Replies

1. 
   Scrit | May 19, 2007 12:43pm | #1

   6in diameter sounds way too small to do the job and I'd be concerned that if there is any innacuracy in the machining of the spacers or timber movement that the steps could move or flex in service. I've worked on laminated box section spirals (veneered plywood and particle board) where the "core" around the pole was 12in diameter with a vertically veneered spacer surfaces which would get around your reflection problem and make it possible to produce a near-invisible veneer joint

2. 
   TomT226 | May 19, 2007 02:05pm | #2

   Take that over to Breaktime.  There's a half-dozen spiral stair builders there who could help you.  Maybe a sketch too.

    

1. 
   Caldoche | May 20, 2007 04:17am | #5

   Thanks to all that took the time to respond to my message.
   My primary occupation is boatbuilding, wood composite construction for the last 25 years. So spiral stairs are new to me. Engineering help is what I need.
   To TomT226. You mentioned taking my problem to Breaktime. I cannot find this. Could you give me some directions.
   Cheers Caldoche.

   Edited 5/19/2007 9:18 pm ET by Caldoche

1. 
   Stuart | May 20, 2007 05:33am | #6

   If you click on "my forums" at the top of the page, you can get to the Breaktime site; it's associated with Fine Homebuilding magazine.  The leader of the pack when it comes to spiral staircases is Stan Foster, who often posts pictures of his stair projects in the photo gallery over there.  You can go directly to his latest project with this link: 

   http://forums.taunton.com/tp-breaktime/messages/?msg=89911.1

   Edited 5/19/2007 10:37 pm by Stuart

   Edited 5/19/2007 10:38 pm by Stuart

3. 
   JohnWW | May 19, 2007 03:47pm | #3

   Caldoche,

   Is there any support on the outboard ends?  Steel rods on the outboard end going up to a handrail are supporting the handrail not taking any weight from the treads.  If the only real support for the treads is the column, the design is woefully weak.

   If you stack up the discs making the donuts you have to consider wood movement.  The column will act like a single board 8 to 10 feet thick, or whatever your floor to floor distance is.  Depending on the climate, the column could gain or lose 2 or 3 inches in height with changes in humidity.

   Spiral stair design is probably about the toughest engineering and woodworking job imaginable.  If neither you, or your designer, have any experience with the technical and design problems involved you are the "blind leading the blind" and you are taking some real risks both professionally and financially. 

   I usually encourage people to take risks with woodworking, but in this case you should be talking to some professional spiral stair builders.  Eighteen stairs for a high end public project is not the place to learn how to design and build a spiral stair, the questions you are asking have already been solved by the pro's.

   John White, Shop Manager, Fine Woodworking Magazine

4. 
   4DThinker | May 19, 2007 11:38pm | #4

   Caldoche,

   I've been playing with spiral stair designs for the last two years, making models instead of full size. I strongly suggest making a scale model first out of the same materials you intend to make the full sized stairs.  Any weaknesses inherit in the design or materials will become evident in the model.  I have my college students make 1/4"=1" scale models of their furniture design class projects and almost always do the students discover the structural/functional flaws if their are any. The aesthetics often change too, toward a more refined and articulated solution.

   If you're designer is smart, he'll have the plans looked over by an engineer.  From your description I concur with your fears.