Storing Cookies (See : http://ec.europa.eu/ipg/basics/legal/cookies/index_en.htm ) help us to bring you our services at overunity.com . If you use this website and our services you declare yourself okay with using cookies .More Infos here:
https://overunity.com/5553/privacy-policy/
If you do not agree with storing cookies, please LEAVE this website now. From the 25th of May 2018, every existing user has to accept the GDPR agreement at first login. If a user is unwilling to accept the GDPR, he should email us and request to erase his account. Many thanks for your understanding

User Menu

Custom Search

Author Topic: Air Temp Nitinol  (Read 206170 times)

Reiyuki

  • Full Member
  • ***
  • Posts: 133
Re: Air Temp Nitinol
« Reply #150 on: February 24, 2017, 07:41:40 PM »
A friction heater using that force could easily achieve.

What about using the movement of one nitinol spring to create friction on the next nitniol spring, creating a kind of cascade-activation?  Lots of outputs from a single input.

Or put it on the spring so the friction aids its own constriction.  That might lower the required thermal gradient.

sm0ky2

  • Hero Member
  • *****
  • Posts: 3948
Re: Air Temp Nitinol
« Reply #151 on: February 24, 2017, 08:00:26 PM »
The point6 for me is that Nitinol engines produce very little power for their cost and size. There are far better heat engines out there.


Most of this has to do with the particular designs
Not the alloys themselves.


When properly applied, these engines can convert heat to work at rates
quite frankly unheard of in the world of heat engines.


While something like a Sterling Engine can easily outperform Nitinol in terms
of overall efficiency, when waste heat is used and system losses are irrelevant
Nitinol can convert more heat into work per unit time.


Cooling the metal seems to be the major hitch in most designs.
Because of the slow rate of cooling, energy is often dumped into
these systems on the cold side in an attempt to increase cyclical rate.


Which brings up another point - generally the alloys used in robotics have a low temp
operation point. This places them close to their super elastic state after current is stopped.
Inherently this decreases the available force over distance of the actuators.
Therefore current limiting or pulsed current should be employed. To keep from overheating
the alloys. In other words, care should be taken to prevent entering into the superelastic state.


Alloys advertised as "superelastic" have heat activation temperatures lower than ambient.
60F is not uncommon.
A heat engine made from these will run on "cold" rather than heat.
As heating would occur naturally and the cold side would require cooling.
We want alloys with a little less nickel composition.


All of these are (roughly) equal molar mass.
Ti55% and Ti60% are two commonly sold alloys.
In general the more nickel, the lower the heat activation temperature
We don't want our heat engine to use too high of a heat
Nor too cold of a cold.


But rather, the alloy we select should have a near ambient cold temp
and as low of a hot temp as possible.


I will try to compile a list of which NiTi alloys fall into this category.
So we have a baseline to source from.


But i must stress the point:
Training techniques can have as much to do with the functionality of
Nitinol as the composition of the alloy itself.




sm0ky2

  • Hero Member
  • *****
  • Posts: 3948
Re: Air Temp Nitinol
« Reply #152 on: February 24, 2017, 08:11:34 PM »
What about using the movement of one nitinol spring to create friction on the next nitniol spring, creating a kind of cascade-activation?  Lots of outputs from a single input.

Or put it on the spring so the friction aids its own constriction.  That might lower the required thermal gradient.


I like that line of thinking
Use one actuator in the hot stage ,to apply friction to another actuator in the cold stage
Both deforming the metal and partially heating it, so less heat is needed to finish the process.


Unfortunately his metal has no problem absorbing heat. It's a natural heat sink.
The problem is getting the heat to leave the metal.


Maybe connect the actuator to a heat pump to separate temperatures
that cause the engine to run.
Not the air-conditioner type of refrigeration heat pump
I'm thinking more along the lines of a Venturi vortex heat pump
That used airflow from a portion of the actuators motion while leaving
some room for mechanical output.


If I remember correctly we needed 150psi to create 100 degree differential
from ambient air.
Compare that to 55tons per sq in


sm0ky2

  • Hero Member
  • *****
  • Posts: 3948
Re: Air Temp Nitinol
« Reply #153 on: February 24, 2017, 08:18:04 PM »
To understand how this metal works in terms of force
You look at the cross sectional area in the direction of
the working force.


The length of the metal is a factor of the distance this force
is applied over, and is therefore proportional to the work.
The length has no effective value in the equation that determines
the magnitude of that force.


This is distinctly a property of the alloy and its' training.
In a wire - the cross sectional area is the area of a slice
of the wire of infinite thinness.
That is to say: Pi R ^2
R is half of the wire's diameter.




sm0ky2

  • Hero Member
  • *****
  • Posts: 3948
Re: Air Temp Nitinol
« Reply #154 on: February 28, 2017, 09:09:45 PM »
The information in this video contains the inventor of Nitinol
And some of the most basic discoveries.
Including the information provided to McDonald-Douglas
When they began their research.


https://m.youtube.com/watch?v=oKmYqUSDch8


Time stamp: 1:34-2:15
This (I believe) is the basic structural approach
to a Nitinol replacement of the combustion chamber.
When attached as linear piston actuators linked to a
crankshaft, rotary motion will be attained.
The combustion chambers, the intake and exhaust systems,
and the fueling system of an ICE can be removed and replaced
with a temperature differential system which contains a heating
system and a cooling system.


The heating system could consist of a trough of warm water
when the piston is compressed, or bent (stressed) by the crankshaft
it curves downward and dips into the warm water ( or fluid) thus
providing a driving force to the crankshaft.
When the metal is "straightened" by the Nitinol action, the cooling
system blasts it with a cooling fan (or circulated fluid, etc).


That's kinda where I'm leaning towards.


I think it is important to analyze each approach in its' own right.
Spring mechanics provides for a wide array of shapes and the work
has already been done for us. However there lies an infinity of
non-conventional spring geometry that was never researched due to
the conservative nature of springs. So for those we are faced with the
raw differential equations and a segment by segment analysis that
rivals each design against the next in a quest for time and resources.
Such time and resources is better spent on the workbench than in the
calculator and notepad. ( for this particular scenario).


Known (common and uncommon) spring designs that have been analyzed
we can simply insert the Nitinol specs into the spring characteristics variables
and see exactly how it will perform. This (I believe) is the basis for almost every
Nitinol mathematical analysis available to us publicly.
I don't think it's because they're lazy, it's  just too much for most to try and do
on their own. I'm still recovering from the gyroscope thing and I only did a dozen
or so. I couldn't imagine the mind boggling task of a full Nitinol mechanical work-up
to relate the metal into our mechanics textbooks.


I don't mind helping out if someone posts an "out of the box" spring design.
But as far as calculating every possibility we have in front of us
You guys are on your own on that one.


Real world tests are probably easier to deal with.


That being said I will discuss over the next few days:
The known Nitinol contraptions, their cons and pros, etc.
As well as several possible Nitinol contraptions, based on
known spring designs. Of which there are enough of, to
recreate every contraption on earth in Nitinol form.
How we get the heat in and out of each system will be a major
determining factor of whether or not someone chooses one design
over another.
It's not just the function of the Nitinol, but our realistic means of
providing the scenario upon which it functions.




Time stamp (in the video at the beginning):
2:50 - 3:50


This horizontal wheel is the worlds first solid-state heat engine.
When the springs contract in the water they push against the water.
Like when the Jesus lizard runs really fast. Except it's  not just surface
tension, its water pressure and gravity and the whole of what keeps
the water in the container. Namely Archemedes Displacement and
water's natural resistance to movement through it, combine to provide
a constant force on the driveshaft as long as the temperature difference
is maintained between the two reservoirs.


More later when I have time to type.


Cherryman

  • Hero Member
  • *****
  • Posts: 642
Re: Air Temp Nitinol
« Reply #155 on: February 28, 2017, 09:21:29 PM »
I have some Nitinol somewhere in house from the last time it was a "hype" on OU.


Although neet and interesting, i found it had not much torque and still needs quite an amount of heat.


Some people forget it is also called bi-metal and most people have it in their (gas) stoves as the sensor to turn the gas on or off depending on heat.


Actually you could "easily" make it yourself, bolt two different material ( metal usually ) together at the ends and heat or cool it, it will bend.


Interesting stuff, specially for artificial muscles i think.. But you still need heat.

memoryman

  • Hero Member
  • *****
  • Posts: 758
Re: Air Temp Nitinol
« Reply #156 on: February 28, 2017, 09:28:34 PM »
Nitinol is nothing like bi-metal.

Cherryman

  • Hero Member
  • *****
  • Posts: 642
Re: Air Temp Nitinol
« Reply #157 on: February 28, 2017, 09:51:13 PM »
Nitinol is nothing like bi-metal.


Ok, fair enough, i'dont claim all knowledge, care to tell me the major difference?

memoryman

  • Hero Member
  • *****
  • Posts: 758
Re: Air Temp Nitinol
« Reply #158 on: February 28, 2017, 10:13:22 PM »
Nitinol is an alloy; bi-metal is two dissimilar metals bonded/joined.

Cherryman

  • Hero Member
  • *****
  • Posts: 642
Re: Air Temp Nitinol
« Reply #159 on: February 28, 2017, 10:20:10 PM »
Nitinol is an alloy; bi-metal is two dissimilar metals bonded/joined.


Ok, thanks for replying.


I still think the basics are the same, one substance expanding/contracting more as the other due to a temperature change, resulting in stress on the joints, joint either be molecular or bolts a meter a part
The material will bent or bent back to the same position at the same temperature, unless it is overheated to the materials Curry point and reset.

memoryman

  • Hero Member
  • *****
  • Posts: 758
Re: Air Temp Nitinol
« Reply #160 on: February 28, 2017, 10:26:57 PM »
No; there is no bending or twisting with Nitinol; just 3 dimensional expansion/contraction. Bi-metal does not have a memory effect. They are totally different.

Cherryman

  • Hero Member
  • *****
  • Posts: 642
Re: Air Temp Nitinol
« Reply #161 on: February 28, 2017, 10:34:06 PM »
No; there is no bending or twisting with Nitinol; just 3 dimensional expansion/contraction. Bi-metal does not have a memory effect. They are totally different.


I beg to differ. It's all the same.


With Respect C'man


Edit:  You do realize that Bi-Metal


A: example :  a simpel temperature Bi-metal ( in for example a gas fired camping cooking stove)  is a bi-metal and does not leave the gas on after its first use. ) iow Memory


B: The word Bi-metal does NOT specify the actual chosen metals


C: It's not rocket science, a metal (or actually any substance) has a certain length (expansion)  at a certain temperature, combine two different metals.. there will be an interaction you can exploit, or trouble you, when experience a delta temp.



Cherryman

  • Hero Member
  • *****
  • Posts: 642
Re: Air Temp Nitinol
« Reply #162 on: February 28, 2017, 10:50:02 PM »
Combine these two charts wisely and pick your own for your project suitable Bi-metal




memoryman

  • Hero Member
  • *****
  • Posts: 758
Re: Air Temp Nitinol
« Reply #163 on: March 01, 2017, 06:04:39 PM »
If you want to believe that bi-metal and Nitinol are the same or very similar, go ahead. I have no desire to convince you.

ramset

  • Hero Member
  • *****
  • Posts: 8073
Re: Air Temp Nitinol
« Reply #164 on: March 01, 2017, 07:57:53 PM »
Well
it is my impression that reaction time in NiTinol both on and off are amazingly fast as well as Strong and the metallurgy to enable these attributes are quite unique , some sort of crystalline alignment which is very hard to do . falls into a higher level of SMA's [Shape metal alloys]

but I do agree that all similar materials [bimetal]should be familiar to experimenters to perhaps mix attributes in the development of more advanced mechanisms ,

to me this is a fascinating area ,especially with Smoky's observation on multiple programming of the same wire
and the ability to train the wire at will for different tasks .as well as NiTinols limitless cycle times that grow in strength over time.

the repurposing of  Nitinol in endless experimental variations and programming  is the closest thing to magic we could play with [and teach with]

a science which needs growth and evolution ..towards new materials which react in ever more user friendly environments...
perhaps real metal muscles which can work with the tiny stimulus our own muscles do ? 

what fun indeed !![building one test bed as I type this]