[TheForge] Re: Length of a Spiral Railing

[Gladish Family]

Well, Bruce, having never actually taken on this job I probably should be
quiet, but like you I enjoy the challenge of sussing things out
theoretically :)  Maybe all this has been said already in much more
sophisticated language...but I'm going to talk myself through it like so....

There are two questions: How many degrees does the handrail turn per unit of
handrail length (NOT per unit of rise, though it would be childs play to
establish deg/length using simple rise/run like on any other stair rail),
and

Is it going to twist so that it's not perpendicular to the vertical axis of
the stairway at any potential picket point.

The first gives you the layout curve for bending it the hard way. It would
look like way too open of a curve, lying there on the shop floor, since we
want to think in terms of degrees per unit of rise instead of per unit of
stock length.
Once you know how much stock you need to make one full turn, then you divide
by pi and then two to get a radius, draw it on the work table and start
bending...

The second, I think, happens without worrying about it.
Outside my door there's a helical wind catcher- maybe you've seen them-
spins in a breeze. When I collapse it, the diameter increases somewhat, but
whether it's expanded or collapsed the rim has no tendency to twist so that
it's not perpendicular to the vertical axis. Any perp. line drawn from the
axis that touches a point on the rim goes through the entire width of the
rim.

My $.02, currently traded at $.01 on Wall St.
Andy G.


>
> I'm not sure I follow you, but it sounds like you're not accounting for
> the contraction of the diameter as you pull the helix vertically.
> Bruce
> NJ
>
> >>> gladish at cnw.com 9/24/2004 10:20:42 AM >>>
> Given this info (below), the "hard way curve" of the railing will be
> simply:
>
>  rads or degrees/foot of rail length   (not per foot of vertical
> travel)
>
> Do that to the straight piece and pull it to height and there it is.
>
> Andy g.