[DocOck]

What do you think about using memory metals as a constant torque spring (which looks like a roll of motion picture film). The idea is to use the spring normally like a regular steel spring for rotation to spin an electric generator. It is wound on one end and its natural tendency is to pull itself onto the take up spool thus providing rotation. It is connected to a generator to spin it to produce electricity. To rewind the memory metal spring you only need apply heat on it near the take up spool to make it go back the other way to rewind, using memory metals that respond to heat. I've seen some that respond to heat and some that respond to water.

This could allow several things. One, if you are just heating say a bar that touches the metal to make it rewind, does this use as much energy as it would to just operate an electric motor to rewind a constant torque spring like you would with a normal spring made out of steel?

Also, if your using a memory metal that responds to water, just add water for the rewinding process? See where I'm going with this? Is this as brilliant an idea as I think? I realize memory metals are hard to come by these days.

I have an invention that is a new way to utilize constant torque springs, stacked in rows to spin a generator. However as you all know using normal steel springs you have several problems 1) lots of weight, and 2) rewinding them typically takes so much power you only have around a 35% efficiency ratio or around there. Maybe just as aluminum made the airplane possible, these new memory metals may make a spring generator feasible and desirable. Um? Anyone?

[johnfp]

Well I don't know about the efficiency but if this spring/motor was enclosed in a box and set out in the sunlight with a lens and a timer the whole thing could be solar powered. The timer used to open a shutter that allowed the focuse light from the lens to heat the memory metal up at inteval timed on the time it takes the spring to unheat and return to the spot to be reheated.

[DocOck]

That's an idea too, however, I was thinking more along the lines of using it for a car engine to power an electric car. I wouldn't want to be dependent upon solar for that, although it could be an option for day time travel, with another option for night.

Also, I do not know everything there is to know about memory metals by a long shot, I just know a little. Does anyone know how available they are and who is involved in their manufacturing?

Also, am I correct to say that they are made in such a way that their molecular structure causes them to return to their original shape? (Memory metal) Or is it some other method? Thanks.

[UncleAl]

What is the energy/kg stored in a rolled Nitinol spring? It's a heat engine and must suffer the Carnot cycle. Given source and sink temps only a couple of hundred C apart, near room temp... it must be an inefficient engine.

An electric generator spins at 60 Hz, 3600 rpm.