48” Featherweight Camelback Straightedge Pattern is Taking Shape. - Page 2
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  1. #21
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    Quote Originally Posted by Fal Grunt View Post
    If you are curious about using FEA, look at getting Fusion 360. Free for hobbyists and it does have a rudimentary FEA. Have not delved into it myself, but I have heard it is... good. Certainly not comparable to high end offerings.
    Thanks for the suggestion. I am sort of curious, but figure you’d have to invest 50 hours or more learning time to start to understand how to use it. Maybe that is not true. Then there is the question that if I were able to determine an optimal design, could I actually execute it both from a pattern making (I am aware of 3-D printing, of course, but on large patterns like this it is very time consuming to print patterns in pieces and glue them together. And they don’t come out of the printer as cast-ready either. I have done some custom casting from them and found they require a fair bit of hand-finishing work to make them suitable for green sand casting) and grey-iron casting point of view. Not every pattern will fill properly and remain reasonably true on cooling. I have spent the last 18 months learning some of the basic nuances of casting... It’s great sport but not for the easily discouraged or casually interested.

    Denis

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    Another basic FEA option is McNeel's Rhinoceros coupled with the Scan-and-Solve plugin from Intact Solutions. Higher price bracket than Fusion 360, but massively cheaper than Solidworks or one of the other "big five" CAD systems. I've used Scan-and-Solve on several projects for basic stress and deformation evaluation. It's got some functional limits I would like to see removed, but it's good within its limits.

  3. #23
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    Regarding FEA, it's not a *huge* amount of work to learn, but also easy to use it in a way that you get garbage results. If you have a CAD model already I'd be happy to run a few basic FEAs for you, as this is part of what I do for a living. Drop me a message and we can talk more if you like.

    Quote Originally Posted by dgfoster View Post
    I really had not considered a level.pad, but maybe I should. I do not think I could add such a pad to the bow since the bow sits off-center fore and aft. This location is intentional to allow the SE to reach under overhanging features like vee-ways. It seems like balancing on such a pad with the SE on a plate would be precarious (if I am understanding your suggestion) on such a pad. However, it would not be difficult to add a pad to the center of top portion of the sole that could be machined flat. A Geier and Bluhm 4-3064-20 high precision vial only requires a space1.25” by 3” for mounting, for example.

    https://www.geier-bluhm.com/gb-conte...20_drawing.pdf

    I could just build up the pattern 1/8” in the center in an aesthetically pleasing way to allow for mounting such a level vial. (On my 18” Featherweight prism/parallel/straight edge/ level I offer special machining to mount such a vial inside the prism on the sole.) I’d be interested to know if folks think it might be worthwhile to add level-vial pad to the 48” and 36” Featherweights. Anyone reading along should please feel free to chime in pro or con.

    Halcohead, thanks for tossing out the idea for consideration! Do you think it would be useful to put a pad on the center, upper portion of the sole?

    Denis
    If it's just a small pad, I don't see the harm in adding a vial mount, but to be honest the ability to flip the straightedge on its back is more useful to me. It made quantifying error on my 24" straightedge super easy, and also allowed me to easily use it to check how straight my surface grinder was running. But understood it doesn't work with this design, so all good. Thanks for the thoughtful response though!

  4. #24
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    I very much appreciate the FEA offer. But, I have no CAD files for the pattern. The only files I have are graphite and paper sketches!

    I think my 18” SE is the one I have intended for use as a parallel and level and designed them from the beginning with that in mind.

    Today I’ll be shaping and installing ribs in the 48 pattern but there will not be a lot of time for that with more babysitting grandkids duty and needing to ship out another SE. This one is an 18 going to Australia. Because of its lightweight design and the fact that it fits in a Flat Rate box, it ships for 100 bucks—-which seems awful to me but is relatively cheap for international shipping. I think the cost would be similar to many countries though I’m not certain about Eastern Europe or the Middle East.

    Sorry I cant post progress pics from my phone to PM. Maybe later today when I’m home.

    Denis

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    FWIW, I machined and scraped the top edge of my 24" and 48" King SE's and occasionally put a level on them as I don't have a scraped parallel that long (or a KingWay setup). Pretty rare for me to do this and a bit of a bodge but it works.

    Just my opinion, but I think the beauty of Denis's 48" design is it's simple, and probably light weight and easy to handle (assuming similar to his 36" SE).

    L7

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    img_e5954.jpg


    I did get out into the shop for a couple hours to use the French curves and a little squinting to establish fair curves on the front side of the uprights. I think I am happy with the curves. But, it’s one of those situations where it is good to let it sit out for a while and just look at it every time you walk by and also to run your hand over the curves feeling for areas of “hardness” of the curve. Then out comes the sand paper for a few swipes here and there.

    You can see that only half of the ribs are contoured. Once those ribs are OK, I will transfer the curves to the corresponding rib on the other side. Then it will be time for cheeks to thicken the ribs and provide draft. The cheeks will be cut just a little oversized, glued and then faired to the pieces shown. Yup, slow, plodding work...


    Denis
    Attached Thumbnails Attached Thumbnails c02756dc-287f-42a0-8100-4d2662ffc0c2.jpg  

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    Having taken possession of one of Denis' 36" featherweights, this pattern work (not to mention his one-man iron foundry work!) really pays off. The casting has very crisp lines and a very elegant shape.

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