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    Re: Manufacture new Bygraves?
    From: Thomas Kleemann
    Date: 2009 Jul 10, 01:23 +0200

    my text woven in below...
    
    glapook---.net schrieb:
    > You're close to the original Bygave which has a cotan scale 8.8 meters
    > long. But you would have to adjust your spacing slightly because there
    > can only be 44 turns between 20' and 89�40' since each turn must equal
    > a change in log cotan of .1. The log cotan of 89� 40' is about  -2.2
    > and the log cotan of 20' is about 2.2, a range of 4.4 making  44
    > changes of .1 which is the reason for the 44 turns on the original
    > Bygrave. 
    
    I did't get that.
    Do you mean, there is some restrictin in the spacing - that one turn on 
    the scale has to have a certain interval (0.1) covered?
    
    I thought I'm free to choose whatever diameter I like and that the 
    scales length divided by the circumference gives the approximate number 
    of turns. Why 44, then?
    
    Or do you just talk about the original dimensions?
    
    > Its tube is 2.5 inches in diameter 
    
    Well, 2 inches was just an example...
    I took it, because anything between 40 and 50mm diameter handles well, 
    haptically.
    
    > times Pi makes the
    > circumfance of 7.85 inches times 44 turns equals 345.58 inches or 8.77
    > meters. If you adjust the spacing but keep the pitch unchanged and
    > make 56 turns it would cover a range of 1'30 to 89� 40' and so
    > eliminate the problem of sun sights near the equinoxes.
    > 
    
    How so? By prolonging the scale down to values below the original
    0� 20'? Twelve turns for 19 minutes of arc?
    
    Regards,
    	Thomas.
    
    
    
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