A Closer Look at Closers
|Subscribe to FREE newsletter||May 31, 2009|
A closers is a closers is a closers! That’s not quiet true. We have cast iron and aluminum closers, rack and pinion and cam action closers, compound arm and track closers, fixed and adjustable spring pressure closers, surface and concealed closers. The considerations of fire safety, ADA compliance, longevity, abuse resistance and maintenance have really crowded out aesthetics. There has been a lack of creativity in solving these problems. We have to be able to step outside of the box of surface closers. It is possible and practical to satisfy all of the concerns listed above including aesthetics. But the solutions are not obvious because there has been an over-reliance on rack and pinion closers. Surface-mounted rack and pinion closers with standard arms are the best solution for exterior doors and some interior doors in high-rise buildings. In comparison, the cam action track closer neatly solves a host of problems on interior doors, including aesthetics, ADA compliance and effective latching.
Selecting closers would be easy if we only had to consider swinging the door, but it is not that simple. We still have to take into account ADA compliance, life and fire safety, abuse resistance, longevity, maintenance and appearance. We must keep all of these elements in mind if the opening is to perform reasonably well. Too often, we are only offered limited options. We are forced to make compromises between fire safety, handicap access (or access by children and senior citizens), abuse resistance and appearance. That we do so is even recognized by ADA regulations. If the door is not a firerated door, it must have a maximum opening pressure of 5 lbs.; if it is a fire door, then the maximum opening pressure should be less than 8.5 lbs., although the AHJ can deviate from this recommendation if fire safety is compromised. Virtually all specifications assume that only a closer with a compound arm (standard or parallel arm) can achieve secure latching—and this is true if the closer construction is of a rack and pinion design. However, this design, if used with a single arm and a track, is absolutely incompatible with ADA requirements. It is impossible in this case to latch the door and meet ADA requirements.
Rack and pinion closers build up closing pressures in direct proportion to the opening angle. The compound arm, by its geometry, compensates for this characteristic and allows the opening pressure to remain relatively constant throughout the opening swing. The consequence is a large box sitting on the face of the door with a pair of arms sticking out at right angles or more or less parallel to the door face. This gives us an architecturally objectionable appearance and a projecting arm that kids can do chin-ups on (at least until the arm breaks or the closer comes off the door). To take this abuse, we are told to use big, super strong, cast iron closers of rack and pinion design that don’t even need pressure relief valves. That sounds like good advice, but let’s examine the validity of this statement one item at a time.
Big – Big isn’t always beautiful, nor is it necessarily better. If half the size and weight would perform the same job better with the same life and reliability, why make it big?
Cast iron – Historically, this has been an advantage, but with modern aluminum alloys and manufacturing techniques, aluminum closers can outlast cast iron. Your automobile probably has a high performance aluminum die cast engine block that can go 200,000 to 400,000 miles.
Pressure relief valves – The enormous internal hydraulic pressures that build up when the door is abused can be handled in one of two ways. One is to beef up all parts of the closer so that it is stronger than the door or frame to which it is attached. Hooray for the closer, but too bad for the frame and door. Why? Any abuse suffered by the opening will be borne by the door and frame. If it is a steel door and frame, the hinge anchor plates will bend or break loose and the doors then can’t be latched. If it is a wood door, the hinge screws will strip out and the door again won’t latch. The result is bragging rights for the closer, but pity the owner who has to replace a frame in a grouted or poured wall. He would have been able to purchase and install 10 replacement closers for the price of replacing one frame.
The second and most logical way is to put a pressure relief valve in the closer so that when internal hydraulic pressures build up to three or more times the designed operating load, the pressure is momentarily relieved, and the hinges, doors and closers aren’t damaged or destroyed.
We are still left with the problem of getting rid of the unsightly, projecting and easily abused two-piece compound arms. There is an alternative. Use a closer with a track and a single straight-arm that is 1/4" ✕1" solid steel. This very neatly gets rid of the projecting arms. There is very little space to grab for chinning. Unfortunately, the rack and pinion closer doesn’t lend itself to this application because a one-piece arm cannot compensate for the rapid buildup of force required to open the door. Figure 1 is a chart that has been taken from published data for a cast iron rack and pinion design track closer and from actual measurements of a cam action track closer.
The curves in the graph above are taken from popular rack and pinion and cam action track closers. The two types of closers are shown on the same chart to demonstrate the differences in efficiency (50–60% for rack and pinion vs. 70–80% for cam action closers). Note the difference between the solid green and the dashed green curve, which represent the different opening forces for the two types of closers to attain the same latching pressures. Four lbs. of latching pressure is reasonable and safe and assures adequate latching to meet fire codes. The solid green and red curves demonstrate that rack and pinion track closers can never meet ADA and fire safety requirements, while cam action closers can do so easily, per the dashed green and red curves. Rack and pinion opening forces increase sharply as the door is opened. Cam action opening forces decrease sharply as the door is opened.
There are significant differences between rack and pinion and cam action closers. First, cam action closers are slightly more expensive. Second, cam action closers operate at approximately 80% efficiency, while rack and pinion work at 60%. Third, rack and pinion closers have a linear increase of forces as the door is opened; a cam action closers’ opening forces decrease as the door is opened. Efficiency is important when you think about getting reliable latching and complying with ADA requirements. Latching forces of 4 lbs. yield reliable latching; 3 lbs. do not. Cam action closers with their high efficiency can have both 4 lbs. latching pressure and 5 lbs. opening pressures. A rack and pinion closer with only 60% efficiency, even with a compound arm, can’t get reliable 4 lbs. latching and 5 lbs. opening pressure. Rack and pinion closers must be satisfied with a compound arm and 3 lb. unreliable latching pressure if they are to comply with ADA. Closer manufacturers publish catalogs verifying this statement.
The cam action track closer is produced by many of the world-class manufacturers of closers, both domestic and foreign. The benefits of this type of closer are obvious to these manufacturers, and concealed cam action track closers are being made for virtually all interior doors and all sizes and with closer sizes 1 through 5.
Rack and pinion and cam action closers each have their place. Rack and pinion closers are the clear winner on exterior doors and on interior doors subject to large pressure differentials. However when the cam action concealed closer is made with modern materials and processes, it fulfills all of the objectives listed earlier in this article on the balance of the interior doors. In addition, they are made specifically for mortising within the steel or wood door bodies, with no telegraphing and with all of the advantages we desire: invisibility, ADA compliance, reliability, fire safety, abuse resistance, and protection of the door, frame and hinge.
Leon Yulkowski is an owner and the product development manager of Total Door, a division of Openings. He is an architectural engineer and city planner with scores of patents worldwide in locks, hinges, high security cylinders, panic devices, closers (patent pending), electromagnetic holders, door body construction, door and hardware systems, building control and access systems. His first company, General Lock, was one of the first companies to promote high quality lever mortise locks in the U.S.
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