Servicing the Santa Clarita Valley Since 1993
Most Garage Doors Are Opened And Closed With Torsion Springs
The torsion springs are slid onto a long pole called a torsion tube (or shaft) located directly above the garage door. At each end of the torsion tube, you will find cable drums.
The springs are mounted in the center using a bracket we call a spring pad. Between the springs is a center bearing to keep the springs centered on the tube.
The ends of the torsion tube are mounted with bearing plates. These plates hold the end of the torsion tube and play a primary role in the tube rotating as the door opens and closes.
There are cables that attach to the bottom of the door and then lock into place on the cable drums. The torsion springs that are attached in the center of the tube are forced to turn by the installer using large winding bars. A set number of “turns” are put on the springs and the springs are then secured to the tube.
The natural reaction of the springs is to want to unwind. The cable drums are secured at the end of the shaft with cables traveling to the bottom of the door. The springs unwind forcing the torsion tube to turn. This forces the cable drums to turn, which forces the cable to wind up on the drums and lift the door.
The Torsion Spring
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here is no “one size fits all” when it comes to torsion springs. You may remember the old style one-piece wood doors and the springs that they use. You could go to the local home improvement store and find replacement springs there. They had about 3 different sizes to choose from and nearly everyone was able to purchase springs that way.
What is important to know is that the adjustments for different weight doors is in the hardware that mounts the door. You can change the leverage used to expand the spring to change how strong it pulls.
One person might have a plain metal door with no insulation and another might have a top-of-the-line, thick-gauge insulated door with metal backing and a glass top section. Those two doors are going to have different weights. So, how would the same spring lift both doors? It can’t. Thus, there are different springs for different door weights.
How Torsion Springs Work
The spring is made from a giant roll of wire. The wire has a certain size or circumference. This is known as wire gauge. For residential doors, wire is fed off the giant spool and forced into small loops usually with an inside diameter of 1 3/4 inches. Once the coils are formed, they are made into lengths that can exceed 20 feet. From these large rolls of “raw” wire, they can be cut down in length to make garage door springs. The most common wire gauges used for garage doors are: .207, .218, .225, .235, .250 and .262. The smaller the wire sized used for the spring, the lighter the lifting capacity.
Lifting Capacity and Cycle Count:
Although garage doors have different balancing weights, there are two constants for standard doors— the drums and lifting height. Standard garage door cable drums have a six inch diameter that collects one foot of cable every time it makes a complete revolution. The standard garage door is seven feet high. Because of these two factors, we need to force the torsion springs to turn seven times— one turn for every foot of vertical lift. Every time the spring unwinds one complete turn, it collects one foot of cable, lifting the door one foot off the ground.
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his is where the tricky part of spring calculations come in. You can change the wire size, inside diameter and overall length of the spring to affect it’s lifting capacity at the seven turns. Additionally, the length of the spring compared to the seven turns affects its cycle count. Generally speaking, if you take a spring with the same wire size and diameter, you can change it’s length to alter it’s lifting capacity at seven turns and it’s cycle count. For example, if I took a spring made from .207 wire and gave it a length of 23″ it would have a lifting capacity around 80lbs if you put seven turns on it. A spring that is only 23″ can only have so many turns forced on it before it just will not turn any more.
Let’s say the 23″ spring has a max output of ten turns. If I have seven turns on a spring that can carry a max of ten, that spring is using most of its output. Springs like this will have relatively low cycle counts— probably 10,000-15,000 cycles. If we take the same wire size of .207, give the spring a total length of 36 inches and put the same seven turns on it, this spring’s lifting capacity at seven turns will be about 55lbs instead of 85. It has the wire size, same seven turns, but lifts less weight. However, because the spring is so much longer, it can handle more turns. This spring might be able to take 20 turns. Since we are only using seven, the cycle count will go way up.