Rocking Chair Product

Overview

A rocking chair is a chair whose legs terminate in two curved runners instead of feet. Each Rocker Runner in the Rocker Set is cut or laminated to an arc of roughly 90–110 cm radius, and the chair tilts by rolling along this arc. The form dates to the mid-18th century, when rockers borrowed from cradles were fitted to standard chairs; the all-wood spindle-back pattern described here is the American Windsor lineage that became the dominant type.

The structure follows Windsor practice: a thick sculpted Sculpted Seat Board is the structural hub, with the Undercarriage socketed into its underside and the Back Assembly and Armrest Set socketed into its top. No component except the seat spans the whole chair, which lets each part use small, straight-grained stock.

How it works

The rocking action is a rolling contact problem. At rest the chair sits at its neutral tilt of about 8–12 degrees, set by the differing lengths and rake of the Front Leg and Rear Leg. When the sitter leans, the contact line between rocker and floor migrates along the arc. Because the rocker radius is much larger than the height of the combined center of gravity above the contact point, the system behaves like a pendulum with a long effective arm: displacing it raises the center of gravity, and gravity supplies the restoring torque. Typical designs oscillate at around 0.5–0.8 Hz, sustained by small leg pushes.

Rocker geometry sets the character of the motion. A tighter radius gives a quick, short rock; a flatter one a slow, long travel. The tips of each runner are flattened or slightly back-curved so the chair cannot roll past the point where it would tip — as the contact line reaches the flat, the restoring arm lengthens sharply and the chair stops. Felt or polyethylene Rocker Wear Strip strips on the underside quiet the motion on hard floors.

Joinery

The chair is held together almost entirely by wedged round mortise-and-tenon joints. Each leg tenon passes through the seat or into the rocker mortise and is split by a Leg Notch Wedge driven across the grain, which flares the tenon into a dovetail shape that cannot withdraw. The Back Spindles and Arm Posts are locked the same way with Spindle Wedges and Arm Joint Wedges. Chairmakers exploit wood movement: tenons are dried to 6–8% moisture content and driven into mortise stock at 10–12%, so the tenon swells as the assembly equalizes and the joint tightens over its first weeks.

Glue is secondary but present. Traditional shops use Hide Glue because a failed joint can be steamed apart and re-glued; Dowel Pins and Glue Blocks reinforce the highest-stress joints. The Seat Battens under the seat are screwed through slotted holes — the one place the design must allow the wide seat board to expand and contract across the grain without splitting.

Back and arms

Comfort comes from controlled flexibility. The seven Back Spindles taper from about 16 mm at the seat to 10 mm near the Crest Rail, and because they are riven or turned with continuous grain they bend several centimetres under shoulder pressure and spring back. The Lumbar Rail gathers the spindles at the height of the lumbar spine, turning the back into a leaf-spring array that distributes load. The crest rail and lumbar rail are steam-bent: stock is heated to about 100 °C at saturated humidity for roughly one hour per 25 mm of thickness, bent over a form, and dried in place.

Each Armrest runs from a tenon in the Back Post to the Arm Post at the seat edge, with short Arm Spindles stiffening the span. Arms see large prying loads when sitters push up to stand, so the arm-to-post joints are wedged through-tenons rather than glued butt joints.

Finish

After assembly the chair receives the Finish Kit system: Wood Stain to even the color between sapwood and heartwood, a penetrating oil or sprayed lacquer Protective Topcoat for moisture and wear protection, and buffed Paste Wax. Oil finishes are favored on chairs because they can be locally renewed on arm wear spots without refinishing the whole piece. A finished chair weighs 9–14 kg and, despite having no metal fasteners, passes the same 120–150 kg cyclic load tests applied to rigid seating.