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Author Topic: Idea of "SMA SunMill"  (Read 15653 times)

Khwartz

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Idea of "SMA SunMill"
« on: July 24, 2015, 05:57:22 PM »
Hello Guys!

I was following the experiments and ideas of Attila Blade with his teeter and sun flower "self-running" on heat energy at very low temperature difference.

https://youtu.be/8BF0UinTAxw

https://youtu.be/4ukwkiUOEs8?list=PLukR_iBSyGXRJNo3KgZIQqJrs-cjWxQ8G


Himself, find his inspiration in a "self-running" moisture wheel invented by one of his friend.

https://youtu.be/GcIeMWNlIGI?list=PLukR_iBSyGXRkd4KOSXuWMJL_fHvr3Y7A


I made some raw calculations and I get an order of magnitude of 10^-5 W for his teeter, for a 10 cm² around area element.

I checked what we could have if implemented of a larger surface but even with 10 m², we would be still in the oom of 1 W.

Indeed, the change of shape are very slow, the mass involved is very little, and same for the length of the displacement.

Then came the idea of using Shape-Memory Alloy to do the same calculations, and what a difference:

- Speed of change from 10 to 100 faster,

- Mass involved from 10 to 100 heavier,

- Length of displacement for 10 to 100 too.

Thus, if we add these windows of improvement, we should expect between 1 000 to 1 000 000 more power for the same size (from 1 kW to 1MW).

But of course, if sun-powered, the power will not exceed the power we will focus on the mill, and for 10 m², if no solar concentrator, the maximum would be in the best conditions as day/night average value 200 W/m², thus 2 kW for 10 m². With wood of else, maybe more.

I do not have Nitinol or other SMA but I wanted to suggest my idea to those who would have some, and if I have messed up in my calculations, don't hesitate to correct me ;)


Here some suggestions:

1. If we use the cylinder sheet technique, with blades going in and out of the cylinder function of the heating, it could works much better the other way! ^_^ I mean when the sun heat, the blades go back in alignment with the average surface of he cylinder. Indeed, we could change the shape of the blade at cold temperature to pull it out and when heated, they just come back at their original location.


2. The width, longer and thickness of the blades should be adjusted to optimise their reactivity to the heat and cold, the simplest system wouldn't have even a liquid side cooling and just cooling by air.


3.  I may be done with just stems for example just plugged in a cylinder wood, for cheap realisations :)


4. A solar concentrator, by lenses of reflectors, may be used to increase the power catching a larger area of sun rays reception to concentrate it in the exposed face of the mill.


5. A cover may be use too to only expose a precise width of the perimeter.


6. A more economical design could be to use indeed blades or stems, rods, wires, but to place masses of much cheaper materials at the extremity, to increase the ratio power available versus average price of materials used.


7. The direction way of the blades, rods, wires, may be significant to use the "kick" of the rotating blades, their momentum while they go back in place or when they take their radial direction.


8. A deflector may be used to guide the sun rays so they only come as per an ideal angle compare to the vertical axis of the mill, so that the changes of shapes of each of both configurations, only occur on one side for each. Let's say sun rays coming right, then blade would be only retracted (along the perimeter) on this side and on left side, only in radius direction ("perpendicular" to the perimeter).

It may be even need to expose the bottom surface of he cylinder so that when the cylinder turns, the blade will reach its austenite start and austenite finish temperatures (As and Af) near the bottom of the cylinder.

At the top, the symmetrical and opposite phenomenon would take place with martensite start en finish temperatures (Ms and Mf). (will try to load a new schematic for this configuration)

Khwartz

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Re: Idea of "SMA SunMill"
« Reply #1 on: July 24, 2015, 06:51:03 PM »
(y, y') is vertical axis

As, austenite start temperature

Ms, martensite start temperature

Green spots symbolise additional masses in cheaper but dense material.

The shift angle "alpha" is to help the rotation.


Some calculation for this example:


1. change of the distance of the centre of gravity of each halve of disc (maybe raw estimate because considered as homogeneous while it is far to be while mass is very in perimeter) :

I have chosen 12 arrays of blades but could be other number.

For here, the length of each blade is 1/12 of the perimeter of course.

Thus, the ratio between the radius difference and the initial radius before extension is:

"Delta r" / r = (perimeter / 12) / r =  ((pi * 2 * r) / 12) / r = (2 * pi) / 12 = pi / 6.

Formula distance of a centre of gravity in a halve of disc:

d = (4 * r) / (3 * pi).

Thus, the ratio of the two distances "d" and "d' " of the two centres of gravity is:

d' / d = ((4 * r') / (3 * pi)) / ((4 * r) / (3 * pi)) = r' / r,

thus,  the ratio of the two distances "d" and "d' " of the two centres of gravity is in the very same proportion than of the difference of radius.


2. Ratio of the torque of each halve:

Let's say

- each halve is of 1 kg.

- "d" is 1 m.

- gravity acceleration is 10 ms^-2.

Torque in "d" is:

1 kg * 10 ms^-2 * 1 m = 10 Nm.

Torque in "d' " is:

1 kg * 10 ms^-2 * (1 m / (pi / 6)) = ((10 * 6) / pi) Nm =~ 19 Nm.

Thus the ratio is:

19 Nm / 10 Nm = 1.9.


PS: I am not at all familiar with these calculations but I think they should demonstrate a potentially in the use of SMA for a SunMill or even any other mill powered by any other source of heating and having its actuators SMA blades or rods, etc.

Khwartz

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Re: Idea of "SMA SunMill"
« Reply #2 on: July 24, 2015, 07:02:50 PM »
Note / classification:

I would qualify this kind of wheel a partial gravity unbalanced wheel by mean of SMA as actuators activated by average temperature difference; heating could be sun or else, and cooling natural or forced like with water or else.

What do you think? and would you have a try?

Khwartz

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Re: Idea of "SMA SunMill"
« Reply #3 on: July 25, 2015, 07:20:23 AM »
Set of NiTi wires orderred.

Khwartz

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Re: Idea of "SMA SunMill"
« Reply #4 on: July 26, 2015, 08:37:50 AM »
Little adding of the initial post (in red), to make it clearer:

"
I made some raw calculations and I get an order of magnitude of 10^-5 W for his teeter, for a 10 cm² around area element.

I checked what we could have if implemented of a larger surface but even with 10 m², we would be still in the oom of 1 W.

Indeed, the change of shape are very slow, the mass involved is very little, and same for the length of the displacement.

Then came the idea of using Shape-Memory Alloy to do the same calculations, and what a difference:

- Speed of change from 10 to 100 faster,

- Mass involved from 10 to 100 heavier,

- Length of displacement for 10 to 100 too.

Thus, if we add these windows of improvement, we should expect between 1 000 to 1 000 000 more power for the same size of 10 m², corresponding to a cylinder of 10 m long and around 2 m of diameter (from 1 kW to 1MW).
"

Khwartz

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Re: Idea of "SMA SunMill"
« Reply #5 on: July 26, 2015, 09:04:17 AM »
Little adding of the second post (in red), to try to make it clearer:

"
Torque in "d' " is:

1 kg * 10 ms^-2 * (d / (pi / 6))

1 kg * 10 ms^-2 * (1 m / (pi / 6))

= ((10 * 6) / pi) Nm =~ 19 Nm.
"

Khwartz

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Re: Idea of "SMA SunMill"
« Reply #6 on: August 02, 2015, 06:30:19 PM »
NiTi not yet received!  :'(

Khwartz

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Re: Idea of "SMA SunMill"
« Reply #7 on: August 05, 2015, 08:20:58 AM »
NiTiCu and Nitinol wires received.

NiTiCu is 0.12 mm diameter and Nitinol is 0.50 mm diameter.

Austenite Start temperatures are respectively around 55°C and 80°C.

Khwartz

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Re: Idea of "SMA SunMill"
« Reply #8 on: August 07, 2015, 11:17:33 PM »
Hi!

After many tries I can say that 0.12 looks useless: to thin too do anything with on a single wire basis, maybe braided or else but not sure.

For the 0.5, I could made some attempts to get "two way memory shapes"; means that after been heat above austenite temperature  (the temperature where the shape corresponds to the denser state), when it cools it comes back at an initial shape, and that is what we want.

Indeed, we want that the "hairs" (if wires around the cylinder), go straight when heated and when they cool recover their initial plied or rolled shape.

I did succeed to make the nitinol 0.5 wire getting straight by just the heat of an incandescent light bulb (but anybody does this) but couldn't obtain more than few percents of self-return to the initial plied shape.

The problem is: "education"!

We are supposed to bring back at cold temperature "a sufficient number of times", the wire after having been straight. I've tried that but only helped with cold water for the cooling, I could get a more important self-return.

Thus, looks to me it is now a matter of having a Shape Memory Alloy allowing us a return to initial shape, and/or a better methodology to "train" the SMA to plie back after having been got straight by the heating phase.

Any help would be appreciated !  ^_^

And sorry, still not have found a way to upload pictures even if less than 5 MO :/

Regards.

Khwartz

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Re: Idea of "SMA SunMill"
« Reply #9 on: August 09, 2015, 04:25:45 PM »
Still only obtain very few return at home temperature when comes back to martensite (the cold state).

When plied to 90° the wire goes indeed straight (0°) but when it cools back by itself down to room temperature, it self-returns only of 12° of shifting angle.

When cooled by cold water (maximum 10°C I think but of course near 0°C works perfect), we gain 23° more of returning shifting angle.


I have found 3 kinds of shape which might work.

. . . 1. The "O" one, the coil, like curly hairs, but I still need to check it with a larger halogen light so I can better simulate sun rays. Indeed, there is a problem when the coil develops: it should go only up and not touch the cylinder which happens only when only the upper side of the coil is heated but as my heating ray was too much focused I wasn't close enough simulating real situation to check if the development would be really fine and not contradicts with neighbour "hairs" or be stopped by the cylinder surface.

. . . 2. the "S" shape. The big advantage is that you're sure to not have the previous problem. Nevertheless, the difference of gravity centre distance with the cylinder surface looks to me less important (= less "travel" possibility for the wire for the same length of wire). An variant of the "S" shape would be the "8" shape, it is the same but we just "pile" the "S" side to side so they form a "8" and thus, this time, we have a very much closer to the cylinder surface, centre of gravity, like if the "O" shape.

. . . 3. The "L"shape. Just a 90°C angle which looks to have the great advantage on the two previous, to give a faster change shape when heated (the fastest and longest travel with most simple form). The problem with this one is that is we can't obtain apparently more than 23° of auto-return shift angle, it is not very much travel, or we need longer "hairs" indeed so the gravity centre of the wire "travels" more. A variant would be only 20° of wire plying so it goes straight when goes to austenite temperature (the highest temperature changing shape).

I will publish the pictures or even maybe videos on my Google+ "Khwartz".

Regards,
Didier

Khwartz

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Re: Idea of "SMA SunMill"
« Reply #10 on: August 09, 2015, 06:33:01 PM »
BTW, an other very different conception I thought was a very "Unbalanced Gravity Wheel" kind.

Indeed, in an ordinary use, an "Unbalanced Gravity Wheel" needs the masses around it to overcome the waste of power due to the friction.

For example, when one of the mass comes to the apex, the top of the wheel, it often needs a kind of "kick" to change of side on the wheel.

Now, imagine that kick is now given by an SMA actuator/muscle (or even any other kind of changing shape actuator, like moisture or expansion ones), shouldn't the mass turns indeed the wheel after each kick made by heating the Nitinol or else, just when the mass needs its kick, so just before it arrives at the top of the wheel?

I will try to make a drawing of an example of how it could function; if I can upload it!  ;D

Khwartz

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Re: Idea of "SMA SunMill"
« Reply #11 on: August 09, 2015, 06:42:54 PM »
For the "pure" SMA Mill (or wheel), I thought about using springs or other piece of SMA wire or else, to no more need a "training" of SMA for 2 ways memory shape; one would "work against" the other:

First the SMA wire or blade or else, is heated and for example straightening, then, when it is cooling, the spring or other piece of SMA or else but an elastic material, "recalls"/pulls back the SMA to its initial or curve or else, shape.

It could function BTW purely by expansion/dilation with no plying nor curving needed but pure straight wires or like.

Khwartz

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Re: Idea of "SMA SunMill"
« Reply #12 on: August 10, 2015, 01:22:55 AM »
Half a dozen of videos made and hope soon available on my YouTube channel (presently uploading but could take few hours), with a new idea of "Skin Spring Mill" but have troubles to upload them on my channel.

Nevertheless, would be far simpler, imho, if we could find a good enough SMA for training it in a "two ways shape memory" (recall of two different shapes : one hot, one cold), while no need of "pull-back springs").

Is there anybody here who knows the perfect nitinol or else for that? :/

Khwartz

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Re: Idea of "SMA SunMill"
« Reply #13 on: August 10, 2015, 04:11:02 PM »
3 videos uploaded:

"SMA Sun Mill": Simple "hair" 2. https://youtu.be/JaNjgtB6hbU

"SMA Sun Mill": Simple "hair" 2. https://youtu.be/TgxlnDYjU5Q

"SMA Sun Mill": "double-hair" 1. https://youtu.be/uea_bsfHnQM

Next "SMA Sun Mill": "double-hair" 2 and "Skin Springs" 1 and 2.




Khwartz

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Re: Idea of "SMA SunMill"
« Reply #14 on: August 12, 2015, 08:54:38 AM »
Video "SMA Sun Mill": "double-hair" 2 : https://youtu.be/uR7NGH9DRMw