The self resetting pendulums are described in the picture below. Yes, I'm aware of the laws of thermodynamics so no need to post snarky links to physics websites. This is a thought experiment or a mental exercise about a simple idea that came to me in a dream.
closed as off-topic by Aify, Jorge Aldo, sdrawkcabdear, Vincent, HDE 226868♦ May 12 '16 at 1:40
This question appears to be off-topic. The users who voted to close gave this specific reason:
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This IS a perpetual motion machine.
From the laws of physics the pendulum can only reach THE SAME height as the one from where it was launched and then only if does not lose ANY energy while they travel. The aerodynamic drag is enough to make the height the pendulum reaches on the first trip lower than the height from which it was launched, and the height reached on the return trip even less high, and so on. Add to it any form of energy draw from it and it will never reach the other side to launch any other pendulum. At long term it will stop.
No matter how you look at it. The pendulum has a constant amount of energy equals to the potential energy that is stored into it at the launch height. It becomes kinetic energy while it travels down, and then becomes gravitational potential energy again while it climbs. Provided that there is no energy transfer from the pendulum to any other thing, it will beat forever.
As soon as you transfer energy from the pendulum, the amount of energy in the system is decreased. Energy is finite, so its motion will eventually die down. On earth this energy drain is usually caused by aerodynamic drag (For a pendulum).
If, lets say, your pendulum is magnetic and it successively makes its magnetic fields cross a series of coils while travelling up and down, it will cause a electric voltage to develop on such coils. But, as soon as you start drawing current from the coils, effectively draining energy from it, the coils will produce a force against the movement of the pendulum, effectively draining its kinetic energy and making it move slower at each pass.
By the way, locking the pendulum after the first trip solves nothing. The locking mechanism itself needs energy and this energy will be drained from the pendulum, if you drain energy from the pendulum while it travels from one side to the other and expect it to move a locking mechanism at the opposite side, you have two energy drains. If the locking mechanism is at the same height as the pendulum when it was launched, it will not have enough energy to move the locking mechanism when it reaches the other side. So, this system wont work.
How are you extracting energy from this system? If you are getting it from the pendulum, then the pendulum will slow down and won't reach the same height at the end of the swing as it did at the beginning. This lower starting height will reduce the height at the end of swing 2 and so forth until the pendulum is at the bottom. So you can't both extract energy from it and have it go forever.
What if you just let the pendulum go and didn't extract energy? Well air friction will gradually slow the pendulum and stop it.
There real problem in the question is the word "limitless" You can definitely get energy out of a pendulum set up, but not limitless. Limitless energy would be enough energy to launch the earth out of orbit and create a new galaxy or an infinite number of galaxies.
Energy generation is a misnomer, we never make energy we just convert it between various forms chemical kinetic potential electrical.