Stress and lifetime: Calculating the maximal stress in the wire is useful for estimating the lifetime. Using the formula above, the bending stress S in the spring wire is 32*238/(π*0.2253^3) = 212 Kpsi. The spring index C is D/d = 2.23 / 0.225 = 9.88. The Wahl correction factor is Kw = (4C-1)/(4C-4) + 0.615/C = 1.15. The Wahl-corrected stress is Kw * S = 1.15 * 212 Kpsi = 244 Kpsi. This predicts about a 10,000-cycle lifetime, which is the standard "cheap spring" configuration originally installed. Note that while this stress is proportional to the torque being applied, it is also in proportion to the inverse third-power of the wire size. Thus slightly heavier wire sizes (and suitably adjusted D and/or L) radically improve the expected cycle lifetime of the spring.
Before purchasing a roll-up door, measure the space between the top of the garage door opening and the ceiling or overhead framing. Standard tracks require headroom of about 14 inches. If you don’t have that, you can get low-headroom track, which costs about $100 more. There are also tracks specially made for garages with unusually high walls or cathedral ceilings.
A rolling code is a protocol used by garage door openers to keep your door safe and secure. When the radio signals from your remote control are broadcast to your garage door opener, it uses a specific code to communicate. Older models used the same code every time, making garage door openers vulnerable to burglars using a radio frequency identifier device. 

Cost was $88 for 2 pairs of springs, plus $21 shipping. (I had to order 2 pairs to meet the $50 minimum order.) They came with new cones inserted as shown at that price, so I didn't bother trying to remove and reuse the old cones to save a few dollars. The cones are quite difficult to remove from old springs and to insert in new ones, and the spring supplier will have the right tooling to do that easily. That was the best price I could find on the Web at the time, and didn't seem out of line with what parts like this might cost at at the building supply (if they only sold them). Contractors buy these much cheaper in quantities; they're just an ordinary high-carbon steel wire turned on a winding machine. I also found Web sites asking a lot more money, obviously trying to cash in on search-engine traffic from do-it-yourselfers. Others report that some local dealers sell springs at retail, but at a high price that eliminates any economy versus having them installed.
Kevin gave 30 mins advance notice via text before arriving, and he was very friendly and knowledgeable about the Chamberlain garage door opener that we ordered on Amazon. I was pleased with the thorough model description provided, and customer reviews which helped with our decision making, and our package came on the same day that it was ordered! I liked the process of choosing 3 preferred appointment times, and receiving a confirmation email which included Kevin's picture. The install price was very reasonable, and I would gladly use your Home Service again!
If your garage door is opening slowly or making a lot of noise, the problem may not be your opener. So before you buy a new one, check for broken or wobbly rollers and brackets. But don’t replace the bottom roller bracket yourself—the cable attached to it is under extreme tension. You’ll need to call a pro. If you’re replacing the rollers, get nylon rollers. They operate quieter than steel rollers and cost only a few bucks more. Next, check the torsion spring (mounted on the header above the door opening) to see if it’s broken. When one breaks, you’ll see a gap in the coils. You’ll need a pro to replace a broken spring.

Electric Garage Door Openers – Service and repair of the electric garage door opener itself, including the lift mechanism that pulls the door up and guides it down. This is typically not part of the garage door itself and is serviced and repaired on its own interval. Typical service includes inspection, repair, adjustment, and lubrication if needed. Also, we typically inspect the mounting of the unit as well as its attachment to the door itself.
Our technicians are specially trained to handle a variety of garage brands, styles, and configurations. After arriving at your home, a Sears technician will diagnose the problem and walk you through the options for fixing it. Next, the technician will make any necessary adjustments or replace broken parts to ensure the door can be operational once again. We always attempt to complete repairs the same day of service, and your satisfaction is guaranteed. Our representatives are standing by for your call and are happy discuss pricing options.
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.

Electric Garage Door Openers – Service and repair of the electric garage door opener itself, including the lift mechanism that pulls the door up and guides it down. This is typically not part of the garage door itself and is serviced and repaired on its own interval. Typical service includes inspection, repair, adjustment, and lubrication if needed. Also, we typically inspect the mounting of the unit as well as its attachment to the door itself.
The most common grade of torsion springs have an expected life of about 10,000 cycles. The hardened and tempered steel experiences tremendous forces each time the door opens or closes. Gradually, the steel fatigues with each flexure, and eventually cracks and breaks, usually releasing its stored energy in an instant with a horrific "sproing" noise or bang. If you average about two car trips per day, opening and closing the door a total of 4 times daily when you come and go, then that expected life becomes 2500 days, or only about 7 years. If you have an automatic opener, then if you're like me, you tend to cycle the door even more frequently, and can expect the need for spring replacement even sooner. Moreover, my three-car garage has three doors, so on average I can expect a repair job every few years. Over a lifetime, it is very economical to do these repairs myself.
If your garage door is opening slowly or making a lot of noise, the problem may not be your opener. So before you buy a new one, check for broken or wobbly rollers and brackets. But don’t replace the bottom roller bracket yourself—the cable attached to it is under extreme tension. You’ll need to call a pro. If you’re replacing the rollers, get nylon rollers. They operate quieter than steel rollers and cost only a few bucks more. Next, check the torsion spring (mounted on the header above the door opening) to see if it’s broken. When one breaks, you’ll see a gap in the coils. You’ll need a pro to replace a broken spring.

The Genie Chain Drive garage door opener combines The Genie Chain Drive garage door opener combines powerful reliable performance with smooth operation to create a long-lasting and easy-to-install garage door opener. The unit's electronic push-button programming makes installation and setup fast and easy. Complete with accessories the system features a reliable DC motor that delivers quiet smooth operation ...  More + Product Details Close
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