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Building a metal sphere

topic posted Tue, January 9, 2007 - 10:17 AM by  Uncle Sticky
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New to this tribe, as well as most things in metal working. Ok, all things. Total noob, so any suggestions, reference books, vids, etc, are welcome. I want to build a six foot diameter hollow metal sphere, in two hemispheres.

Basically, I'm building a globe out of sheet metal. How do I do it? I'm open to all ideas right now.

My thought was to bend square tubing around a jib in the right circle, and cut the sheet (very thin gauge) into triangles, and weld them together, like orange sections. How do I bend them? How do I weld them? What's the best internal structure? Help!
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  • Re: Building a metal sphere

    Tue, January 9, 2007 - 3:07 PM
    I've never done anything to this scale. When I made very small hollow spheres (we're talking like max 1 inch diameter) I had a block (can't remeber the name of it for some reason) that was concaved and you would tap the piece until it was how you wanted it.
    • Re: Building a metal sphere

      Tue, January 9, 2007 - 4:08 PM
      Uncle Sticky,

      Building a sphere this large will present some problems, but I think you can work with it. This is a big thing to try and work under an English wheel, but it could be done… probably could use a few extra hands to roll it back and forth.

      There are several ways to accomplish this that I can think of and having an understanding of how they are done will only help you with whichever way you choose.

      Most hemispheres are formed by being spun. Check here for an idea of this process:

      en.wikipedia.org/wiki/Metal_spinning

      But your globe would take a mighty big lathe to spin each half.

      Many small hemispheres can be form with a Die/Punch set up. Check here for what I’m referring to:

      www.harborfreight.com/cpi/cta...item.taf

      Again, you’re looking for bigger.

      I think you are probably on the right track with your triangle construction method. The biggest potential problems I can see are:

      #1) Rolling the tubing to form the frame of the sphere. You could try and use very small tubing and just pull it into the circle around a fixture, then weld it together. But its best if the tubing would hold the desired form on its own, or at least close. Otherwise there are lots of stresses trying to push and pull at different angles. This means you’d have to either bend them by hand (which is certainly doable) over a curved fixture or roll them into the radius via a tool like this:

      cgi.ebay.com/large-Radiu...photohosting

      The circumference of the globe divided into quarters is just under 5’. You could bend a bunch of appropriately sized sections of your structural material and assemble a hemispherical “basket” for each half with the pieces arrayed around a center point (think of the globe's poles) and connected to a ring (think the equator). Then measure the resulting triangles formed and cut out your pieces for the skin. I think if you build the frame sturdy, perhaps with some cross bracing, AND you use thin sheet metal, you could just tack your triangles to ring and bend them around to the pole point without much fuss. Which leads me to…

      #2) When you go to weld this up, it is going to stand the potential to warp all over the place. You’ll want to tack it on with alternating tack welds to minimize the warping (think like the star pattern for putting on lug nuts). You’ll probably want to apply the same idea to the pattern of placing the triangle skin pieces on too, skipping from one side of the globe to the other to try and balance it out. If you do this patiently enough, then you will eventually get it completely welded up, but it’s gonna be a job no matter how you look at it. Then you get to grind them all down nice and smooth.

      Here’s a thought… you could do some sheet metal research at a local shop and then try and actually fold a full length tab on the triangle’s edges, forming seams that would snap together. Then they could be riveted together, rather than welded. That might give a cool effect in the end too, sort of Art Deco, but that may not be what you’re looking for.

      Hope this helps. Don’t hesitate to ask for clarification or additional ideas.

      LCN
      • Re: Building a metal sphere

        Tue, January 9, 2007 - 4:11 PM
        Doh!! I see Troy already made mention of the arc idea while I was digging up links. And he also raises a good point... You could make a geodesic dome ball out of electrical conduit!!

        Check here:

        www.desertdomes.com/
        • Re: Building a metal sphere

          Tue, January 9, 2007 - 10:32 PM
          Ack! No more domes! We built replacement poles for our 22' dome, and made a small, six foot dome for our art car. It was ALOT of work. Of course, that car is now much safer than when it had a roof. That does raise an interesting idea, though, in which I can use the dome we built for the car as a template/form to hammer out the metal sheets. Awesome! Thanks!
  • Re: Building a metal sphere

    Wed, January 10, 2007 - 9:22 AM
    Unless you build the sphere from multiple fusiform (orange sections) strips, bonded together, you will certainly need to employ sheet metal shrinking or stretching. This will require an English wheel (slow, especially with steel) or a hammer. Even with a Yoder, something this big will take many hours. Even large orange sections will require plastic metal deformation (whhel, hammer) if you want a true sphere.

    Kent White (the Tin Man) has a video about hydraulic fluid forming using a mold and water pump. He's made large wheel pants for antique aircraft this way. But these large molds are engineering feats in themselves.

    Welding on thin metal can be done either with Tig or gas. Preheat the part by waving a torch on the seam and adjoining metal to avoid a lot of shrinkage.

    You've got a big job ahead of you. If you've got money to burn you might ask Fay Butler to do it on his Yoders.
    • Re: Building a metal sphere

      Wed, January 10, 2007 - 10:34 AM
      I saw a large metal globe for sale, and it used a different approach. I'm grateful for all of the help you folks have been giving me, so I'll ask another question. If I go with multiple longitude and latitude crossings (think the lines on a globe), and tack the snowflakes to the crossing lines, what is a good, efficient way to do the cut outs? I'm making snowflakes, some of them a good foot or two across. What do you folks think of the concept?
      • Re: Building a metal sphere

        Wed, January 10, 2007 - 12:23 PM
        Just to make sure I'm understanding you, do you mean that you are goinng to skin the skeleton of the globe with siholette cutouts n the shape of snowflakes, instead of solid sheets of material?

        If so, sounds like a plasma cutter is the way to go. If you have more funding than time, then you could get them CNC plasma cut at a local shop.
        • Re: Building a metal sphere

          Wed, January 10, 2007 - 9:14 PM
          The original idea was to build a sphere, and then cut out the snowflake shapes with a plasma cutter.. That way the snowflakes would be "negative space" in the skin of the sphere. I may not have the money, time, or skill to build the sphere, as I'm finding out. Really, the skill part is what concerns me the most. So, I'm thinking that if I cut out a bunch of "positive space" snowflakes, and then weld them to the skeleton of a sphere, I can achieve something similar, and still get it to burning man this year!
          • Re: Building a metal sphere

            Wed, January 10, 2007 - 9:55 PM
            Man... you can do this. Plenty of time before heading to the playa

            If you were really ging all out, you could form concave form in the end of a log and slightly round (via grinder and flap disk) the face of a good sized hammer, then use them to hollowform your curved panels and/or snowflakes. But even if you just cut them out of flat stock, don't hollowform them, and bend them around the frame... it'll still work. The only way I've ever accomplished anything at all is to be too stupid (or maybe ornery) to know that I can't... and then I find out that I really can.

            Trying a mock up in a small scale could help you figure out any problems too... but I rarely do that. I usually do the hardhead thing and dive right in.

            Just make sre you wear your safety glasses.
  • Unsu...
     

    Re: Building a metal sphere

    Thu, January 11, 2007 - 4:54 PM
    : )


    Have you done a calculation on how heavy the device you want to make is? Off the top of my head if you want a 6 foot sphere [4*pi*r^2] that would be about 110 square feet of metal. So lets call this 3-4 sheets of 4x8 metal. How thick were you thinking?

    I vote you simply make a single hoop (like a hula hoop), you mount it, and spin it really fast…

    You can put lights on the edge, and with the use of a computer, you can project an image of anything you like.

    Given the Safety third rule of the Playa, you gain the advantage of having a piece of art that kill or maim anyone that comes near it, that makes it worth extra points.

    If the dead, er, late Sagan is right…spinning it fast enough will allow you to travel through space and time.

    You could have this whole design up and running in a day.
    • Re: Building a metal sphere

      Thu, January 11, 2007 - 5:40 PM
      Oh!! Oh!!! And you could put some computer sequenced flame throwers on it!!
      • Unsu...
         

        Re: Building a metal sphere

        Thu, January 11, 2007 - 6:22 PM
        Now you're talking my language!

        Although I think it will make a pretty good deal of noise on its own, one could always add small metal whistles which would produce a harmonic resonance. Low frequencies will make people feel……..funny inside…



    • Re: Building a metal sphere

      Mon, January 15, 2007 - 10:34 AM
      I'm thinking that my revised idea is less likely to have yahoos stick their faces up against the sphere and look in just as jets of flame shoot out. Safety third. If safety were first, we'd never leave our homes!
      • Re: Building a metal sphere

        Mon, January 15, 2007 - 9:03 PM
        Okay. Now I would like to celebrate our discussion with a painting of "how to make a sphere from one metal sheet".

        Like an instruction page.. or template... but I'll eventually then paint it on canvas, and in ... umh.. paint.

        Hmm.... I'll go off and look for what I can find.... anyone got one, feel free to post!
        • Re: Building a metal sphere

          Tue, January 16, 2007 - 11:08 AM
          Kent has done what you describe--from a single sheet! Of titanium!

          See www.tinmantech.com/html/the_sphere.php


          • Re: Building a metal sphere

            Tue, January 16, 2007 - 10:17 PM
            Sassy m*therf*cker, isn't he? I need diagrams. Still looking....
            • Re: Building a metal sphere

              Wed, January 17, 2007 - 7:20 PM
              Would be very surprised if you find any. Making a near perfect sphere from a single sheet is a skill held by only 4 to 5 people in the world. Kent has done it, but is not very forthcoming about exactly how. Fay Butler (faybutler.com) could do this, but I bet he would make the sphere in two halves on a power hammer and weld together. In any case without innovative trickery (spinning titanium sheet over aluminum sphere and melting the aluminun out, etc) this task takes a monumental command over metal stretching and shrinking.

              Wiedershau'n

              Eric
              • Re: Building a metal sphere

                Thu, January 18, 2007 - 6:54 PM
                Ah, Eric- vielen dank.

                So what I was thinking of, was the different diagrams of actually cutting out the metal and welding it back together.

                I met a guy last year that could pound a vase from one sheet (or, actually a cluster of metal/ a lump), and he was explaining to me how complicated it was and how he learned the technique from somehwere very important... Umh.. well, I don't remember now... I can ask him again next summer... but you get the point. Very fascinatin, really. I don't think I have the patience.
                • Re: Building a metal sphere

                  Fri, January 19, 2007 - 1:35 AM
                  For some bizarre reason, I wasn't expecting to run into playa family in this Tribe.. silly me :) Hi LCN and Karine!

                  Not spherical, but a related question: I want to build a Roux Cyr (er... 6' diameter hula hoop I can spin in.. check my Tribes list to see it in action - lots of video links)... or actually get someone to make one for me. My dad tried to get someone in my hometown to create one, but that person kinked the aluminum tube when they started to try.

                  So, my questions:
                  What industry heading would I look under to find people skilled in curving aluminum tubing?
                  Would these skilled people also be tubing suppliers, or would I find them elsewhere in the phone book?
                  Is there a particular name/language/jargon to use, to help these people understand what I want to do, which is get a 6' metal hoop that breaks down into 5 parts, plus figure some sort of connector system for it all...

                  and last.. any idea what a reasonable amount of design and fabrication time I can expect to be charged for?

                  Thanks, y'all :) I so miss sequenced flame effects.. (when I'm not having nightmares that they mean those scary people from Apokalyptica are coming to get me.. ./grin)

                  X.
                  • This is the maximum depth. Additional responses will not be threaded.

                    Re: Building a metal sphere

                    Fri, January 19, 2007 - 10:28 AM
                    Heya X-ta!! Fancy seeing you here.

                    Check under "Machine Shops” and "Metal Fabricators" (or similar such headings) first. If the shops listed can't do it, they would most likely would know of someone who "rolls" tubing because they've had to such things out. There have been rare occasions that I've seen listings under "Metal Fabricators - Rolling"... but generally its an operation that is part of a larger shop and is not advertised exclusively.

                    Tubing is very easy to kink, because it is, of course, hollow. The most common way is to roll it in a machine like these that use fitted dies:

                    www.oceanmachinery.com/eagle-benders.htm

                    I'd expect to pay around $60 an hour for labor plus materials (I’m guessing at least an hour plus 19' of tubing at +/- $25 or so?). You could probably use short sections of smaller tubing fitted inside the ends of the hoop sections. Then couple them together with a small set-screw at both sides of the joint (set screws are those teeny, tiny little headless screws, often with a pointed end and tightened by an Allen wrench). Go in and talk to the folks who are doing it, if you can. When I worked in the machine shop, I'd always give folks in situations like yours a break if I could.

                    Hope this helps... feel free to message me if you need anything else.
                    • Re: Building a metal sphere

                      Fri, January 19, 2007 - 11:58 AM
                      Oh, you rock.. and I was totally picturing those Allen key/screwy things, now I know what to call them!
                      .. now, just as soon as I figure out how well I'm actually doing at this whole self-employment thing (gotta see what my January work totals up to), I'll know if I can afford it.. but I really really really want one! :)


                      Thanks babe :)

                      X.
                • Re: Building a metal sphere

                  Fri, January 19, 2007 - 6:23 PM
                  I posted a diagram about how to lay out the sheet(s) to make a sphere. This is in my public photo section.
                  • This is the maximum depth. Additional responses will not be threaded.

                    Re: Building a metal sphere

                    Fri, January 19, 2007 - 10:00 PM
                    Eric- You are awesome! I am going to use this, too! You guys sure know how to keep girls smiling!
                    • Re: Building a metal sphere

                      Sat, January 20, 2007 - 12:45 AM
                      Heh.. that's my favourite guy, actually.. the kind who tries to keep me happy :) Gets me to work hard at keeping it balanced the other way, too!

                      I was mentioning this tribe and all y'all helpful folks when I was at our hooping practice session tonight.. much gratitude extended again!

                      X.
                      • Re: Building a metal sphere

                        Tue, April 24, 2007 - 11:54 PM
                        Guess I'm a bit late but,
                        I've built a metal sphere(stainless steel). I've posted a photo and a short description in my photo gallery.
                        I use a hydraulic press to pre-form the pieces that will make up the skin.
                        people.tribe.net/stephenfi...5d31c15300
                        • Re: Building a metal sphere

                          Wed, April 25, 2007 - 8:23 PM
                          How did you create the spherical form to press? Great work, beautiful work, by the way.
                          • Re: Building a metal sphere

                            Sat, April 28, 2007 - 12:22 AM
                            There's a tank company outside L.A. that makes spherical tanks. I bought a half sphere 19 inches in diameter that was3/4 inch thick(strong enough to withstand the pressure of the 85 ton(I think) press that I planned to use. The half sphere I used as my female die. I pressed 10 inch diameter x 1/8th stainless discs (which I got as scrap)using as my male die another bowl shaped form. I had to do some figuring to be sure that at this diameter 12 discs would completely cover the surface,a near perfect fit...
                            I had another idea for your project for Burning Man. Why not use preformed bowl shapes as sections of your final sphere just as I have done, only with a shaped objects that're already formed and readily available almost everywhere,albeit allot larger...Satellite dishes.

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