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    Re: Home made artificial horizon
    From: Gary LaPook
    Date: 2011 Oct 4, 15:59 -0700
    But, enlarging the pictures it doesn't look like the bubble is present so check with the seller about the bubble. Without a bubble it is useless.

    gl

    --- On Tue, 10/4/11, Gary LaPook <garylapook@pacbell.net> wrote:

    From: Gary LaPook <garylapook@pacbell.net>
    Subject: [NavList] Re: Home made artificial horizon
    To: NavList@fer3.com
    Date: Tuesday, October 4, 2011, 3:56 PM

    There is an older model of the gunner's quadrant for sale right now on E-bay.

    http://www.ebay.com/itm/WW1-WWII-Model-1918-Gunners-Quadrant-/140614597066?pt=LH_DefaultDomain_0&hash=item20bd4879ca

    gl

    --- On Tue, 10/4/11, Gary LaPook <garylapook@pacbell.net> wrote:

    From: Gary LaPook <garylapook@pacbell.net>
    Subject: [NavList] Re: Home made artificial horizon
    To: NavList@fer3.com
    Date: Tuesday, October 4, 2011, 3:14 PM

    Attached are four photos showing the sensitivity of the level bubble in a M1A1 gunner's quadrant. The first shows the bubble centered and the second shows the micrometer set to zero mils with the bubble centered. The third shows the bubble shifted one full hash mark and the fourth shows how much the the micrometer had to be turned to move the bubble this one full hash mark, 1.4 mils. I turned the micrometer back to zero and the bubble re-centered, very good repeatability.

    gl

    --- On Tue, 10/4/11, Gary LaPook <garylapook@pacbell.net> wrote:

    From: Gary LaPook <garylapook@pacbell.net>
    Subject: [NavList] Re: Home made artificial horizon
    To: NavList@fer3.com
    Date: Tuesday, October 4, 2011, 1:15 PM

    According to the manual it is. Using the normal quadrant mounted on the cannon you could only set in elevations to one mil precision, about three minutes. But when doing "precision fire," we computed the elevation for the cannons to one-tenth of a mil and then set the gunner's quadrant to one-tenth of a mil before placing it on the quadrant seats located on the breech ring of the cannon. We then elevated the tube until the bubble was centered.

    We also had to periodically test the accuracy of the gunner's quadrant, first doing an "end for end test" and then a "micrometer test" so I am confident in their accuracy.

    gl

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