Simple Nitinol heat engines

[gwill67]

On a practical level how to heat to 500 degrees C without buying expensive oven or is there a better way?

[Tom Booth]

On a practical level how to heat to 500 degrees C without buying expensive oven or is there a better way?

For small projects you don't need an oven.

Just heating it red hot in a candle flame will do.

https://youtu.be/4Yi4epJ83EE

[Tom Booth]

...
For your idea to work you need to know the force a bent piece of Nitinol will exert when heated and is trying to straighten which I would think you will only find by experiment. I suspect that force is quite low and similar to the force that was put into the metal to bend it in the first place (not a lot?). ...

Just to test the force involved, I found a plastic bottle with a spherical shaped bottom so that the nitinol wire could not just "jump out" when heated.

For it to straighten itself, it would have to stretch or break through the bottle.

Compress_20240718_023813_3664.jpg (24.61 KiB) Viewed 3693 times

https://youtu.be/gu3Q4Ea3liw

[Fool]

It seems to me that the force of expansion from heating would need to be higher than the force of bending. That is necessary for positive work output.

I'm thinking of a way to test it by weighting it down to flex it. Leaving the weight on then warming it to see it lift the weight.

It would need a deformation limit, stop, to keep it from over bending.

Maybe heat it red hot bending it into a U shape. Maybe with two eyes at the two ends. Attach it with an upper and lower chain or cable and hang it. Attached weights to the lower chain until it deforms and hits a lower stop platform or table top.

Or

A platform on a hinge. Put it underneath. Maybe straight across a valley with a plunger to push it down into the valley. Add weight until it bends. Then warm it.

Add weight until it won't lift it anymore at that deformation level. Measure bend weight and lift weight. Try different deformation distances.

The strength of the material and response to warming would require very strong apparatuses.

You probably already have these ideas. Enjoy.

[Tom Booth]

. ...
I'm thinking of a way to test it by weighting it down to flex it. Leaving the weight on then warming it to see it lift the weight. ..

There are already dozens of videos on YouTube demonstrating that, Nitinol wires lifting weights etc.

[Fool]

Makes sense. Thanks.

[MikeB]

That much force from a piece of wire and a glass of warm water is pretty extraordinary.

But to get 15 actual tonnes (or is that 15 imperial tons?) of force would require a 1 inch bar, not a 0.25mm wire.

[Tom Booth]

My latest Nitinol engine design:

http://peoplesresearchcenter.com/nitino ... ngine.html

I received a comment on my YouTube video that someone thought the design could not work because the Nitinol, after being dunked in the bowl of hot water would need to be cooled down to remove the heat.

https://youtu.be/_ZFPKvooFH0

Of course I replied that I didn't think cooling the Nitinol would be necessary because the heat would be converted into work so the Nitinol should revert to its "wet noodle" like condition almost instantly.

I'll probably start out with just one "arm" and one Nitinol "elbow" to begin with.

If it works for the air or "working fluid" in a Stirling engine running at 4000 RPM with what little "cool down" time that involves, I have a hunch it will work in the same way using Nitinol.

BTW, MikeB, of course. That is what is meant by "per inch"

I think I figured one of my thin wires would have a driving force of about 20 pounds.

I'm also practicing how to weave cable and woven straps.

Take, say, 8 thin Nitinol wires and weave them into a cable. Still only a few mm wide, but 10X the driving force.

Practicing on string first:

Compress_20240801_175649_9352.jpg (27.94 KiB) Viewed 2668 times