Looking for a source of information on building a handrail for a circular staircase. The handrail must be circular diameter 3 – 3 1/2 inches.
I proposed to laminate from 1/8 to 3/16 strips to form a square, but am stuck at how to machine the circular surface of the handrail. I am thinking of making each section 4 – 8 feet long. The sections would be machined to circular shape. Each end would have staggered laminations.
I would stagger the laminations by randomizing a full cross-section of laminate layers about of a uniform length. Glue this template together. then use this template to (uniformly) randomize the laminate of the sections. When installed on the stairway the laminates of each section would then fit head-to-toe. When when the sections are shaped, a template can be inserted at the end of a section to prevent the laminate from flexing away from the tool.
The only problem I think I have is how to shape each of the sectons into a circular shape. If you see other problems with this method, don’t be shy.
Suggestions? experiences that you might be willing to talk about?
Anwalt
Replies
Anwalt,
Sounds like a fun geometry problem to work out! I've never done what you're describing, but I imagine you're going to have to start by building some sort of jig to which to bend your hand rail to proper curvature.
Another idea: start with simple linear pieces of the cross-section you want, and then rip it into thin strips. To make up for the kerf width of waste, you'll have to start with two pieces of a given length to yield one "layered" piece. In this manner, you can avoid having to machine the cross-section onto the handrail after it's been curved. I've used this approach for bending moldings into single-plane curves. (When I think about it, isn't the handrail on a circular staircase essentially in a simple, planar curve????)
One final note: if you're having to go through the permit process, I don't know if you'll be able to get away with using a 3" to 3-1/2" round section. Code typically mandates the use of a cross section which can easily be grasped by the hand --something on the order of 1-1/2" to 2" if round. I'm not saying I agree with this -- just letting you avoid problems. I can imagine spending several weeks working this thing out and building it, only to be told by the inspector that it needs to be changed. Isn't big government great? <g>
Ragnar
Ragnar, Stan, Ian and Bake,
Thank each of you for your suggestions.
Ragnar, I also thought that the stair rail could be a planar curve. But as I look at Stan's pictures, I now wonder if one attempted to install a planar curve on the staircase as a rail that at a minimum, it would twist. hence Stan's rectangular shape would be tipped (moving the top of the rail outward?) thereby tipping the entire curve up like an elephant tusk. If a planar curve works would it not be limited to less than 360o?
Perhaps Stan could answer if a planar curve would work for a rail that is less than a full circle? My guess is that Stan would not build the jig he did of he could have built it planar.
Stan, thank you for the pictures. Words could not explain the detail and character visible in the pictures. The stairs and the rail are works of art! (More clamps in one place than I have ever seen.)
Anwalt
Anwalt,
The shape of a spiral staircase handrail is a helical curve. I must follow the radial path and axially path simultaneously. There was an article in FH some years ago about laying up a laminated handrail. I don't remember the issue but the list might be of help. Good luck!
Anwalt.....the laminate twists around the form as well as bends. If for example you have a 90 degree curved railing to do that is on a 37 degree incline. The laminates fo this rail will bend 90 degrees..and also twist the amount that the railing is inclined at....in this example 37 degrees. The laminates twist the inclination angle for every 90 degrees of turn.
Stan,
Again, thank you for the reply. the angle of twist =s angle of inclination for every 90o rotation of the rail.
Anwalt
I'd be real tempted to use the staircase as my template somehow!
Anwalt: Here is a 30 inch radius handrail for a spiral stairs being glued up. Normally I use the stairs itself as a form..but as you can see I just assembled a drum form in my shop and laminated up the 1.5 x 3.5 inch rail. This particular rail was just rectangular in cross-section but it could be either profiled now..or glued up with the profiles already milled into the outside laminates.
Stan- What kind of flooring system do you have in your shop there? Did you pour a floor then joists with the osb? Let the thunder crack and the waves roar.
We're going on.
Rez: I have a concrete slab floor...with just some osb thrown down to screw my curved forms to.
I think Stan has your answer as to how to fabricate the rail. Make it as a single piece from laminated strips. I suggest you build it as a rectangular or square section then machine it round. Using a router and suitable jigs, you will be able to machine close to the circular cross section. Which you may then have to finish by hand with a sanding block. The jig I envisage slides down the rail itself and keeps the router aligned at right angles to the centre of the cross section, and allows you to cut the cross section in a manner analogous with using a router to flatten a table top.
post a picture of the finished rail