I'm searching for a mechanism to slowly release gravitational energy. I've attached an image of an example scenario where a 10kg weight slowly raises the 1kg weight over a set period of time, for example 1 week.

I'm aware that what I'm looking for is a release mechanism and I'm exploring inspiration from antique clocks but I wanted to ask this question here to see if any intersting alternative suggestions come to mind.

A few key aspects:

  1. It doesn't have to be very precise. A deviation of a few hours within a week is ok.
  2. It would preferrably not make any noticable sound.
  3. The beauty of the simplicity of the mechanism is very important.
  4. It needs to be easily repeatable. (Lifting the 10kg weight would ideally reset the motion)
  5. It needs to last a very long time. Ideally 100 years.

What would be the absolute simplest mechanism to perform this task? Where would you suggest to look for inspiration besides clocks? Besides gears are their any alternive mechanisms I that would be interesting to consider such as those using friction or pressure of some sort?

I hope this is the right place to ask this question. If not please direct me to a forum where this might be more approriate. Thank you

example scenario


2 Answers 2


Have a look at the principle of operation of the eddy current brake - a device used to slow or stop a moving object by generating eddy currents and thus dissipating its kinetic energy as heat. These have the major advantage of no wearing parts (unlike brake pads, for example).

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Image from linked article.

To make this with reasonably sized discs and magnets you will need to gear the disk up to run at much (much-much) higher speed than the shafts in your diagram. I have never done calculations involving these devices but I suspect that you're looking at 1:10000 or more! This may be enough to make the idea unworkable.


  • Why have 10 kg to lift 1 kg? The driving force should be a little greater than the 1 kg force + maximum friction from bearings, etc., expected in 100 years.
  • $\begingroup$ I think the last comment is probably the most important thing to take away from this answer. Sure, the 10kg mass stores more energy but the purpose of the mechanism being asked for is to literally waste that energy. It's so important I think it should be the main part of the answer. $\endgroup$
    – DKNguyen
    Sep 4, 2022 at 0:16

You could use a piston filled with viscous pitch and the 10kg weight tries to force the pitch through a small orifice: https://en.wikipedia.org/wiki/Pitch_drop_experiment.

Not sure how hard you would have to push to reset it though since you would need to force the pitch back through the orifice in which it came unless you provided other accommodations. Seems like that would be easier and more repeatable then trying to tune a friction clutch so that the static friction is just barely overcome.


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