamped = to it in=20 order to made the pendulum as close as possible to=20 horizontal. 
 
By moving the pivots laterally I = could see=20 the effect, and cause the mass to stop where ever I wanted within=20 reason.
 
OK  comes the problem.  = After=20 putting guitar tensioner on the top of the vertical member, so I could = adjust=20 the pendulum level, I could no longer cause the mass to stop=20 anywhere.
It seemed that no combination of = level the=20 pendulum, changing the mass position moving the bottom pivot would allow = the=20 pendulum to stop.
 
After a couple hours of messing = around, I=20 reverted back to the original setup and Bingo... perfect = balance.
 
So... blah. blah, blah, =
 
Finally I realized that the = adjustment=20 apparatus had moved the top wire suspension point back slightly so that = it was a=20 bit behind the vertical member.
No longer directly vertical of the = bottom=20 pivot.
 
I find that I need to have the top = pivot=20 just slightly forward of the bottom pivot to get any pendulum I build to = balance.
 
Is there some rule of = thumb...  It=20 seems the closer to 90 degrees the angle between pendulum and vertical = becomes=20 the easier the pendulum will shift off balance.
 
Currently my bottom pivot is = crossed hard=20 cylinders, and I want to do the top this way, but I would like to know = more=20 about the "Pivotal Relationship" before I construct the = bearing.
 
Phew!!!.. I hope this makes sense = to=20 someone.
Thank you
 
PauLC
W1VLF
 
 

[ Top ] [ Back ] [ Home Page ]