cone forming

huangyhg

cone forming
i have a cone to fabricate out of 3/8" plate.  cone is approx. 15' vertical, 22' major diameter and 14" at the nozzle.  is there a code or spec. available to assist in determining increments of break lines when rolling is not available?
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this is very basic geometry and is the the reason why they taught you geometry in university.
you will not find a code for this.
without rolling, it would have to be a hexagon approximation.
if you are building the cone to a specific code such as awwa, asme, or api, then you will need to follow the welding requirements for the code; however, the geometry is up to you.
since you will not be rolling the plates, you could consider the following procedure:
1.  lay out the cone, unfolded...bottom width 44",top width 69', height 15'.
2.  weld all sheets together as rectangular plates, then cut above dimensions out of welded plates.
3.  stand on long width and work into circle using jigs and plate "dogs".
4.  temporarily weld turnbuckle on outside of plates to pull together as closed circle.
5.  working upward, using chains, "comealongs", plate dogs, and turnbuckles, close the vertical seam and weld according to specifications.  
you should be able to do this with 3/8" plate.  i know it can be done with 1/4" plate.  it shouldn't be too stiff on that large starting diameter.  it will be increasingly difficult as you move up the seam to the nozzle and might required strategic heat application with a "rosebud".  we used similar procedures to build conical clarifier sections for package treatment plants in the 70's.
this is a large fabricated structure so use lots of safety precautions for stabilizing, lifting, and pulling the plates in place.  use chains around the od rather than cable and weld temporary lugs around the diameter to keep the chain from sliding up as you pull on it.
there's not any fixed answer.  you might talk to the people doing the forming and get their input.
if you make radial sections the full length, i would think 6" spacing on the outer end would be close enough.  you can cut nested pie-shape plates out of rectangles.  you may have to form the bottom couple of feet as a separate piece to keep the forming and weld spacing from getting too close together there.
you could make it in two or more courses so that the plates could be roll-formed to the radius.  there's not a lot of motivation to do it one way or the other, other than available equipment and overall cost.  cones are commonly done either way.
is this a ben and jerry's attempt at a world record?
mike mccann
mmc engineering