As a nation we Americans are particularly devoted to a number of artifacts and icons from our past. On the domestic front there is a category of national passion - comfort - and one of the primary instruments of American comfort is the venerable rocking chair. There is even the reassuring fable that we actually invented that handsome little critter somewhere around the Revolution. Unfortunately that's just a rumor.

As early as the 15th century curved runners or skates were added to cradles so they could rock the baby. Skates were added to the occasional English chair in the early 18th century and by the 1740s the Windsor chair had sprouted rockers for use as outside garden seating in southern England. At the same time the Swedes were making their own version of the rocker, a six legged affair with curved skates known as a "gungstol."

On the other hand we can rightly take credit for the successor to the regular skate mounted rocker, the platform rocker. Platform rockers came about because of several problems inherit in the design of the standard rocker. The first problem is that if the rocker is used on a plank floor, the rockee has to face in the direction of the length of the planks in the floor or the rocker will uncomfortably bump along across the joints in the floor boards. And if the rockee pursues a vigorous rocking motion the chair will creep across the floor, moving forward in the direction of the rocking motion. Finally if the rocker is used on a carpeted surface the constant motion of the skates, added to the weight of the inhabitant, will eventually wear a telltale path into expensive floor covering. The platform rocker solves all of these problems allowing the rockee to face any direction without discomfort, remain in the same vicinity and without wearing out the rug.

But as with all technological advances, which the platform rocker certainly was, there are always technological problems with the equipment. In the case of the platform rocker the weak link in the chain is the spring mechanism that keeps the rocker rocking with minimal effort. There were some very innovative approaches to the spring problem just after the middle of the 19th century but eventually the standard spring became the coil steel spring in a cast iron mounting plate. Coil steel springs were first used in furniture upholstery in the US in the mid 19th century and it was not a long step to adapt them to the platform rocker.

But the problem was that eventually, like all springs, the rocker springs lost their tension and the chairs became sloppy seats sitting atop a platform with the feeling that they are about to tip over. That is a common problem with almost all platform rockers from the mid to late 19th century that have survived into the 21st century, especially if they have been ridden hard over the years.

If the rocker is just meant to be a showpiece and not for human use, forget about the springs and just show off the rocker. However, if the chair is meant to be used as a rocker, the problem with the old springs must be addressed before somebody tumbles headfirst out of the seat. Since there is no commonly known way to rejuvenate the old springs the answer is replacement. But most of the old springs are a single heavy coil on an iron base. New springs don't look like that. Most newer springs come as a two coil unit mounted on a stamped steel frame. They are available from almost any upholstery supply house or from a number of supply houses such as Van Dyke's Restorers (www.vandykes.com).

Installation is fairly simple if you know the trick. It is very important that you do not change the pivot point at which the rockers reach equilibrium on the base. The center point of the original springs identifies the optimum pivot location. Measure and mark this point on both sides of the platform and the rockers before removing the old springs. The new springs come as set with two springs enclosed in frame as opposed to the open spring you are replacing. This means you will need to drill new pilot holes for screws in both the rockers and the base. Place the new spring unit on the base, centered over the pivot point, with the edge of the spring frame slightly below the top of the base. Mark and drill your pilot holes on both sides of the base and install the spring unit securely, parallel to the top edge of the base. Then, with the chair on its side, place the top part of the chair in position on the base and mark and drill pilot holes where the rear screw hole of the spring unit lines up.

Now comes the tricky part. The location of the front screw holes must be identified while the spring unit is under tension. Otherwise the chair will just flop back over when you are done. Use a small crowbar or a screwdriver inserted into the middle of the front coil of the spring unit and open the spring 1/4 to 1/2 in. With the spring open under pressure, mark where the front screw hole is. Release the pressure, drill the pilot hole and install the spring unit after opening it back up with the crowbar. Repeat the procedure on the other side making sure you open the spring the same amount on both sides. Be very careful and get someone to help you if needed. Those springs can really pinch you if you are not in control at all times.

Installing springs by this method may result in the chair appearing to tilt too far forward at first. This will cure itself over time as the springs loosen but if the tilt is too severe just relocate the forward screw positions.