Force Amplification (Nitinol-assisted Pneumatics)

[Reiyuki]

I've been pondering the possibility of using pressure-based temperature changes (was it called adiabatic heating?) to cause Nitinol transition and harvest the extra force.

We only need a 30-70degF temperature change, which seems doable with fairly small pressure changes (20-50psi).

So, on input, we'd have 50psi on a piston, but on output we have 50psi plus the nitinol's spring force.

Forgive my horrible drawing, but hopefully you all get the concept. It has a ton of potential variations too (like a rotary actuator that is triggered by air but powered by nitinol).


Anyone else ever attempt this or have any thoughts on it?

[sprocket]

I've been pondering the possibility of using pressure-based temperature changes (was it called adiabatic heating?) to cause Nitinol transition and harvest the extra force.

We only need a 30-70degF temperature change, which seems doable with fairly small pressure changes (20-50psi).

So, on input, we'd have 50psi on a piston, but on output we have 50psi plus the nitinol's spring force.

Forgive my horrible drawing, but hopefully you all get the concept. It has a ton of potential variations too (like a rotary actuator that is triggered by air but powered by nitinol).


Anyone else ever attempt this or have any thoughts on it?

I'm still watiting for someone to come up with a 'workable' nitinol engine. A few years back, I bought a fair bit of 'untreated' 1mm nitinol wire with great expectations. Unfortunately, with my primitive setup, I couldn't even get past stage 1 - treating the wire to 'remember'. Untreated nitinol wriggles like a live snake when you try heat-treating it, and you get some idea of the trapped energy-potential it has. But how do you exploit it???

I think one of the best ways of providing the temperature differential would be with a type of fridge-based evaporator setup - there you've got hot & cold temperatures immediately at your disposal. My wire 'transitioned' at about just 40degC, so very doable I would think. I tried some experiments using electricity as the switch but it proved very uneconomical.

Regarding compressed-air, of much of a consideration would be cooling the air - how would you achieve this in your piston-setup? When playing with electricity, one thing that became evident was that even with amps flowing, the transitioning frequency was really slow, and I would expect you would have the same problems with compressed-air. Nitinol looks really fantastic when plunged from a very cold to a very hot environment, but not so great when you don't have a way of rapidly heating/cooling it. Just my 2 cents.

[Peter Lindemann]

Idea Published 3 years ago!

I've been pondering the possibility of using pressure-based temperature changes (was it called adiabatic heating?) to cause Nitinol transition and harvest the extra force.

We only need a 30-70degF temperature change, which seems doable with fairly small pressure changes (20-50psi).

So, on input, we'd have 50psi on a piston, but on output we have 50psi plus the nitinol's spring force.

Forgive my horrible drawing, but hopefully you all get the concept. It has a ton of potential variations too (like a rotary actuator that is triggered by air but powered by nitinol).

Anyone else ever attempt this or have any thoughts on it?

Good Thinking Reiyuki,

Actually, this idea already has a thread called Perpetual Motion Reality by Peter Lindemann. In that thread, from 3 years ago, I also published this image from my conference Lecture of the same title.



Hope this helps.

Best regards,
Peter

[Reiyuki]

Good Thinking Reiyuki,

Actually, this idea already has a thread called Perpetual Motion Reality by Peter Lindemann. In that thread, from 3 years ago, I also published this image from my conference Lecture of the same title.



Hope this helps.

Best regards,
Peter

Yep, you gave me that idea 　 (pressure change resulting in 'free-ish' temperature changes)　


I love the elegance of that setup, I just didn't think it would work as-written. Suppose I'm probably missing something.

Most nitinol setups need at least 30degF to complete their cycle, which would translate to a good 10-15psi if memory serves correctly.
This would mean you need a LOT of mass and inertia on that weight to apply enough pressure to each cavity.. Which would mean you would be forced to either:
1: Use thin nitinol which would probably not generate the 10lbs+ force needed, or
2: Use thick nitinol which has low conductivity and wouldn't counter-spring fast enough.
If there was a self-sustaining region it would be razor-thin under that theory.


So, since full-transition range is out of the question, I assume you mean the device would operate somewhere in the middle of the transition range, right? Like a few degrees?
I can't find much data on nitinol operating within the fuzzy region; suppose I'll have to do some benchwork and see what kind of force vs temperature curves we get...


I kinda like a simple piston-type setup just because it's easy to measure inputs/outputs of energy under it　and see if the concept can achieve a high enough COP to sustain.


Thanks