DIY Nitinol engine questions

Hello everyone! First post here on Permies. This may be a little unorganized, but I will try.

I am searching for information from anyone has built their own nitinol engine for home use? Generator? Or anyone who has more info on nitinol engines in general.

I have been reading into the small amounts of info on nitinol heat engines online, and have come across a few different pages of interest. It seems to me that Permies has very limited topics on this subject.

I am in the beginning stages of building a similar nitinol engine to the first wheel style one Ridgeway Banks describes in the video of nitinol here https://permies.com/t/24035/energy/Nitinol-engine-amazing-stuff .

A few questions I have are-

With this engine, would having more Nitinol wire loops or thicker gauge wire give the engine more torque or faster revolutions? Both? The engine in his video is said to be running at 70 rpm for over 23,000,000 revolutions. If the engine could put off more torque with thicker/more wires, it then could be geared to a separate axle. Say 1 to 10 ratio. Now with more torque, you can run at 700 rpm. I have also read that the nitinol can degrade much faster if you ask too much of it, as with many things. With more/thicker wires, the nitinol wire should be able to stand up to more resistance.

I have not looked into generator options yet, but take an old VW bus generator for example. It does not need as high of revolutions to charge a battery as say, a normal alternator, so 700 rpm might be enough to charge.

I have learned that even though this style engine from Banks is very aesthetic, it may not be the most efficient approach for a potential electricity generating engine. This engine caught my eye and I hope to make a basic design to see it working and go bigger, stronger from there. The possibilities could be endless with this incredible alloy.

Imagine having a few of these constantly charging a series of DIY nickle iron batteries. As long as you keep a steady supply of warm water flowing into your system, you could potentially have a generator system that may only need a yearly swap of nitinol wires. Thats my idea at least! haha

I found a few useful pages about detailed nitinol research and haven't even come close to reading all of it, but others may find if useful also.

Here is a thesis done on nitinol engines dated back to 2001 http://scholar.lib.vt.edu/theses/available/etd-02102001-172947/unrestricted/ETD.pdf

This is the cumulative research of nitinol from the 70s http://www.dtic.mil/dtic/tr/fulltext/u2/a108973.pdf

This website sells nitinol https://www.kelloggsresearchlabs.com/catalog/84

Anyone who has info or interested in a potential nitinol engine for home use, please look into this topic.

Thank you!! Be happy

One unfortunate fact leads to further discussion:

Despite the fact that the technology has been around for more than 40 years, no commercially viable engine has yet to be made.

Why not? Well, the reason is right there in the research paper from the 70's. Nitinol engines are about 4% efficient (absolute). By comparison a Sterling engine can be up to 30% efficient, almost ten times as efficient, and Peltier bridges, which have no moving parts at all, are up to 8% efficient, still double what the Nitinol promises.

Now there is one use that I can see for Nitinol engines: Despite their low efficiency, they can create power at very low temperature differentials. So you can conceivably extract power from huge amounts of "warm" fluids vice small amounts of hot fluids.