Create a simple mechanism to simulate a rocking chair

[moog]

TL;DR Summary

I'm a carpenter with basic knowledge of electronics. I have created a chair that is supported with 20 mattress springs (under the chair).

The chair is springy now, which is what I need.


Now I need to run some kind of a motor, which i can install at the bottom of the chair... and pull the chair 'downwards' towards the floor in a constant motion ... which hopefully i can adjust the speed of the motion....

So the chair will be moving up and down constantly...

help.. Need to create a simple mechanism to simulate a rocking chair..

I'm a carpenter with basic knowledge of electronics. I have created a chair that is supported with 20 mattress springs (under the chair).
The chair is springy now, which is what I need.

Now I need to run some kind of a motor, which i can install at the bottom of the chair... and pull the chair 'downwards' towards the floor in a constant motion ... which hopefully i can adjust the speed of the motion...
So the chair will be moving up and down constantly...

Anyone has any idea how I can do this?

 

[Lnewqban]

Welcome, moog!

I believe that you are describing two different types of movements: rocking and up-down in a leveled fashion.
Which one is the one you need to create?
How long the amplitude of the movement needs to be and how long the springs are?

 

[moog]

hellloo Lnewqban!
i need the up-down movement... i don't want the rocking movement ... not sure I got the technical terms right.. basically it needs to go vertically up by about 5cm and vertically down by about 5 cm...

not sure about the amplitude... but i'll need around 170 cycles in a minute (up and down = 1 cycle)

 

[jrmichler]

Do you intend that a person sit in this chair? The motion you describe is 10 cm peak to peak at 2.83 cycles per second. That motion will throw the occupant into the air, then hammer them on the way down. More technically, the acceleration will be 1.6 G's. When the acceleration is greater than 1.0 G, the chair goes down faster than the occupant falls, then moves up while the occupant is still falling, which will hammer the occupant.

If you want to make a massage chair, try a much smaller amplitude. I would start with 2 or 3 mm peak to peak, although somebody else might have a better number.

This article about vibrating conveyors might give you some ideas: https://www.thomasnet.com/articles/materials-handling/all-about-vibrating-conveyors/

 

[moog]

thank you for your advice! I'm trying to simulate a space shutter for a music video...
let me read up about the vibrating conveyors..!

 

[some bloke]

If your goal is for the chair to shake as if the shuttle is taking off / experiencing turbulence then you can try using an offset cam to shake it - basically, just get something like a drill and clamp something which isn't balanced into it, like the end of a golf club, then attach this under the chair, with guards to prevent injury from the spinning lump of metal. This might give you the vibrations you're after.

 

[Rive]

i'm trying to simulate a space shutter for a music video

That's not just up and down, I think.
Also, the weight of the chair (and the person sitting on it) certainly requires some power behind the mechanism.
I would try to use two or three (variable speed) electric motors, with gears to reduce the speed and excenter to provide the up-down movement.

 

[Spinnor]

I bet using rope and pulleys and a couple of strong people you could accomplish what you want. Humans are very easy to program.

 

[Spinnor]

I bet using rope and pulleys and a couple of strong people you could accomplish what you want. Humans are very easy to program.

I missed the part about constant vibration, people will get tired.

You can buy relatively inexpensive things that vibrate that have electric or pneumatic motors. Some electric motors can be speed controlled and pneumatic motors can have the speed controlled by varying the air pressure. Most of them vibrate at high frequencies so at lower frequencies the forces will be smaller. If you had several at different speeds you might get more realistic vibration. Seems like you need large forces to really get the chair and someone shaking almost violently like liftoff.

https://www.google.com/search?safe=off&sa=X&hl=en&biw=1280&bih=579&tbm=shop&sxsrf=ALeKk02cVBAupwWyA7ReVkULt-yInASgag:1604439436976&psb=1&q=vibrating+motor&oq=vibrating+motor&gs_lcp=Cgtwcm9kdWN0cy1jYxADMgIIADICCAAyAggAMgIIADICCAAyAggAMgIIADICCAAyAggAMgIIADoECAAQGFDFpAdYzrAHYJ6_B2gAcAB4AIABTIgB4QKSAQE2mAEAoAEBqgEPcHJvZHVjdHMtY2Mtd2l6wAEB&sclient=products-cc

 

[jrmichler]

If you drive an eccentric weight with one of these, you will have plenty of power and good speed control at your desired speed: https://www.amazon.com/dp/B0000223HF/?tag=pfamazon01-20. I have one of these drills, and highly recommend it. Stay away from small high speed motors because it is too difficult to get the exact speed you want at the low speeds you will need.

 

[Frodo]

Keep the chair stationary and shake the camera.

You will not hurt anyone and, as the camera is so much lighter than the person and chair, the device will be much simpler.

If necessary, use a "blue-screen" background and electronically (live or image processing) replace it with a matching vibrating background to get the background to appear stationary.

 

[Spinnor]

I am sure we are all curious, what will this vibrating chair be used for? Its use will help the scientists here determine the best solution to your problem.