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Speed of a falling door:: Physics tells us that the transit time of a free-falling body is sqrt(2x/g), where x is the length of the fall and g is the acceleration due to gravity (32.2 ft/sec^2). If this typical 150 lb door were to fall an equivalent of 3.75 feet, this falling time would be sqrt(2*3.75/32.2) = 0.48 seconds (480 milliseconds). The terminal velocity is gt, or 0.48 seconds * 32.2 ft/sec^2 = 15.5 ft/sec = 10.6 mph.
Sears garage repair technicians are fast, with same-day, emergency repairs available in most areas. We can replace garage door broken springs, rollers, cables, hinges, sensors and weather seals. We can also adjust garage door tracks and springs to make sure your door operates smoothly. Having problems with your garage door opener? We can repair or replace that too. Check out our line of Craftsman Garage Door Openers. Craftsman is America’s #1 brand of garage door openers! 1
A spring design manual, also called a rate book, gives tables that relate the torque constant ("rate") and maximum turns for springs of given wire size, diameter, and length. For example, a typical page in a rate book would show a table for a given wire size and inside diameter, the maximum inch-pounds (MIP) of torque available for a standard lifetime of 10,000 cycles in that size, the weight of the spring per linear inch, and the rates of the spring (as IPPT, inch-pounds per turn) for each of various lengths. From these figures one can calculate the lifting capacity, substitutions, conversions, and cycle life upgrades for a door of given weight and drum geometry. The weight-lifting capacity of a given spring is calculated based on its torque constant (IPPT, or inch-pounds per turn), which is the rotational version of the spring constant that characterizes the spring. The IPPT constant is found from tables giving IPPT for given spring dimensions (wire-size/diameter/length). The same tables may indicate the maximum number of turns for various expected lifetimes in cycles. The torque required to balance a given door can be calculated from the weight of the door times the moment arm of the drums (as we do below under "Calculating the Forces We Will Be Handling"). The ultimate torque of the spring in the fully-wound condition is the number of turns (when fully-wound) times the IPPT constant. Choosing a spring to balance the door then simply requires matching the ultimate torque of the spring to the balancing torque.
You might genuinely need some extra parts when you thought you simply needed a broken spring replaced, and a good serviceman will perform a simple inspection to identify such parts. Nor is it unreasonable for a business to charge separately for a service call versus repair work actually performed. But the best protection for you as a buyer, being somewhat at the mercy of whomever you decide to bring on site, is to understand what is being done, and ask intelligently for a clear explanation or demonstration of why extra parts are required.
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A torsion spring counterbalance system consists of one or two tightly wound up springs on a steel shaft with cable drums at both ends. The entire apparatus mounts on the header wall above the garage door and has three supports: a center bearing plate with a steel or nylon bearing and two end bearing plates at both ends. The springs themselves consist of the steel wire with a stationary cone at one end and a winding cone at the other end. The stationary cone is attached to the center bearing plate. The winding cone consists of holes every 90 degrees for winding the springs and two set screws to secure the springs to the shaft. Steel counterbalance cables run from the roller brackets at the bottom corners of the door to a notch in the cable drums. When the door is raised, the springs unwind and the stored tension lifts the door by turning the shaft, thus turning the cable drums, wrapping the cables around the grooves on the cable drums. When the door is lowered, the cables unwrap from the drums and the springs are rewound to full tension.
To make sure the job gets done right, our professional installers are local, licensed and insured. With a 9.7 out of 10 VOC score, our garage installers will exceed your expectations, provide reliable service, and install attractive garage doors that will transform your home’s appearance. All labor, products and installations are 100% backed by The Home Depot. Service you can trust.
A knowledgeable installer with good inventory can offer you upgraded spring lifetimes by using longer, heavier springs than were originally installed. For example, you may be offered more expensive springs with expected lifetimes of 15, 25, or even 100 thousand cycles, instead of the standard 10 thousand. The difference in labor to substitute this upgrade is nil. Since the dealer's cost of springs is proportional to weight, and typically a small part of the job price anyway, the dealer's cost for this upgrade is slight. This would seem to be a excellent option to offer every customer, and if correctly calculated and reasonably priced, one that you should take as cost-effective. Yet you may not be offered such an upgrade, if the installer is not adept at making the rather simple calculations, or if the optional springs are not on his truck, or if you're not around to be asked, or if the installer just doesn't like selling or taking time to discuss such details.
In my case, removing and replacing the relaxed springs required that I take down the assembly: torsion shaft, lift drums, and bearings. Doing that requires unbolting the center bearing plate from the wall, removing the drums from the shaft, and finally sliding the shaft back and forth out of the end bearings to remove the whole assembly off the wall. I am fortunate to have a lot of clearance in this garage to make the disassembly simpler. Tighter clearance to walls or ceiling would make disassembly a more difficult manipulation.
(The Wahl correction factor accounts for additional stress in the material due to shear forces, although these forces do not contribute to the spring's torque. These shear forces become significant in designs using a low spring index, which is to say, a relatively thick wire for the coil diameter. The correction factor is applied to scale up the stress S to better predict the fatigue lifetime of the spring.)
I obtained my parts, as described on this page, from American Garage Door Supply Inc. (http://www.americandoorsupply.com/) They may have raised their small-order prices or imposed a minimum order since I ordered from them in 2002 at the prices in my essay above. The Web site offers a free catalog by PDF download or mail. Springs in 2005 were priced at $2.25/lb.
And for some extra features, you'll appreciate accessing the system through the MyQ smartphone app. You can set up this Chamberlain opener to automatically close the door after 1, 5, or 10 minutes, which is great for people who are a bit forgetful. We also really like the motion-detecting control panel, which turns on lights whenever it records nearby movement.