[Scott[_6_]]

On Oct 6, 5:48=A0pm, Dick Pierce wrote:
Scott wrote:

If on the other hand, you're talking about what I refer
to as patholigical designs like the old Dennisen air-
bearing linear "tracker", well, they are just plain old
bad designs, and their operation defies any conventional
analysis. You can't simply state that they have one
resonant frequency in the horizontal plane and another
in the vertical: the behavior is much more complex than
that. It's not so much like the simple two-pendulum model
where both pendulums are coupled to the same non-rigid
pivot point, it's more like where one pendulum is hanging
off the mass of the other: the result, rather than being
a simple double-resonant system, actually acts more
chaotically. SInce it is very rarely the case that the
stimulus is strictly in one plane or another, the resonant
energy is chaotically exchanged between the two planes
in a very complex fashion. It's NOT a pretty sight, and
leads to a VERY interesting output of teh system, an output
that often has little to do with what's actually in the
groove.


I don't know about the Dennisen but I can state it with my Forsell. It
clearly got excited on the test record at two distinctly different
frequencies that corolated with what one would expect from having two
distinct resonances in the lateral and vertical difections due to the
differences in effective mass. And I certainly have not had any
problems with the arm's performance.


Whatever inspired some of these "designers" of these air-
bearing linear arms, I really hope they got it out of
their system.

I also have a linear tracking arm. Mine may be one of, if not the most
difficult arm to set up.

WHat kind? There's a BIG difference between them. Like I said
above, the air-bearing non-servos linear trackers are nightmare
designs to begin with.


Forsell