mass center of solid bodies

[kerkam]

Hello, everyone.
are federic and use autocad 2009. I'm not very experienced about the 3d, but I'm wired for what interests me. I would like to know from you if there is a function able to calculate the mass center of a solid and give it or the spatial coordinates or a visible element like a circle or a sphere. Thank you very much for the time.

 

[AntonioV]

or a visible element like a circle or a sphere

test with _masprop while I did not understand the question circle/sphere.. .

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[kerkam]

test with _masprop while I did not understand the question circle/sphere.. .

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Thank you very much for the answer speed and for the accuracy. was what I needed.

 

[AntonioV]

You won't believe it, but tonight I dreamed of this discussion, I understand what you meant with the phrase "or a visible element like a circle or a sphere" (I have to take care of myself, young people.. . )

You'd like to see the center of the solid somehow, right?

now, in the site http://www.cadforum.cz I found This is lispino that draws a point in correspondence of the 3d coordinates of the mass center.

advice: before launching the centroid command, type the variable pdmode e settala bet a 35, so that the point is really "visible".

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[PlannerRoad]

for completeness of information in case it can be useful in the future for other cases, the lisp indicated by cadlandian allows to draw the centroid not only of solids, but also of political e regions. as reported qui.

 

[AntonioV]

another interesting phenomenon: the baricentre is "disegned" also for groups of disjoining solids, and I explain.

We think of e.g. on earth and moon: they are physically disconnected celestial bodies, but in fact "united" by gravitational forces.

If we therefore have 2 solids detached and connect them (virtually) through the _union command, the centroid routine will however mark the point in the void between the 2 objects.

Kerkam, it's not a circle or a sphere, but better than nothing.

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[Giuseppe Mauro]

In fact, that is the geometric center of the solid system.
autocad, through the union command, implies that there is a rigid and uniform bond between the various solids and calculates the system center.
The only real limit is that autocad implies a single density for all volumes, so the calculated centerpiece is only the geometric one.

In fact, they could have different density solids (e.g. a sphere of wood and a lead), so by calculating the centre of the masses, this would move very close to the lead.
this in autocad (at least I know), you can't get it, and you're a member of the analysis programs (but they don't draw: )

 

[kerkam]

You won't believe it, but tonight I dreamed of this discussion, I understand what you meant with the phrase "or a visible element like a circle or a sphere" (I have to take care of myself, young people.. . )

You'd like to see the center of the solid somehow, right?

now, in the site http://www.cadforum.cz I found This is lispino that draws a point in correspondence of the 3d coordinates of the mass center.

advice: before launching the centroid command, type the variable pdmode e settala bet a 35, so that the point is really "visible".

:

Thank you very much, you have been very helpful to me in the country; That's what I meant. So many times dreams make us have genius blows and solve problems, I happen often, so we are hurt in two.

In fact, that is the geometric center of the solid system.
autocad, through the union command, implies that there is a rigid and uniform bond between the various solids and calculates the system center.
The only real limit is that autocad implies a single density for all volumes, so the calculated centerpiece is only the geometric one.

In fact, they could have different density solids (e.g. a sphere of wood and a lead), so by calculating the centre of the masses, this would move very close to the lead.
this in autocad (at least I know), you can't get it, and you're a member of the analysis programs (but they don't draw: )

I thought of this; and I think we can circumvent the obstacle by making a weight average of the positions of the mass centers (in this case geometric center) of the bodies with equal density. sure the method is uncomfortable to use for a high number of objects, but up to 3-4 you can do quietly. Not to mention that by forming groups of 2 to 2 you can perform less calculations. I don't know if this idea is for granted, and I apologize if it is, but I decided to put a small example to better illustrate it to those who don't want to create a model or doverselo go look for the books of physics now piled up in garage (even if they should be at hand xd).
found the mass centers of the two objects and properly marked them with points, join the latter with a straight (in fact the mass center will be on this straight in the segment between the two points). calculating the distance between the two centers we will call ab; we can get the distance of the mass center from point to point thanks to this simple proportion.
m(a)/m(a)+m(b)= d(a)/d(a)+d(b). this problem can be easily solved with a formula obtained: d(a)= m(a)d(ab)/m(ab). made this draws a center sphere in a and radius d(a) and the point we wanted is the intersection of the sphere with the segment ab.
I repeat, it is a very trivial and perhaps boring way of solving the question. if you have another way to solve it well come!! I love alternative methods! !

Thanks again for the help.

 

[AntonioV]

in This is what discussion, it is possible to find a lispino that takes a step forward.

not only draws a point in the center of gravity, but returns the mass for specific weights of steel, aluminum and concrete, so as to say:

Who knows if we live enough to have a carcad that has density as one of the bylayer properties, type of color and type of line. . .

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