under the dome
Oct 15, 2013
this photo shows my brother in law peter moore on the left, and my assistant, trevor mott, checking out the 'collapse' mechanism. there's a hub and a handwheel that, when turned, allows the hub to fall and the ribs and plates to collapse and be withdrawn through the oven door,
this was not really a ‘fine’ woodworking project, but it was a serious conceptual and technical project. the challenge was to design a collapsible, reusuable, easy to set up form in the shape of a dome. we have made other arched and domed forms for pete in the past, but they were generally difficult and time consuming to set up. we kicked around a number of ideas before settling on the ‘turtle shell’ concept, with 8 ribs, a central hub, and a 24 piece domed top. wood does not like to bend into a spherical shape, so there was a bit of experimentation and trial and error until we got the method down. we eventually used 4 layers of 1/8″ bending poplar, (4′ cylinder) and one layer in the center of the stack of 3/8ths inch ‘wacky’ wood. we discovered we had to cut 5 narrow triangles from the wacky wood and two of the 1/8th inch pieces to allow them to roughly conform to the form … there are more photos of the process and better descriptions on my dorset custom furniture blog.
three posts total there so far
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this photo shows my brother in law peter moore on the left, and my assistant, trevor mott, checking out the 'collapse' mechanism. there's a hub and a handwheel that, when turned, allows the hub to fall and the ribs and plates to collapse and be withdrawn through the oven door,
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this is the form set up on site ... what peter is building is a 72" diameter, 26" high brick oven for cooking wood fired pizzas. it looks easy now and only took 15 minutes to set up, but trust me, i won't be going into the wood globe business..
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we started at the computer and went from there to the cnc to cut the ribs and spacers and the actual 5 piece sandwhiches .. i would have hated to trace and bandsaw them.
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here's the concept .. we first made a multi ribbed 1/8th of the circle and cut, let's see, that would be 24 x 5 = 120 curved piece of bending plywood in 1/8 and 3/8ths thickness and glued them oversize to the 'build' form you see in this photo.
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the bottom section was the largest and distorted the bending ply the most. to encourage it to behave, we had to add additonal ribs to screw the glued laminates to.
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here's the goal when it's done .. the ceiling of this oven was built using a 24 rib form with the ribs connected with thin pieces of wood connecting the ribs to support the bricks .. i heard it was 'tedious' and i can truly imagine that. lucky i got paid for that one
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coming along now ... starting to fit them up .. i believe i missed solid geometry class, or at least, it missed me ...
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after all the pieces were glued, we switched to the real form for fitting, which consisted of 8 pieces and the central hub. in the end, we added additional thickness to the ribs to make it a little less collapsible while it was being set up.
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domed form bondoed and ready for sanding
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the force of the weight of the bricks is tranfered to the vertical soldier course, laid outside the dome, and backed with the concrete and rebar you see in the photo below. this is again, the previous oven .. you can see more photos of that at this link
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on site again. part of the arched door and showing the buttresses soldier course that supports the domed masonry
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ok .. this was last friday. i'll be going back to attend the 'collapse' ceremony sometime later this week ... all for now
Comments
Brilliant!
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