48” Featherweight Camelback Straightedge Pattern is Taking Shape.
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    Default 48” Featherweight Camelback Straightedge Pattern is Taking Shape.

    At long last I have time to make the pattern for my 48” Featherweight straight edge. Folks have been asking about it for a year and all I could say was “as soon as possible.” I am hoping to complete the pattern in the next week to ten days. I have completed the necessary upgrades to my foundry capacity to allow pouring this big brother to my very successful 36” Featherweight camelback which is now (as of 2 days ago) available on eBay as a raw casting and as a nicely machined casting. Those changes are larger flasks for the green sand molds, larger crucible, larger pouring trolley and altered lifting hoist for single-handed lifting of the 2600 degree 80 pound crucible out of the furnace. It all entails a fair bit of welding and metal cutting. And there have been improvements to my furnace tuyere and burner arrangement, new furnace lid etc. What I am saying is there a bit more to making this step than simply making the pattern—that’s the easy part.

    Here’s a link to a recent short video of a 20 pound pour of a custom gear I cast for a guy in Michigan who is restoring a 100-year-old windmill.

    The 48” will look very similar to the 36.” It will be just a little taller and the same sole width.

    Here are a couple pics of the first cuts being made to the web portion of the pattern. Making it light in weight and with a curved bow means a lot more pattern making work than if it were more rectangular. But the extra work is worth it given the weight savings and improved rigidity.

    I plan to post a few pics here and there as progress is made on the pattern.

    Once the pattern is complete I’ll be casting the new 48. However, I anticipate some tweaking of the process as complex and somewhat delicate patterns often need some finessing to get them to pour perfectly.


    The last pic is a photo of the crucible at night---included just cuz I like it. ;-)

    Denis
    Attached Thumbnails Attached Thumbnails 3683ad0f-35cf-4674-90f9-aae9f911d4a3.jpg   4405a154-a2b6-4c2a-984c-5fb6609493eb.jpg   a242a1f8-3f2e-4c5a-bcc8-720d0cfb8f2b.jpg   crucible-iron.jpg  
    Last edited by dgfoster; 08-14-2019 at 02:25 PM.

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    Nice video! Thanks for posting that.

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    Quote Originally Posted by dgfoster View Post
    The last pic is a photo of the crucible at night---included jut cuz I like it. ;-)
    Shudda been born "Northside", Pittsburgh, 1940's... Just getting to and from, most any direction, was a cannot-be-avoided tour of anything from Bessemer converters to coke ovens to open-hearth. You name it, it was within a hundred miles or so if not five or ten miles.

    And in our soil, rivers, air, lungs, and bloodstream, of course. "Iron Titty beer" was not entirely a joke - even if it tasted like one.



    But keep up the good work. "Tough job, but somebody has to do it."

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    The router template for the web is starting to emerge. the process is to first bore the holes for the corner radii of the individual cutouts of the web. Then mill flats to connect them. After all routing and boring is done, the template edges will be harened by applying polyurethane varnish. then the template should be ready for use.
    Attached Thumbnails Attached Thumbnails 48-pattern-1-.jpg   48-pattern-3-.jpg   48-pattern-2-.jpg  
    Last edited by dgfoster; 08-15-2019 at 08:14 AM.

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    Denis, how wide is the board?

    L7

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    Quote Originally Posted by lucky7 View Post
    Denis, how wide is the board?

    L7
    The template board is presently 7" wide. So the SE will end up just a smidge under 7" high as the board has the sole and bow drawn in.

    The sole and bow have a mortise cut into them to recieve the web as that makes the pattern stronger and it makes accurate assembly much easier. Otherwise, when you try to put the sole onto the web or bow onto the web, the epoxy glue acts like grease and you have parts wanting to squirm all over the place. On the other hand, if I cut the mortise right, the parts ought to more or less snap together. Complicating accurate assembly is the fact that the bow and sole have to have draft on their upper and lower surfaces. So that means squareness of assembly is also tricky. I will probably leave the top of the bow square (no draft) and the sole bottom square until after the glue is setup and then plane the draft into those surfaces. That way I can use the undrafted surfaces as guides to accurate assembly.

    Taking my time at this stage getting the cutouts smoothly cut with good blending of round corners to straight side and getting the sole and bow on right can save hours and hours of sanding and planing later. That is a lesson hard learned from prior pattern building experience.

    Denis

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    I had a few more bits and pieces of time in the shop. Here are a few more pics. The small ribs you see in the pattern for my 36 have to be accurately positioned or they won't have draft. So, I am cutting slots in the top of the sole and both sides of the web to recieve small tenons which will be cut into the ribs and which will hold the ribs in place while glue dries. Here is where the DRO, right-angle attachment, and a 1/8" slitting saw make location of slots wthat will line up front to back and web to sole relatively easy. This may not make a lot of sense to readers right now, but the next installation of photos should pull it all together---that will coincide with the pieces being put together. ;-)

    I included a photo in the next post (hit my max of 5 per post) of the pattern I have been using for my 36" SE as the 48 will look a lot like it and it may provide a reference for viewing the current pics.

    Denis
    Attached Thumbnails Attached Thumbnails img_5924.jpg   img_5916.jpg   img_5917.jpg   img_5919.jpg   img_5922.jpg  


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    Here is the 36 Pattern
    Attached Thumbnails Attached Thumbnails reworkedpattern-3-.jpg  

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    Suggest making the end parts of your pattern 1/8" thicker than other ribs to allow some extra meat for machining of ends instead of leaving rough cast. (For those of us who are neat freaks...)

    L7

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    Quote Originally Posted by lucky7 View Post
    Suggest making the end parts of your pattern 1/8" thicker than other ribs to allow some extra meat for machining of ends instead of leaving rough cast. (For those of us who are neat freaks...)

    L7
    Good idea and already planned. Doing so will also provide a place on the pattern to insert draw spikes to aid in pulling the pattern from the green sand. On the 36 I had to add bosses to the ends which were later trimmed off—-extra work and the bosses tended to pull from the sand poorly. I was able to modify them to work ok, but don’t need that complexity. The photo attached here shows the boss I added to the 36 pattern. The photo of the pattern shown in post#8 predates the boss.

    Please, anybody chime in with other thoughts. Additional eyes on a problem are helpful.

    Denis
    Attached Thumbnails Attached Thumbnails pattern-making-7-.jpg  

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    Now cutting the curve for the bow using a 100-year-old Stanley compass plane. Not a plane that I use often, but the plane perfect for the job. The curve cut is "automatically" smooth and fair in minutes. Next will be routing the cutouts in the web.
    Attached Thumbnails Attached Thumbnails img_e5927.jpg   img_e5928.jpg  

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    Now all the cutouts are routed. I used the template I have been showing along with a good-sized router and a flush-trim bit. That step is always a bit nervous-making as the router can potentially tear up a pattern and piece pretty easily. I used brads to nail the pattern to the web piece. I took my time and all went well.

    Next is routing out a groove for the web to set into the sole and attaching a bow (no ribbon!). The sole top an web bottom will need each to ahve draft added before attachment as removing material to provide draft would be really hard after assembly.

    Denis
    Attached Thumbnails Attached Thumbnails pattern-making-10-.jpg   pattern-making-11-.jpg   pattern-making-12-.jpg  

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    Hi Denis,

    I loved your video.

    So how did you come up with your exact design?

    I have suggested in the past, that people should use finite
    element analysis to develop straight edge designs to get
    the optimal shape - did you?

    I would love to come up and see your operation in process,
    and maybe help if the need should arise. I met you once
    before to ask for scraping hints and to autocollimate
    your granite.

    Just another (75 year old) fanboy,

    Paul

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    Quote Originally Posted by toolnuts View Post
    Hi Denis,

    I loved your video.

    So how did you come up with your exact design?

    I have suggested in the past, that people should use finite
    element analysis to develop straight edge designs to get
    the optimal shape - did you?

    I would love to come up and see your operation in process,
    and maybe help if the need should arise. I met you once
    before to ask for scraping hints and to autocollimate
    your granite.

    Just another (75 year old) fanboy,

    Paul
    Paul, The short answer is “no.” I do not doubt that my design is not the perfect solution to making a better straight edge that is lighter in weight and as stiffer than necessary to do its job. But, intuition and study of many existing designs informed the choices I made. I feel pretty good (lucky might be a good choice of words) about the results of my two designs to date. The 36” is far lighter (about half) than any 36 that is capable of reaching under an overhanging 45 degree vee-way. And yet it is so stiff that it deflects less than a tenth when loaded at its midpoint with greater than its own weight and support only at each end on 1-2-3 blocks. My prism is just plain stiff—being only 18” long and ribbed it does not deflect even part of a tenth when measured by a tenths indicator in response to greater than its own weight loading.

    Could those performance features be improved upon? Surely they could. By how much is a good question. One thing to consider is that I have to be careful about “analysis paralysis” inhibiting getting it done. If FEA were available and I had climbed the learning curve of learning to use it, I would surely use it.

    I remember well well the very pleasant part of a day we spent playing with your very excellent metrology equipment and testing the rigidity and flatness of the “ generic” surface plates I had purchased from the “Big G” and from Woodcraft Supply. Both exceeded their specified flatness by a wide margin—-eye opening to me! And they were extremely stiff as well. Good times. I think we have had some interesting emails concerning LVDT’s as well.

    Good to hear from you as well. Visitors to the foundry are always welcome as it is fun to show it off and sometimes get suggestions for improvements as well.

    Denis

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    Now the bow is glued to the web. I cut a groove into the bow to center it on the web and then cut draft on the grooved bottom of the bow. Now the trick was to glue the bow so that its undrafted (flat) top was very square to the web. Otherwise the draft would be increased on one side and possibly lost on the other. So I made the little brackets pictured to hold the bow square. To use them, I lightly clamped them in place and the used a plastic mallet to drive them toward the sole until the bow was solidly seated on the web and then snuggled up the clamp. That seemed to work well as checking the bow for square looks very good.


    To give myself plenty of assembly time, I used a 12 hr epoxy rather than a 5min epoxy as I usually do. I was worried this somewhat springy limber piece might give trouble. But, it went on smoothly. Tomorrow will be the day for rib assembly.

    Denis
    Attached Thumbnails Attached Thumbnails 6a0c4187-7632-44bd-a258-04d32a8c4efd.jpg   64881b49-2af5-4d2d-b9bb-222df3a1871a.jpg   3cd79a17-327b-4c4f-afbc-b0d0f52df2b6.jpg   b9a61145-2086-4e19-8f1b-1ee2e2ae59bb.jpg  

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    Default 48” Featherweight Camelback Straightedge Pattern is Taking Shape.

    Double post deleted.

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    Looks super good Denis. Very impressive work!

    Have you considered adding a short pad in the top center for scraping/grinding parallel to the sole? I find this makes it easy to flip the straightedge on its back and directly indicate flatness (by checking parallelism to the surface plate), as well as being a good pad for attaching a level.

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    Quote Originally Posted by Halcohead View Post
    Looks super good Denis. Very impressive work!

    Have you considered adding a short pad in the top center for scraping/grinding parallel to the sole? I find this makes it easy to flip the straightedge on its back and directly indicate flatness (by checking parallelism to the surface plate), as well as being a good pad for attaching a level.
    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
    Attached Thumbnails Attached Thumbnails f8331be4-d73d-4084-89b3-1c1e9a750979.jpg   b8d1f0b7-d5fa-4e40-8ed9-3a8875616167.jpg  

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    I do not have a lot of building progress to post today as yesterday was busy with grand kids ands boxing up and shipping a straight edge. I did check the bow for squareness and it is spot-on the whole length. Whew! That bow could have easily been skewed. I did get a little done on fitting the ribs that stiffen each upright. They have to be fittied individually since the curve on each varies as they go from shortest to longest. I think I have a system figured out to make that fitting process reasonably quick and accurate. I'll post that after using it enough to be sure it is a winner.

    With the basic outline of the pattern done now that the bow is on, I was curious about how the weight of the 48 will compare with the 36. By weighing the two patterns, the relative weight of the castings can be predicted with pretty good accuracy. The 36 pattern weighs 45 ounces and the 48 is 60 ounces. Since the weight of the 36 with the minimal material removed from the sloe to just make it cleanup is 25 pounds, it is likely the 48 with the sole just cleaned up wil be about 33 pounds. I machine the 36 to a target weight as requested by individual buyers ranging from 19 pounds to 25 pounds so the machined weight of the 48 should range from 26 pounds to 33 pounds or so. That is a little less than my targets, so I am pretty happy. The caution is there is still some wood to add and also remove from the pattern, so those predictions should be taken with a grain of salt. But, they should be in the ballpark. The users' backs and arms will appreciate it!

    Denis

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    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.


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