Postwar cars started to use the no-sag or zigzag springs in car seats because they were faster to install and cut the cost of manufacturing. By the mid-1960s, manufacturers had started using less metal in the seats, and the spring work began to get weaker. When fewer rows of springs are used the result is going to be a lot of broken springs. By the early 1970s the spring was replaced by a solid foam cushion. The foam used was very dense, and yet it made a comfortable seat cushion.
Tensioner Removal
Begin working the springs by removing the tensioning burlap along the top and bottom of the springs. This piece of burlap limits the expansion of the springs. Having a small amount of tension on the springs as a unit gives the seat cover some definition. Label and save the tension burlap pieces so that new pieces can be made.
Spring Removal
The springs need to be removed from the seat frame so that they can be cleaned and re-cased. Cut all the hog rings that hold the springs along the edge wire of the spring frame. This frees the spring unit from the edge wire frame. A legend card can be created to map the position of tension rods and the rows of springs. Component location and measurements are taken and recorded on the legend card. This information helps when it comes time to rebuild the spring unit.
To get the springs out of the wire frame, you need to remove the edge wire clips from the tensioning rods and then mark and number the tensioning rod position with masking tape to aid in reassembly. To release the tension rods, carefully open the edge wire clips without destroying them. You will reuse the clips when the unit is put back together. If a clip is broken, a replacement clip must be fabricated from sheet metal. Remove the spring unit from the seat frame by lifting it out of the frame. Set the seat frame out of the way and begin to cut the hog rings holding the coils to each other. Do not cut the springs when removing the hog rings. Work on one row of springs at a time to prevent a mix-up of the spring placement. When a row of springs has been cut free, it should be numbered on the right-hand end of the row to identify its position and orientation. After the row has been numbered it can be set aside. Continue with the next row until all the rows of springs have been separated and numbered.
Double-Check Your Work
Before any further disassembly occurs, lay all the rows of cased springs out along with the other components that were removed and check them against the legend card you made. This way you begin to understand how they were assembled and it makes it easier for you to rebuild the spring unit. Make any corrections or add any additional information to the legend card now; it will be very difficult to remember later.
Keep Your Springs in Order
To remove the springs from the old casing, begin by cutting the stitching along the top of the casing and pull the spring out. Observe that the outside springs are sometimes a heavier gauge than the inside springs, so keep the springs in the same order that they were placed in the original casing. Flex and squeeze the springs to check for cracked or broken springs. Any spring component that is broken, worn, or rusted through must be replaced with a new part. Unfortunately, welding cannot repair a broken spring. The nature of a spring is to flex and, if you weld the metal, it draws the temper in the metal and it becomes brittle and prone to breaking, which brings me back to a broken spring.
Casing Measurements
After the springs are removed from the old casing, lay the casing out flat and carefully measure the overall height and width of each compartment. Also remember to measure the spacing distance between the spring compartments. These measurements allow you to accurately make the new spring casing.
Some compartments may have an extra seam in the bottom to add more tension to the spring. Record these measurements on the legend sheet as well. This will be your guide to help make sure that the springs are tensioned and spaced correctly when they are reassembled. Each row of springs is most likely different in height and by the number of springs it holds. Carefully measure and mark each row as you lay out the original pattern onto the new burlap. If your old casing measures 8 inches tall by 37 inches wide, mark the new burlap 16 inches tall by 37 inches wide. Then when you fold the strip in half it will be the correct size. Continue to mark the selvage on the ends of each row along with the closing allowance at the top. Include the tensioning seam along the bottom if needed. Now the new casing row can be cut out and sewn according to the original measurements.
Reinsert the Springs
Straighten any bent springs. Wire brush any rust off the springs to clean them before you insert the springs into their new pocket. It is easier to work with just one spring at a time. Compress the spring flat and insert it horizontally into the pocket of the burlap casing. Sew along the top of the casing to lock the spring into its new pocket. After all the springs are encased in burlap they must be turned to a vertical position and expanded. Rotate the spring inside the pocket until it is correctly positioned. Continue doing this until the row of springs are all turned and then set the row aside. Repeat this process until all the rows of springs have been restored. When all of the springs are re-cased, insert the back row of springs into the wire frame first and progress forward. Insert each tensioning rod in its correct position as you add rows of springs.
When all the rows of springs are in place, secure the tension rods to the edge wire with their clips. Hog ring the lower edge of the springs along the outside edges of the seat frame and then finish hog ringing the rows together just like they were. Do this one row at a time to prevent any missed springs. When you are finished with the top of the springs, turn the seat over and hog ring the bottoms of the springs in the same way as the top.
Reconditioning Coil Springs
1 Several rows of coil springs make up the cushion system of the backrest. Being sewn into a burlap casing tensions the springs. Collectively, the springs work as a unit to provide comfort and support for the driver and passenger.
2 Each part of the spring system plays an important role. Along the top and bottom of the spring unit are tensioners that limit the amount of expansion of the springs. An edge wire frame contains the springs, allowing them to work as a unit.
3 The spring unit is attached to the edge wire frame with hog rings. Removing the hog rings to free the spring unit from the seat frame is the start of the rebuilding process. Parts removed are labeled for reassembly.
4 To keep track of all the parts and their positions a legend card is created. As pieces are removed their size and position are tagged with tape and recorded onto the legend card. Accuracy and detail are key elements to a successful spring unit rebuild.
5 With the spring unit on the workbench, it can be cut apart carefully. All the hog rings that connect the rows of springs are removed without cutting or damaging the coil springs. To keep the process simple, only work one row of springs at a time.
6 Each row of springs is numbered to identify its location and position. Knowing that the row number is on the right helps with the orientation of the row of springs as well as its position during the reassembly of the spring unit.