Hi all,

Here is another idea, for a possible vertical pivot.  It uses the outer
concave shaped
ball  bearing assembly raceway salvaged from a larger ball bearing assembly
for one part of the pivot.  I got the complete ball bearing assembly
(used/discard)
from a local surplus store for ~ $1.50.  Of course one needs a raceway with
the
raceway on the outer shell; as alot of raceways could have it inside the
shell.

The rod resting in the (concave) raceway is smaller in diameter that the
diameter than
raceway was built for...this reduces the contact surface to one point.  It
would be relatively self
centering in one lateral direction of course.  One end of the rod can hold
the spring; and of
course the other end would be for the mass.

Its very possible to have two such assemblys for added stability; and
interconnect the
"boom" rod/s...otherwise the boom would spin around the pivot contact
without having
to add some kind of mechanical control.

http://home.earthlink.net/~meredithlamb/ballbearingracewaypivot/

With two such assemblys; the pivot in effect becomes a "crossed
rod/cyclinder" pivot.
In the picture (no text added yet), the bolts are only to keep the round
raceway from
rolling in the example picture....the raceway could be easily affixed to a
"L" bracket/s.
If you connect the read ends of the rods, and then add the spring (or
possible two springs?),
then the mass end of the unit shouldn't be too hard to control.

I've yet no idea of the hardness of the raceway assembly; but I'd think it
would be
adequate.  A tough Stainless steel rod could be used for the boom rod
other side of
the pivot contact.

I used a abrasive cut off saw, to cut through the (not shown in the
picture), outer
shell of the original ball bearing assembly.  Cutting it was easy with such
a machine.

Meredith Lamb
Hi all,
 
Here is another idea, for a possible vertical pivot.  It uses the outer concave shaped
ball  bearing assembly raceway salvaged from a larger ball bearing assembly
for one part of the pivot.  I got the complete ball bearing assembly (used/discard)
from a local surplus store for ~ $1.50.  Of course one needs a raceway with the
raceway on the outer shell; as alot of raceways could have it inside the shell.
 
The rod resting in the (concave) raceway is smaller in diameter that the diameter than
raceway was built for...this reduces the contact surface to one point.  It would be relatively self
centering in one lateral direction of course.  One end of the rod can hold the spring; and of
course the other end would be for the mass.
 
Its very possible to have two such assemblys for added stability; and interconnect the
"boom" rod/s...otherwise the boom would spin around the pivot contact without having
to add some kind of mechanical control.
 
http://home.earthlink.net/~meredithlamb/ballbearingracewaypivot/
 
With two such assemblys; the pivot in effect becomes a "crossed rod/cyclinder" pivot.
In the picture (no text added yet), the bolts are only to keep the round raceway from
rolling in the example picture....the raceway could be easily affixed to a "L" bracket/s.
If you connect the read ends of the rods, and then add the spring (or possible two springs?),
then the mass end of the unit shouldn't be too hard to control.
 
I've yet no idea of the hardness of the raceway assembly; but I'd think it would be
adequate.  A tough Stainless steel rod could be used for the boom rod other side of
the pivot contact.
 
I used a abrasive cut off saw, to cut through the (not shown in the picture), outer
shell of the original ball bearing assembly.  Cutting it was easy with such a machine.
 
Meredith Lamb