It's real, I can tell because of the pixels.
Spin the concrete block and you have a star drive or a doomsday weapon.
Or you're using the elastic portion of the steel's stress-strain curve to store up a respectable amount of potential energy (measure the strain of each part of that system and force*distance is the energy stored). One of the linkages or cogs is going to fail at some point and it's a little difficult to predict how the energy will come out. Leaving aside the grandiose terms like 'doomsday weapon', right now it certainly is a bomb.
Not sure if joking or suffering from poor physical intuition.
Click on the youtube link posted below and you'll find that the builder says the final output turns at a rate of once every 2 trillion years. That's a long time. Even if you assume so little play in the gears that taking up all the slack requires only the motion equivalent to turning the concrete block one one millionth of a revolution, the machine will be doing nothing but taking up slack for the first 2 million years of operation. Friction will grind the gear teeth of the first stages into dust long before the machine can begin storing energy as you describe.
Even if you assumed that there is no slack, isn't that a rather massive amount of torque increase? I expect that there would be no energy build up, but instead the final gear would just grind its way ever so slowly through the concrete.
This is Artur Ganson's work, yes? Artist in residence MIT
Yes, I am aware.
Video of it, in action:
I'm not sure "action" is the right word.