Difference between Extension and Torsion Springs
At Overhead Door Co. of Central Jersey, we are often asked ‘what is the difference between an extension spring and a torsion spring.
Extension springs may also often be referred to as ‘stretch springs’. Very simply, extension springs provide a counterbalancing effect to the weight of the door and torsion springs are wound around a pipe or shaft which is attached to the door via cable drums to create torque on the shaft which creates a counterbalancing effect. Without some type of counterbalance it would not be possible to operate your garage door. It would be dead weight, difficult or impossible to lift, without any means to keep it in the open or partially open position. Here is a bit more information regarding how these two different springing methods make your garage door easy to operate.
Extension Springs are attached at both ends to other parts of the counterbalance assembly. When these components move apart, the extension spring will pull them together again. In the case of a garage door counterbalance assembly, the components would be the rear track hanger, pulleys and cables. The spring is attached to the bottom of the door with a lift cable that is routed over a stationary pulley, around a pulley attached to one end of the spring and terminated at the forward portion of the upper or horizontal door track. As the door is closed, the cable pulls or extends the spring at a constant rate which counterbalances the weight of the door. As the door is opened, the spring retracts at a constant rate balancing only the portion of the door that remains vertical or ‘hanging’ in the opening. This allows the door to be easily operated either manually or via an automatic electric opener system. See image below.
Torsion Springs are helical springs that exert a torque or rotary force. The ends of torsion springs are attached to other parts of the garage door counterbalance. When these components rotate around the center of the spring, the spring tries to return them to their original position. When torsion springs are used to counterbalance a garage door, the springs are mounted on a shaft or tube across the top of the door. This shaft or tube has a cable drum or spool on each end. A cable is attached to the bottom corner of the door and the drum on each side of the door. The spring is then wound around the shaft to a predetermined tension and secured. When the door is moved, the spring either winds (if the door is up and being closed) or unwinds (if the door is closed and being opened. As the door weight is transferred to the horizontal portion of the track assembly the tension is reduced by the unwinding action, which keeps the door balanced throughout its travel. Again, this makes your garage door very manageable for either manual or automated operation.
The follow up question we hear most is ‘what are the advantages of one type of spring over the other?’
It is generally preferable to use a torsion spring counterbalance whenever possible. This spring is contained on a shaft or tube rather than being stretched out with a cable and pulley system. Torsion spring installations reduce the amount of hardware above the upper track assembly and provide a much cleaner appearance. These springs also often have a longer service life than standard extension springs. While we normally recommend torsion springs, there can be site conditions that make extension springs more appropriate.
To learn more about what counterbalance choice might be best for your needs, contact us today. Overhead Door Co. of Central Jersey has been selling, installing and servicing quality garage door and opener systems since 1972 – for 47 years – and we are always here to answer your questions. We are conveniently located in Branchburg, NJ at 952 Route 202 South and River Road. We can be reached at 908-521-4713 or on the web at www.OverheadDoorCo.com.