ChrisAtUpw@....... wrote:
  >        The correct reference is:
> 
>        http://home.earthlink.net/~meredithlamb/crbs.html  
> 

All this discussion of using parts from ball bearings as hinge 
bearings, and it finally dawns on me that people ate talking about 
everything except the surfaces that are made precisely as low friction 
bearing surfaces.

I haven't yet gotten my seismometer completed, but here is how I built 
my hinges.

I sawed a small (3/4 inch O.D.) ball bearing outer race in half with a 
moto cut off wheel and used the two halves as one side of the each of 
the hinge bearings.  I dimpled a piece of aluminum and epoxied a ball 
from the same bearing into the dimple as the other bearing surface.

The lower bearing (in compression) is just the half outer race epoxied 
to the head of a bolt with the groove facing out and the groove 
vertical.  The matching half is a bullet nosed piece of aluminum with 
a dimple in the end and the ball in the dimple.

The upper bearing is made with the other half of the outer race 
epoxied to a small slice of aluminum U channel so that it completes a 
loop.  The part that holds the ball is slotted with the dimple in the 
inside of the slot, so it can pull on the ball.  The channel slice has 
a hole for a mounting bolt, opposite the half of the bearing race. 
The groove is horizontal.

This combination seems very stable but also self aligning to some 
extent to allow for sloppy tolerances in the match between the boom 
and the base.

This hinge makes use of the exquisitely precise, smooth and hard 
surfaces intended to carry load in the original bearing.  I hope to 
get around to testing the design soon, but life keeps getting in the way.

I don't have a web page set up yet, either, but if anyone is 
interested, having trouble understanding my description and emails me 
with their address, I will take some photos and send them to you.

__________________________________________________________

Public Seismic Network Mailing List (PSN-L)