Pattern for Gimbal Stove Bracket

Discussion in 'Pattern making' started by Tops, May 6, 2022.

  1. Tops

    Tops Silver Banner Member

    I have a small sailboat with an even smaller cabin and an even smaller cookstove.
    The mounting brackets for the discontinued stove are also discontinued and fetch about 175$ US.
    I was hoping to pattern and cast some things to unify the hobbies and let the stove swing when needed.
    Currently all that I have cast are 3D prints. Wondering if I should break down the barrier and make some honest to goodness wooden patterns, either with the CNC or with my own two mitts.
    Encosed are pics of the factory units ( which can be lifted and folded into a sitting-on-the-counter position), a couple of proposals, and the upright that I prefer at the moment.
    I would appreciate any design, constructions, and pouring tips for this pattern. Thanks!

    origo_1500_gimbals.png
    tops_stove1.jpg
    tops_pillar1_drawing.jpg
     
  2. rocco

    rocco Silver

    Depends on what type of person you are, if you're a nostalgic type, go with the hand made wooden pattern, you'll find there's something oddly satisfying about the process, it connects you to all the generations of foundrymen that have come before, however, if you're a "means to an end" sort of guy, stick with the 3d printed patterns.
     
    Tops likes this.
  3. FishbonzWV

    FishbonzWV Silver Banner Member

    For one/two offs, lost foam is the way to go.

    IMG_1702.JPG
     
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  4. Tops

    Tops Silver Banner Member

    I guess I am sort of fishing for a more hands-on experience for this one. I already started a new flask for this part which will also work for something the kid wants to try. I did buy a tapered ballmill cutter that I have yet to run successfully for a pattern. I could split the difference between man and machine and make the tapered pieces on the CNC and glue and fillet them but hand.

    Nice picture! If I close my eyes I can feel the wind...I read through Kelly's pin on the lost foam section, a few hours after I got confused about loose sand and green sand on Bruce's post. I have 1.5PCF EPS left over from other projects. The process does seem interesting.
     
  5. Tops

    Tops Silver Banner Member

    I did 2D CAD long enough to make a shrink-compensated rule and to take dimensions of the outer triangle and then did the rest without CAD or CNC or 3D printing...so I am like 1/3 done...:p
    The tools that saved the day were the hand-me-down combination belt/disk sander and a manual coping saw. I broke a blade early on with the secondhand electric scroll saw and could not find any spares at home. I also could not find my box with drafting tools to fix the compass to strike the arc. I ended up using holes in a Ames lettering guide. Once the bracket was glued and brad nailed and clamped to the saw table, with a machinist's square, I assembled the flask and marked and ground the round bolster for the bracket, using the bracket as a marking guide. Easy work rounding with the disk sander, including adding a little draft. I am thinking of removing the center rib and making full ribs on the sides. tops_stovebracket_flask_pattern1.jpg .
     
  6. Tops

    Tops Silver Banner Member

    Trying to imagine this as metal, could it be that there is enough there already...? Skip the side gussets ?

    tops_pillar1_1.jpg
    tops_pillar1_2.jpg
     
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  7. Tops

    Tops Silver Banner Member

    'The cake was iced with a buttercream frosting with a distinct note of styrene...'

    I made the call, too many ribs as designed. I drafted the vertical rib and installed with glue and brads. 15g PE resin + 5 drops accelerator + glass spheres (filler, ease of sanding) + fumed silica (thickener) was enough to add fillets, fill dents and misfired brad nail holes (where did those come from?) , and patch another pock hole in my concrete garage floor.

    tops_buttercream1.jpg
     
  8. Tops

    Tops Silver Banner Member

    Weekend results.
    -flasks assembled and guide strips installed
    -pattern through first coat fillets
    -proposed pouring scheme and weights calculated

    tops_bracket_progress1.jpg

    tops_bracket_schema1.jpg

    I think I will be getting some Bondo and/or glazing putty to clean up the fillets. The regular PE resin takes longer to cure and stays sticky on the surface as it is laminating (air-inhibited) to bond with subsequent coats. So one gums up sandpaper until the sticky is gone. I could have used some metal fillet tools and more glass spheres in the sauce to make it easier to sand as well. I asked for 'the experience' and I seem to be getting some. :)

    Q: How does the pouring scheme look?
     
  9. ESC

    ESC Silver Banner Member

    These are the patterns for the crankshaft balancer I made when I built the V8. The swing arm is a split pattern, but the sidestand is simple draft. I use super glue extensively and fillet with baking soda, sand, prime and finish with shellac (Bullseye). Recently I have started using wax fillet because it has less cleanup.
    As I remember I gated into the base, no riser and flat on the floor. No need to overcomplicate the pour, but I weight all my molds.

    IMG_20220508_180219.jpg
     
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  10. Tops

    Tops Silver Banner Member

    Thanks ESC, I appreciate the picture and tips. What did you use to bind the soda in the fillets?
     
  11. ESC

    ESC Silver Banner Member

    The old super glue trick, it's instantaneous. Just make sure the powdered fillet is the way you want it because it is hard when set.
     
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  12. Melterskelter

    Melterskelter Gold Banner Member

    Back in 2019 this method was a new idea for me. Since then I have used it many many times. Your pattern would lend itself nicely to this method with exception of the round spigot. The filets so formed are flawless and practically effortless. Epoxy sets up without a sticky surface as opposed to polyester-based laminating resin.

    http://forums.thehomefoundry.org/in...straightedge-pattern-is-in-process.830/page-3

    Denis.
     
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  13. Tops

    Tops Silver Banner Member

    That is a very interesting technique,thanks for sharing it Denis. I will try that in the future. Today at 80 degrees F the Bondo was setting before I was content with the application and I ended up discarding more than what hit the pattern.

    I reverse engineered the pattern back into CAD and ran it through the slicer for the 3D printer and the front end software for the CNC mill. Printer was about 9.5 hours at .16mm layer height and CNC was 4.5 hours using 1/8" diameter end mills (my normal settings for both machines).

    Thanks for clarifying ESC. My fingers stick together just thinking about it! :)
     
    Last edited: May 9, 2022
  14. Tops

    Tops Silver Banner Member

    The Bondo looked and sanded better in the 'dawning light of the new day'... :) I was only using an old 80 grit sanding disk yesterday and the day before. Today I repeated with a better 120 sanding disk ( I save the Velcro backed ones and use the 'centers' up for misc. jobs) and 1/4 sheets of fresh budget 150 and 240, and then honest to goodness 3M P320. I suppose I need to set my expectations for finishing somewhere between primer over still-warm chipped stick welds and compounded show car clear coat. The primer color makes me think of metal, looking forward to giving this a try. Wondering if doing the resin or Bondo in stages like Denis' epoxy method would have helped with the inside corners not to have to manage a soft material in three directions. I could also see wax working well in those corners too and mechanical (leather, wood, 3D print) working for the straight sections as well.
    tops_pillar_paint1.jpg

    tops_pillar_paint2.jpg
     
  15. PortaMelt

    PortaMelt Copper

    Looks nice :)
     
    Tops likes this.
  16. Melterskelter

    Melterskelter Gold Banner Member

    Tops,

    I used to use sand paper too long because buying it a few sheets at a time seemed expensive. I now order good Si-C paper in 100-sheet boxes. And I remind myself to consider a it a perishable consumable. Just use it for those first ten or fifteen stokes while it is good and sharp and then move to a new area of paper. I am inherently cheap, so it is a constant battle. But, my time also is worth something, I guess.

    For me, finishing to 220 seems good enough for my pattern work.

    Wax filleting has not worked well for sand patterns for me. For use on a master from which more working patterns would be cast—-that’s where it makes more sense for me. Unfortunately that is rare in my shop.

    Denis
     
    Last edited: May 12, 2022
    Tops likes this.
  17. Tops

    Tops Silver Banner Member

    Denis, that makes sense about the sandpaper. I have similar thoughts about sieving big box store sand lately.

    I had a chance to spend some time with the stove in its mock-up'ed cabinet (sent to the basement for a storm warning) and came to realize that the mock-up gimbal has some 'revisions' that did not make it to my CAD model.
    It looks like I cut off the tops of the bracket/pillar thingies to allow the stove to sit lower in the cabinet and so it can be covered for a flat working surface.
    It usually goes faster the second time, right...?
    tops_bracket_oops1.jpg
    tops_bracket_oops2.jpg
    tops_bracket_oops3.jpg
     
  18. Melterskelter

    Melterskelter Gold Banner Member

    No need to start over, right? Just tablesaw off a couple inches on the bottom. Glue on a new flange and now's your chance to try the epoxy fillet on the new inside corner. ;-)

    Using 5 min epoxy for the flange joint and standard epoxy for the fillet, you can be ready to go in less than a day.

    Denis
     
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  19. ESC

    ESC Silver Banner Member

    What Melter says, but use super glue and baking soda and ram up five minutes later.
     
    Tops likes this.
  20. Tops

    Tops Silver Banner Member

    Thanks Everyone.
    The radius end is hitting on the future cover. It would need some off the base and the top to fit as previously planned. I may end up remodelling the pattern all on that end instead. image001.jpg
     

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