NavList:

Here are some pictures of the Bygrave replica I am using. The first
picture, 2891, shows the co-tan scale. When printed the scale only had
tick marks every 10 minutes and I added some 5 minute marks near each
end of the scale. I used the periodicity of the scale to figure out
where to place these tick marks. For example, to place the mark for 89º
15' I took its tan,  76.39, divided by 10, 7.639, and took the arc tan
of that giving me 82º 32'. I used the mark for that value (visually
interpolating) and with the use of a t-square I placed the mark for 89º
15' directly above it. I also hand labeled a number of tick marks to make
it easier to find the value I was looking for.
Picture 8292 shows the scale along side of the 12 inch drain pipe that I
mounted the scale on.
Pictures 8297 and 98 shows all three components, the tube with the
co-tan scale mounted and covered in clear plastic sheet; the cosine
scale sealed between two sheets of plastic formed into a tube and the
sheet of plastic formed  into a tube and marked as the cursor.




gl




gl

Gary LaPook wrote:

I have had great success with printing the scales of the flat Bygrave
and wrapping them around a tube and sealing them in place with clear
adhesive plastic sheets.

Here are some pictures of one example:

http://www.fer3.com/arc/m2.aspx?i=106329&y=200809

Links to the scales:

http://www.fer3.com/arc/img/107473.lapook2.pdf

http://www.fer3.com/arc/img/107473.lapook1.pdf

http://www.fer3.com/arc/img/108719.revised%20form%206-18-09.pdf

http://www.fer3.com/arc/img/107419.bygrave-manual.pdf

I picture of one made by Geoffrey Kolb:

http://www.pisces-press.com/graphics/Bygrave.jpg



Try it.

gl



Hanno Ix wrote:
  

Hello:

I agree. Bygraves could be build.

However, there are some cumbersome questions, the most obvious being,
How to generate a drum-shaped scales with the required accuracy and
resolution. Remember, we will have to maintain sub-millimeter acc/res
over many turns, with "many" meaning perhaps 20 to 50. This should be
possible, but is still not easy.

If someone could generate the mechanical construction and quality
assurance methods for this challenge we could talk about manufacturing
more seriously. Her are my ideas:

Personally, I am thinking of an ink-jet head printing on a turning
drum where the printing is synchronised with a digital encoder on the
drum' s axis. The process control could be handled by one of the
relatively simple contollers on the market.

Another approach would be to replace the ink-jet printing with an
engraving system.
With the first  I personally have experience, with the second none
whatsoever.

However, more problems lurk. What are the limits for excentricity of
the drums when in use? How about friction? How to stabilize the thing
when under the influence of temparature changes, humidity, sun's UV,
spray salt water, etc, etc.

So, you can see that the conceptual simplicity of the Byraves is
offset by many practical obstacles.

Compare this, for instance, with the Ageton method (H.O. 211)! Only 12
pages of a table, a sheet of paper and a pencil is virtually all you
need to get a generally higher res/acc than with a practical Bygrave.

Yes, you will also need the skill and concentration to exercise the HO
211 calculations under virtually any condition at sea - particularly
when you are a submarine commander at war. Well, I guess, in this case
a Bygrave, well designed under a government contract, does make sense!






--- On *Fri, 7/3/09, Greg Rudzinski /<gregrudzinski@yahoo.com>/* wrote:


    From: Greg Rudzinski <gregrudzinski@yahoo.com>
    Subject: [NavList 8924] Re: Manufacture new Bygraves?
    To: "NavList" <NavList@fer3.com>
    Date: Friday, July 3, 2009, 9:40 AM


    There must be a combination of PVC tubing that fits on itself snugly.
    If the white PVC were engraved with black and red scale markings as a
    regular plastic slide rule is then I think you would have something.

    On Jul 3, 12:18 am, <engin...@clear.net.nz
    </mc/compose?to=engin...@clear.net.nz>> wrote:
    > A few years ago, when I and a couple of friends wanted each to
    own a gear hobbing machine, we cooperated. One made the casting
    patterns and saw them through the local foundry, another did the
    heavy machining and I did the small parts like feedscrews and
    their nuts. It occurs to me that several handy people could
    combine their skills to produce replica Bygraves slide rules.
    There will surely be someone who knows where to access tubing in
    which each size nests snuggly in the next largest size, someone
    else will know how to produce hard-wearing replica scales, another
    may be prepared to turn the bobbins at each end and I would
    volunteer to do small bits of metalwork. The results do not have
    to make profits, though a little would be nice. Since there seem
    to be very few surviving Bygraves calculators, one could at least
    have the satisfaction of owning a replica. The starting point of
    course would have to be accurate, dimensioned drawings of an
    original, preferably following the metric system, so the
    manufacturing consortium would not have to be confined to the USA.
    >
    > Any offers/takers?



    

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