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Re: Altitude Bearing Pressure

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  • jpcannavo
    Tom, Roy The UC18 (and 15 as well). Yeah the bearing arc looks like its no more than 60 degrees. What s interesting is that as far as I know, no one - until
    Message 1 of 10 , Aug 1, 2008
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      Tom, Roy
      The UC18 (and 15 as well).
      Yeah the bearing arc looks like its no more than 60 degrees. What's
      interesting is that as far as I know, no one - until now - has
      commented on this difference in the altitude bearing geometry.
      It is remarkable that the difference in loading Teflon has had that
      dramatic an effect. My own experiments with loading have shown more
      subtle differences in static friction - but I did not get down to the
      low psi range that obtains with a 60 degree arc of Teflon.
      By the way Tom, about how wide...1 inch?
      In terms of a fix, it would seem that Toms approach is the way to go.
      I also wonder if the mating edges of the trunions could be slightly
      beveled so that the EbStr slightly slopes away at the edge. I can't
      imagine that this would then hang-up, especially considering that the
      surface of EbStr has its own surface irregularities with no
      consequent problems. Also, speaking of taping on Teflon - I have to
      share - every one should own some of this stuff. I make great use of
      it - the adhesive doesn't creep/fail - even at higher temp.
      See in Photos under "Joes Stuff"

      --- In bigdob@yahoogroups.com, "Roy Diffrient" <diffrient@...> wrote:
      > Tom,
      > Have you communicated this problem and fix to Kriege? Since he's
      > them about as fast as they're made, I wonder how receptive he is to
      > significant changes/improvements.
      > Roy
      > ----- Original Message -----
      > From: "Tom Polakis" <tpolakis@...>
      > To: <bigdob@yahoogroups.com>
      > Sent: Wednesday, July 30, 2008 11:42 PM
      > Subject: Re: [bigdob] Altitude Bearing Pressure
      > > ---- Roy Diffrient <diffrient@...> wrote:
      > >> I believe that scope (Obsession compact 18, right?) has long,
      > >> Teflon strips to avoid hang-ups on the discontinuity in the
      joint between
      > >> halves of the altitude trunions. So small Teflon pads are not
      really a
      > >> solution_unless_you change to conventional one-piece trunions.
      > >
      > >
      > > Roy,
      > >
      > > Actually, 4 individual pads has turned out to be a very good
      > > since there is only one altitude (about 60 degrees) where the pad
      > > encounters the split in the Ebony Star. I went into making the
      > > knowing that I would only be working at that altitude for some
      very small
      > > percentage of the observing time. I expected an
      objectionable "bump" at
      > > that altitude, but how it has really worked out is that the
      telescope is
      > > only a bit more difficult to move for a half degree or so across
      > > split line. And I didn't even taper the Teflon pads.
      > >
      > > So now, instead of a telescope with very poor altitude motion at
      > > elevations, it has moderately poor altitude motion for a half
      > > around one discrete elevation, and excellent motion otherwise. I
      > > pleasantly surprised by this result.
      > >
      > > Tom
      > >
      > > ------------------------------------
      > >
      > > Yahoo! Groups Links
      > >
      > >
      > >
      > >
      > >
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