Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Pet project. Sane or not?

  1. Feb 4, 2010 #1
    Hi all.
    I have a pet project of mine I have been occasionally taking off the back burner for years. The recent hike in Electrical costs has really cheesed me off and has re-flourished my ambition for this project.
    It is a self contained generator. I know the very idea of it exposes me to ridicule but I thought about it many years ago when I was reading a Popular Science mag and it had a segment on perpetual motion generators.
    I will state now that my project is NOT perpetual motion, but could be considered perpetual process.
    Think clock work… I will give a general overview.
    My hopes are for someone to critique it and tell me if I am missing something, because at this point the project seems to me to be valid.

    The project is basically a large mass suspended on a chain fall that falls governed by a large escapement. The mass would drive a gear system to run a generator.
    The mass would continue to fall until it reaches full stroke (the bottom) and then be rewound by a DC powered winch.
    The fall of the mass would be very slow and the mass itself very heavy to power the gear system and provide both the required RPM and Toque to run the generator.
    During the rewind cycle a second unit would work in series to cover the voltage loss from the first unit’s generator voltage drop.
    Together both machines could continue to function and provide constant electricity and trickle charge a DC system in parallel to work the DC winches for the rewind cycles.

    I actually have a majority of the parts required to assemble a prototype, but I am hesitant to sink any serious money into it.
    I am weak on the applications of the physics of this unit. I have been out of school for many years. But I do know that the mechanics are really simple and work out.

    I do have some suspicions around the escapement, but I have designed a rather smooth operating escapement that I think will minimize the slap in the gear train. Also installing the escapement very near to the mass’s chain fall (within the gear system) will minimize the slap effect. (Effectively bleeding it out over the tolerance of the gear mesh throughout the rest of the gear system.)
    Any criticism on the theory of this?
  2. jcsd
  3. Feb 4, 2010 #2
    Hi Jim
    Unfortunately what you describe is perpetual motion. The power you produce from the falling mass will never be enough to power the winch system to raise it back to the same height, it will be slightly lower. So this machine will run some cycles and eventually stop. I wouldnt waste too much money on it. Maybe like 20 bucks to see that it doesnt work and learn from it.
  4. Feb 4, 2010 #3


    User Avatar
    Gold Member

    Simply calling it a perpetual "process" instead of perpetual motion doesn't mean there is actually a difference. Almost any perpetual motion machine conceptualized will be some sort of process.

    Unless I'm misunderstanding, you are describing perpetual motion and wasting your time and money.
  5. Feb 4, 2010 #4
    How do you mean the power produced will not be enough to raise the winch system?
    The winch system would be DC operated (similar to that of one used on a truck or Jeep)

    The falling mass could be any given amount of weight to drive the gear train and generator.

    My thought was that the load (amount of torque required to drive gear train plus the generator) would be achieved at some point. Automotive winches can lift 2000lbs more if run through a pulley system.

    In industry we have similar systems that run hydraulic pumps using a large electrical motor. The motor has a torque to drive both the gear system and the pump. In this case we would be swapping out the motor for a falling mass producing torque, and the pump would be replaced with a generator.

    The theory is also similar to that of push starting a manual car. You would be using kinetic energy (gravity on the falling mass) to drive a gears system to turn a generator. In the car you push it and drive the gear train to spin the alternator to power the ignition system momentarily to start the motor.

    For example say we use a 3000lb or even an 8000lb mass if it drops 30ft over a period of say 30minutes. Would that not automatically have a torque equal to 8000lbs x r (r = the radius of the chain fall spool) throughout the 30 minutes of fall?

    I know it is not a simple as this, there is initial torque required to overcome the static state of the gear train, but as stated above I think we could continue to increase the mass until this is over come.

    I know that the machine only works in the fall process. And would not work during the rest of the cycle. But that is the intent for the machine to only work on the fall process and then reset and fall again. So it only has to work for 1 cycle.
    We would have to have an additional unit working in series (working opposite cycles) to cover the rewind process of the first machine.

    This is why I was hesitant to call it perpetual motion. Becuse the machine doesn't perpetually work. It only works for the one fall. THe process of the second machine covering the power production to charge the first machine's rewind process (winch system) is what would continue to reset the process.
    Two or more machines working together in opposite cycles would make a perpetual energy source. (through the process of perpetual operation)

    Perhaps I am missing something basic? (It’s been a long time since I did these kind of calculations in school)
    Either way I really do appreciate the time and effort you took to read and answer my post.
    Also thanks for the current replies
    Last edited: Feb 4, 2010
  6. Feb 4, 2010 #5


    User Avatar
    Gold Member

    Before this thread is locked, I'd like to establish whether what Jim_M is trying to build is a PMM or simply an energy battery.

    If it's an energy battery then he'll simply be putting energy into it prior to some sort of power grid loss, then he can extract it as needed.

    Jim_M, can you please clarify? Is this machine meant to store energy for some short-term purpose, such as power grid failure, or are you hoping to power your electrical needs on a continuing basis?
  7. Feb 4, 2010 #6


    User Avatar
    Gold Member

    Where does the second machine get its energy from to charge the first machine's rewind process?
  8. Feb 4, 2010 #7
    I'm looking to subsidize the power to my house. If it would create enough surplus I would get off the grid completely.

  9. Feb 4, 2010 #8
    The second machine would be a duplicate of the first and just be opposite cycle.
  10. Feb 4, 2010 #9


    User Avatar
    Gold Member

    Then you are indeed trying to create a PPM, or more accurately, an over-unity machine (get more work out than you put in).

    That's unfortunate.

    Your efforts are as doomed as this thread.
  11. Feb 4, 2010 #10


    User Avatar

    Staff: Mentor

    Yes, sorry Jim. Discussions of PMM and over-unity scenarios are not permitted here. They're a waste of brain cycles. Thread closed.
  12. Feb 4, 2010 #11


    User Avatar

    Staff: Mentor

    I know this was locked, but just a piece of advice, Jim: The math required to analyze the device you are talking about is Junior High simple and takes all of half an hour to run through (depending on how deep you need to go to convince yourself). Save yourself the years of wasted brain power from fanasizing and actually run the numbers so you can prove to yourself that conservation of energy is real. Google (or wiki) the following equations/concepts:

    1. Gravitational potential energy
    2. Power, energy relationship
    3. Torque, rpm, power equation
    4. Mechanical advantage equation
    5. Voltage amperage power equation

    Take a given weight and a given timeframe (such as your 8,000 lb and 30 min - though working in SI units is easier for this) and calculate how much energy and power you can get out of it by dropping it (then decide if that's even a useful amount of power!). Then calculate the energy stored in your battery. Then calculate the energy gained by discharging the battery. Then calculate the energy required to lift the weight. You can use the potential energy equation or play with torques rpms and power until you realize that no mechanical advantage (playing with gear ratios) ever changes the power output of a winch or generator. Then you'll realize that the energy gained by lowering a weight is exactly the same as the energy required to lift it - which kinda makes sense since if you hang two weights from a pulley, they balance each other out!.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook