Structural Considerations of Swing Gate Automation
© 2007 Door & Access Systems
Publish Date: Spring 2007
Author: Rachel Bailey
Structural Considerations of Swing Gate Automation
How to Avoid Noncompliance and Extend the Life of Gate Operators
By Rachel Bailey, DAS Special Correspondent
Standards like ASTM F2200 and UL 325 are developed to ensure safe vehicular gate construction and automation. But according to DASMA President Rick Sedivy, many gate operator dealers are not intimately familiar with these standards. He worries that dealers wrongfully believe their minimal role in installation relieves them of code compliance liability.
“Dealers should feel an obligation to the ultimate user,” Sedivy says. In addition to helping dealers avoid litigation, meeting safety standards is good business.
Gate system designers like Brent Nichols of Picasso Gate, Cheyenne, Wyo., and Robert Rayson of Stratford Gates in Clackamas, Ore., are dedicated to complying with ASTM F2200 and UL 325. They design their gates and installations to ensure safety, gate operator longevity, and optimal customer service.
When installing an automated gate, many things can go wrong. “It’s probably a good business plan to eliminate as many of those issues as possible,” Rayson says.
Both are active members of the National Ornamental & Miscellaneous Metals Association (NOMMA). On NOMMA’s behalf, Nichols has been dedicated to the development of ASTM F2200 and UL 325 since 1996. Although he believes it’s important for installers and dealers to appreciate the structural considerations involved in safe gate automation, he warns against suggesting inaccurate standards.
“There are many variables dictating adequate structural support, from geography to the size of the gate,” Nichols says.
Nichols and Rayson offer some tips to help dealers avoid noncompliance issues while automating swing gates.
Gate Operator Considerations
With both new and old construction, knowing which operators you are going to use is a good place to start.
“The operator will affect post construction, footing depth, and gate design,” Nichols says.
For example, Nichols explains, if the job calls for a linear-drive operator, the installer/dealer should ensure that the gate’s steel post is of adequate thickness and the gate is of a certain width to avoid a spring effect.
Bear in mind, too, that gate length affects the swing’s speed. Because longer gates have more momentum behind them, the in-swing speeds up. Nichols prefers an 18-second speed for a 20-foot opening. If he works with gate openings longer than 20 feet, he gets the manufacturer to slow down the operator. To avoid noncompliance, only the manufacturer—and not the installer or designer—should modify an operator.
Post Construction Issues
Proper support for the gate is fundamentally important, Rayson says. However, according to Nichols, there is no minimum post size to adequately support a gate and its operator. Any structure can be reinforced to ensure proper support, according to Nichols.
To check whether a preexisting gate’s post is adequate, Nichols suggests opening and closing the gate manually. If the post bends from the ground up when opening and closing, then the post is probably not strong enough.
If the gate will be mounted on existing columns, determine the sturdiness of the columns. “Most preexisting columns are there for decorative purposes and usually are not sturdy enough to actually support a gate, let alone one that is automated to open and close several times a day,” Rayson says.
Ideally, the gate should be attached to a steel post inside the column. Either way, Nichols suggests checking the fasteners. Loose fasteners suggest that the column does not adequately support the gate.
In addition to the strength of the post or column, dealers and installers should determine proper footings. Certain soil types require different depths, widths, and amounts of concrete for the footings.
Rayson suggests digging behind the preexisting column or post to see how deep into the ground its footing goes. “In 17 years, I’ve never seen a preexisting column that had footings adequate to support an automated gate,” Rayson says.
If the sturdiness of the preexisting column remains undetermined, Rayson suggests setting a new post behind the column or removing and replacing the columns.
Proper gate construction involves many variables, but how a gate moves manually offers clues as to its “automatability.”
“If the gate is still plumb when it is open, then the fabricator probably did a good job,” Nichols says. “But if it binds when it opens and closes, the gate will challenge the operator. If the gate has a lot of flex built into it—if it shakes a lot when in motion and the leaf sags—gate operators will not work well with that gate. Too much flex reduces the life of the operator and increases service calls.”
Typically, Nichols only works with new construction. But if he were to automate an existing gate, he says the first thing he would do to check it would be to step on a horizontal bar of the gate with his full weight. Then, after taking his foot off, he could see how much it flexes.
Automation: Hinging on Hinges?
Hinges are an integral component of gate construction. Although price may indicate quality, the proper installation of a hinge is essential.
“A hinge’s tight tolerances enable the gate to swing with ease,” Nichols says. “But no matter what kind of hinge is used or how much a gate weighs, the life of the hinge and the operator will be limited if the hinge is not square or applied correctly.”
According to Nichols and Rayson, there are some very good hinges out there. Both men believe attending trade shows is a good way to check out the variety of hinges available.
Rayson and Nichols also agree that having a gate professionally engineered or rebuilt is the best way to ensure quality and compliant automation.
Nichols believes, too, that standardizing equipment will maximize the serviceability of an operator. “It’s a function of repeat business. The more comfortable an installer or dealer is with the equipment he uses, the better customer service he’ll be able to give.”
Rachel Bailey has authored several magazine articles about gate operators. She is a former editor of Fabricator, the magazine of the National Ornamental & Miscellaneous Metals Association (NOMMA).
Avoid Noncompliance with Corner Mounts
PROBLEM: Center Mount on a 10-Inch or Wider Column
If the columns supporting the automated gate are wider than 10 inches and the installer plans to mount the gate to the center of those columns, the gate and its operator will be noncompliant. According to ASTM F2200, a crushing or entrapment condition can be created when a gate moves in the direction of a fixed object, such as the column to which the gate is mounted.
The maximum clearance allowed by ASTM F2200 is four inches. But, if the column is 10 inches wide, mounting the gate at the center of the column creates a five-inch overlap. One option toward compliance is to use reverse edges to clear entrapment guidelines, but these can be expensive.
SOLUTION: Corner Mount to Avoid Pinch Points
Another option is to mount the gate on the pivot point of the column corner. This is called a corner mount.
IMPLICATION: Reinforced Corner Angles
This option requires reinforcing the horizontal angles attached to the posts. Be sure the installer ties back the angles with flat bar every 12 inches. This keeps the angles from flexing left or right with the weight of the gate and challenging the life of the operator. Securing the angles will enhance the life of the operator and add support to the column.