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    Re: SNO-M arc accuracy -- errors from one degree to the next?
    From: Richard Reed
    Date: 2010 May 5, 08:01 -0700

    I'm still learning the fine details. This wasn't backlash but 'stiction'. I saw what was happening when I noticed irregular movement when my hand got tired after about 30 adjustments. The drum was moving slightly crossways to the plane of the frame and the spring wasn't bringing it back. I have begun very lightly wiggling the drum after setting it, and this has eliminated the 'backlash'. I'm still working on the new numbers for the drum eccentricity.

    I suspect the oil I'm using is too thin for the SNO-M arc -- it's Moebius 8030. I don't think there is anything to be done with the drum assembly 'keepers', as they seem to work against slight tension of the arm that keeps the assembly from scratching the arc index.

    Does anyone use heavier lubricant on the arc of the SNO-M or the pre/early-war C. Plath 'W Frame', which Bill Morris says has the identical frame?

    Richard

    "I just tried Frank Reed's 2005 'test pattern' method of measuring drum eccentricity on my SNO-M as here:

    http://www.fer3.com/arc/m2.aspx?i=026884&y=200512
    .
    .
    .
    There also seemed to be about 0.5' backlash..."


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