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    Re: Bob Goethe's Mark 2 Navigators slide rule, test drive comparisons.
    From: Sean Johnston
    Date: 2019 Nov 15, 13:48 -0600

    First, thanks you for making your files available!!
    Extending and duplicating the tangent scales for direct multiplication and division is brilliant.

    I?ve spent some time building my own version of your Slide Rule and have attached some printable files below.
    The great thing about reworking a slide rule?e design today is that you can steal previously patented innovations from the major slide rule companies of yore and combine the best attributes : ) - K&E, Nestler, Faber Castell, Aristo, etc. I took the liberty of rearranging some of the scales and added a CI scale for easier division when needed. 
    On the back are some illustrations to help jog my memory when reducing sights.
    I plan on using Ponoko (Ponokohttps://www.ponoko.com) to laser etch/cut the parts and have added some images of how it will look once assembled.

    Also attached are worksheets(sized to fit a day-timer) for reducing a sight based on your instruction manual.
    I?m a novice in the math department, so please feel free to let me know if anything looks off. 

    On Nov 14, 2019, at 9:16 PM, Bob Goethe <NoReply_Goethe@fer3.com> wrote:

    >>Bob, did your rule ever reach the market?<<

    Not to market...but the project is still alive. 

    I completed the basic design for the face of the rule 3 years ago.  At that time, I talked to a representative from the MakerBot 3D printing company who told me that 3D technology was, at that time, not mature enough for the kind of project I had in mind.  He recommended that I wait.  Time has now passed, and 3D printing has advanced.  I am going to take another whirl at fabricating a slide rule.

    I got a quotation from an industrial 3D printing shop a month ago to produce the rule, but it was astronomically expensive, $800 CDN (and this price does not include the etching cost).  I could purchase my own, fairly large format 3D printer for less than the price of a single rule from them (the least expensive printers cannot manage a rule with a 10 inch scale, together with the overhang on the right and left of the scale; you must purchase a bit larger printer to make a full-sized slide rule).

    Presumably the quality would be better on industrial-grade printers...but the only way to know if the quality is adequate on a hobby-grade 3D printer is to buy such a printer and try it out.  I have a friend who lives 180 miles south of me who has offered to come up for a weekend, and help me assemble and calibrate a printer if I go ahead to purchase one.

    The other thing I am noticing is that the 3D printing shop doesn't really need (or want) me to come on site to discuss my project with them.  They just want the 3D printing drawings (STL files).  That being the case, it occurs to me that I can equally well send my files to businesses in Vancouver or Ontario to get quotes.  There is no particular virtue in "dealing locally".

    The other possibility is to convert the STL files into engineering drawings that a machine shop could work with, and investigate the cost of fabricating the rule in metal...presumably aluminum, though stainless steel and nickel alloys are also possibilities.  We have several machine shops here in Edmonton that could potentially do the job.

    In both the 3D printing and CNC metal-machining options, the hash marks and numbers could be added either with laser or chemical etching (I don't yet know what mechanical etching, with a CNC machine, is capable of).  We have places here in Edmonton that do chemical etching of gauges/instruments used in the oil industry, as well as laser-etching businesses.

    So I am still working on the project.  My goal is to get the unit price down to where I could supply them to the dozen or so people in the world who would be interested in such a rule.  If I could break even financially as I sell those dozen rules, I would be content.

    The slide rules I have are ones that my father used in his career as a mechnical engineer.  They were manufactured in the early 1940s, and came to me for free.   I have no idea what the market value for a new slide rule might be.  "What the market will bear" is going to play a role in the feasibility of trying to bring the rule to market...where the "market" is most likely a handful of NavList members. 

    The value of such a rule is limited by what a slide-rule or navigational enthusiast is going to pay.  One can work all the navigational calculations he could ever want on a Casio Fx-260 Solar II for just $10 CDN.  So this kind of project will NEVER stand on its own legs, financially.  But I knew that all along.  Electronic calculators wiped out almost the whole world-wide slide rule market 45 years ago.

    Do you have an opinion on what people might think was a fair price for a slide rule that was optimized for navigation?  If people say "I wouldn't pay a nickle more than $50" then that tells me one thing.  If people say, "I could spend as much as $200 for such a rule" then that would tell me something else.

    I expect to get a picture semi-soon of what the various manufacturing options would cost.  If I know what people might think a fair price would be, it tells me whether I should be just making one rule for myself -- for I will surely do that -- or if I should hold open the option of making several rules and selling them.

    We are settling into the Canadian winter now...which makes it a good time for me to stay indoors, and goof around with manufacturing quotations.  All the sailboats have been pulled out of the lakes, in preparation for the lakes freezing over. So without flying to a warmer climate, there is no more sailing to be done for several months in Alberta.


    p.s. I have one friend who has mused aloud about whether his celestial navigation students might all be doing their sight reduction with Mark 1 Navigator's Slide Rules soon.  The truth is that sailors are into anacronistic ways of travelling.  They are a bit of a niche group.  And celestial navigators are into anacronisitic ways of figuring out where they are (a niche within the niche).  Among this group of people, doing things the fast/cheap way is not always their preference.  They do what they do for fun. 

    Who knows?  It could turn out that doing Bygrave equations on a slide rule could, in a small sort of way, turn out to be a popular thing to do (a niche within a niche within a niche?).

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    File: 146175.nav-slide-rule-1a.pdf
    File: 146175.nav-slide-rule-1b.pdf
    File: 146175.nav-slide-rule-back.pdf



    File: 146175.slide-rule-reduction-worksheets.pdf
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