Four Spring Residential Torsion Systems

Posted August 11th, 2017 at 3:49 pm by Dan Musick

Many years ago when we first posted our residential torsion spring database program, we discovered customers were ordering longer life springs that were so heavy that the shaft would bend from the extra weight.

Because of this we began recommending that customers add idler support brackets if either of their springs weighs over 20 pounds.

And, as could be expected, longer life spring orders for heavier doors weighing 30 pounds or more require different solutions. The more common is to install two solid shafts with a cast iron connecting coupler in addition to the idler brackets. With the additional shipping this solution costs an additional $300-400.

A less expensive option is to convert a two spring system to a four spring system using smaller springs. This option costs less than $50.

Because of the lighter shafts on many of the garage doors, we now recommend converting to a four spring system on a 16′ or wider door if each spring weighs over 25 pounds. Rather than order and install idler support brackets we recommend that customers install spring anchor brackets, such as our more popular SAB-450K.

Here is an actual photo of a four spring torsion system that Charlie sent us.

 

Notice that the two center springs are mounted as before.

The two outer springs mount to what would have been idler brackets. To support the spring anchor brackets on each side Charlie added 2 X 6 lumber and painted it.

The difference with these brackets is that they include the extra bolts and nuts for attaching the stationary cones to the brackets. Both springs to the left of the center support bracket above are right wind; the winding cone is marked with red paint.

The two springs to the right shown below are left wind; the winding cones are marked with black paint.

Beyond the outer winding cone on each side is the cable drum. Here is the cable drum at the left end of the torsion shaft.To the right of the drum is the right wind torsion spring.

A second reason for installing four springs is if additional lift is needed as a result of the door not having the correct springs. This can be caused by weight being added to the door. It may also be due to an earlier technician installing the wrong springs, or by the homeowner measuring and ordering the incorrect springs.

One problem with converting to four springs can be limited shaft space. When calculating the space needed for the springs, first measure the distance between the drums. The wound springs, cones and brackets need to fit inside this space.

Next, determine the wound length of each spring. On 1 3/4″ and 2″ springs the cones for each spring require 2.25.” Add to this the width of the coils you add when winding the spring. On standard seven foot high doors figure eight coils and multiply this by the wire size. For example, 41.75″ X .2253 = 1.8.” Hence, 2.25″ for the cones + 41.75″ for the length of the spring + 1.8″ of turns = 45.8.” Add to this the gaps between the coils on the cones which is sometimes as much as 1/2.” Figure an additional 1/8″ for the thickness of the bracket.

This Wound Torsion Spring Lengths Spreadsheet may come in handy.

If there is not enough space on the shaft, you can always increase the inside diameter of your springs. If you have 1 3/4″ ID springs you can easily convert to 2″ because all the bolt holes are the same. If you have 2″ ID springs you can convert to 2 5/8″ ID and use the same brackets if the bolt holes are slotted. This torsion spring inside diameter converter should help.

On Charlie’s door above we tried to match the longer cycle life with the existing 1 3/4″ ID springs attached to the center support bracket, but there wasn’t enough space on the shaft. So we converted the inside diameter of the outer springs to two inches. If you look closely you can see that the coil diameter of the outer spring is bigger than the coil diameter of the inner spring.

 

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