To estimate the maximum physical force required to wind these springs, consider that they are balancing the weight of the door with a torque applied to a lift drum on each end of the torsion shaft. The lift drums have a 2-inch radius, which is the standard residential size, and corresponds conveniently to about a 1-foot circumference. If we pessimistically assume the 10-by-7-foot door has a weight of 350 pounds, this implies a torque of 350 pounds on a 2-inch radius, that is, 700 inch-pounds, or 58 foot-pounds. Each of the two springs should be exerting slightly less than half of the balancing torque, or 29 foot-pounds. Compare this to, say, the bolts in an automobile, which are typically torqued to values of about 50 foot-pounds, or tire lug nuts, which may be torqued to well over 100 foot-pounds.
The not-so-competitive advertising trick: How about this racket: We have all heard how you should get at least three bids for any home improvement jobs, right? In some areas the largest ads in the yellow pages are from a single business using various names and phone numbers, masquerading as independent competitors. When you call asking for prices, "they" all quote you very high numbers. You are tricked into thinking you have shopped around for the prevailing price. (The more modern version of this is multiple Web sites that all direct you to call the same person.) If you've ever had to call a plumber you may have unknowingly been a victim of a similar trick.
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.
Garage Door Repair