arches and curved tops on iron gates
Nothing about an arched top is decorative until the posts are measured, since an arch that does not meet the posts square looks wrong from the street. The running record ornamental iron gates georgetown thetaxpayers holds shows the same pattern in Georgetown, TX, where an arch is drawn full size before the tubing is rolled.
How is the arch rolled?
A curved top rail is made by feeding tubing through a bending roll that pushes it to a set radius. The shop makes a plywood or steel template of the arch and checks the rail against it after every pass, since steel springs back a little. A tight radius on thick tubing can kink or flatten the wall, so a wider radius or a heavier wall is chosen for a clean curve.
What does the arch change in the frame?
An arched leaf loses the straight top rail that normally braces the frame against racking. The shop adds a diagonal brace, a heavier bottom rail or a horizontal middle rail to hold the leaf square. Pickets are cut to different lengths along the curve, and each one is welded at the top and bottom.
How is it fitted to the posts?
The top of an arched gate is measured at the post and at the center, because the opening is wider at the bottom than at the arch peak on some designs. Posts are set plumb and their tops are cut or capped to a matching height. A dual swing pair meets at the center with the arches mirrored, and the gap between leaves is kept even from bottom to peak, which only works if both posts stand plumb in the limestone soil.
What does a curve do to swing and wind?
A taller center means more sail area at the middle of the leaf, so a tall arched swing gate takes more wind than a flat top of the same height. Hinges are sized for the extra moment, and the gate opener, if there is one, is chosen to match the weight.
How is the finish handled?
Curved rails trap water at the low points of the arch, so drain holes are drilled where moisture can collect. The weld seams are ground smooth and galvanized or primed before the powder coat. Heat during bending can burn off galvanizing, so the rail is coated after rolling, not before.
When is an arch a poor fit?
An arch is a poor fit on a sloped opening where the posts do not match in height, or on a very wide leaf that would need heavy bracing. A flat top with decorative finials suits those cases, and the top line can still be kept clean and level to the house.