Screw-drive garage door openers aren't as popular as some other types, but feedback indicates that those that give the Genie Excelerator a try are largely very happy that they did. It's a fast performer, owners say, and the company claims that it can move a door at a rate of up to a foot per second. It's relatively quiet, too -- perhaps not the absolute quietest that you can buy, but certainly quieter than a chain-drive opener, and quieter than older screw-drive openers, users report.
Next, the torsion shaft is reassembled with the new springs, the drums repositioned loosely on the shaft, this whole assembly slid back into the end bearings, and the drum set-screws tightened down. I tightened the set-screws about 1/2 or 3/4 of a turn after contact with the shaft, which provides a good grip, but does not distort the shaft. The drums can be set on their old positions, if they were correctly installed, which is snug up against the end bearings to remove any longitudinal play in the torsion shaft. Now the lift cable can be reattached to the drums, and a slight temporary torque applied to the shaft to keep the cable taut while the first spring is wound. This temporary torque is conveniently applied with a pair of locking pliers clamped on the shaft, positioned such that they hold the torque by pressing lightly against the wall above the door, before you start the spring winding, The locking pliers stay on the torsion shaft until you have finished the spring winding locked down the spring cone(s) with the setscrew(s), and removed the winding bars. Then you simply remove them with the release on the wrench handle. I feel that any job that doesn't require a trick manipulation with either locking pliers or duct tape (or in the ultimate case, both!) is just too boring. My trusty pliers look a trifle rusty ever since I used them to clamp something on my outdoor TV antenna "temporarily" and left them out in the weather for, oh, several years. The white stuff on the drum is paint overspray from the original painting of the garage interior.
Checking if the lift drums need resetting: The old position of the lift drums on the shaft may have slipped or otherwise lost the the proper position, requiring a reset of the drum position on the torsion shaft. You will also reset the drums if you are replacing the lift cables, since the new cables will not exactly match the length of the old ones. Problems like uneven tension on the cables, or a tilted door, or a door that doesn't easily stay aligned with the tracks, can be due to an improper "set" of the drums on the shaft. So one shouldn't assume the old positions are correct. Setting the drums on a "fresh" part of the shaft will avoid the possibility of damaging the shaft from retightening in the same dimples.
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.
Even if one could somehow stretch and clamp the springs to the proper extra length, the process would still be more trouble, and there would be little or no reduction of risk. Lifting the full weight of the unsprung door by hand and clamping it in the raised position is dangerous in itself, and creates the same amount of stored energy as winding the springs, ready to slip out of your hands. Many doors won't travel far enough up the track to provide clearance to access the springs. You're also going to have to deal with winding stiff steel cables onto both lift drums at once without any resistance to maintain tension. Finally, even if you managed to complete the installation with the door raised, you then have to lower the massive door against an untested balancing torque. If you've made a mistake, then that massive door has nothing but your skeletal force applied through your meat clamps (hands) to prevent it from falling down and crushing whatever is in the way (perhaps your feet?).
I was careful not to assume that the previous installation correctly oriented the right- and left-hand springs on the correct sides of the center bearing plate. They could have been installed backwards by an incompetent installer, resulting in them having been wound looser (larger diameter coil) instead of tighter (smaller diameter coil) than when in their relaxed state, and if so I would have corrected them on the new installation. The proper orientation of the springs applies their reaction torque from tighter winding such that it turns the drums to lift the door. Verifying this is a rather simple exercise in mechanical visualization, but does require some care to be certain of correctness. If you were to install the springs backwards, and then start to wind them in the wrong direction, then the torsion bar will start winding the drums backwards, and not holding against the vise pliers, which should be obvious to inspection. Winding a spring backwards also tends to screw the spring off the cones; this error cannot proceed too far before the spring slips off the cones.
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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.
We were very pleased with the service we received. The receptionist that took our information over the phone was courteous and efficient. The young man, Nate, who came to the house was on time, respectful of our wants and needs, and very knowledgeable about the job. He was able to fix our door easily. Finally we have a garage door that works with a push of the button! We highly recommend this company for your garage door needs.read more