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  #81  
Old 11-21-2015
tomoy tomoy is offline
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Quote:
Originally Posted by Streak View Post
Shinji really breaks it down nicely here.
I have not found this video except via Facebook.

https://www.facebook.com/swimlikeshi...1724267225424/
Nice find. What stands out for me is how simple and quiet the underwater hand and arm motion is. The transition from extended spear to catch, then catch to anchor, then anchor to recovery is very gradual and smooth. At each point it seem like an ideal position.

I'm pretty sure that my spear to catch is rougher-quicker and that the geometric angles of my pull-anchor-push are more complicated. I'll have to work on that.

Next, how quiet the hand exits the water - no shooting spray. Nice. Seems quicker tempo also than the hit youtube video.
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  #82  
Old 11-21-2015
Mike Wray Mike Wray is offline
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Shinji really does have an amazing style. He exemplifies the TI method with perfect balance and streamlining. I have a feeling it has something to do with the proportions of his body and legs. Can anyone else swim like that?
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  #83  
Old 11-21-2015
Zenturtle Zenturtle is offline
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Nobody with any knowledge of physics or mechanical engineering on the forum who can give some worthwile comments on my little skateboard propulsion mechanism? Or have different ideas?
In that case we keep on talking about throwing energy forward in space, like throwing the price of milk forward.
I find it interesting to find out how the kick can help arm propulsionm be it in TI swim style or any other, and not only talk about swim perceptions.

To compare the ballistic recovery with other sports.
I do also some inline skating and putting effort in the recovery feels a bit the same as the double push technique in skating.
You spread the load in time, chop the powerphases, use smaller loads with less rest between them and use different muscles instead of bigger pushes with more rest on the same muscles.

https://www.youtube.com/watch?v=EmMf91AVUXc
https://www.youtube.com/watch?v=xTHvlyW6aBo

Some explanation.
https://www.youtube.com/watch?v=QmFZxNEuJH8
https://en.wikipedia.org/wiki/Double_push

The crazy fast inventor
https://www.youtube.com/watch?v=O0ZNmMlRTB8

Bart Swings beautifull technique
https://www.youtube.com/watch?v=1m1Om87rfhA

Last edited by Zenturtle : 11-21-2015 at 02:45 PM.
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  #84  
Old 11-21-2015
Janos Janos is offline
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I think Terry covered the idea of 'continual propulsion' with his Perpetual Motion instruction videos. I can see the similarity in thinking, and the skating looks great fun by the way.

Regarding the skateboard propulsion analogy analogy, and the video from Boomer, I think the main point has been missed, and people are focused too much on the arm itself, as alluded to by Fooboo. Terry has long taught that arms and legs should be treated as outliers as does Boomer. So it is important to remember that when trying to analyse a swim from Terry, Shinji, or a video from Boomer.

I am no physics expert, but I do realise that some of the posts on here about the ballistic movement of the arm and its affect on propulsion are not fully thought through.
If you were to swap the skateboard for a shopping trolley and sit in that and wave your arms about, you would not go anywhere, as has already been discussed, but if you were to load some bricks into the trolley and started throwing them behind you, you would soon start to move. Which confirms the transfer of weight affecting propulsion as advocated by TI. This concept transfers to swimming technique in the action of the shoulder dropping down as the leading arm enters the water. This action sends the body forward, the turning of the hips and the subsequent catch is our 'brick throwing' moment, although we are throwing our bricks forward against the catch and creating propulsion.

The 'pull' is a completely different concept here, and has no place in this theory. Perhaps that is why there is less emphasis on this part of swimming in TI, to stop people becoming fixated with it and making it harder to understand the benefits of weight transfer, balance and streamlining.

Last edited by Janos : 11-21-2015 at 03:55 PM.
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  #85  
Old 11-21-2015
Mike Wray Mike Wray is offline
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Quote:
Originally Posted by Zenturtle View Post
Nobody with any knowledge of physics or mechanical engineering on the forum who can give some worthwile comments on my little skateboard propulsion mechanism?
I can comment on that. The gunpowder powers the rod(your arm) round. The paddle at the end, which is your angled hand, will indeed provide some propulsion when it enters the water. That isn't a very efficient way of using the gunpowder. In any case the issue is about arm momentum creating forward force. As you say yourself the net effect on horizontal force of rod and weight(arm) momentum provided by your gunpowder powered skateboard is zero.
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  #86  
Old 11-21-2015
Zenturtle Zenturtle is offline
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well, it was your example.
Its certainly not the most efficient use of the gunpowder.
That would be to attach a vertical plate on the back of the skatboard. push the plate against a wall and lett the stuff explode between the plate and the wall.
In swimming terms, this would be the same as making a big surface perpendicular to the swim axis and push water back, or push yourself forward against the water. (just a matter of choosen reference point).
And we werent talking about the underwater arm were we?

The explosion power is not used that bad if you let the weight drop on a 45 slope in front of the skateboard.
How much forward speed do you get from a weight dropped on a 45 degree slope?
A zero degree slope will destroy all the energy.Thats an arm slapped flat on the water.
A paddle dropped under an angle of 30 degrees will shoot forward, but still a lot of energy will be waisted.

Since we seem to go back to the weight shift, maybe you can explain the ever returning question how weight shift can produce propulsion by itself?
When I compare with skating, weight shift is simply moving your weight from one leg to the other.
I can do that while standing still.
I have to start to push backward (under and angle) and throw the bodyweight around dynamically to start going forward.
So if arms and legs dont push water backward while rolling from left to right side, what is causing my body to move forward in the water?

Last edited by Zenturtle : 11-21-2015 at 06:22 PM.
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  #87  
Old 11-21-2015
Mike Wray Mike Wray is offline
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Quote:
Originally Posted by Zenturtle View Post
well, it was your example.......1


maybe you can explain the ever returning question how weight shift can produce propulsion by itself?.....2
The idea of the arm with a paddle at the end was not my example. I simply said that forward momentum of the arm cannot produce forward motion and we have agreed on that.

On the second issue, weight shift cannot cause forward propulsion. Why this issue keeps returning is certainly a mystery. In skating, weight shift occurs as you transfer your weight from one skate to the other, but it does not cause propulsion. All forward propulsion is achieved by the reaction of pushing back against the ice. In swimming all forward propulsion is achieved by pushing back against the water. Any other explanation is simply wrong.

Last edited by Mike Wray : 11-21-2015 at 06:45 PM.
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  #88  
Old 11-22-2015
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CoachStuartMcDougal CoachStuartMcDougal is offline
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We are all in agreement? That doesn't include me. Pressing back against water back is not the only part of propulsion, and paraphrasing Boomer, pushing water back will not make you go forward very well. It's whole body movement, directing energy forward whether throwing from the hip or driving from the hip. On the pull impulse, if hand moves back faster than the body moves forward, you're slipping and pushing water back.

You seem have a very binary outlook, abstract is foreign. I recall you dismissing pressing or leaning on the armpit or collarbone, pivoting about center of buoyancy to lift the hips. In the black or white world, that seems impossible, until you try it and feel the pivot. The same goes with driving momentum forward, not sending it backward or behind the body. Most of which Terry has been trying to tell us for years now.

I'm sure we'll continue to disagree - and that's ok, it's not a majority rules.

Stuart
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  #89  
Old 11-22-2015
tomoy tomoy is offline
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Minor side point. I've actually done the waving arms around on a skateboard, snow-sled and office chair - similar to a grocery cart, and you CAN motivate yourself forward. But it's mostly a trick of momentum change and friction. You start moving your arms from back to front gradually accelerating them. At no point does the acceleration break the static friction of the wheels so nothing happens. But once they're going fast I stop the motion instantly. That stopping of the moving arms creates an impulse of force which can break the static friction, rotate the wheels and move me forward. Then "recovering" my arms rearward slowly can be done without moving me forward.

Just to say that there are many exceptions to common physics assumptions.
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  #90  
Old 11-22-2015
tomoy tomoy is offline
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On the broader point of of propulsion, Stuart has run this by us in class, and while I haven't found an aha moment with this technique, I am open to the point. It doesn't take much imagination to see that eels and skates in the water can move quite well without moving an arm from front to back.

The rotating process is very dynamic and can create a swirling screw type of force to contribute to propulsion and the way the body follows the recovering arm thrown forward may very well setup the type of body motion which propels us forward. Of course we're human and a large part of forward propulsion will come from that anchoring hand/arm.

In the meantime I chase down these other focal points in search of whatever works for me.
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