The typical electric garage door opener consists of a power unit that contains the electric motor. The power unit attaches to a track. A trolley connected to an arm that attaches to the top of the garage door slides back and forth on the track, thus opening and closing the garage door. The trolley is pulled along the track by a chain, belt, or screw that turns when the motor is operated. A quick-release mechanism is attached to the trolley to allow the garage door to be disconnected from the opener for manual operation during a power failure or in case of emergency. Limit switches on the power unit control the distance the garage door opens and closes once the motor receives a signal from the remote control or wall push button to operate the door.[3]
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.
Dodging a falling door:: Reversing this equation gives us x=gt^2/2 as the fallen distance x for a given time t. How much time would you have to dodge a falling door if the spring were to suddenly break at the top of travel? Let us assume you are 5.5 feet tall, so the door will hit your head after falling 2 feet from its 7.5 foot fully-raised height. This 2-foot fall takes sqrt(2*2/32.2) = 0.35 seconds (350 milliseconds). The quickest human response time is about 200 milliseconds, so even if you are alert to the hazard, this leaves you only about 150 milliseconds to accelerate and move your noggin out of the way. If you are an Olympic gold medalist in the 100 meter dash, you can accelerate (horizontally) about 10 feet/second^2, and your 150 milliseconds of wide-eyed panic will move you all of 10*0.15^2/2 = 0.11 foot = 1.35 inch.

Garage doors are the largest moving object inside your home. If you have a problematic garage door, it compromises the safety of your family and home. Ankmar Denver is a professional company you can count on. We provide you with quality service at a reasonable price. We offer FREE estimates on replacement garage doors and are spring replacement specialists. 24 hours a day 7 days a week we are your number one garage door repair service.

Having a mismatched pair makes it difficult to specify the correct matched-pair replacements. To obtain replacement springs for a mismatched pair, you can either specify the same odd pair, try to calculate the equivalent matched pair sizes, or (this is the best method:) measure an accurate door weight and calculate the right spring size(s) "from scratch". The spring seller should be able to do the calculations from your accurate measurements of weight, height, and drum size; or you can attempt the calculations yourself using my engineering formulas below.
Install the stiffening strut on top of the top section of steel doors with the section lying flat. Then install the opener bracket that replaces the center bracket between the top two sections. While you’re working on the sections, protect them from scratches by putting carpet scraps on top of your sawhorses. Now, slide the rollers into the roller brackets.

If you’re looking for a stylish garage door that is a statement of your good taste, we have customized solutions that fit your family’s lifestyle. Or if it’s the safety and security of an integrated, commercial door and operator system that your workplace needs, Overhead Door™ products make operating your facility safer and easier. Our products are manufactured to give you durable, long-lasting performance for years of extended use and trouble-free operation. Each product, from residential to industrial to commercial applications, is backed by knowledgeable and professional customer support for troubleshooting and answers to your questions.


We are a family owned and operated, local garage door company in the Carlisle area that believes in attention to detail and an emphasis on customer service and satisfaction. We even offer same-day service because we know that when your garage door isn’t working the way it should, you need it fixed fast. We offer affordable rates that will fit your budget, and we’re confident you won’t find another garage door installation company in Carlisle or the surrounding areas with the same dedication to our customers and the quality of our work at the affordable rates we offer our clients.

Garage Door Opener Company

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