[TheForge] Re: Length of a Spiral Railing

[terry l. ridder]

hello;

On Fri, 24 Sep 2004, Bruce Freeman wrote:

bruce>
bruce> I'm not sure I follow you, but it sounds like you're not accounting for
bruce> the contraction of the diameter as you pull the helix vertically.
bruce> Bruce
bruce> NJ
bruce> 

it would appear to me that what you are asking for it relatively easy to
obtain.

one revolution of helix railing would be given by:

length = sqrt( ( pi * dh )^2 + (lead)^2 )

where:
dh   == diameter of helix
lead == the pitch (think screw thread) of the helix railing
^2   == squared
sqrt == square root

length, is the circumference of the circle to be used to approximate the
helix. therefore, the diameter of the circle is simply:

dc = length / pi == sqrt((pi * dh)^2 + (lead)^2) / pi

where:
dc == diameter of circle used to approximate the helix;

so roughly the diameter of the circle used to approximate the helix is
is a function of  the diameter of the helix and the lead of the helix.


andy> >>> gladish at cnw.com 9/24/2004 10:20:42 AM >>>
andy> Given this info (below), the "hard way curve" of the railing will be
andy> simply:
andy> 
andy>  rads or degrees/foot of rail length   (not per foot of vertical
andy> travel)
andy> 
andy> Do that to the straight piece and pull it to height and there it is.
andy> 
andy> Andy g.

-- 
terry l. ridder ><>