4251  Axis vs. Balance

Date: Mon, 8 May 2006 14:58:31 -0400
From: "Michael" <tangomaniac@cavtel.net>
Subject: [Tango-L] Axis vs. Balance
To: "Tango L" <Tango-L@Mit.Edu>
Cc: Michael <tangomaniac@cavtel.net>

I've read the "off axis" messages. I got the impression that some were using balance and axis synonymously. They're not. Here's an experiment. Take a belt with a heavy buckle. Put the end without the buckle in your sternum. (This is the indentation in your chest). Put your feet together. Stand on your right foot. The belt buckle will move over your right foot. Now shift all your weigh to the left foot. The belt buckle will move over your left foot. Your axis is over the foot you're standing.

Now stand with your feet apart. Shift as much weight as you can to your right foot. The belt buckle won't move completely over your right foot because some weight will be on the left foot because the feet are apart. In this case, your axis is somewhere between your feet because all your weight ISN'T on one foot.

You have balance AND axis in both cases. However, your axis isn't in the same place when your feet are apart compared to when they are together. This is why your feet have to be together before pivoting. If the axis isn't over one foot, your turn will not be completely circular (such as the man leading a molinete). If a woman's feet aren't together, as she pivots for an ocho, some of the momentum from the pivot will send her outside the circle.

Hope this helps.

Michael Ditkoff
Washington, DC
Hated geometry in high school. Maybe I'd be a better dancer if I understood it better XX years ago.


I'd rather be dancing Argentine Tango

Date: Mon, 8 May 2006 16:10:16 EDT
From: Euroking@aol.com
Subject: Re: [Tango-L] Axis vs. Balance


At the risk of over analyzing, I think we need to agree on some basic
definitions. I will posit the following with the knowledge there are exceptions and
expansions but IMHO are at best marginally useful to this thread.

Axis: Is a vertical imaginary line running through the dancer's Center of
Mass and is perpendicular to a point on the floor at any instant of time.
(dynamic or stationary)

Balance: Is the ability of the dancer to maintain their center of mass over
that point on the floor without assistance from another dancer or object.

Shared Axis or Shared Balance: When the dancers become dependent on each
other or the other they create a common center of mass for themselves. When this
occurs we no longer worry about individual axis but move on and around the
shared axis.

I recognize that this may not be the basics as outlined in the depths of
science, but I think it is close, IMHO.

Just some thoughts,

Bill in Seattle

In a message dated 5/8/2006 11:59:01 A.M. Pacific Daylight Time,
tangomaniac@cavtel.net writes:

I've read the "off axis" messages. I got the impression that some were using
balance and axis synonymously. They're not. Here's an experiment. Take a
belt with a heavy buckle. Put the end without the buckle in your sternum. (This
is the indentation in your chest). Put your feet together. Stand on your
right foot. The belt buckle will move over your right foot. Now shift all your
weigh to the left foot. The belt buckle will move over your left foot. Your
axis is over the foot you're standing.

Now stand with your feet apart. Shift as much weight as you can to your
right foot. The belt buckle won't move completely over your right foot because
some weight will be on the left foot because the feet are apart. In this case,
your axis is somewhere between your feet because all your weight ISN'T on one
foot.

You have balance AND axis in both cases. However, your axis isn't in the
same place when your feet are apart compared to when they are together. This is
why your feet have to be together before pivoting. If the axis isn't over one
foot, your turn will not be completely circular (such as the man leading a
molinete). If a woman's feet aren't together, as she pivots for an ocho, some
of the momentum from the pivot will send her outside the circle.

Hope this helps.

Michael Ditkoff
Washington, DC
Hated geometry in high school. Maybe I'd be a better dancer if I understood
it better XX years ago.


I'd rather be dancing Argentine Tango
Tango-L mailing list

Date: Mon, 08 May 2006 20:27:50 +0000
From: "Jay Rabe" <jayrabe@hotmail.com>
Subject: Re: [Tango-L] Axis vs. Balance

Apologies to those who just want to dance, but some of us find benefit
in highly technical analysis...

:-)

Michael and Evan have both clarified the respective definitions of axis
and balance. Being "balanced" means that your center of mass is vertically
inside your footprint, and you can be motionless without falling. Axis
really only has meaning in the context of rotation. Strictly speaking,
Michael's hanging belt defines the center of mass, though I too use the term
axis to refer to it. Perhaps Even can confirm, but my suspician is that the
axis of rotation of a dancer is always a line that passes through the center
of mass.

OK so far. But I want to present a separate, though related concept. I
call it the "precision of the axis." I believe it relates to the
mathematical property of "moment." If a follower is standing motionless on
one leg, then two things are true. She is balanced, and her center of mass
is within the footprint of her standing foot. These things are true
regardless of what her free foot is doing (assuming at the start, for
simplicity, that it too is motionless.)
Now consider two cases: First, in which her free foot is collected
close beside her standing leg. Second, she is holding her free foot/leg out
away from her body. In both cases she is still balanced, and her center of
mass (axis) is vertically above her standing foot. But her rotational
properties are very different. With her free foot collected, she can pivot
and turn very quickly. With her free foot extended, it takes more effort to
generate the momentum needed to make a quick turn.
Another, more subtle effect, is that, with her free foot collected, she
cannot sustain much movement off her axis before she will be out of balance.
If at the start her axis is precisely over the center of her foot, then the
most she can move sideways is 1/2 the width of her foot, and the most she
can move front-to-back is 1/2 the length of her foot, before she will be out
of balance.
If OTOH her free foot is extended, and her torso (most of her mass) is
moved, she can compensate by slightly moving her free foot, and its
associated mass, effectively moving her center of mass, and thereby
maintaining her balance, keeping her center of mass within her footprint.

As a leader, the dynamics of doing a single-axis turn are quite
different depending on whether the follower's free leg is collected or
whether it is extended, as I mentioned above. But the most challenging
situation occurs when the follower changes the position of her free leg
(changes the position of her center of mass and her resulting axis of
rotation) DURING the turn. A leader must be sensitive to where her axis is.
In practice, it sometimes happens that the axis of such a turn wobbles
like a slowly-spinning top during the turn. Ideally both dancers should be
balanced at the End of the turn, so that they could pause without having to
"fall out of the turn" by stepping to regain their balance.

J
www.TangoMoments.com


----Original Message Follows----

Date: Mon, 08 May 2006 21:25:24 +0000
From: "Jay Rabe" <jayrabe@hotmail.com>
Subject: Re: [Tango-L] Axis vs. Balance

If you are stationary, or perfectly spinning like an ice skater, then your
axis of rotation is indeed vertical, perpendicular to the ground and passing
through your center of mass. But if you're doing a colgada, each dancer's
axis of rotation, while it may still pass through their center of mass, is
now angled, quite off-vertical, though the axis of rotation Of The Couple is
presumably still vertical.

J
www.tangoMoments.com


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