PSN-L Email List Message
Subject: Re: Crossed rod hinge/suspensions v/s ball bearings hinge/suspensions
From: Brett Nordgren Brett3kg@.............
Date: Tue, 25 Oct 2005 10:37:29 -0400
It was interesting to hear about some real-world testing of the
zero-force/zero-moment hinge design. A few years ago I did some analysis
of its geometry aimed at seeing how well it simulated a pivot about a
single point, i.e. how well the end of a pendulum using that hinge would
track a true circle, and where was the center? At the time I was looking
at using the design in a leaf-spring horizontal.
Although, when I worked on it, I knew the design had been around before, at
the time I wasn't aware of how long and how widely it had been in use.
Rather than trying to do a mathematical analysis, I used a CAD program to
draw the pendulum in various positions and tried to see how well the locus
of the pendulum endpoints would fit a circle. For the test, I assumed
pivot rods of 1-inch diameter with a pendulum only 5-inches long, measured
from the center of the "lower" pivot rod. Even for that extreme case the
pendulum tip tracked a circle within 0.00025" [0.0063mm] over the range
of +/- 5 degrees of swing.
There had been some discussion about where the center of the arc would
be. From what I could see, the effective center of the arc was very near
the crossing point of the support flexures/wires.
At 12:21 AM 10/24/2005 +0000, you wrote:
>Could you post pictures of the rod hinge/suspensions "your setup"
>This sounds like somthing I would like to try.
>Thanks Bryan Goss
>From: meredith lamb
>Subject: Crossed rod hinge/suspensions v/s ball bearings hinge/suspensions
>Date: Sun, 23 Oct 2005 20:54:01 +0000
>Chris Chapman recently stated in a private email that he thought a crossed
>suspension would have less friction/dampening than a ball bearing
>hinge...and he is
>so very right!
Take care, Meredith Lamb
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