Does anyone have any thoughts about how we can measure some of this? I can definitely imagine a force pad on someone's back to measure the tension, but I'm a bit lost as to how he can measure the ground forces (including possibly torque around a vertical axis)?

I think normal force should be easy. That can be built into a pad on the ground if nothing else, but friction would be harder.

Unless we had multiple pads each of which had force sensors in all 3 axes (plus a rotational sensor) does anyone know how much such an apparatus would cost to build?

Now that I think about 3 axis force sensors, i wonder if there's much lateral or vertical force in the connection point and whether I'd there is that feels bad in some natural way.

On Sat, Mar 30, 2024, 13:37 Joe Harrington via Contra Callers <contracallers@lists.sharedweight.net> wrote:
Funny thing, I wrote the email below last Sunday and thought, do the world's callers really want a physics calculation on their mailing list?  I decided the better of it and didn't send it.  Ok, I guess I was wrong...

What I call support is against centrifugal force, not vertical. Of course, there's no need to lift the other dancer, and it's a really poor idea.

As Jeff pointed out, in a fast swing, there's a lot of centrifugal force, as seen from our rotating frame of reference in the swing.  For physics buffs, centrifugal force increases as the square of velocity, so a swing that goes around three times in 8 beats rather than twice (1.5x faster rotation, the first-level "fast swing") has 2.25 times as much outward force to support.  Estimating a 25 cm radius (about 50 cm between the centers of mass of the two dancers, in the middles of their abdomens, which I measured with a tape measure) and a 70 kg (150 lb) dancer, that's an outward force for each of the two bodies of almost 390 Newtons, or nearly 90 pounds.  Much of that will be borne by the friction between the dancer's feet and the floor, but the rest will be held by the supporting dancer(s).  How much depends on how they lean.  For a standard swing (2 rotations per 8 beats), it's just under 40 lbs.  Fortunately, you only have to hold it for four to eight seconds at a time, or actually less as you accelerate and decelerate inside that time, though the peak force will then be higher.

...and now I add...

Despite starting with it above, myself, I think we're somewhat misleading ourselves with this Mv**2/r calculation.

The key thing here is that a centrifugal-force calculation (centripetal, actually) makes some assumptions that we dramatically violate when we dance. We are not rigid bodies. At best, we're collections of many light rigid bodies (our bones) linked by ligaments, tendons, and muscles, and bearing all sorts of other masses that move relative to one another, storing momentum until we can deal with it in the next step.  We effectively pump momentum up from our feet, into our bodies, and down to our feet on each step. We transfer it to the other dancer through our arms and theirs, and their back, if we have a hand there.

With that in mind, consider this model of a swing.  Each dancer's upper half is trying to execute rigid circular motion.  Our lower bodies (hips down) are doing something else, and half our mass is down there.  So, drop my estimated 90 lbs to 45 just for that (I'll drop it more in a minute).  The lower half is essentially stepping a figure with 90 or 135 degree corners on each beat.  Consider the left foot.  In a standard swing (2x in 8 beats), it is walking a square, directing momentum along the sides of the square that the upper body picks up and turns into rotation.  Half of each square side brings that leg closer to the middle, the other half takes it farther away.  We land, push off, and do it again and again. That push-off supports the centripetal needs of both legs (through the hip joint) and some of the upper body.  If there is an outward lean off the right foot, additional centripetal support is needed from either the legs or arms.  The right foot is mainly a pivot, while both feet support gravitational weight.

Good dancers constantly adjust how far out their left feet land on each step and how hard they push off, simultaneously satisfying both their centripetal needs and the required spin rate.  This lets them control how much inward force they draw from their feet into the upper-body rotation to supplement the arms.  That reduces the support needed from the arms well below 45 lbs.  It can reduce it to zero.  Tweaking the lean also adjusts where the axis of rotation is, to balance the different masses of the dancers and make their differing force impulses produce matched torque impulses.  Dancers use the beat to step in sync with the other dancer's legs, or these torque impulses would come at different times, and the swing would wobble and fall apart, as Chris Lacey alluded to.

So, yeah, it's complicated, yet even children solve this problem when they swing.  Everyone is an intuitive physicist!  And, each time I think about this kind of thing, I get more amazed at the engineers who make robots.  Has anyone taught a robot to do a contra swing, yet?

--jh--


On Sun, Mar 24, 2024 at 3:24 PM Julian Blechner <juliancallsdances@gmail.com> wrote:
Hi Joe,

You mean, palms flat on the back of shoulderblades? If so, it's how I teach it, lots of callers teach it, and this is the first I've heard a complaint about it.

That said, you describe: "I've had my elbow bent backward by eager robins pressing my elbow in to get their elbow in the right place."

That _sounds like_ what I call "arm clamping". While yes, putting Robin's hand on the outside of the shoulder also alleviates the clamping, it's not the only way to fix it. A Robin can lift their elbow. (I just workshopped the issue with my partner in the living room to test a variety of height and holds out to confirm what you were saying, as well.)

The other issue is that if both dancers don't have hands flat on the backs of each other, it's more difficult to maintain an open frame when swinging. One usually winds up _closer_ when hands are resting on shoulders, unless one dancer is significantly stronger and the other is fairly petite.

I know that my right arm will get seriously fatigued and sore if I have an evening too many times as Lark with Robins providing insufficient support. And I've heard plenty of dancers say similar. 

That said, all bodies are different. If yours works where the swing hold works better for you the way you describe, that is what it is, yeah? But I might recommend considering workshopping swings further, because what you're requesting is counter to prevailing teaching. If I understand correctly (and it's always possible I'm missing something.)

In dance,
Julian Blechner


On Sun, Mar 24, 2024, 1:13 PM Joe Harrington <contradancerjoe@gmail.com> wrote:
Not the standard ballroom, with the robin's arm on top of the lark's, but an alternative that I've seen occasionally, but for a number of years now, where the robin tries to put their left hand in the same location on the lark's back as the lark has their right hand on the robin's back.  I know at least one prominent caller who teaches this hold in their newbie workshop and tells their dancers that both sides need to do this to provide equal support in the swing.

While I like the principle, the practice can hurt. If the dancers are not grossly mismatched in size/arm length, it won't be possible to do this without their elbows occupying the same space.  I've had my elbow bent backward by eager robins pressing my elbow in to get their elbow in the right place.  Even if it doesn't go all the way to pain, it pretty much eliminates my ability to provide any support, unless I "fight back" by pushing my elbow out and resisting the inward pressure, essentially refusing the position.  I'm also focusing entirely on protecting my elbow, so it kills any enjoyment in that swing.

Please gently discourage this hold.  If a robin wants to give major support in a swing, the symmetric swing holds, the barrel, the one Jeff described, or even a mirror of the ballroom where the lark's arm is on top are much better opportunities.  A robin whose arm is longer than their lark's arm can also reach over or around the shoulder in a ballroom hold (robin's arm on top) to add support.  Just don't push down on the shoulder.

--jh--


On Fri, Mar 22, 2024 at 9:21 AM Julian Blechner <juliancallsdances@gmail.com> wrote:
JJ,

I like your point about the sort of code-switching that the asymmetry of a ballroom hold provides to reinforce what role one is dancing.

Joe,

I don't understand what you mean about the ballroom hold having elbows occupy the same space. I think I'd need to see it (in person or picture). That said, it raises the broader issue, which is the overall topic, that everyone has different physical needs and finding happy mediums is our goal for everyone dancing together. Your issue with ballroom hold handholds as such is a good reminder for me that no one - not even seasoned callers - can anticipate every need or difference.

In dance,
Julian Blechner

On Thu, Mar 21, 2024, 10:38 PM JJ <jcgj95@gmail.com> wrote:
Personally for me, the standard ballroom swing helps me to "flip the switch" in the brain on which side of the swing I'm "supposed to" end on (assuming we're not switching roles back and forth for fun lol). If my left arm is the "pointy arm," I'm ending on the left; if my right arm is the "pointy arm," I'm ending on the right. I don't have to consciously tell myself "I'm the Lark" or "I'm the Robin," my muscle memory just takes over and I just end on whichever side my arm position tells me to 😅.

I enjoy neutral swings, but if we're not planning on switching roles without warning through an individual dance, I tend to stick with the traditional ballroom figure.

On Thu, Mar 21, 2024, 22:33 Jeff Kaufman via Contra Callers <contracallers@lists.sharedweight.net> wrote:
"At the time, it almost never happened that the one in the lady's role actually swung like a lady.  I'm not sure when that became the norm."

When I started dancing both roles, around 2005, I remember initially doing it as you said, with gender-neutral swings with the gents I encountered.  I remember being surprised sometime around 2006-2007 when I ran into a few guys dancing switch who indicated they wanted to do the standard ballroom hold.  By 2008-2009 I think my male friends and I were dancing the lady's role in the standard way?

Jeff

On Thu, Mar 21, 2024 at 10:16 PM Joe Harrington via Contra Callers <contracallers@lists.sharedweight.net> wrote:
I love the barrel hold, but some of my partners have reacted in a way that indicated it was too intimate for them.  This is especially true if I have to lean over to do it, as that puts my face pretty close to theirs (I'm pretty tall).  It's also difficult to do without frontal contact if one or both partners is well on the heavy side.  But, all that aside, if you and your partner like fast swings, it's a great hold, more stable than ballroom, with four arms providing support rather than one.

In the late 1980s and early 1990s, when guys danced the lady's role (using the terminology of the time for reasons you'll see in a moment), we'd almost universally be offered the "gender-neutral swing", which is symmetrical and very stable for fast swinging: both right arms are around the other's back and both left arms go over/around the other's right arm, bend 90 degrees at the elbow, pass between you, and clasp left hands around each other's forearms between your bodies.  At the time, it almost never happened that the one in the lady's role actually swung like a lady.  I'm not sure when that became the norm.  I would occasionally do it with a particular guy partner whom I liked to dance with.  We practiced it first and then did it with each other, but we gender-neutral-swung our neighbors.  We got some pretty surprised looks from our neighbors when we swung each other. At least one guy asked me if that partner and I were an item.  Times and role terms and what people read into dance behavior change...

In general, I'm quite happy to swing with guys in either role when they're happy to swing with me.  But, it's awkward and uncomfortable in the extreme to be going up an entire line of consecutive frowns, growls, and looks of disgust as a guy dancing the robbin...enough that I haven't returned to the dance weekend where that happened in Fall 2022, even though it was pretty great in other ways.

The one swing style I really dislike is a modified ballroom position where the robbin tries to put their hand on the lark's back in the same place where the lark's hand is on theirs.  I know some people actually teach it this way, I guess as some kind of equality thing.  It's terrible, because their elbow and the lark's elbow then have to occupy the same space, which, well, physics.  If I'm the lark and their arm is outside mine, when they try to provide support, it hyperextends my right elbow, eliminating any chance I can provide support and sometimes inducing pain before I can either force my elbow back out, displacing their hand from my back, or pull my arm up to rest it on their arm in a mirror of the traditional ballroom hold.  I hope we can convince everyone to stop teaching this hold, as it usually doesn't work as intended and it can hurt the lark.

One assist that does work in ballroom position and requires no communication is, if the robbin's arm is as long as or longer than the lark's, they rest their left arm on the lark's right, extending the entire length of the arm and then reaching around/over the lark's shoulder to provide some support on the shoulder blade.  In my case, at least, if they are short enough that they can't do this, then they're often also light enough that additional support isn't critical, though it does make for more connection.  It's important not to press down on the shoulder, though. Only pull forward.

--jh--


On Thu, Mar 21, 2024 at 12:52 PM Julian Blechner via Contra Callers <contracallers@lists.sharedweight.net> wrote:
At the last couple of dances in the last few days, I thought about this email thread and observations.

Short and simple:
A "barrel hold" swing:
- Seemed to provide a little bit more space than a ballroom hold
- One neighbor offered it (by chance) really clearly, as a lark, with his left arm curved into a sort of "offer a hug" type position. As we engaged in the swing hold, he placed his left arm in place, and it guided things in. It worked pretty well for me, at least as an experienced dancer.

In dance,
-Julian Blechner

On Sat, Mar 16, 2024 at 4:18 PM becky.liddle--- via Contra Callers <contracallers@lists.sharedweight.net> wrote:
I can’t answer whether the robin's would always HAVE to go above the lark’s in the modified ballroom swing, but I would intuitively think that having that rule/understanding might make it easier for dancers to make the transition from ballroom to modified ballroom because the robin’s arm is always on top in standard ballroom swing. Also, the lark’s hand is typically cupped upwards with the robin’s hand above the lark’s in things like a balance or even a handhold in a circle move, so having the hand/arm orientations the same in the swing would also seem more intuitive to me if I were just learning this swing. 
Becky

On Mar 16, 2024, at 12:25 PM, Katherine Kitching via Contra Callers <contracallers@lists.sharedweight.net> wrote:

Hi John, thanks for all your comments. I like this swing at https://www.youtube.com/watch?v=FUiXStkCHGs from 0:05 to 0:15 - for spacing -- and I'm going to introduce it at our next dance!  Though what I think Becky found interesting about the variation we're working on is that it retains the "pointy hands", which can be useful.

The one thing that I was confused about when I read your message:  you say when you tried the swing variation our group has been experimenting with (visual at https://www.dropbox.com/scl/fi/ebotfe2jksbr3dqbjyiuf/Modified-Ballroom-Swing-elbow-hold.jpg?rlkey=ekblzvpc2tk2hkbtfrh9u96au&dl=0 )
-- you say that you found the grip insufficient, for the arms that are holding just above the elbow.

But in my mind, this hold that me and my partner are doing with his left hand my right hand ,  is supposed to be the same as the hold you use in this video of yours - (but in your case, your left hand and her right hand.)
Maybe I didn't execute it properly, but it is what I intended: 
https://youtu.be/yUbi1B2Edk0?si=HL-3jgI95LtGZBQ_&t=198
Starts at 3:18.
Thoughts?

Also, is anyone able to answer my question to Winston -

Is it a given, due to something in the asymmetric nature of the hold, that in this video referenced by Allan - 
https://www.youtube.com/watch?v=lQ0R5iHT-l8   or in the photo I shared above via Dropbox, that the Robin's arm will *always* go above the Lark's arm?

Or could the placement of the arms vary depending on the relative height of the two dancing partners?
(for example with a 6' tall Lark and a 5' tall Robin, would the Robin's arm still be above the Lark's? 

Thanks all!
Kat K in Halifax
Thursday, March 14, 2024 7:23 AM
Hi Kat,
Yes, I thought you meant something like you show in your photo. When you mentioned Jeff's photo I did wonder, as it is what I call a Foreshortened Hold in my video and brings you closer together rather than further apart.

I picked up the Foreshortened Hold from the cover of Zesty Contras and love it. I was surprised when I analysed the 600 dancers at a contra dance at The Flurry and realised that nobody else was using it!

We tried your Modified Ballroom Hold Swing and didn't feel that it really worked. With my right arm underneath there didn't seem to be enough connection to have a really good swing unless Karen gripped my arm. I felt that my hand might slide down. With my right arm on top Karen felt that it was pulling on her shoulder even though I wasn't gripping - it was just awkward. So, sorry, but I won't be using that one.

Re all the references to sore arms/hands/wrists/etc. The biggest problem is that people are told to "give weight". I don't want your weight! People misunderstand and lean back or sideways. If people control their own weight then all the connection has to do is counter centrifugal force and that it not a lot inless you spin really fast.

I always start a Swing lesson by getting the dancers to Buzz on the spot BY THEMSELVES. Then when they connect they keep their own balance and weight.

I have had major operations on both my shoulders (too much Repetitive Strain Injury from another style of dance that is taught badly, and then lots of Aerials: https://youtu.be/CJnL_Y63AnY?si=RqKHSw5MQmhiuIFT - maybe I shouldn't have started doing those in my fifties!). Anyway, I can't afford to let people damage my shoulders. With a good partner I can Swing at high speeds with no problem. Whenever someone leans back or sideways I just slow the Swing down and lessen my connection so that they have to take their own weight or fall over.

Anyway, if you can get everyone to keep their own weight you will find it is much less strain on your arm/hand/wrist.

The standard Quebecois Swing has the feet interleaved. They seem to do it without any problem. It is just a different feel and takes some getting used to.

Someone mentioned the challenges with being too close in a Ceilidh Swing (http://contrafusion.co.uk/SwingWorkshop.html#Ceilidh ) - you could always try the Forearm Swing instead (http://contrafusion.co.uk/SwingWorkshop.html#Linked ) - same principle, but further apart so no bodily contact.

Happy dancing,
John

John Sweeney, Dancer, England john@modernjive.com 01233 625 362 & 07802 940 574
http://www.contrafusion.co.uk for Dancing in Kent


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Wednesday, March 13, 2024 10:20 PM
For me, the enforced intimacy is about the proximity of bodies and lack of physical air space between them. The huge difference between a swing in contra vs., say, agreeing to dance a waltz or a swing dance with someone, is that by agreeing to dance you’re agreeing to swing with EVERY opposite-role person in the line, not just the person you asked to dance. That’s a much bigger commitment to physical contact/intimacy than saying yes to one person.

As a side note, before we got rid of a lecherous dancer in our group a few years ago, MANY women in our dance group chose their contra dance line specifically to avoid having to swing with him. The most important intervention was, of course, to establish a code of conduct which we used to remove him from the dance group (when it became clear he would not agree to change his behaviour). But for women (and others, but it’s always been women who have said this to me over the years), when they come to a dance not KNOWING whether there MIGHT be a letch in the line, it is asking quite a lot to expect them to do a ballroom swing with whoever comes at them. I am wondering whether the modified ballroom hold might make contra feel safer, especially for new dancers.

I’d love to hear what folks who have used both feel about the difference.

Becky


On Mar 13, 2024, at 4:34 PM, Julian Blechner <juliancallsdances@gmail.com> wrote:

I would love to read elaboration / articulation on why a ballroom hold feels more "intimate" than other holds?

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Wednesday, March 13, 2024 5:34 PM
I would love to read elaboration / articulation on why a ballroom hold feels more "intimate" than other holds? 

Is it a matter of the historical social attachment we have in our minds with couples dances that use the hold, and romance in our culture?

Is it a physical proximity? (I find ceilidh holds to be closer, crossed arms has my hands bearish their belly which has its own intimacy to me, though sometimes barrel holds can be done with a bit more space - though I wouldn't say the default)

Is it something else?

Maybe if we looked at the why, it'd give insight to what a solution to an alternate swing hold and/or an adjusted mindset might entail?

In dance,
Julian Blechner
He/him
Western Mass



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