Rocking chair rockers

[Dclifton2]

I'm wanting to make some rocking chairs and was wondering if anyone had a proven layout of the rocker design or formulas that works.
Thanks in advance for any help
Don Clifton

[martin54]

Have you seen this thread?? All the plans done for you.

http://forum.vectric.com/viewtopic.php? ... ns#p156880

[Dclifton2]

I'm sure the plans are great but $500 is a little steep for my blood, plus I want to build and design my own. His chair a great looking.
Don

[4DThinker]

I teach furniture design and am happy to help. For the most part a rocker radius (not diameter) should be 39" or within an inch + or -. You want the center of gravity of the occupant when at rest (not rocking) to be in line with the radial line to the center of that arc when vertical. For (average) male occupants just assume their belly button is the center of gravity when seated. For (average) women pick a point slightly in front of their belly button. Ideally a great rocker occupant's feet can rock the chair by going from heel to toe and back on the floor.

The period of rock should be close to the at-rest breathing rate of the seated occupant. You can tweak the period by lengthening or shortening the radius of the rocker arc. Make it shorter and the period will get longer (the rocker will rock farther forward and back). Make it longer and the period will get shorter.

My students make "test" bucks when designing rocking chairs. Usually with plywood sides, some 2x4 cross braces, plywood seat and back. The rocker radius cut using a bandsaw with a jig to hold the center of the board relative to the tip of the blade, or easily on a CNC. Start with a radius a little larger than 39", and you can always cut it shorter and shorter until it tests "perfect" when rocked in. These test bucks also allow moving the seat forward or back slightly to find the best resting position when not rocking. Once these buck prove good then their details are transferred to the final rocking chair design. A good rocker won't scare you by rocking too far back, and it won't put pressure on your legs to keep it at a comfortable angle.

4D

[zeeway]

Rockingchairuniversity.com has a write up you should read.

Angie

[Dclifton2]

Thanks 4D I'll play around with it, most of it I will make the old fashion way with hand tools. And thanks Angie I look at the link also.
Thanks
Don Clifton

[John Murphy]

My center of gravity is increasing every year

[4DThinker]

My center of gravity is increasing every year

Luckily your seated center of gravity stays in roughly the same place as your body/weight changes from toe to crown. No one makes a standing rocker for the same reason.

[rscrawford]

The roughly 39" radius is because you want the centre of gravity right in the centre of the diameter of the rockers. This gives the least effort to rock, because you are not lifting your weight up as you rock, your centre of gravity is simply moving horizontally. Think of the rockers as part of a ball - if the centre of gravity is in the centre of the ball, it will roll along nice and smoothly. If the centre of gravity is offset, the ball will wobble as it rolls along.

[4DThinker]

It is the wobble that make a rocking chair rock. With the COG below the rocker arc center point any roll forward or back lifts the load uphill. Move the COG closer to the arc center and you'll get farther uphill for your effort before oscillating back down to a centered stop.

When I have students make lounge rockers, where their feet are off the floor, a good one will rock naturally as the occupant breathes. Almost spooky.

[Dclifton2]

Doesn't the rocker flatten out at the ends to stop it from tipping over?
Don

[zeeway]

Basically, no. Most rockers I have seen have true radius. With your center of gravity back into the chair as described above, it is difficult to tip it forward, but your feet ultimately stop it. Maloof rockers have an inverse curve at the rear...but if you rock the chair violently enough to have that part of the rockers contact the floor, you will likely flip backwards.

Angie

[Dclifton2]

The rocker I have drawn now allows for a 14 degree tilt back, I don't know if that will be enough, I guess I will have to cut one and see. When I rock it back in aspire it looks good. I'm wanting to make a rocker like one my annt had when I was a kid, it was big and all black with a old man's head carved on each side of the back. I had back surgery and I trying to shift from building machinery to doing more wood working. My dad built sail boats when I was a kid and I always like making thing in the shop.
Don

[rscrawford]

It is the wobble that make a rocking chair rock. With the COG below the rocker arc center point any roll forward or back lifts the load uphill. Move the COG closer to the arc center and you'll get farther uphill for your effort before oscillating back down to a centered stop.

When I have students make lounge rockers, where their feet are off the floor, a good one will rock naturally as the occupant breathes. Almost spooky.

I guess that makes more sense - if the centre of gravity was at the arc centre, you'd never come back to resting position after rocking back. I've always just gone with a set radius on my rockers, without actually looking into why that makes it work properly.

[Ms Wolffie]

[quote="4DThinker"
When I have students make lounge rockers, where their feet are off the floor, a good one will rock naturally as the occupant breathes. Almost spooky.[/quote]

Just like the swing lounge I have on my front deck.
It swings gently by itself, I never realised it was my breathing coursing it.
Mindblowing to think what would happen with heavy breathing