We have all seen small generators that are turned by bicycles. They generate a small amount of electricity, but you have to be in very good shape to use them.

My idea is similar, but you use a swing set instead of a bicycle. The top of the swing set chains are connected to a ratchet. When the
kid swings back it turns the ratchet, which has belt to a generator (everything would have to be appropriately geared). When he swings forward the ratchet spins through. So for each set of forward/back swings you only have one power swing.

The generator would need to have flywheel to keep it spinning during the non-power swing. Does anyone know how you would even calculate the theoretical power of a swing set?

Can't picture it being much at all. All the postential energy you have at the top of the swing will be expended onto the generator as you decend, leaving you no energy for the upswing. The only energy you add to the generator is though the normal leg swinging/leaning in and out stuff that gets you going, and you have to do a LOT of that before you get serious height.

This would be the equivalent of generating hydroelectric power with a bucket brigade.

My rough guess would be: potential energy from one child at the top of its swing (generously, 1.5m) is mgh = 65kg x 9.8 x 1.5 = 955 joules (are my units right?). If you want this to be continuous, then you have to leave most of the energy in the system (think how much leg-swinging is involved in getting started), but let's be generous and say you can take out 5%. That's 50J(ish). Top of my head, let's say it takes 1 sec to go from aphelion to aphelion (or is that perihelion? ah, who cares). That makes 50W extractable power. nearly a light bulb. That's being incredibly generous (and using quite a large child) - you're more likely to get about a quarter of that I'd guess.

Yes, but imagine child swingset energy farms! We can stuff them with cookies for weight, and put even more cookies at the front aphelion (nice word whichever it is) for incentive. Ahh, if only cookies grew on trees!

[moomintroll] You are indeed being
incredibly generous in your estimates.
If you extract 5% of the potential
energy, and waste another 5% (ie, you
have a 50%-efficient generator), your
removing 10% of the swing energy at
each cycle. This means that this poor
fat kid is going to have to continuously
put in the effort equivalent to going
from a standing start to a 1.5m swing in
only ten swings (if you see what I
mean). So, the poor fat kid is soon
going to be a poor thin kid.

You know, I sometimes imagine an HB
in a parallel universe, where all energy
has only ever been generated from
renewable resources. Their world is
cluttered with a trillion rusty little
boxes, each turning out a few watts
when the wind blows or the kid swings,
and the boxes need replacing every
couple of years when they break or the
kid wants a new swing, all so that these
parallel HBers can sit round a 40W
lightbulb.

Then somebody
posts this idea of Centralized Power,
with big power stations generating
continuous power beyond their wildest
dreams, and this somebody is hailed as
a radical genius. (Then, of course,
they all drown as a result of global
warming, alas.)

To calculate the theoretical power of a continuously-operating swingset generator: weigh the child, then determine how long it takes him to increase his altitude by a certain amount, then do the math to see how much power has been added during that time.

Which is about what [Basepair] said.

Then divide by the kid's attention span, and deduct the total from your life for destroying one of the pleasures of childhood.

Like [Ccapleland] said, alot of the energy would go into the machine, and not into the momentum of the swinger. Thus, all speed would be lost. If you have ever pedaled on one of those electricity bikes, you would know they are harder to use then regular bikes, because your pedalling power is being taken and turned into electrical power.

What if the energy were used to power a gameboy or something? Wouldn't that be more fun and also not very demanding in terms of the power needed? Might this not be a way of motivating lazy children to exercise rather than a form of power generation?