Rocking Chair Calculator

Rocking chairs may not be one of your favorite subjects, but when it comes time to learn how-to make a rocking chair rock, you are going to need to do some math or at least spend some time reading up on radius (or should I say looking around at radii) because it is the radius of the rocker that makes the rocking chair rock right.

As a general rule, building a better rocker all boils down to pi. In order for a rocking chair to rock just right simply apply π.

π = 3.14 multiplied by the finished height of your rocking chairs’ seat height (your leg length) M , at your belly button. This will give you the required radius length of your rocking chair rails.

To fine the R = Radius of the rocker arc rails. Multiply 3.14 times M , which is normally located at a person's belly button when he/she is in a sitting position. (Persons leg length when sitting.) M Times 3.14 = The rocker rail radius needed.

M = Center of (the occupant's) mass above the floor plane, leg length. This is what will vary.

R = Pi Times, The Height Of Rockers Seat at the belly button or M. This is a simple way to calculate your perfect rocker rail radius needed to make the perfect high tech rocker that is fined tuned to your breathing.

Wow thats right you can make a "high tech" rocker that is tuned to your breathing. Who knew?

A perfect high tech rocker will be tuned to your breathing. I doubt you will find this at cracker barrel.

You will need to get a custom make rocker made to your specifications that is tuned to your breathing. You can make your own knowing how to figure the rocker rail radius. (3.14 times you leg length when sitting.) I call it M.

Figure out your "M" position above the floor in a comfortable at-rest sitting position.

M is normally located at a Human's belly button when he/she is in a sitting position.

The Radius of the rocker arc, the runner, must be tuned so your M center of mass, leg length when sitting, is tuned to your breathing, inhaling and exhaling.

When the Radius of the rocker is tuned correctly your breathing will be tuned to your M, at your belly button, (Leg Length when sitting), causing the chair to rock back with each inhale and forward on exhale.

The shorter the finished rocking chair the tighter or smaller the radius of the runners or rails need be. It is a simple mathematical equation that will rock your world.

So the next time someone asks you how-to make a rocking chair rock, tell them to apply (π).

Let’s face it, rocking chairs are comfortable because they rock. And when a user sits in one without rocking, the chair automatically reclines until the sitter’s center of gravity is met. This is what allows just about any type of rocking chair such a comfortable advantage over the standard, four-legged, fixed chair.

Typically, the rockers for rocking chairs are not designed based on a single angle of measurement. Rather, you must take into consideration the curve of the rockers, any difference between the front and back of the rockers, the rockers' overall length and their orientation in relationship to the chair legs. For example, you can produce a very different chair with the same rockers, depending on whether you slide the chair an inch forward or backward along the rockers.

Determining the Curves

If you are designing your own rocking chair, you can easily determine the angle of the rockers by using a string to draw an even curve along a straight piece of wood. For a fairly standard-sized rocker, cut a piece of string 42 inches in length. Have a partner hold one end of the string in place on the floor. Extend the string out straight so its other end reaches the middle of the wood you will use for the first rocker. With the first end held in place, gently pull the other end left and right against the wood to form a gentle arc. Trace this arc onto the wood with a pencil and use it as your pattern for both rockers.

To fine tune your rocking chair use the formula 3.14 times M, Persons leg length when sitting, to find your perfect radius for your rocking chair rails or runners. M will vary for everyone of course.

A rocking chair is comfortable because it will naturally move to your center of gravity when you sit in it. When you rock, it will naturally try to return to your center of gravity. Its a type of zero gravity chair.

Different Chairs, Different Angles

While the string technique, 42" average rocker radius, works well for designing rocking chairs of all sizes, you may need slightly different string lengths for very large or small chairs. For a custom-made rocker, measure the leg of the person who will be using the chair when sitting. This is called M. Multiply m times 3.14 to find the valuse of your rocker rail radius length. It will vary according to the persons leg length when in a sitting position.

What is the physics theory about rocking chairs?

M = Center of (the occupant's) mass above the floor plane. Leg length when sitting.

When M is less than R, or your center of mass is lower than the center of the rocker arc, the chair will return to center when rocked forward or back. The center position is when M is directly below the center point of the rocker arc.

From a side view, M is normally located at a Human's belly button when he/she is in a sitting position. For women it may be slightly forward of the belly button. A value for M can be found by positioning the human above the floor in a comfortable at-rest sitting position. Measure from the belly button to the floor to find M.

R > M, and a good dimension for R is 42" or so. Increasing R reduces the period of a rocking cycle. Reducing R increases the period of a rocking cycle. By changing R slightly the rocking period can be "tuned" to match the breathing rate of the occupant. The simple act of breathing, then, will shift the occupant's mass, causing the chair to rock back with each inhale and forward on exhale.

How cool is this! Tune your rock to your breathing rate to cause the rocking chair to rock back and forth with each inhale and exhale.

Feet on the floor will impede rocking motion. Ideally the occupant's feet will cycle from touching at toes to touching down the heel as the chair rocks.

A small shift in where you place the legs of the chair can make a big difference in how the rocker will rock. You may need to test this first before permanently attaching the chair legs to the rails.

.Balance of chair on rocker is more crucial than length. When you sit in the chair, it should not lean too far forward or too far back.

Health benefits from rocking!

Rocking chairs are a great way of exercising without too much effort, especially for those who have limited mobility. Rocking provides a way to tone the leg muscles of those who cannot tolerate weight-bearing exercise, bringing a safe activity to people who might live an otherwise sedentary lifestyle. Forget about all those high tech gadgets when an old fashioned rocking chair (which may even already be in your home) can do the job.

1. Rocking works the muscles and the tendons of the thighs, the lower legs and even the ankles, helping to keep you fitter.

2. As little as 10 minutes of rocking per day can reduce your blood pressure and improve your circulation. A few minutes longer, even more benefits.

3. Rocking can reduce the impact of diseases such arthritis. This is because the increased blood flow sends more oxygen to the joints while the relaxation effect boosts the immune system. Just a minimum of one hour per day lulls the into a natural rhythm that is believed to speed healing while the physical operating increases muscle tone and flexibility around the knees.

4. Recently undergone surgery? Rocking promotes healing as those who rock seem to have fewer complications and recover faster than patients on a more traditional recovery program.

5. Rocking causes the release of endorphins that elevates the mood and relieves pain plus rocking can even lead to some weight loss as you burn 150 calories per hour with this form of exercise.

6. Rocking causes a reduction in the anxiety and depression often present in the elderly. But rocking is a relaxing activity for all age groups and you can even do it while watching TV!

7. Worried about your sense of balance? The motion of rocking stimulates the body to maintain the momentum, resulting in greater balance capabilities. This can be especially useful in older people who often fear the risk of injury by falling.

8. Rocking in a rocking chair is recommended as the perfect exercise to stimulate the circulatory system and the leg muscles. This is especially helpful for those who are elderly or housebound and are unable to do other forms of exercise.

9. Rocking chairs have become invaluable in those nursing homes caring for residents with dementia. A study published in the American Journal of Alzheimer’s Disease and Other Dementia found that “there were improvements in depression/anxiety and reductions in PRN pain medication significantly related to amount of rocking.” Those residents that enjoyed the program and wanted to continue rocking past the six weeks of the study “demonstrated significant improvements in balance as measured by center of gravity.” Useful for those taking care of someone at home with mid-stage dementia as they are often the most difficult to calm. At this mid-stage, sadly they are losing their faculties at a noticeable rate but are still aware of what is happening leading to fear, anger and anxiety. The act of rocking leads to a calming and relaxing effect to reduce anxiety as well as pain.

10. The rocking chair combined with some basic exercises can help relieve chronic back pain partically because of the relaxation it affords but also the flexibility and strengthening the act of rocking can bring to the muscles. The late JF Kennedy frequently used his rocking chair to help ease his chronic back problems.

Free DIY Outdoor Rocking Chair Plan (estimated cost between $50 to $100, this DIY offers you a wooden rocking chair plan with 7 building steps.)

M = Center of (the occupant's) mass above the floor plane Slightly change R to tune your rocker.

This plans rails are 35" which will need to be adjusted according to the height of your belly button above the floor when seated.

Sit in a chair that you can measure your M. R will depend on the height of your M which is Pi times M.

The higher your M the bigger the rails. The smaller your M the smaller the rails.

The correct size rails will balance your center of gravity so when you exhale and inhale the rocker will rock. It will be fine tuned to your breathing.

Rocker Basics

Determining the Curves

Different Chairs, Different Angles

What is the physics theory about rocking chairs?

Health benefits from rocking!

Heirloom Project: A rocker is on just about every woodworker’s ‘bucket list’. If you can appreciate smooth, subtle curves and are up for a challenge, this design might be for you.