Hat tip to Peter Roberts for the "hinge" terminology.
Goal: There's a steel disc that needs to sit atop the fire like a hat. It needs to be located about four inches above the top of the reactor core, and the disc needs to be an integral part of the bell.
One technique is to build upper part of the bell as a cone or dome, with the disc forming the keystone. The cob builders suggest using willow branches to build such forms, leaving the form in place to be burned out later.
Well I don't have willow trees. There was a whole bunch of 'em just two miles away but that part of the creek got bulldozed last spring, and there's nothing much growing there now except poison hemlock and wild lettuce.
I do have a few elms. Not hundreds, but certainly dozens. That's what is pictured above. See the graceful, smooth curves in the form? Yeah, me neither. Sure, my skills in elm-bending are meagre but I'm still placing much of the blame on the elms' unwillingness to do anything gracefully.
So it ain't gonna work. I'm reverting to a cylindrical bell with a relatively flat top. And nope, I don't know exactly how that's going to happen but I suspect that a few steel fence posts will be employed.
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