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Author Topic: Air Temp Nitinol  (Read 206164 times)

memoryman

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Re: Air Temp Nitinol
« Reply #135 on: February 23, 2017, 03:23:52 AM »
Nitinol engine are very inefficient<10%). Cost vs output energy is too high for practical use. I have extensive practial experience with Nitinol and Flexinol. The specifications are widely available.

ramset

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Re: Air Temp Nitinol
« Reply #136 on: February 23, 2017, 05:48:01 AM »
memoryman

this thread Gadgets first reply #1
Quote
This type of Nitinol wire can lift 30 pounds 30 inches with just a 30 degree F shift in tempature differential
end quote

Seems a big movement of a heavy weight at a small temperature differential ?

if accurate

do you have any data
respectfully
Chet K

memoryman

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Re: Air Temp Nitinol
« Reply #137 on: February 23, 2017, 02:07:10 PM »
"This type of Nitinol wire can lift 30 pounds 30 inches with just a 30 degree F shift in tempature differential "
Seems impossible if done directly; see http://www.tinialloy.com/pdf/introductiontosma.pdf

sm0ky2

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Re: Air Temp Nitinol
« Reply #138 on: February 23, 2017, 03:57:48 PM »
The real test for Nitinol would be to graph how much force is exerted from a specific thermal change in a nitinol spring.

Something like:
* Acquire a nitinol spring with a known mass (for example, 10g).
* Attach the spring to a fixed weight and place both in a sealed air-tight container.
* Add a heating element, hair dryer, hot-plate, or other type of heater to the chamber, along with a small fan to recirculate air.
* Graph the change in the mass's height with changes of temperature in the chamber.  That temp gradient is dependent on what variety Nitinol you purchased.

After that is all done, take the mass of the spring and temperature gradients to get joules input to the system. (0.20 cal/g * deg. C for Nitinol)
Graph that against the change in height of the test mass (convert ft-lbs to joules).
The result should look like a 'joules input vs joules output' COP chart spanning a temperature range.

If Nitinol is as magic as it sometimes seems, there should be a small window on that graph where Joules output exceed Joules input.


As mentioned in the video from the 70's this was done
The results were something to the tune of 75lbs per sq inch
With some negligible temperature difference.
A friction heater using that force could easily achieve.

sm0ky2

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Re: Air Temp Nitinol
« Reply #139 on: February 23, 2017, 04:04:30 PM »
Nitinol engine are very inefficient<10%). Cost vs output energy is too high for practical use. I have extensive practial experience with Nitinol and Flexinol. The specifications are widely available.


Not sure what this is based from. Sounds like it could be the toy
Which is just a loop of wire on 2 pulleys.
Many of these are inefficient and just ad-hocked together
The actual engine this was based on used 2 different sized pulleys
And the lower pulley was angled to allow a specific dimension of wire
to be submerged in the warm water. Which gave the motor a higher
efficiency than any Carnot cycle based engine.
In laboratory settings thermal conversion efficiencies of 60-90+%
have been reached. Note that a Carnot engine caps out at 50%


As far as "Flexinol" is concerned, I would steer clear from these guys
They are overpriced and the only real function they serve as a Nitinol
Manufacturer is their ability to fill large bulk orders, such as that required
by large research firms, educational institutions, and NASA.


We have available many low-cost suppliers that can fill our small needs
at a fraction of the cost of "Flexinol". Which is the same alloy, just has a
brand name attached to it.


There are also people that "resell" this stuff. Sometimes for thousands of dollars.
so be careful when purchasing large quantities.


The wire is easy to come by, but the real magic is in plates or strips
The same heat source can provide much more power


There are also many ways to use this stuff, some are better than others
Most of that has to do with the builders engineering skills.
Not the Nitinol itself.
The weighted test gives the most accurate results.
Because we have a direct work function
A Nitinol engine, based on rotary crankshaft, performs tens to hundreds
of times better than an ICE or steam engine, with the same BTU of fuel.
This of course is expanded over longer tests, which is the reason for variance.
But what the tests proved was that the metal itself could replace the
combustion chamber as a piston actuator.
I think this should be a major focus of our tests.
A linear reaction tied to a crankshaft.
I have about 9 days before I get to set my new lab up, but I'll be getting some wire
and as many large pieces as I can afford.
The alloy itself has been standardized to the specs of the most active alloy recipe.
So they are literally the same, regardless of the source.
 ( 3 forms: memory alloy, superelastic, and the more rare magnetoreactive alloy)


The memory alloy is the one we want for thermal to mechanical conversion


Still thinking through all the ways to achieve linear actuation with the timing of
warm to cold,
My mind made a funny with a tea-light candle on top of a pendulum, so the
flame went back and forth across the Nitinol actuators.
the flywheel stretches the metal back out
the heat "pulls" the crankshaft around.


It's backwards from the ICE, more in line with a vacuum engine, in that it pulls.


Which brings us to the Nitinol Vacuum pump and engine.
The linear actuator operates a piston which draws a vacuum into a chamber.
Through a check valve, resulting in a drop in pressure in the chamber.
This negative (to ambient) pressure can be used in any standard way, or
a small wind turbine jet fan can be placed on the chamber to generate electricity
by stabilizing the vacuum pressure.


Nitinol can also be heated by passing an electric current through the wire.
This incurs a great loss, so it cannot be used for energy generation
However there are infinite applications in robotics, artificial muscles are the new thing.
This, when incorporated with a stabilization of system temperature, (cooling system)
can make a very robust and stable robotics platform, that simulates any form of life.
At least in the muscular sense, (and circulatory when considering the cooling lines)
So far the scientists have stuck to insects and earthworms
But building a humanoid android is not far from reach.


New knowledge and understanding of Nitinol "training" has brought forth
'artificial muscles', that not only can sustain indefinite use, but get stronger
over time, more resilient against factors that reduce 'training'.
This may lead to higher overall efficiency of electro to mechanical conversion
What interesting, is that the circuitry to control a multitude of large muscle groups
made from Nitinol 'muscles', begins to resemble the electrical circuit of a primitive brain.
This can be simplified with IC chips and make it appear less organic on the inside, but
the electrical connections and the way everything is wired up,
It's truly an artificial muscle.
I wouldn't by surprised to see an experiment of Nitinol being actuated by a nerve signal
from one or more of the higher mammals.


sm0ky2

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Re: Air Temp Nitinol
« Reply #140 on: February 23, 2017, 04:53:53 PM »
I guess they already hooked it up to rats
https://www.ncbi.nlm.nih.gov/m/pubmed/9659619/


memoryman

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Re: Air Temp Nitinol
« Reply #141 on: February 23, 2017, 05:04:36 PM »
Not sure what you base your numbers on.
If someone wants to experiment, I have ~900 ft of 0.016" dia Nitinol for sale; shape change temp ~40C. If interested, send a pm.
Flexinol is different from Nitinol in performance; my application was as an actuator, using pulsed current.

sm0ky2

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Re: Air Temp Nitinol
« Reply #142 on: February 24, 2017, 03:40:26 PM »
memoryman

this thread Gadgets first reply #1
Quote
This type of Nitinol wire can lift 30 pounds 30 inches with just a 30 degree F shift in tempature differential
end quote

Seems a big movement of a heavy weight at a small temperature differential ?

if accurate

do you have any data
respectfully
Chet K


Several top research facilities have quotes 55-75 tons per sq inch, with temps slightly above
room temperature. (70-90F)
The stress state was inconveniently low temp for me personally
Seemed as if the best of these heat reactive alloys is actually powered
by "cold".


Ideally we sacrifice raw power for a trained reactive temperature that is
1) room temperature on the cold side
And
2) not too high on the hot end of things, such as to be easily attainable.


The double-training techniques are interesting because we can set two points
A hot configuration and a cold configuration, making an ideal actuator for oscillatory action.


sm0ky2

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Re: Air Temp Nitinol
« Reply #143 on: February 24, 2017, 03:50:07 PM »
thermal conversion efficiency would have to be more than
100% efficient for us to use "cold power".
In more detail: we would have to compensate for the energy
we consume while creating the cold situation. Wether it is a refrigerated
fluid, or dry ice, liquid nitrogen, etc.
these systems themselves being less than100% efficient


So to be 'useful' as a thermo-mechanical generator
We need the cold side to be ambient, or within a range we
can sustain with minimal energy input. The hot side therefore
being the driving force of the differential.
These alloys have significantly lower force per mass ratios.
Something like 8lbs per 4% stress.
[why 4%?  This is the limitation of degradation, stresses of greater
 than 4% can lead to limitations on the sustainable lifetime of the alloys.
  Within the 4% stress range, prototype engines have sustained billions
of cycles.]


[edit:  sorry forgot a detail- that 8lbs was for the hot side reaction
 a 0.5 mm wire coiled spring
      Something like 9 inches in total length. Active temp cold stress (70F)
   Hot memory (110F).]


The memory curie point to train these is something like
916F
And involves locking them in position and repeatedly heating
Then quickly cooling ( ice bath)


memoryman

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Re: Air Temp Nitinol
« Reply #144 on: February 24, 2017, 04:36:15 PM »
I have actually trained my own springs using a small oven (max 1,000degC). The cooling cycle does not have to involve ice water.

ramset

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memoryman

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Re: Air Temp Nitinol
« Reply #146 on: February 24, 2017, 05:59:45 PM »
The point for me is that Nitinol engines produce very little power for their cost and size. There are far better heat engines out there.
« Last Edit: February 24, 2017, 08:18:25 PM by memoryman »

ramset

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Re: Air Temp Nitinol
« Reply #147 on: February 24, 2017, 06:19:52 PM »
memoryman
NASA engines ?[Sterling] yes please more info/ideas ?

this Nitinol is cheaper now to play with ... we have been discussing a bit in PM's what is the best wire for My Build [Gwandau hybrid wheel]

I have a weakness for this wheel [I believe it can work] and must build it , but at the same time wish to keep the door open for
a Gwandau/ nitinol hybrid  ,[if the original wheel proves too difficult to replicate.

you should keep in mind that some of us here wish to stimulate younger minds with these builds [involve the kids]
with the whatifs on the kitchen table at night [magnets and gravity and now nitinol....
simple  open source projects...
and yes a sterling engine  does this too but a bit more involved for the kids

respectfully
Chet K

memoryman

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Re: Air Temp Nitinol
« Reply #148 on: February 24, 2017, 07:14:15 PM »
I personally am not interested in the traditional 'OU' ideas involving gravity, buoancy, flywheels, magnets etc, as I see them as dead ends. Involving kids in critical thinking is great (adults too!). Imho critical thinking is key to determine where efforts are most likely to pay off. Don't confuse wild ideas with critical thinking.

sm0ky2

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Re: Air Temp Nitinol
« Reply #149 on: February 24, 2017, 07:41:06 PM »
I have actually trained my own springs using a small oven (max 1,000degC). The cooling cycle does not have to involve ice water.


True - any ad-hoc method can produce 'some' functionality
But to truly exploit these alloys I think the methods developed
by the industry over the last 30 years may prove beneficial.
Training techniques have led to higher quality functionality
as well as increased durability.


Recently, these techniques have opened the door to multiple memories
imbedded in the same piece of metal.