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    Re: Bygraves
    From: Martin T
    Date: 2009 Jul 21, 09:24 -0700

    A while back I wrote some flat Bygrave scales in Postscript. It's
    essentially a programming language to create graphics, so I made my
    own rules regarding frequency of tick marks and labels. Essentially
    for each level of graduation (tens of degrees, degrees, tens of
    minutes, five minutes, minutes, etc) I defined a minimum size of
    division in (1/72 inch) pixels for which this particular division is
    either subdivided with tick marks. Same goes for label positions:
    By playing with numbers in table below I was able to fine tune
    frequency of tick marks and labels to my liking.
    /divsize      [ 1   9    2   5    6   10   ] def   % - Number of
    divisions on this level
    across                                             % in each division
    of previous level
    /divstep      [ 90  10   5   1    1/6 1/60 ] def   % - Size of each
    division in degrees
    /ticklen      [ 8   7    6.5 5    3   2    ] def   % - height of the
    tick mark
    /tickbottom   [-1.5 -1.5 -1  0    0   0    ] def   % - bottom of
    /tickweight   [ 1.5 1.5  0.5 0.25 0.25 0.1 ] def   % - width of the
    tick mark
    /subticklimit [ 15  10 	 10  20   20  25   ] def   % - minimum size of
                                                       % which is still
    subdivied on next level
    /labellimit   [ 120 60 	 100 180  250 200  ] def   % - minimum size of
    						   % which still has tick labels drawn
    						   % for subdivision
    /minutesonly true def % If true degrees are dropped from minute labels
    See following post for working adjustable scales.
    If you look in files you can also see variables for distance of labels
    from tick marks, font size etc.
    BTW These scales are produced for flat Bygrave, for cylindrical
    version you need to cut them in half vertically.
    On Jul 18, 11:36�am, Hanno Ix  wrote:
    > Hello:
    > One of the difficulties I presently face in making test samples of Bygraves 
    is the creation of accurate and well readable scales. The topic sounds 
    perhaps trivial but well designed scales contributes much to the quality of 
    the end product.
    > In non-linear scales,
    > how do you choose the graduations, and what is the rule to change them when the
    > labels become "too close" ?� Where do you
    > put the numbers - on top or next to the corresponding mark? Also, there 
    should be means to shift and stretch them for certain amounts so as to adapt 
    them to the drums, paper thickness, etc. Are there any programs or algorithms 
    specifically for rulers and scales?
    > I know some of you have made scales. Please let me know how you did it 
    before I get lost in re-inventing this wheel.
    > Regards
    > --- On Thu, 7/16/09, engin...@clear.net.nz  wrote:
    > From: engin...@clear.net.nz 
    > Subject: [NavList 9119] Re: Bygraves
    > To: NavList@fer3.com
    > Date: Thursday, July 16, 2009, 7:59 PM
    > Frncis has made a great start. I think it is possible to get something 
    looking even more like the original.
    > Ronald van Riet gives the dimensions of the tubes in millimetres, but I 
    think the original outside diameters would have been imperial sizes:
    > 2 1/2 in; 2 5/16 in; and 2 1/8 in. Nowadays, the only stock imperial sizes 
    that are near are 2 1/2 and 2 1/4 in.� There is a wide range of tube wall 
    thicknesses, so it will be possible to get to the required dimensions by 
    turning and/or boring.
    > The hexagonal top and the fluted base will be easy to make if a suitable material can be sourced.
    > I suggest we make a start with the simplest item, the Bygrave, and graduate 
    to the more complex German instrument. I can obtain suitable aluminium tubing 
    for only the two larger diameters - and only in 5 metre lengths. If someone 
    out there can send me 10 inch lengths of tubing with the right inside and 
    outside diameters to reach the required diameters, I would be happy to make a 
    start and pass the results on to the "scale fitters". This could prove the 
    concept as well as setting up a cooperative to supply those who don't own the 
    necessary machine tools.
    > Bill Morris
    > Pukenui
    > New Zealand
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