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  • ftl
    replied
    When one of my door springs broke a few years ago, I did some research.

    It turns out that most coil garage door springs are designed for about 20,000 cycles. So, twice a day, 350 times a year = 700 cycles per year which is about 28 years. If you come and go more often you reduce this to around 20 years which is about when mine broke.

    A larger diameter spring with more turns (also thicker wire) takes less stress per cycle and lasts longer, so it is possible to get 50,000 cycles, but costs more so most doors are not installed that way.

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  • Black_Moons
    replied
    Hmm uses for a huge spring...
    How about to launch something..
    Launch a small model aircraft at mach 1?
    Crossbow?
    Model rocket takeoff assist?
    catapult?

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  • michigan doug
    replied
    Pretty nice steel to make a sword. Hard enough to take a good edge, springy enough to take some punishment. Of course, it takes some pounding to change it from a coil into something that looks like a traditional sword. Unless you want a real live spring sword:

    http://www.youtube.com/watch?v=Mbz8UdVcjNc



    My son and I are going to make a couple swords this summer for his birthday. There is nothing quite like hammering on incandescent pliable steel.

    Finest regards,

    doug

    Leave a comment:


  • noah katz
    replied
    If everything has stopped moving, including vibration of the air (i.e. sound) there's no question that the energy has been converted to heat.

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  • A.K. Boomer
    replied
    Originally posted by Paul Alciatore

    Heat is the final resting place for all forms of energy. That's a law of thermodynamics and you can't escape it in the long run. Even if a spring breaks in your garage and goes flying around, eventually it comes to rest and all of that mechanical energy of the flying pieces has become heat in both the spring itself and in the walls and other objects it has struck in it's path. It all goes into heat. All of it.

    Yes, even the sound of the spring heard rapidly unwinding a block away is heat dissipation...

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  • Paul Alciatore
    replied
    Safety Note!

    It has been my observation as well as that of many others that these garage door springs eventually WILL break. I have had to replace several in my two door garage. Fatigue seems to be a major factor here as the more they are used, the sooner they will fail. No abuse is involved here, just normal use. It is standard practice to put safety wires inside these springs or other restraints to prevent them from flying about when (not if but WHEN) they do break. I had to add such safety wires to the springs in my garage. Some newer ones may have safety devices included in the basic design.

    The point is, if you make use of old, used springs, you may be asking for trouble. The companies who throw them away know what they are doing. Used ones are already well on the way to failure. DO take precautions if they are used in other applications. Be very sure the springs or pieces of them can not fly off when (not if, but WHEN) they break. This is absolutely necessary for both new or used springs.

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  • Paul Alciatore
    replied
    Originally posted by darryl
    True, but then the spring has kinetic energy, so there's an oscillation going on as the energy changes form. But the action does eventually stop, with all the energy having gone somewhere. If there was a considerable amount stored in the wound-up spring and you suddenly let it go (or the spring broke) you would expect to have that energy on your hands somehow (not literally). Kind of like shorting out a battery- the large discharge is going to manifest itself in one way or another. We're pretty good with the idea that it will be as heat in the case of the battery, but it's not so well understood in the case of the spring.
    Yes, you will have the energy "on your hands". So, starting with a wound spring that is storing energy. And assuming that that spring has come to thermal equilibrium with it's surroundings, no matter what those surrounds are (air, liquid, vacuum, whatever). By thermal equilibrium I mean that it is at the same temperature. It is neither absorbing nor radiating any net heat energy. OK, so it is suddenly released. Suddenly, as in there is no external friction involved, just suddenly released from whatever was restraining it in the coiled condition. If it is released in a balanced manner, then there should be no net motion imparted to it in relation to it's surroundings. So it does not fly around with kinetic energy. What it will do is oscillate for a period of time with each oscillation being a bit less than the previous one. The key question is, what provides the dampening action to cause the oscillations to decrease? It is friction between the atoms or crystals of the material of the spring itself. That friction will convert the energy present in the oscillating spring into heat. All of it will be converted into heat. If it is in air or a liquid, then that air or liquid will be a direct recipient of some of that heat energy, but even in these cases, most of it will be created inside the spring itself. In a vacuum, all of it will be created inside the spring.

    Now, since we assumed that the spring was in thermal equilibrium with the surroundings to begin with and since this added heat will raise it's temperature, then it will now begin to loose this extra heat to the surroundings. In a vacuum, the only way to do this will be through radiation. All objects that are above absolute zero do radiate some thermal radiation. If it is in air (a gas) or in a liquid then other forms of heat transfer will take some of it away. But all if it will eventually be lost from the spring until the thermal equilibrium condition is again established.

    And that is what happens to the energy that was stored in the spring.

    Heat is the final resting place for all forms of energy. That's a law of thermodynamics and you can't escape it in the long run. Even if a spring breaks in your garage and goes flying around, eventually it comes to rest and all of that mechanical energy of the flying pieces has become heat in both the spring itself and in the walls and other objects it has struck in it's path. It all goes into heat. All of it.

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  • darryl
    replied
    Yes, yes- I've pondered that problem for a long time already-

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  • wierdscience
    replied
    Use several of those springs as a regenerative braking system on a small car.I'll leave the whole get the power back out to the wheels problem to you

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  • A.K. Boomer
    replied
    Originally posted by mayfieldtm
    I've built spring cycle testers that use liquid cooling to keep the springs cool.
    Springs can generate a hell of a lot of heat.
    There is a lot of internal friction and is the leading cause of failure.
    Tom M.

    They must not generate too much, look at your typical valve spring rapping out at 75 times a second,,, yet they still want you to install the mild wind part of the spring towards the cylinder head for heat dissipation - not heat dissipation of the spring to the head but to guard against the heads heat creeping into the springs more radical wind - this is where the springs compression ratio changes drastically.

    And as far as failure rate of a valve spring - all these decades working on vehicles of all kinds and I still have not seen it yet --- it puts springs right up there with about the most dependable thing inside the IC piston engine iv seen...

    and here were talking about metal actually bending back and forth --- like I stated before - springs in both design and material used are the king of resiliency...

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  • darryl
    replied
    Well, there you go. Springs have inefficiencies in their action too. I wonder what would have the best 'springiness'- crystals?

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  • mayfieldtm
    replied
    I've built spring cycle testers that use liquid cooling to keep the springs cool.
    Springs can generate a hell of a lot of heat.
    There is a lot of internal friction and is the leading cause of failure.
    Tom M.

    Leave a comment:


  • darryl
    replied
    That is certainly a big factor- the limited amount of energy that can be 'pumped' into a spring. I have read recently about carbon nano-tubes being able to store more than a LiIon battery, but that's meaningless at this point.

    Lately I've been trying to re-explore ways in which energy can be stored for later use. For very specific uses, springs are the best way, but that's not the direction I'm going. Because the sun is the only source of energy that comes into my realm freely, that's what I want to make use of. Of course we do everyday anyway- without the sun we wouldn't have hydro power, and all our fossil fuel use is simply a delayed use of something derived from the sun.

    Nobody I know has harnessed a nuclear process. The solar panel/battery/heat-your-home routine is cumbersome and expensive. Storing heat for later use seems about the most practical thing to explore. Hence my interest in heat-storage salts.

    I also like the idea of heat-powered separation of chemicals, in which when you re-combine the chemicals you get heat back. Salts and water can be made to work together- some of the salts give off heat while absorbing moisture. Let the sun heat the salt and the moisture is driven off. Seems like a fairly elegant system.

    One which I would really like to see is a controlled electrolysis of pure water, in which the two gasses produced are driven off into separate storage tanks. Re-combining those in a cell produces electricity- there's the fuel cell. The real problem there as I see it is in segregating the hydrogen and oxygen and storing them in high density form, then valving them reliably into the cell. Nothing cheap or easy about all that.

    When you can store 100 times as much heat in a cubic foot of salt than you can in a cubic foot of water, you have no high pressures, liquids, or potential for explosions or major malfunctions, and no reason why you can't build the system at home- now that's interesting to me.

    I've also been very interested lately in solar lighting. Obviously that doesn't work at night, but during the day it would be very nice to have indoor light which is actually sunlight.

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  • A.K. Boomer
    replied
    Yeah but, the batterys capable of winding up a 100 or more of those springs --- think about all the heat energies being released at once by all those springs -- for sure not as hot and localized but a heat camera would show a vast field of lesser temperature....

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  • darryl
    replied
    True, but then the spring has kinetic energy, so there's an oscillation going on as the energy changes form. But the action does eventually stop, with all the energy having gone somewhere. If there was a considerable amount stored in the wound-up spring and you suddenly let it go (or the spring broke) you would expect to have that energy on your hands somehow (not literally). Kind of like shorting out a battery- the large discharge is going to manifest itself in one way or another. We're pretty good with the idea that it will be as heat in the case of the battery, but it's not so well understood in the case of the spring.

    Leave a comment:

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