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    Re: Borrowed Bygrave
    From: Francis Upchurch
    Date: 2021 Jun 16, 05:00 +0100
    Hi David,
    I have a virtually perfect Bygrave 11A bought ebay 2013. No serial number but probably 1929-30. I built a replica which works perfectly, so the original has stayed in the tin can .  I got the original to work by simple dismantling  via the 3 brass screws and replacing the felt friction spacer strips which had deteriorated.
    All documented in my many previous reports on navlist but can send  you more on request .
    If you want to build a replica, with plastic tubes, I have done that and all details in my report.
    Best wishes

    On Fri, 15 Jan 2016 at 01:18, David Pike <NoReply_DavidPike@fer3.com> wrote:

    I’ve got the loan of a Bygrave Position Slide Rule MkIIA from the Royal Institute of Navigation for a couple of months (photos below).  Apparently, they had two, a good one and a poor one.  Unfortunately, I was only able to find the poor one; nobody seemed to know what happened to the good one.  It carries the inscription that it was produced by the Air Ministry Laboratory South Kensington in August 1920.  If the number was ever filled in, it’s long since rubbed off.  I’d like to teach myself to use it prior to possibly making a copy for myself with plastic piping.  Is the best set of usage instructions those on Gary’s Freddie Noonan page?  Also, does anyone know where I can find a photo or print out of the explanation off the side of the MkIIA?  Finally, does anybody know what went down the inside of the cylinders?  All I can see is the remains of a brass chain.  DaveP

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