radius handrail, goin down stairs....

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so I have to price out a radius hand rail, goes down stairs, its about 20 ft long, not to tight of a radius kinda like the same as the railings I just finished....im wondering how best to measure for the handrail???? I could make a form, but it would be huge!!! is there some way I could measure and bend the handrail without goin back and forth to the jobsite a million times?? I think im gonna ddo it in 2 sections, so theyd be about 10 ft long each...its gonna be normal caprail with a piece of channel underneath to stiffen it, and itll have elbows that get anchored into a stone wall...suggestions?? theres gotta be some formulas that I can use,  right now im just pricing it out, gonna do it really heavy with enough money to go to the job a few times if I have to, and to build a form if I have to as well... thanks http://www.philswelding.com
Reply:There are two measurements that you need.  The actual radius of the stair rail or stringer and the slope of the stairs.  You can drop a plumb bob down to the floor from the edge of the stair stringer then connect the dots and find the radius.  The slope is found by measuring the rise over the run on the circumference.   Most rolling shops have software that gives them the settings for the rolls.  You just need to give them the radius, total rise and how many degrees the turn is... say 180 or 270 .... most spiral stairs avoid 360 plus because of head clearance problems but doable.   If you have the prints for the stair then that is all the rolling shop needs.  They can roll tubing, flat bar, angle or channel to the spiral.... Use a proper shop that does this regularly.
Reply:compliments of DSW: Originally Posted by DSWlets see if this posts right or not.Attachment 296091The arc is the radius you want to try and duplicate. Draw a straight line between the two ends. Then draw perpendicular lines from this "base line" with a square, until they intersect the arc. Note the vertical distance off the base line. You draw these verticals at regular intervals. The more intervals, the closer to the actual arc you get. do only 3 or 4 verticals and just like when you bump bent the rails, you'd get a very "angular" curve. Do say 10 lines instead, and the curve gets more "round".Transfer all these measurements to your work surface, then simply connect the dots with straight lines. Same exact idea you used to bend the rails you just did, only with math rather than a template.Make sense?
Reply:So  it is a wall mounted handrail.  I would probably just bend and twist a section or sections of channel on site.  Brace it and use it as a model.   Bend and twist the cap to match.   I usually bend  channel  by hand between bending forks.  I use F-bars or a pipe wrench for twisting.  My pipe wrench has two handles, like blacksmiths use for twisting.  Just lay it along the nosing of the  steps.   Since, I rarely run into a true continuous radius,  I usually am not concerned about calculating the radius.  Perhaps a spiral?  The stone wall,  is it irregular?  Can mounting bracket be all the same length?I like using large rolls of paper for making patterns also.
Reply:Originally Posted by tapwelderSo  it is a wall mounted handrail.  I would probably just bend and twist a section or sections of channel on site.  Brace it and use it as a model.   Bend and twist the cap to match.   I usually bend  channel  by hand between bending forks.  I use F-bars or a pipe wrench for twisting.  My pipe wrench has two handles, like blacksmiths use for twisting.  Just lay it along the nosing of the  steps.   Since, I rarely run into a true continuous radius,  I usually am not concerned about calculating the radius.  Perhaps a spiral?  The stone wall,  is it irregular?  Can mounting bracket be all the same length?I like using large rolls of paper for making patterns also.