A puzzling issue: object with 8 degrees of freedom
john_m_...@yahoo.co.uk
A friend and I are having a bet. He states that there must be
objects or mechanisms with 8 degrees of freedom
(not counting translation} which
have 3-fold symmetry (at least in some
configurations). But we cannot find any.
He is thinking of objects like a deformable cubus with corners
whose angles are not fixed. But such a cubus has
- three orientational degrees of freedom
- three internal angles
which makes a total of only 6 degrees of freedom.
A cubus has 3fold symmetry when seen along
a diagonal, so that would fit; but 6 are not 8
degrees of freedom.
I brought up the idea of a tetrahedral skeleton,
(like a methane molecule http://en.wikipedia.org/wiki/Methane ) .
It has 8 degrees of freedom,
it has 3fold symmetry in some configurations,
but we do not see a way to build that in metal
or rubber without having more or less than 8 degrees
of freedom.
On the other hand, I am not able to prove
that the puzzle is impossible to solve.
Is there another solution? Where can one look for such
objects or related theorems? Are there books or sites
on these issues?
Thanks in advance!
John
Spaceman
Hi John,
The shape or makeup of an object does not change the freedom
of it's motion.
Freedom of motion has 6 directions, up- down, forward- backward,left-right.
Those are the 6 "so called degrees" that I would call planes of motion
instead.
6 maximum planes of motion only.
--
James M Driscoll Jr
Creator of the Clock Malfunction Theory
Spaceman
Greg Neill
news:RNqdnUP-EoLM-gnV...@comcast.com
In his first paragraph John specifically discounted
translational degrees of freedom. Another swing and
a miss for James.
Spaceman
Poor Greg, does not understand I was simply stating that
discounting translational degrees of freedom is simply wrong.
But of course, you live in rubber ruler world where everything
is wrong so you think all that crap is right even if it is wrong.
:)
Greg Neill
Perhaps that's what you intended. If so it is a mystery
how what you intended bears no resemblance to what you
actually said. You're reply was a non-sequitur, since
John is specifically not considering motion in his
consideration of geometrical properties.
Douglas Eagleson
> A friend and I are having a bet. He states that there must be
> objects or mechanisms with 8 degrees of freedom
> (not counting translation} which
> have 3-fold symmetry (at least in some
> configurations). But we cannot find any.
>
> He is thinking of objects like a deformable cubus with corners
> whose angles are not fixed. But such a cubus has
> - three orientational degrees of freedom
> - three internal angles
> which makes a total of only 6 degrees of freedom.
> A cubus has 3fold symmetry when seen along
> a diagonal, so that would fit; but 6 are not 8
> degrees of freedom.
>
> I brought up the idea of a tetrahedral skeleton,
> It has 8 degrees of freedom,
> it has 3fold symmetry in some configurations,
> but we do not see a way to build that in metal
> or rubber without having more or less than 8 degrees
> of freedom.
>
> On the other hand, I am not able to prove
> that the puzzle is impossible to solve.
>
> Is there another solution? Where can one look for such
> objects or related theorems? Are there books or sites
> on these issues?
>
> Thanks in advance!
>
> John
A pentagram has five sides. A vertex angle makes 5 a symmetry.
Making one degree of freedom and one symmetry.
A line length or side length makes a five degree of freedom change,
each side may be independent of the other. Allowing a legnth as a
cause to ratio of side to side then making a ratio symmetry.
And a mirror of set of sides allows a ratio of areas. Draw a line
between vertexes and mirror.
Making the third degree symmetry. And two degrees of freedom for
there are only two axis? NO there are three axis, making 9 degree of
freedom.
SO use a square.
A square is a cubic and all cubic exhibit this majic property. Gold
as a cubic crystal system allows a functional method of set to be
developed. 3 symmetries and 8 degrees of freedom allows a functional
set to be designed.
D(3)
Length(4)
Mirror ratio(2)
Wait the square has only 7 degree of freedom, sorry!
I went through several shapes and found this one.
*
__________
A triangloid with a certain number of sides. It haa No mirror
property because the axis appears a side! SO the angle vertex makes a
ratio of side length to side length For all equal sides, two vertexs
exist. One degree for each.
Allowing the dies to equal the rest of the degrees of freedom.
And the third mirror symmetry exists only as a NON-degree of freedom
effect.
Spaceman
Greg, when one talks about degrees of freedom
They have jumped on the motion bus.
I am sorry you can't grasp such a simple fact.
Douglas Eagleson
>
> - Show quoted text -
I forgot to mention. A base line or axis drawn through the base to
mirror CAN NOT because the Volume of the mirror appears nonexistent.
You can not mirror a volume with a line in other words, except as
given. A top vertex line only appears to have the property of
symmetric formal applied volume, but it appears ZERO.
If the base was square
_________
| |
| |
| |
| |
_________________________
axis
An axis trough the base side can not make a volume mirrior as with the
top vertex because the DEGREE of Freedom of the top vertex was a third
symmetrical form. It depends as a symmetry on base and side legnth,
while the base verticies depende only on square side length.
Greg Neill
> Greg, when one talks about degrees of freedom
> They have jumped on the motion bus.
> I am sorry you can't grasp such a simple fact.
If translational motion is specifically being
discounted for the given problem then it is
simply not germaine to the problem. Case closed.
Spaceman
Specifically discounting translational motion
only makes the problem, not a problem of
degrees of freedom at all.
If you have 0 translational motion, you are not moving
in any degree of freedom at all.
Poor Greg,
You skipped over all that classical stuff to jump
into your "warped" mathematical joke world.
LOL
zzbu...@netscape.net
wrote:
> Greg Neill wrote:
> > "Spaceman" <space...@yourclockmalfunctioned.duh> wrote in message
> >news:CJudnZTqsPZA7AnV...@comcast.com
>
> >> Greg, when one talks about degrees of freedom
> >> They have jumped on the motion bus.
> >> I am sorry you can't grasp such a simple fact.
>
> > If translational motion is specifically being
> > discounted for the given problem then it is
> > simply not germaine to the problem. Case closed.
>
> Specifically discounting translational motion
> only makes the problem, not a problem of
> degrees of freedom at all.
> If you have 0 translational motion, you are not moving
> in any degree of freedom at all.
> Poor Greg,
> You skipped over all that classical stuff to jump
> into your "warped" mathematical joke world.
> LOL
The reason there's only 6 degrees of freedom in in idiot
translational physics though,
is because they only live in the moron universe of "entropy says".
Rather than in the non-zero intellgence world of lasers, digital,
robo++, satellites, and cruise missiles.
Greg Neill
>> "Spaceman" <spac...@yourclockmalfunctioned.duh> wrote in message
>> news:CJudnZTqsPZA7AnV...@comcast.com
>>
>>> Greg, when one talks about degrees of freedom
>>> They have jumped on the motion bus.
>>> I am sorry you can't grasp such a simple fact.
>>
>> If translational motion is specifically being
>> discounted for the given problem then it is
>> simply not germaine to the problem. Case closed.
>
> Specifically discounting translational motion
> only makes the problem, not a problem of
> degrees of freedom at all.
Nonsense.
> If you have 0 translational motion, you are not moving
> in any degree of freedom at all.
So you don't believe in rotational motion? Or
the motion associated with "flexing" the angles
of the vertexes of a geometrical object, or
vibrational motions? How very narrow minded of
you. It seems that you don't understand what the
term "degree of freedom" means. We'll add it to
the growing list.
Spaceman
> "Spaceman" <spac...@yourclockmalfunctioned.duh> wrote in message
> news:ZuWdncYrwv8s5QnV...@comcast.com
>> Greg Neill wrote:
>>> "Spaceman" <spac...@yourclockmalfunctioned.duh> wrote in message
>>> news:CJudnZTqsPZA7AnV...@comcast.com
>>>
>>>> Greg, when one talks about degrees of freedom
>>>> They have jumped on the motion bus.
>>>> I am sorry you can't grasp such a simple fact.
>>>
>>> If translational motion is specifically being
>>> discounted for the given problem then it is
>>> simply not germaine to the problem. Case closed.
>>
>> Specifically discounting translational motion
>> only makes the problem, not a problem of
>> degrees of freedom at all.
>
> Nonsense.
Nope,
The only nonsense is motion without a translational motion
from one point to another like you wish you believe can occur.
>
>> If you have 0 translational motion, you are not moving
>> in any degree of freedom at all.
>
> So you don't believe in rotational motion? Or
> the motion associated with "flexing" the angles
> of the vertexes of a geometrical object, or
> vibrational motions?
All translational motion still Greg.
one point or more "translating" to another point
or more.
You sure are lost without a clue about motion
anymore huh?
Spaceman
> The reason there's only 6 degrees of freedom in in idiot
> translational physics though,
> is because they only live in the moron universe of "entropy says".
>
> Rather than in the non-zero intellgence world of lasers, digital,
> robo++, satellites, and cruise missiles.
Poor guy,
You also must have lost the simple fact that all motion
is translational motion and all such motion only has
6 planes to move in.
You poor things, all warped beyond repair.
LOL
Greg Neill
So we add "translational motion" to the list of terms
that you don't understand. Fine. Keep up the good
work.
Spaceman
LOL
Too bad that list you are making actually shows
your own faults and misunderstandings.
Do you really think a rotation or a flexing has no translational motion?
You poor poor thing..
LOL
Dave
> Is there another solution? Where can one look for such
> objects or related theorems? Are there books or sites
> on these issues?
An object with movable appendages, such as the human body, has
multiple degrees of freedom.
Dave
Greg Neill
>> So we add "translational motion" to the list of terms
>> that you don't understand. Fine. Keep up the good
>> work.
>
> LOL
> Too bad that list you are making actually shows
> your own faults and misunderstandings.
>
> Do you really think a rotation or a flexing has no translational
> motion? You poor poor thing..
See? You don't understand what translational motion
of an object is. Why don't you look it up?
Spaceman
I know all about it Greg.
It is you that is clueless that any motion is still a
translational motion.
I think it is amazing how ignorant you are to such a fact.
I will ask you again,
Do you really think rotational motion has no translational motion?
Greg Neill
> I know all about it Greg.
You certainly don't show it.
> It is you that is clueless that any motion is still a
> translational motion.
Wrong.
> I think it is amazing how ignorant you are to such a fact.
> I will ask you again,
> Do you really think rotational motion has no translational motion?
A rotational motion of an object is not translational motion.
Spaceman
So you say that not even a single point of the object that is
rotating will translate to another position.
Poor thing.
You are lost as usual.
LOL
zzbu...@netscape.net
wrote:
> zzbun...@netscape.net wrote:
> > The reason there's only 6 degrees of freedom in in idiot
> > translational physics though,
> > is because they only live in the moron universe of "entropy says".
>
> > Rather than in the non-zero intellgence world of lasers, digital,
> > robo++, satellites, and cruise missiles.
>
> Poor guy,
> You also must have lost the simple fact that all motion
> is translational motion and all such motion only has
> 6 planes to move in.
> You poor things, all warped beyond repair.
The only thing that is translation is moron physics
is idiot Galileo wannabees, and that's ALL folks.
Uncle Al
Uncle Al counts 10 external sides. Idiot.
<http://img74.imageshack.us/img74/5304/pentagram9hm.gif>
<http://i.peperonity.com/c/9936AE/991727/ssc3/home/073/wicca.wisdom/the_pentagram.jpg_320_320_0_9223372036854775000_0_1_0.jpg>
<http://adoptanamerican.com/version/imgs/pentagram.jpg>
<hhttp://i175.photobucket.com/albums/w145/The_Advenger/pentagram_bm.jpg>
http://www.electricwitch.com/pentagram2.gif
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2
Douglas Eagleson
> <http://adoptanamerican.com/version/imgs/pentagram.jpg>
> <hhttp://i175.photobucket.com/albums/w145/The_Advenger/pentagram_bm.jpg>http://www.electricwitch.com/pentagram2.gif
>
> --
> (Toxic URL! Unsafe for children and most mammals)http://www.mazepath.com/uncleal/lajos.htm#a2- Hide quoted text -
>
> - Show quoted text -
The pentagram was a postulated shape, I then tried a square, then a
triangloziod. THe last was OK.
*
__________
The formal name escapes me now.
Brian Whatcott
wrote:
>
>A friend and I are having a bet. He states that there must be
>objects or mechanisms with 8 degrees of freedom
>(not counting translation} which
>have 3-fold symmetry (at least in some
>configurations). But we cannot find any.
///
>John
Better not take the other end of the bet.
A rotational degree of freedom occurs in one object capable of
rotating with respect to another.
An object with several rotatable links can provide several degrees of
rotary freedom for each successive link with respect to the base
attachment.
An object like the Manx three-legged object, can rotate three ways at
each ankle with respect to its limb.
Brian W
Ray Vickson
wrote:
> john_m_stan...@yahoo.co.uk wrote:
> > A friend and I are having a bet. He states that there must be
> > objects or mechanisms with 8 degrees of freedom
> > (not counting translation} which
> > have 3-fold symmetry (at least in some
> > configurations). But we cannot find any.
>
> > He is thinking of objects like a deformable cubus with corners
> > whose angles are not fixed. But such a cubus has
> > - three orientational degrees of freedom
> > - three internal angles
> > which makes a total of only 6 degrees of freedom.
> > A cubus has 3fold symmetry when seen along
> > a diagonal, so that would fit; but 6 are not 8
> > degrees of freedom.
>
> > I brought up the idea of a tetrahedral skeleton,
> > It has 8 degrees of freedom,
> > it has 3fold symmetry in some configurations,
> > but we do not see a way to build that in metal
> > or rubber without having more or less than 8 degrees
> > of freedom.
>
> > On the other hand, I am not able to prove
> > that the puzzle is impossible to solve.
>
> > Is there another solution? Where can one look for such
> > objects or related theorems? Are there books or sites
> > on these issues?
>
> > Thanks in advance!
>
> Hi John,
> The shape or makeup of an object does not change the freedom
> of it's motion.
> Freedom of motion has 6 directions, up- down, forward- backward,left-right.
> Those are the 6 "so called degrees" that I would call planes of motion
> instead.
No: under the conventions that mathematicians and physicists use (and
those *are* the relevant ones, after all, in this "math" newsgroup)
you have described only three degrees of freedom, not six. These three
degrees are East-West, up-down and in-out. This just says that there
are three lines along which the motion can be projected, or three
coordinates needed to describe velocity. For a generally-shaped so-
called rigid body there can be two more degrees of freedom, associated
with rotational angles and the like (i.e., the object's orientation).
For non-rigid bodies there can be additional degrees of freedom,
associated with vibrational modes, internal angles, etc. You need to
be careful to count these correctly in order to obtain correct figures
for specific heats in polyatomic gasses when doing statistical
thermodynamics.
Anyway, the OP is, presumably, dealing with only orientation and
internal-structure degrees of freedom. I'm still not sure about the
exact answer to the OP's question.
R.G. Vickson
Spaceman
Funny, I am posting from the "sci.physics" group.
So you do not understand that the three planes have two directions
each that creates the 6 directions (degrees) of motion?
> For a generally-shaped so-
> called rigid body there can be two more degrees of freedom, associated
> with rotational angles and the like (i.e., the object's orientation).
Rotation is just a curving change in the 6 degrees of freedom.
> For non-rigid bodies there can be additional degrees of freedom,
> associated with vibrational modes, internal angles, etc. You need to
> be careful to count these correctly in order to obtain correct figures
> for specific heats in polyatomic gasses when doing statistical
> thermodynamics.
These are all still motions in the 6 degrees of freedom again.
No need to add "extra" degrees of freedom at all.
> Anyway, the OP is, presumably, dealing with only orientation and
> internal-structure degrees of freedom. I'm still not sure about the
> exact answer to the OP's question.
Adding "degrees of freedom" and ignoring that the degrees
you add are just curved or vibrational in the already 6 degrees
known is a joke to science.
It might be fun math but it is still just ignorant of physical motion
and the scientific 6 degrees of freedom.
Androcles
"Ray Vickson" <RGVi...@shaw.ca> wrote in message
news:2d09bc06-1c34-4c54...@i20g2000prf.googlegroups.com...
6-DOF
x, y, z, pitch, roll, yaw.
6-DOF platforms:
http://www.inmotionsimulation.com/images/6-dof-2.jpg
http://www.inmotionsimulation.com/images/6-dof-1.jpg
http://www.ckas.com.au/CKAS%20V4%206DOF%20Motion%20Platform.jpg
Ray Vickson
wrote:
I understand perfectly well. If you are moving to the East with speed
10 (in some units) your velocity is v = 10; but if you are going West
at speed 10 your velocity is v = -10. If you 5 units to the right of
the origin your coordinate is x = 5, but if you are 5 units to the
left it is c = -5. That is how physicists use these concepts;
mathematicians do so as well.
>
> > For a generally-shaped so-
> > called rigid body there can be two more degrees of freedom, associated
> > with rotational angles and the like (i.e., the object's orientation).
>
> Rotation is just a curving change in the 6 degrees of freedom.
Nonsense.
>
> > For non-rigid bodies there can be additional degrees of freedom,
> > associated with vibrational modes, internal angles, etc. You need to
> > be careful to count these correctly in order to obtain correct figures
> > for specific heats in polyatomic gasses when doing statistical
> > thermodynamics.
>
> These are all still motions in the 6 degrees of freedom again.
> No need to add "extra" degrees of freedom at all.
Well, some bodies have fewer than 6 degrees of freedom, while others
have more than 6. They can have as many as 8 degrees, but if counting
the three "position" coordinates (which the OP did not want to do).
>
> > Anyway, the OP is, presumably, dealing with only orientation and
> > internal-structure degrees of freedom. I'm still not sure about the
> > exact answer to the OP's question.
>
> Adding "degrees of freedom" and ignoring that the degrees
> you add are just curved or vibrational in the already 6 degrees
> known is a joke to science.
No, it is well-documented dynamics. For example, when studying the
specific heats of dilute gasses by statistical thermodynamics, we need
to worry about these thing; and if we count correctly, we get perfect
agreement with experiment. That matters, because physics is an
experimental science, after all.
> It might be fun math but it is still just ignorant of physical motion
> and the scientific 6 degrees of freedom.
No, it is not just fun mathematics; it is known to anybody who has
taken undergraduate statistical mechanics or undergraduate classical
mechanics. People who go to the library and read appropriate textbooks
know about these things.
R.G. Vickson
Spaceman
You say you understand the above and then you prove you
actually do not by stating that.
Sorry.
>>> For non-rigid bodies there can be additional degrees of freedom,
>>> associated with vibrational modes, internal angles, etc. You need to
>>> be careful to count these correctly in order to obtain correct
>>> figures for specific heats in polyatomic gasses when doing
>>> statistical thermodynamics.
>>
>> These are all still motions in the 6 degrees of freedom again.
>> No need to add "extra" degrees of freedom at all.
>
> Well, some bodies have fewer than 6 degrees of freedom, while others
> have more than 6. They can have as many as 8 degrees, but if counting
> the three "position" coordinates (which the OP did not want to do).
Some bodies have less than 6 only when something is in the way.
There are no extra degrees of freedom just because of a shape
or position of an object.
>>> Anyway, the OP is, presumably, dealing with only orientation and
>>> internal-structure degrees of freedom. I'm still not sure about the
>>> exact answer to the OP's question.
>>
>> Adding "degrees of freedom" and ignoring that the degrees
>> you add are just curved or vibrational in the already 6 degrees
>> known is a joke to science.
>
> No, it is well-documented dynamics. For example, when studying the
> specific heats of dilute gasses by statistical thermodynamics, we need
> to worry about these thing; and if we count correctly, we get perfect
> agreement with experiment. That matters, because physics is an
> experimental science, after all.
So you can't do basic math anymore using 3 dimensions
and 6 degrees of freedom?
>> It might be fun math but it is still just ignorant of physical motion
>> and the scientific 6 degrees of freedom.
>
> No, it is not just fun mathematics; it is known to anybody who has
> taken undergraduate statistical mechanics or undergraduate classical
> mechanics. People who go to the library and read appropriate textbooks
> know about these things.
Classical mechanics has no such bullshit at all.
physical objects also have no such bullshit about extra degrees
of freedom at all.
You are only fooling yourself with "multiple dimension bullshit
if you are finding more than 6 degrees of freedom.
Douglas Eagleson
Just to clarify the meaning of a degree of freedom in my thinking.
"An independent geometric variable."
Angle as a side length appear to be the issue and the basic variable
where angle appears dependent was all that need be discussed.
_______
|
|
|
here is a right angle and it is clearly independent of side length. A
constructed geometric as a whole then allows side to cause angle.
IN mechanical interpretation a machine can be described as a geometric
function. MY right angle machine above has three apparent degrees of
freedom. Two sides and the angle. As soon as a machine is a triangle
it has three again, but the angles are side length determined and the
meaning as machine itself in abstract appear to be a school idea I am
trying to understand.
A function of machine applies to any design wheather a robot like
device or not. A location of machine parts as function allows a
complexity design such as a robot to be discussed, but exact question
was apparently unclear to me.
A thoughtful man would allow all machine whether a simple constant
structure to be a fuunctionally defined structure.
A robot type of machine appears the issue. A three fold symmetry mean
it has three axises and so all machines with threee axis are
functionally equivalent.
An inverted triangleoizoid;) was used at the National Insitute of
Standards and Technology, NIST as a robot arm/platform. Cables
varying the side lengths functionally could cause the tip of the
volume to be motionable in an exact functional fashion. It translates
left and right and up and down and spins in the center in a circle if
required.
So all that was required was to allow an actual usage to be stated. I
thought it was a crystallike common question and not a mechanical
engineeering question. Analogy to crystal was a possible reason for
the NIST discovery as a class of robot though.
If there is a question concerning the usage of crystal design in
robots I would entertain them because there are few machines able to
be used in crystal analogy!
Here is a small novel machine design based on a crystal geometric.
A cubic structure has like maybe ten degree of freedom. And to
functionally control side length to cause the function meant the
solution would be indeterminate! A rather airfcraft like control
function would have to be defined for a cubic to be used as a robot
and a test loop in control code would have to prevent nonsolution
motion.
Making the nIST inverted triangleosoid a truely novel discovery.
Maechanical design is very interesting and the basic question here is
to either talk of the method of machine analogy or not.
Thanks Doug
Spaceman
Hi Doug,
The cubic structure still does not have more than 6 degrees of freedom,
What you are doing is allowing for the degrees to have
a multiple of positions or multiple motions within the normal 6 degrees.
That is not "extra degrees" that is still just an extra motion in the normal
6
degrees of freedom.
Any point of the object can have no more than 6 different directions
(up, down, left, right, forward, backward)
of motion in the 3 planes of 3D space they reside it.
Motions that combine lets say up and left, are not an extra
degree of freedom.
They are a combination of 2 or more of the normal degrees of freedom.
freddy osbourne
which is the axial force at both ends. a frame member has six degree of
freedom, namely translation in the x, y axis plus a rotation at each ends.
that means 3 degree of freedom at each end. a cubic would would have three
degree of freedom on each faces which is 6 times 3 which is 18 degree of
freedom. a material is not measure by it's atomic structure but rather the
material property of isotropical or anisotropical which is measure by the
modulus of elasticity and the possion ratio.....done
"Spaceman" <spac...@yourclockmalfunctioned.duh> wrote in message
news:NMCdnXvH8IBiKwjV...@comcast.com...
Spaceman
> a truss member has two degree of freedom, namely compress and
> extension which is the axial force at both ends. a frame member has
> six degree of freedom, namely translation in the x, y axis plus a
> rotation at each ends. that means 3 degree of freedom at each end. a
> cubic would would have three degree of freedom on each faces which is
> 6 times 3 which is 18 degree of freedom. a material is not measure
> by it's atomic structure but rather the material property of
> isotropical or anisotropical which is measure by the modulus of
> elasticity and the possion ratio.....done
Again,
The rotation at each end you speak of is still just freedom
of motion in the same 6 degrees known.
and each end also has a compression factor to allow
6 degrees to still exist at each end.
You are merely mixing already known degrees of freedom into
"extra" degrees that are not actually there.
You are adding already known degrees of freedom as
"extra" degrees.
A cube, has 6 degrees of freedom only,
Any single point on the cube or inside the cube also
only has 6 degrees of freedom.
You can combine any of the degrees for different motion
in such free 3D space.
But it still only moves with 6 degrees of freedom.
Just because it has ends does not give it "extra" degrees
by adding the same degrees.
Each end can move in the same 6 degrees the other end can
move in.
There is no "addition of degrees occuring".
N:dlzc D:aol T:com (dlzc)
"freddy osbourne" <freddysh...@shaw.ca> wrote in message
news:Tbmlk.55307$nD.14209@pd7urf1no...
>a truss member has two degree of freedom,
> namely compress and extension which is
> the axial force at both ends.
A truss member has at least three degrees of freedom:
1) change in length (+/-)
2) bending off the central axis (up/down, left/right, etc., Euler
column)
3) torsion around the central axis
David A. Smith
freddy osbourne
degree of freedom total. i was thinking about 2d instead of 3d solution. a
cubic would have six degree of freedom at each faces making it 6 times 6
equals to 36 degree of freedom. i think yahoo answer is more fun because i
can correct each answer before it is consolidated within a reasonable
time...
"freddy osbourne" <freddysh...@shaw.ca> wrote in message news:...
>a truss member has two degree of freedom, namely compress and extension
>which is the axial force at both ends. a frame member has six degree of
>freedom, namely translation in the x, y axis plus a rotation at each ends.
>that means 3 degree of freedom at each end. a cubic would would have three
>degree of freedom on each faces which is 6 times 3 which is 18 degree of
>freedom. a material is not measure by it's atomic structure but rather the
>material property of isotropical or anisotropical which is measure by the
>modulus of elasticity and the possion ratio.....done
>
Spaceman
> Dear freddy osbourne:
>
> "freddy osbourne" <freddysh...@shaw.ca> wrote in message
> news:Tbmlk.55307$nD.14209@pd7urf1no...
>> a truss member has two degree of freedom,
>> namely compress and extension which is
>> the axial force at both ends.
>
> A truss member has at least three degrees of freedom:
> 1) change in length (+/-)
Using only 2 degrees of the 6 known.
> 2) bending off the central axis (up/down, left/right, etc., Euler
> column)
Using 4 degrees of the 6 known.
> 3) torsion around the central axis
Again Using same 4 degrees of (2) of the 6 known.
(up down left right motion of points with a variable of
motion for each point)
Still only 6 degrees of actual freedom total.
Spaceman
> correction, a frame member has six degree of freedom at each end
> which is 12 degree of freedom total. i was thinking about 2d instead
> of 3d solution. a cubic would have six degree of freedom at each
> faces making it 6 times 6 equals to 36 degree of freedom. i think
> yahoo answer is more fun because i can correct each answer before it
> is consolidated within a reasonable time...
Dear freddy,
The 6 degrees of freedom on one side are the same 6 degrees
of freedom on the other side.
You have not added "actual" degrees of freedom,
You are using the same 6 known degrees of freedom.
N:dlzc D:aol T:com (dlzc)
"Spaceman" <spac...@yourclockmalfunctioned.duh> wrote in message
news:Ssmdnb-PUfKaaAjV...@comcast.com...
> N:dlzc D:aol T:com (dlzc) wrote:
>> Dear freddy osbourne:
>>
>> "freddy osbourne" <freddysh...@shaw.ca> wrote in message
>> news:Tbmlk.55307$nD.14209@pd7urf1no...
>>> a truss member has two degree of freedom,
>>> namely compress and extension which is
>>> the axial force at both ends.
>>
>> A truss member has at least three degrees of freedom:
>> 1) change in length (+/-)
>
> Using only 2 degrees of the 6 known.
No, that is a single degree of freedom.
>> 2) bending off the central axis (up/down, left/right,
>> etc., Euler column)
>
> Using 4 degrees of the 6 known.
Only two.
>> 3) torsion around the central axis
>
> Again Using same 4 degrees of (2)
> of the 6 known. (up down left right motion
> of points with a variable of motion for each
> point)
No, this is three degrees of freedom.
David A. Smith
N:dlzc D:aol T:com (dlzc)
"Spaceman" <spac...@yourclockmalfunctioned.duh> wrote in message
news:VdOdnfewZKmMawjV...@comcast.com...
...
> The 6 degrees of freedom on one side are the
> same 6 degrees of freedom on the other side.
> You have not added "actual" degrees of freedom,
> You are using the same 6 known degrees of freedom.
He has correctly described 6 additional degrees of freedom, that
describes unique configurations of the total structure. You
don't know physics, you don't know mechanics, you are wasting
time.
David A. Smith
Spaceman
> Dear Spaceman:
>
> "Spaceman" <spac...@yourclockmalfunctioned.duh> wrote in message
> news:Ssmdnb-PUfKaaAjV...@comcast.com...
>> N:dlzc D:aol T:com (dlzc) wrote:
>>> Dear freddy osbourne:
>>>
>>> "freddy osbourne" <freddysh...@shaw.ca> wrote in message
>>> news:Tbmlk.55307$nD.14209@pd7urf1no...
>>>> a truss member has two degree of freedom,
>>>> namely compress and extension which is
>>>> the axial force at both ends.
>>>
>>> A truss member has at least three degrees of freedom:
>>> 1) change in length (+/-)
>>
>> Using only 2 degrees of the 6 known.
>
> No, that is a single degree of freedom.
No,
two directions of motion is 2 degrees of freedom
in a single plane of motion.
>>> 2) bending off the central axis (up/down, left/right,
>>> etc., Euler column)
>>
>> Using 4 degrees of the 6 known.
>
> Only two.
No, again 4 degrees but now in two planes.
I think you are confusing planes with degrees.
Each plane has 2 directions of freedom.
(2 degrees)
>>> 3) torsion around the central axis
>>
>> Again Using same 4 degrees of (2)
>> of the 6 known. (up down left right motion
>> of points with a variable of motion for each
>> point)
>
> No, this is three degrees of freedom.
Nope.
It is the same as above.
It has 2 directions for for any point in one plane
and 2 more directions in the other
again,
4 degrees of freedom.
Spaceman
Actually because I know mechanics is why I know
he has not found any "extra" degrees of freedom.
He has simply "re-used" the already known degrees of freedom.
:)
Androcles
"N:dlzc D:aol T:com (dlzc)" <dl...@cox.net> wrote in message
news:Vmmlk.6305$LF2....@newsfe09.iad...
| Dear freddy osbourne:
|
| "freddy osbourne" <freddysh...@shaw.ca> wrote in message
| news:Tbmlk.55307$nD.14209@pd7urf1no...
| >a truss member has two degree of freedom,
| > namely compress and extension which is
| > the axial force at both ends.
|
| A truss member has at least three degrees of freedom:
| 1) change in length (+/-)
A hydraulic ram is free to change in length. It is not a fucking truss.
A truss has no FREEDOM to change its length, you dork.
The six degrees of freedom are x,y,z, pitch, roll, yaw.
An aircraft is free to move in any of them.
8-DOF is meaningless drivel.
Google 6-DOF.
john_m_...@yahoo.co.uk
Many answers! Of course a rigid body has only six
degrees of freedom. That is why we are thinking about
deformable objects or mechanisms.
Are there any canonical lists of such mechanisms?
We are looking for one with threefold symmetry and
8 degrees of freedom in total.
John
Brian Whatcott
<dl...@cox.net> wrote:
>Dear Spaceman:
///
>>> A truss member has at least three degrees of freedom:
>>> 1) change in length (+/-)
>>
>> Using only 2 degrees of the 6 known.
>
>No, that is a single degree of freedom.
/and so on/
>David A. Smith
Dave,
I see a problem for you; debating with the folks who
have strayed onto an engineering group that actually
uses the concept of DoF:
it's the one called "rassling with pigs...."
You WILL get muddy! :-)
Better to leave them to campout on
sci.physics, sci.maths.....
Brian W
Brian Whatcott
<spac...@yourclockmalfunctioned.duh> wrote:
>N:dlzc D:aol T:com (dlzc) wrote:
>> Dear Spaceman:
>>
>>...You don't know physics, you don't know mechanics,
>> you are wasting time.
>
>Actually because I know mechanics is why I know
>he has not found any "extra" degrees of freedom.
.....
You are embarrassing yourself spaceman, I am
sorry to report.
Wouldn't you feel more comfortable on a
non-engineering group?
BrianW
Androcles
<john_m_...@yahoo.co.uk> wrote in message
news:8ef38bd1-d7e0-4c39...@k37g2000hsf.googlegroups.com...
| On Aug 2, 7:03 am, john_m_stan...@yahoo.co.uk wrote:
| > A friend and I are having a bet. He states that there must be
| > objects or mechanisms with 8 degrees of freedom
| > (not counting translation} which
| > have 3-fold symmetry (at least in some
| > configurations). But we cannot find any.
| >
| > He is thinking of objects like a deformable cubus with corners
| > whose angles are not fixed. But such a cubus has
| > - three orientational degrees of freedom
| > - three internal angles
| > which makes a total of only 6 degrees of freedom.
| > A cubus has 3fold symmetry when seen along
| > a diagonal, so that would fit; but 6 are not 8
| > degrees of freedom.
| >
| > I brought up the idea of a tetrahedral skeleton,
| > It has 8 degrees of freedom,
| > it has 3fold symmetry in some configurations,
| > but we do not see a way to build that in metal
| > or rubber without having more or less than 8 degrees
| > of freedom.
| >
| > On the other hand, I am not able to prove
| > that the puzzle is impossible to solve.
| >
| > Is there another solution? Where can one look for such
| > objects or related theorems? Are there books or sites
| > on these issues?
| >
| > Thanks in advance!
| >
| > John
|
| Many answers! Of course a rigid body has only six
| degrees of freedom. That is why we are thinking about
| deformable objects or mechanisms.
|
| Are there any canonical lists of such mechanisms?
| We are looking for one with threefold symmetry and
| 8 degrees of freedom in total.
|
| John
An object deformed is not symmetric about one of
its three axes of symmetry unless the deformation is
also symmetric; but that merely returns the 6-DOF
of the rigid body. You can't have your cake with
a bite out of it.
Spaceman
> Many answers! Of course a rigid body has only six
> degrees of freedom. That is why we are thinking about
> deformable objects or mechanisms.
>
> Are there any canonical lists of such mechanisms?
> We are looking for one with threefold symmetry and
> 8 degrees of freedom in total.
You are not truly finding 2 extra degrees of freedom
You are counting a degree more than once.
If you really think that creates multiple degrees of freedom
Then a porcupines needles must really blow your mind for
degrees of freedom.
and boy oh boy Don't even try to think about a forest
full of trees and millions (and billions) of branches and leaves
etc.
Spaceman
Actually physics does not actually use more than 6 degrees of freedom
It is only the math heads that play with such sillyness instead of
realizing they are just re-using the same known degrees of freedom
already.
So it would be best to play with such porcupine needled degrees of
freedom that increase with the amount of objects and rubberyness
in the math group alone.
:)
Spaceman
Hmm?
There is an engineer here that states there are more
than 6 degrees of freedom?
Where?
I would like to see how he makes up degrees as new
degrees even though they already exist.
Brian Whatcott
wrote:
>...we are thinking about
>deformable objects or mechanisms.
>.....
>We are looking for one with threefold symmetry and
>8 degrees of freedom in total.
>
>John
>
>
Will this one suit your purpose?
On the axis of trifold symmetry, a long finger (1) with a central
ball joint permitting the one half (1a) to rotate in the axis of
symmetry only,
At the end of this member, three fingers (2,3,4) attached to it, with
pin joints, so they can each rotate in just one plane.
At the tip of each of these three members (2,3,4) , a finger joined to
each with a pin joint also permitting just one axis of rotation,
(labeled 2a,3a,4a).
This appears to provide the trifold symmetry you want, in that the
mechanism can rotate on the axis of finger (1) and in the
colinear axis of finger (1a).
Each of three fingers can sweep an angle about the axis of finger (1a)
and each of three finger tips (2a,3a,4a) can also sweep an angle
with respect to the finger to which they connect.
This is only one of numerous way to provide this specification, it
seems.
Brian W
Spaceman
> Will this one suit your purpose?
>
> On the axis of trifold symmetry, a long finger (1) with a central
> ball joint permitting the one half (1a) to rotate in the axis of
> symmetry only,
>
> At the end of this member, three fingers (2,3,4) attached to it, with
> pin joints, so they can each rotate in just one plane.
>
> At the tip of each of these three members (2,3,4) , a finger joined to
> each with a pin joint also permitting just one axis of rotation,
> (labeled 2a,3a,4a).
> This appears to provide the trifold symmetry you want, in that the
> mechanism can rotate on the axis of finger (1) and in the
> colinear axis of finger (1a).
> Each of three fingers can sweep an angle about the axis of finger (1a)
> and each of three finger tips (2a,3a,4a) can also sweep an angle
> with respect to the finger to which they connect.
>
> This is only one of numerous way to provide this specification, it
> seems.
So as I stated,
re-using the degrees already known is how you would play with the
term "more than six degrees of freedom".
Sadly,
You are only using the same 6 degrees of freedom of motions more than
once.
You have a multiple angles of motion in the same 6 degrees
occuring in different places only.
Don't ever try and engineer the hair on a shaggy dog.
:)
Androcles
"Brian Whatcott" <bet...@sbcglobal.net> wrote in message
news:117c949m75619f1nl...@4ax.com...
HAHAHA!
http://www.insanesoccer.com/games/files/thefinger.jpg
I love it!
Ken Pledger
<532ef290-591b-49ca...@p25g2000hsf.googlegroups.com>,
john_m_...@yahoo.co.uk wrote:
> A friend and I are having a bet. He states that there must be
> objects or mechanisms with 8 degrees of freedom
> (not counting translation} which
> have 3-fold symmetry (at least in some
> configurations). But we cannot find any.
>
> He is thinking of objects like a deformable cubus ....
You may find it useful to google for the combination "kinematic
geometry" and "robotics".
Ken Pledger.
Traveler
<Headm...@Hogwarts.physics> wrote:
[cut]
ahahaha... Is somebody kissing Hanson's ass by any chance? Yep. Once
an ass kisser, always an ass kisser. ahahaha... AHAHAHA... ahahaha...
Louis Savain
Rebel Science News:
http://rebelscience.blogspot.com/
hanson
news:2Cplk.36220$hR4....@newsfe24.ams2...
> |
john_m_...@yahoo.co.uk wrote:
> | >...we are thinking about deformable objects
> | >We are looking for one with threefold symmetry
> | >and 8 degrees of freedom in total.
> | >John
> | >
> | >
> | Will this one suit your purpose?
> | On the axis of trifold symmetry, a long finger (1) with a central
> | ball joint permitting the one half (1a) to rotate in the axis of
> | symmetry only,
> | At the end of this member, three fingers (2,3,4) attached to it, with
> | pin joints, so they can each rotate in just one plane.
> |
> | At the tip of each of these three members (2,3,4) , a finger joined to
> | each with a pin joint also permitting just one axis of rotation,
> | (labeled 2a,3a,4a).
> | This appears to provide the trifold symmetry you want, in that the
> | mechanism can rotate on the axis of finger (1) and in the
> | colinear axis of finger (1a).
> | Each of three fingers can sweep an angle about the axis of finger (1a)
> | and each of three finger tips (2a,3a,4a) can also sweep an angle
> | with respect to the finger to which they connect.
> | This is only one of numerous way to provide this specification, it
> | seems.
> | Brian W
>
... ahahahaha... Yeah, to you their exchange may sound
funny... ahahahahaha... but John and Brian are simply
having a standard "machine shop operator" talk. That
is their line and their language. Why they posted that
into sci.physics & sci math that is the funny part.... ahaha...
Both of them are probably laughing louder then you do...
ahahaha... Thanks for the laughs, guys... ahahahahanson
hanson
"Traveler" <noassk...@nowhere.net> wrote in message
news:3gdc94l00mlh8ldkf...@4ax.com...
> Louis Savain... [snip]...hanson wrote:
Shhh... Louis... shhhh ... ahahahaha...
When fancy strikes I will tell you why
your thought after grav .& charge field
gradient velocity is not instantaneous
(for that would lead to infinite regression)
but may turn out to be (on first principles)
a whopping 6*10^71 cm/sec..... which
for practical purposes is instantaneous
and it quantifies Mach's Principle... ahahaha..
>
Talk to you later after all the aggrieved Einstein
Dingleberries, in the other thread that you
have started, will have said their prayers...
ahahahaha... ahahahanson
Androcles
"hanson" <han...@quick.net> wrote in message
news:fZqlk.177$7N1.47@trnddc06...
Brian W is definitely having a laugh, John Stanton may have his
head up his arse.
Traveler
Well, for lack of a better word, 'instantaneous' is mostly a manner of
speaking since nothing is instantaneous in a universe ruled by cause
and effect. Cause must always precede effect by a fundamental
interval. What I really want to say is that, as far as gravity and
electrostatic fields are concerned, the time between cause and effect
does not depend on distance. It's non-local. It's a very short time,
though, possibly on the order of Planck time. It's hard to prove
experimentally since our instruments cannot measure intervals at that
minute scale. However, it should be possible to prove that distance
does not affect the measured interval. I'll wait to hear what you have
to say about infinite regress.
Louis Savain
john_m_...@yahoo.co.uk
> On Sun, 3 Aug 2008 13:43:04 -0700 (PDT), john_m_stan...@yahoo.co.uk
Brian, thank you for the proposal. (It almost looks as if it had 4fold
symmetry - or am I wrong?)
You also mention "numerous ways" to do this. Can you give a few
more?
In any case, thank you very much!
John