Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: New compact backup CELNAV system
    From: Geoffrey Kolbe
    Date: 2009 Feb 27, 06:53 +0000

    Brad, as someone who has also made a Bygrave cardboard copy, I think you
    are making problems where they do not exist. Sure, it would be better if
    the scales were on stiff tubes, but even if they are printed on a couple of
    rolled up transparencies and slid, one inside the other, I don't think
    squashing, bending or poking the thing would (within reason) make any
    significant difference. Both scales will be distorted in the same way and
    so - and this is the important thing - will not move against each other
    Too, I don't see any real need to lock the scale tubes while moving the
    cursor about. It is a fact that 99.999% of all slide rules ever made rely
    on friction to stop the scales moving against each other while the cursor
    is being manipulated. If necessary, it is easy enough to use one hand to
    clamp the scales together while moving the cursor with the other. With
    typical German thoroughness, Dennert & Pape decided to put a lock ring onto
    the MHR1, so the scale tubes could not move against each other as the
    cursor tube was being manipulated. Perhaps they made the scale tubes so
    well that there was not enough friction to do the job. That was certainly
    not a complaint you could make about the Bygrave I tried! The fact that
    Dennert & Pape put a lock ring on the MHR1 does not mean that all Bygraves
    were thereby redundant. And I don't think a lack of friction is going to be
    a problem in the Lapook version of it.
    While I have got my hands on the megaphone, I would like to say a big
    thanks to Gary for all the work he has done in coming up with a cheap,
    practical, usable version of the Bygrave/MHR1 that anyone can get up and
    running with a minimum of effort - and have a lot of fun too. As a
    navigational computer, the Lapook/Bygrave ticks all the boxes. It is cheap,
    easy to use, has good accuracy and needs no batteries. It is waterproof (to
    any depth), shock proof, nuclear bomb EMP proof and - the ultimate accolade
    - may even be child proof!
    Geoffrey Kolbe
    Brad [7439] wrote:
    >Hi Gary
    >Just to be clear, I was not questioning the accuracy of the Flat Bygrave,
    >WHEN FLAT.  Just as you have indicated, when flat, the device yields
    >perfectly acceptable results.  Since the scales are a realization of the
    >equations, unquestionably, they should work when used as directed.
    >If, however, one scale was distorted by an out-of-flat condition, then we
    >would see errors proportional to the error in flatness. One scale flat,
    >with the other distorted will yield problems. That was my assertion and
    >remains so.  Sharp as you are, you should see that as well.
    >My comments also indicated wrapping the scales around cylinders, which
    >eliminates the distortion of one scale to another.  That solves the
    >out-of-flat condition by making the surfaces stiff.  The follow-on
    >problem, how to lock one cylinder to another securely, forces a mechanical
    >solution.  Bygrave himself didn't solve that properly.  There are a few
    >mechanical arrangements I can think of to do that, all involving multiple
    >moving parts.  This would force your simple Flat Bygrave solution to a
    >more complicated cylindrical Bygrave solution, and keep the device out of
    >the hands of many who would try.
    >Again: Nothing wrong with the Flat Bygrave when used properly.  You should
    >be rightly proud of it.  Gosh knows I would be!
    >Best Regards
    Navigation List archive: www.fer3.com/arc
    To post, email NavList@fer3.com
    To unsubscribe, email NavList-unsubscribe@fer3.com

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site