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Cones and conic calculations
This month's headache is a four-piece copper finial brought to me by an architect. It is a Feng-Shui or Vaastu ornament designed for a new custom home, and it is supposed to be accurate to the drawing supplied to me.
Three of the four elements are cones or conic sections. I am no great whiz at flatwork, although I have worked some with others who were/are, so I am trying to hold the accuracy. This job is/was a headache, even so. I did the google thing for a few hours before finding "conecalc," a subset of http://www.i-logic.com/ http://www.i-logic.com/conecalc.htm is the page that I have now spent several hours with. (Kerry, Dan, Per, you guys might appreciate this?) I think I may be far enough along to show something worthwhile. The illustration here is now shopworn from having a lot of traffic across it, but perhaps enough info remains to give you an idea of the four elements needed, from the boxed base up to the witch's hat. 1_plan_dwg.jpg The cone here was easy, height, side and radius. The harder part was the hand roll, but I had an old candlestick iron that I rolled around, using the wood slapper. 2_cone blank.jpg 3_cone forming.jpg 4_cone_hand roll.jpg 5_cone closure_tighten.jpg Control of closure is by hammering the apex. Second stage, the bowl, which fits to the cone, starts life as a conic section. Blanked out and then roughed in the hammer. 6_conic layout_blank.jpg Stretching continues by more roughing in the hammer, after the bowl is rolled up. (APH saves my old arm from slugging the bag) 7_roll the bowl and hammer.jpg Contour gauge checks the optimism. Sigh, more to go yet. 8_contour gage check.jpg I go back and check the gauge against the dwg. 9_check the dwg.jpg Getting the final few hits on the money. 010_contour checking.jpg The APH is designed for stuff like this. 011_AP hammer does all the work.jpg ... more coming.
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Kent http://www.tinmantech.com "All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919. |
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trying for more accuracy
Next, the bowl is checked for height, and both top and bottom diameters have to correspond. I am optimistic I can hold 1.5mm...
But ..... surprises await me below the bowl. I got the bowl accurate enough on countour, upper and lower diameters, and the total height, so I can mark and turn in the lower edge. 012_mark for edge turning.jpg Turning is two minutes or so in the APH, because the dies turn and shrink at the same time, keeping the edge going where it is supposed to. 013_turning and shrinking in the APH.jpg I measure the total height and mark for trim. 014_marking for trim.jpg Trim clean to the line, as this edge gloves to the cone. 015_trimming.jpg I get the bowl and cone to fit tightly, with height and diameter very good. But now I try to get the math for the lower conic. Galvanized is cheaper than copper. 016_trying for accuracy.jpg Two tries, and I think I am close enough to lay out. 017_yet another layout.jpg Cut and roll up the section. 018_roll up the section.jpg Might as well make another, since I need the height, both the diameters, and the angle, all together. The dwg indicates 53 deg, but 50 works better, since the reverse was eliminated by the architect. . Love that concecalc. 019_check the math_again.jpg Secure the section with more copper pops, and turn in the top edge to mate with the bowl, and turn the bottom out to meet the boxed base. 020_turn in the top edge_ turn out the bottom.jpg So far, everything fits. Time to solder the inside seams and the rivets. Then, more assembly and soldering. The copper is 24oz, .036. Rivets are copper pops with steel mandrels. Ag soft solder gives a good service strength. 021_check the fit against the bowl.jpg The conecalc program works very well, and it allows me to insert various parameters to arrive at what works for the job. Very handy and fast, at least for me.
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Kent http://www.tinmantech.com "All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919. |
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I don't care what the rest of them say Kent, I reckon you are a clever bugger...
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Richard "I know nothing. I from Barcelona" (Manuel - Fawlty Towers) Link to our racecar project https://www.facebook.com/pages/Elan-...ab=public&view |
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Very nice. Thanks for sharing.
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Will |
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Question about the reverse
If the reverse on the base had been retained, when/how would it have been developed? Even if not impossible, would it be impractical to produce that portion in one piece for the entire circular element?
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AC Button II http://CarolinaSculptureStudio.com https://www.youtube.com/channel/UCzSYaYdis55gE-vqifzjA6A Carolina Sculpture Studio Channel |
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I believe I could make that lower conical reverse in 1 piece by running a piece cut like yours thru my reversing dies .Ken6inch reverse dies and pcs2.jpg
Last edited by Ken Hosford; 02-25-2015 at 07:18 PM. Reason: see if I can make picture show |
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Kent,
As always lovely work. I have had to make a bunch of different cones in the past and found a great program for laying out flat patterns for cones. It's not a free one but it works great and will produce a .dxf file for having parts cut with laser, plasma or whatever or you can print out the cone and it will tile them on multiple pages that can be taped together for large cones. It's called Cone Layout and it can be downloaded here. Just thought I'd pass it on. Thanx for the progress pictures. Jaysin
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Whether you think you can, or you think you can't, you're right. Henry Ford Last edited by JaysinSpaceman; 02-25-2015 at 08:00 PM. Reason: Forgot a bit. |
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Kent,
Thanks for posting, not only your work, but more importantly your process. Here is another cone generating tool and also several other useful spreadsheet generators here that will be of interest to metal shapers: http://www.pveng.com/ASME/DesignTools/DesignTools.php Obviously, from a trusted source as well.
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Mark from Illinois |
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Richard, Will, Cliffrod, Ken, and Mark:
Quote:
Will, You are very welcome! Cliffrod, Here below is your answer - I did tonight. Ken, Yes, absolutely .... and holding the 4 dimensional specs, too, I'll wager! Mark - You are very welcome. Process photos take a lot of time - for me - and I'd hate to say how much. So, here is a blank riveted conic: conic.jpg and here is the reversed version: conic reverse.jpg This was made after being riveted. It takes steady hands, 11 minutes of patience, and a good steady air motor that can be slowed down to a horse trot. ... and a minimal setup. I use these same pair of dies to make some different reverses, but not all of them.The copper bell is another, big reverse job I did, using the same dies. But that is a digression... Joe Helming and the bell.jpg Joe smiles with the bell.jpg I only digressed but to show more examples of a regular/constant reverse, versus an irregular or complex reverse. If a reverse is a compound shape, then a complex reverse would be a double compound, (according to the old boys I hang out with .) ZB, i.e.: Grumman Duck hull.jpg Grumman Duck horiz fairing.jpg saddle.jpg P40 fairing.jpg Spirit.jpg Waco gearleg fairing.jpg One finger fit, wingroot fairing.jpg Thank you for your patience. Now, back to cones and conics ...
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Kent http://www.tinmantech.com "All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919. |
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Moving forward on the conic base, let's go over making the conic into a reverse. Mark the conic into thirds.
conic.jpg Using a set of reverse dies, make steady consistent hits all the way around the edges, and keep track of each revolution - while moving the stretch into the conic towards the first line. Do this bottom and top. As your curve begins from the edge, go further in, stretching farther in, but gradually so the stretch is in a taper towards the center section marked. 022 conic reverse.jpg The edge grows so it needs to be trimmed back. 023 trim upper edge.jpg Turn the top edge in, to match the bowl above it. These two flanges will rivet and silver solder to each other. 024 flange in upper edge.jpg Cut a steel circle to round out both the bowl and reverse flanges, so they will fit together. 025 fit flanged circle to round steel pattern.jpg 026 check steel circle pattern_round out.jpg Now trim lower edge. 027 trim lower edge.jpg Flange out to make a foot for mounting. 028 turn out lower edge_foot.jpg Set up center two parts and cleco them together. Then cleco assy to base. Then set pointy cap in place and check all for straight and level. 029 cleco assy to base.jpg Next comes tinning and soldering, and riveting.
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Kent http://www.tinmantech.com "All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919. |
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