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    Re: The Bygrave
    From: Ronald van Riet
    Date: 2009 Jun 30, 02:44 -0700

    Yes, I do have both a Bygrave and an HR1 (am I the only one to own a
    copy of both?)
    As far as rarity (rareness?) of these go, here are the numbers I know
    to exist:
    Bygrave: 6 in private collections, 2 in museums.
    HR1: 3 in private collections, 3 in museums.
    MHR1: 9 in private collections, 2 in museums, 1 known to have been in
    private hands but missing since this person died.
    HR2: 1 in private collection, 1 in museum, 1 known to have been in
    private hands but missing since this person died.
    Anybody owning one of these, please contact me off list so I can
    update my document on these position line slide rules. Please include
    serial numbers if possible
    On Jun 29, 8:00�pm, Brad Morris  wrote:
    > Hi Douglas
    > I actually DO have an MHR-1 (German Version of the Bygrave). �Get ready to 
    hear the collectors moaning, I USE it, without gloves.
    > It is a joy to use. �The solution of Az and h are just as fast as can be. 
    �The MHR-1 doesn't suffer from the actual Bygrave problem where the scales 
    slipped relative to one another. �Weighs alot less than HO229 and much 
    smaller too.
    > Gary's Flat Bygrave is even lighter and smaller, essentially �two sheets of 
    mylar. �You may wish to try it. �It really does work and give the feel 
    without selling your house to own one. Or the my Visual Bygrave, which 
    extends the scales perfectly from 0 to 90 degrees, far beyond what either 
    physical realization can do.
    > I do believe that Ronald has a sample of actual Bygraves//MHR-1's
    > They do appear on eBay from time to time. �Be prepared to spend a bundle.
    > Best Regards
    > Brad
    > ________________________________________
    > From: NavList@fer3.com [NavList@fer3.com] On Behalf Of 
    douglas.de...{at}btopenworld.com [douglas.de...{at}btopenworld.com]
    > Sent: Monday, June 29, 2009 12:11 PM
    > To: NavList@fer3.com
    > Subject: [NavList 8877] Re: Star-star distances for arc error
    > I should have also commented:
    > I would dearly like to get my hands on a real Bygrave slide rule or the 
    German equivalent to play with and try it 'for real'; (hands covered in white 
    gloves to preserve it of course).
    > I have only seen one example and that was in the Aviation museuum in Hendon. 
    It looked in poor condition too.
    > From a programme supplied by Dr. Kolbe I made one with a cardboard tube and 
    a sliding clear outer ("cos") scale just to try the operations for the fun of 
    it. �It proves the principle but is near impossible to use as the two scales 
    become so confusing one on top of the other.
    > I have not yet tried using different colours for the different scales to see 
    if it is then possible to use it more successfully.
    > Interesting to speculate if Mr. Bygrave tried this and rejected it as being 
    impracticable, reverting to the separated scales of a conventional 
    cylindrical slide rule and movable cursor to reduce confusion possibilities. 
    �Probably not.
    > What I do wonder is what happened to all these Bygrave slide rules - and the 
    German ones? �There must have been hundreds made and yet now they are 
    incredibly rare it seems. �The Air Ministry must have had boxes full of them 
    somehwere on the shelves of some nondescript warehouse in teh middle of 
    nowhere. �It is nice to contemplate that perhaps they are still there? ..
    > ...though much more likely thrown out by some idiot who was following orders 
    to throw away "that rubbish over there on the shelves released from the Air 
    Ministry inventory as uselss and obsolete!
    > Vandals!
    > Douglas Denny.
    > Chichester. �England.
    > Douglas Denny.
    > Chichester. �England.
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