The physics of swinging in a hammock and how to make it frictionless

[old4hats]

No science involved with what I am about to say, but I use short lengths of chain to hang from on my indoor set up, continuous loop amsteel on hammock, attached to chain, and chain anchored to wall. On the other side of the room I use whoopies from hammock to large eye screws. It probably is only in my mind, but I seem to have much longer swings from the chain suspension. By the way, I really do not like to swing, so the faster it stops is what I am after, but still, chain seems to swing longer.

[Gsx-rboy750]

Ceramic bearings like they use on high end skateboards...

I put Boca ceramic hybrid bearings in my land speed bike wheels. Yes some sort of attachment with cermaics would definitely work. I was thinking about this problem last night.
I can spin my wheel so it turns about 1 time per second and it will stay spinning for about 2-3 minutes.
They make smaller sizes and you could easily makes a small rigging.

[Boston]

Use a small leg motion (swing your knee, or something) to maintain momentum, similar to pumping your legs in a swing. You should be able to maintain a gentle swing with a slight motion. I can keep this up unconsciously until I fall asleep..but then again I fidget...

You might also try simplifying your suspension. I use a dynaglide whoopee which goes to a screw link (carabiner basically) when goes to the surface mount (d-ring is horizontal). They key is every element can pivot without resistance. My hammock will maintain a swing for quite a while without my help.

[OldRagFreeze]

Gravity not friction is your problem.

This was my thought. You could totally eliminate all friction, which of course is impossible anyway, and you'd still stop pretty quickly because your weight is pulling the hammock down to the center with each swing.

Maybe a line perpendicular to the hammock with a heavy bungee on it would help, though.

[Vincethebutcher]

So im not mathmagician but.... it sounds to me like you need to add a counter weight. Something like a fixed pendulum, that would swing opposite to you that would add force to the momentum with every swing or at least keep it going longer. I dont maybe im totally wrong, maybe this would actually make you swing less by adding force in the opposite direction.

I do love problems like this though so i will continue to follow this thread.

The other thought i had was to add a motor to the idea i had above to continuously apply force. Granted with this approach you would be adding noise to the system which may just keep you up at night, or at least no be able to hear the birds chirping in the morning.

It makes sense though that with less friction you will swing longer, so using amsteel or even the chain idea above. Fabric is rough so finding 2 like materials that can glide by each other will help continue the swing.

[gmcttr]

Gravity not friction is your problem. When you figure it out let me know and i make you rich. But seriously maybe some type of baby crib mechanism might be able to be integrated. Unfortunately it takes energy to release energy.

^^^^THIS!!!

Gravity and wind resistance have more to do with stopping the swing than friction. And don't bother figuring a way to defeat gravity because if you did, you would just go around in full circles instead of swinging.

For those saying they swing 100 times with whoopies...I wonder if it has more to do with length of the suspension and hang angles (length of the pendulum).

[Gsx-rboy750]

This was my thought. You could totally eliminate all friction, which of course is impossible anyway, and you'd still stop pretty quickly because your weight is pulling the hammock down to the center with each swing.

Maybe a line perpendicular to the hammock with a heavy bungee on it would help, though.

Your still trying to make energy. The force of the cord pulling will be equal to it of it moving the other way. You would need a motor of some type and a cam.

[Gsx-rboy750]

So im not mathmagician but.... it sounds to me like you need to add a counter weight. Something like a fixed pendulum, that would swing opposite to you that would add force to the momentum with every swing or at least keep it going longer. I dont maybe im totally wrong, maybe this would actually make you swing less by adding force in the opposite direction.

I do love problems like this though so i will continue to follow this thread.

The other thought i had was to add a motor to the idea i had above to continuously apply force. Granted with this approach you would be adding noise to the system which may just keep you up at night, or at least no be able to hear the birds chirping in the morning.

It makes sense though that with less friction you will swing longer, so using amsteel or even the chain idea above. Fabric is rough so finding 2 like materials that can glide by each other will help continue the swing.

Still attempting to create energy

[SilvrSurfr]

Physics doesn't allow perpetual motion (which hasn't stopped people from trying to invent perpetual motion machines). Friction, air drag and gravity will all work against you till the amplitude of your swing will inevitably decline. You'll need some external form of energy to maintain the amplitude of the swing.

My neighbor has one of those motorized baby hammocks that swing. I've only seen it through his window, but I imagine it has an electric motor that keeps the hammock swinging.

[NJTroutstalker]

This was my thought. You could totally eliminate all friction, which of course is impossible anyway, and you'd still stop pretty quickly because your weight is pulling the hammock down to the center with each swing.



Maybe a line perpendicular to the hammock with a heavy bungee on it would help, though.

This is incorrect. Ever see the pendulum at the smithsonian? It swings all day with one "push".

This is a classic pendulum problem. You have basically 4 variables you can effect. Inertia, harmonic resonance, friction and dampening. Inertia is what you want. You want to stay in motion. More energy or more weight affect this. Harmonic resonance, is all of the suspension spring effects of the suspension. Friction primarily is from air and the axis/suspension. Dampening could be caused by air, fabric stretch, etc. period is determined by the center of gravity vs the distance from the axis. Think metronome.

So what you need to look at it make a perfect axis, and increase momentum. If you took a metal frame with a ball bearing axis, then added a bunch of weight to the bottom it would swing for a long time because you made dampening and friction a very small order of the equation. By making it a simple axis you simplify the harmonics.

So a perfect hammock swing would be 2 rods sticking down. Both mounted to a solid axel with ball bearings to swing. You'd hang your hammock between them. Each rod would have a butt load of weight, say 200-300 lbs. you could move the weight up or down to decrease or increase swing period. A simple clockwork mechanism could add back the friction losses of air and the ball bearings.


Now this is a mental exercise but maybe it'll help you understand what your problem is.

I'm a chemical engineer so I'd make it with pipes!