Replies

1. 
   rangersteve | Oct 06, 2005 06:52am | #1

   darn,  you mean to tell me there's a formula for that.   I've always just framed the studs long and cut them off after the treads were in.  Then I just bent the finished cap when I trimmed the house.    I never made an angled top plate other than the trim cap.

1. 
   jimatgreatwhite | Oct 06, 2005 07:15am | #2

   Rangersteve

   There is I saw it in a book. Didn't think I'd need it ever so didn't write it down. I'll just do the keep cuttin' on'er till she fits method if I can't find it.

    

   JIm

1. 
   junkhound | Oct 06, 2005 07:24am | #3

   Straightforward trig or pythagoran theorem formula. 

   Visualize a Pillsbury doughboy biscuit package where you peel off the paper in a spiral - the rail is the same thing.  The triangle hypotenuese is the total rail length.  Subtract spacing of the rail from the wall from the stair diam at the wall for the triangel base.  Apply cosine or pythagoran math and you have your answer.   

1. 
   Mark | Oct 06, 2005 02:08pm | #4

      I think I'm understanding...  but....Could you give some more detailed instructions for those of us who haven't cracked open a math textbook since the stone age?" If I were a carpenter"

2. 
   jimatgreatwhite | Oct 06, 2005 02:56pm | #5

   thanks junkhound, but,  I may need to be walked through it as though I am an idiot.:)

    

   Jim

1. 
   JoeBartok | Oct 06, 2005 07:14pm | #6

   Jim, a few years ago I did some calcs for a set of stairs for a friend. The job ended up being subbed out (we didn't have time) so I never had the opportunity to actually test the math in this Helix Calculator. There's a link to how I derived the formula for the Baluster Radius. This would be the radius we would have to make a steel handrail to wrap properly in a spiral for a given radius in plan ... if that's what you're looking for.Joe Bartok

2. 
   jimatgreatwhite | Oct 07, 2005 02:45am | #7

   Thanks Joe I'll have a few opportunities to check it out. I'll let you know how well it works.

    

   Jim

3. 
   JoeBartok | Oct 07, 2005 08:17pm | #8

   Jim, you likely know how to do the following. If so, disregard this post. The value for the height may have to be determined before entering in the Helix Calculator. Substitute your own numbers in place of those in the examples.

   Example Calcs:

   Riser = 7.5

   Tread = 12

   Radius = 40

   Entry Value for Height = 40 × 2 × 3.14159 × 7.5 ÷ 12 = 157.0795

   Helix Section Length = 296.377188

   Baluster Radius = 55.624974

   Let’s say the stairs only make a 75° turn as viewed in plan.

   75° ÷ 360° = .20833

   Entry Value for Height = .20833 × 157.0795 = 32.72437

   Entry Value for Angle in Plan = 75°

   Helix Section Length = 61.744969

   Baluster Radius = 55.624471

   Note that the Baluster Radius remains the same. (Minor variations are due to rounding off; some of the calcs were done on a scientific calculator). I have made scale models and the numbers work O.K. I just didn’t get to test drive the calcs on a real set of stairs.Joe Bartok