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# Dan Dipiro's Mogul Book - Page 23

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Originally Posted by Jamt

It is not about horizontal or vertical. if i run into a friction-less tree on the flat my "horizontal" energy will be converted into cracked bones.

Yes, in many many posts, I said let's exclude collisions.

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Also, if there is no friction there is no terminal velocity unless it is zero.

Further, as I said in a previous post. You have to be very careful if you are going to use the conservation of angular momentum argument. It is only valid around a fixed point of rotation.

Yes, you have to ski along a curved surface.  Across a halfpipe will do.

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Another example, take the half-pipe example where you implied you can only speed up.

Every time you come to a stop, jump to the bottom of the half pipe and absorb the perpendicular component.

Will the speed decrease or increase after each jump?

The first jump is simple and it is easy to show that at the bottom you will have a kinetic energy which is about 1/4 of what you would have if you only slided down the surface.

This mean you will only make it 1/4 up the other side. Now jump again to the bottom.

You will get an energy time series which converges to zero.

I never said that or meant to imply that.  CTkook and I had many conversations about slowing down in the halfpipe and also stopping on top of the bump, all of which I agreed with.  The only point I've made is that Jonny Moseley and the Canadian freestyle team say to actively pull up the legs so that your COM doesn't get pushed up.  Effects that slow you down by raising your COM in many circumstances are counter productive because the dominant effect for speed control is not allowing gravity to accelerate you on steep surfaces.

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You could also jump to a place where the velocity at the point of impact is perpendicular to the surface. You would get a zero velocity after absorbing and then start sliding back much slower, or you could immediately jump to the corresponding place on the other side. You would never have a speed component along the surface and it would converge quite rapidly.

True,  I would maybe oversimplify this and lump it in with collisions.  There are many many effects.  My point is that friction is dominant enough that we can understand A&E over the broadest circumstances just by analyzing the effects of gravity and friction.

Quote:
Originally Posted by jack97

Here's Moseley, he's is acheiving speed by moving his CoM on curved surfaces. The timing is close to how he would have "pop" at the kickers. In principle, speed can be reduce by doing the opposite.

Maybe someone can post stills from this as he goes up the bumps. He's not going 90 degrees to the surface as he goes up. He's projecting his body forward so he has an acute angle to his skis as he goes up. This would tend to increase pressure on the front of the skis and contribute to slowing I would think. I guess the benefits of getting the body projected in direction of travel outweigh the increased friction. That and lifting the feet to reduce friction and displacement at the top of the bump. He then pumps on the back face.

It seems similar to what he advocates in moguls - projecting hips forward, lifting feet over "the fence" - top of mogul. Big difference is the backside pump instead of turn, not wanting contact at the top to slow down and not going to the outside foot for the turn on backside ( he calls it uphill ski, not outside)

It's common for people skiiing in a halfpipe to be too far toward their tips as they go up the wall. It's scary to be 90 degrees to the surface. This makes it hard to pivot the skis in a turn so they have to jump a lot or plant a pole to get themselves turned.
Edited by Tog - 5/5/15 at 10:20am
Those more interested in skiing than physics shouldn't miss this hidden gem:

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Originally Posted by borntoski683

....play around with varrying degrees of retraction intensity. In this spectrum of pressure management you can get different results and it all effects speed. Retract too quickly and you get too much pressure loss and no speed control. Retract too slowly, which is probably more commonly seen, and you will get tossed around by the bump too much by excessive pressure on the face. We do need to actively retract our legs in order to reduce that pressure on the face, but there is more subtlety to talk about there. You don't want to reduce ALL of the pressure to zero, unless you're trying to avoid slowing down of course, then by all means retract faster, eliminate the blockage and go fast.

I also want to emphasize that this is not the only speed control tool. Extending on the backside of the bump is not about pumping it, which in theory would speed the skier up. Extension there is just enough to again maintain some pressure, just enough that the edges can be engaged and creating speed control with steering angle and turn shaping. Someone posted a Canadian freestyle video earlier and note they were talking about retracting more quickly then extending. The extension move shouldn't be a pumping move. It's just enough extension to maintain the required pressure to edge, not so much as to push yourself faster.

The crux of all of this is that pressure management is an extremely important skill in bump skiing. It is not just about flexing your legs out of the way of the bumps and reaching into the troughs. It's about very carefully managing the amount of pressure on the face of the bump, the back of the bump and pretty much all phases of the turn. This is all about touch.

Expanding on touch, there are a couple related simple things I like to think about when skiing bumps:

- Keep your skis touching the snow at all times.

- Ski with at soft touch, minimizing the impact on each bump.

touch is good.  Not necessarily as soft as we might think.  That is my whole point.

Let's go back to a staircase analogy.  Let's say your running down some stairs.  You have to be a little bit soft on each step to avoid catapulting yourself.  But if you're too soft you will start flying too fast, as the only thing controlling your speed is how you resist with pressure on each step.  You have to find a balance between resisting with pressure and not pumping yourself.  That is the touch.  its definitely softer then pumping!  its definitely a little bit softer then a rigid leg.  But not so soft like walking on eggshells.

I should add, minimizing my impact on each bump is my old man bump skiing technique.  I want to still be skiing bumps when I'm an even older man, so I've tried to modify my technique to minimize the impact.

Unlike stairs, in the bumps you have other means of controlling speed, edging, friction, etc.    I can only be non-egg-breaking at slower speeds, though.   I do think really good bump skiers can keep from breaking eggs at much, much faster speeds. Think about a world cup mogul skier going 70% speed.  I'm guessing that's way faster than my 100% speed, but still lower impact than my 70% speed.

Quote:
Originally Posted by Tog

Maybe someone can post stills from this as he goes up the bumps. He's not going 90 degrees to the surface as he goes up. He's projecting his body forward so he has an acute angle to his skis as he goes up. This would tend to increase pressure on the front of the skis and contribute to slowing I would think. I guess the benefits of getting the body projected in direction of travel outweigh the increased friction. That and lifting the feet to reduce friction and displacement at the top of the bump. He then pumps on the back face.

It seems similar to what he advocates in moguls - projecting hips forward, lifting feet over "the fence" - top of mogul. Big difference is the backside pump instead of turn, not wanting contact at the top to slow down and not going to the outside foot for the turn on backside ( he calls it uphill ski, not outside)

It's common for people skiiing in a halfpipe to be too far toward their tips as they go up the wall. It's scary to be 90 degrees to the surface. This makes it hard to pivot the skis in a turn so they have to jump a lot or plant a pole to get themselves turned.

In that video, Mosely is creating his speed.  The motions to create speed are opposite to the motions that slow speed for parametric pumping.  He may not be used to creating speed this way, because usually gravity is enough to gain speed, so he may not be doing it just right.  These motions for creating speed on a flat trajectory will need to be reversed to slow you down on a downward slope.  Whatever you do to make you move, you would have to do the opposite to make you stop.

Quote:
Originally Posted by Tog

Maybe someone can post stills from this as he goes up the bumps. He's not going 90 degrees to the surface as he goes up. He's projecting his body forward so he has an acute angle to his skis as he goes up. This would tend to increase pressure on the front of the skis and contribute to slowing I would think. I guess the benefits of getting the body projected in direction of travel outweigh the increased friction. That and lifting the feet to reduce friction and displacement at the top of the bump. He then pumps on the back face.

It seems similar to what he advocates in moguls - projecting hips forward, lifting feet over "the fence" - top of mogul. Big difference is the backside pump instead of turn, not wanting contact at the top to slow down and not going to the outside foot for the turn on backside ( he calls it uphill ski, not outside)

It's common for people skiiing in a halfpipe to be too far toward their tips as they go up the wall. It's scary to be 90 degrees to the surface. This makes it hard to pivot the skis in a turn so they have to jump a lot or plant a pole to get themselves turned.

Also, he looks exhausted just going around this circle, so he's not very efficient with it, unless there's just not that much energy that can be converted by that method.  If it must compare to the amount of energy dissipated while skiing down a steep slope, he should be ripping around that circle at 30 miles per hour without giving any more energy than he would use to ski down a mogul run.

Quote:
Originally Posted by borntoski683

Heheh yea I hear that, slush bumps are fun. But I want to challenge your thinking here. Is it truly and fully passive, even when you feel like you are blasting through? I am willing to bet you are still actively retracting your legs, you're just doing it with a sense of touch that allows more pressure. The slush factor softens the blow of that pressure. That actually helps control your speed even more due to the larger pressure. The soft snow softens the blow in much the same way that flexing your legs more aggressively would. Quite likely though if you try to be passive your head will be bobbing up and down a lot which is probably why tog told you to flex more

"they are the ducks, we are the bullets"    (moguls = ducks).

When *he* went past there was snow flying all over.  But yet he stayed on the snow.  How?  The combination of touch (his energy into the frontside)

and pressure management (absorbing enough to stay on the snow, but still impacting the snow)

I think very high end mogul skiers go into the frontside with a very tight and strong core, and absorb only as much as they need to.

They are not trying "jump" the mogul as a skateboarder might jump a parking block but rather manage the forces:

their skis into the snow

snow pushing back through the ski bases

Watch how quickly the tips get back on snow around 29-30 seconds:

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Originally Posted by tball

I should add, minimizing my impact on each bump is my old man bump skiing technique.  I want to still be skiing bumps when I'm an even older man, so I've tried to modify my technique to minimize the impact.

Unlike stairs, in the bumps you have other means of controlling speed, edging, friction, etc.    I can only be non-egg-breaking at slower speeds, though.   I do think really good bump skiers can keep from breaking eggs at much, much faster speeds. Think about a world cup mogul skier going 70% speed.  I'm guessing that's way faster than my 100% speed, but still lower impact than my 70% speed.

Hehehe.  Got you.  Well the pressure we are talking about here, is not necessarily any harder on the body then walking down the street.  More pressure then walking on egg shells, but not so impactful that it feels like an "impact"

Smoothing out the pressure so that its not a sudden impact, but a smooth and continuous pressure even as the bump faces rises up under your skis, is part of the sense of touch.  This particular aspect of technique, is NOT hard on the body when done correctly.  Quite the opposite, anything you can do to control your speed at any juncture, contributes to an overall easier time of controlling your speed.  If you pass through some phase of the turn without speed control, then you'll have to make up for it later and it will be that much harder to do so at that time.  When I see people pounding their way through the bumps and complaining about how hard it is on them, its precisely because they are missing opportunities to manage speed control.  They are out of sync, they are fighting it.  They are experiencing impact after impact, rather then smoothed out continuous pressure.

Unfortunately a lot of people do experience bumps this way and thus they have the mistaken conclusion that some of these techniques are only for the young that can take a beating.  But actually, taking a beating is not what zipperline rippers are doing.  These techniques will all contribute to making it all easier on your body and thusly perfectly suited for old men like you and me.  Really awesome skiers that you see ripping the zipperline are not pounding their body like you think they are.  They are able to ski that way due to technique!  Yes the bionic body parts do come in handy when they miss something and have to switch into brute force mode to recover.  Old guys like us have to go slower just in case that happens or to help prevent it from happening to begin with. But the actual ski technique when its working right, is NOT impactful and not hard on the body.

The only thing I find supremely more difficult as I age, is my quickness is just not there anymore.  For this reason I try to keep my speed down.  But I find that even when I'm leisurely just cruising down some bumps in a way that seems leisurely to me, I will leave many of my peers in the dust and they will start making comments like "Yea I wish I was young like you so I can beat up my body".  First off I'm 50, so they are wrong about the young part.  Second of all, its not pounding my body in the least or else I wouldn't be doing it.  They just don't understand what they are seeing.

Good mogul skiing is hard to do (but easy on the body)

Bad mogul skiing is easy to do (but hard on the body)

you pick :)

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"they are the ducks, we are the bullets"    (moguls = ducks).

Makes no sense to me. Possibly he's just describing the external view as opposed to actions the skier takes. Bullets are not good absorbers. .What's your take away?

Moseley is pretty specific about talking about his jumping. Possibly his analogy is not communicating his actions.
Quote:
Originally Posted by The Engineer

In that video, Mosely is creating his speed.  The motions to create speed are opposite to the motions that slow speed for parametric pumping.  He may not be used to creating speed this way, because usually gravity is enough to gain speed, so he may not be doing it just right.  These motions for creating speed on a flat trajectory will need to be reversed to slow you down on a downward slope.  Whatever you do to make you move, you would have to do the opposite to make you stop.
Way to punt on the analysis of possibly the most relevant video of the current topic. Btw, there is little to no slope on that course which is why he's tired.
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Originally Posted by Tog

Way to punt on the analysis of possibly the most relevant video of the current topic. Btw, there is little to no slope on that course which is why he's tired.

I gave the most relevant analysis yet, but I was a bit subtle, letting others make the conclusions.  I'm sorry you did not understand it.

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Originally Posted by The Engineer

Quote:
Originally Posted by Tog

Way to punt on the analysis of possibly the most relevant video of the current topic. Btw, there is little to no slope on that course which is why he's tired.
I gave the most relevant analysis yet, but I was a bit subtle, letting others make the conclusions.  I'm sorry you did not understand it.
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Some of these things are like 2+2=4 for me.  I am highly trained and highly skilled in these areas.  When talking about physics it would be best to treat me as a physics professor and work to understand what I'm saying rather than arguing with me. - TheEngineer to bts683 post 649
Ok professor, but the student gives you an NA or F for the lack of analysis of Mosely's pumping vid. Platitudes do not an analysis make.
Quote:
Originally Posted by Tog
"they are the ducks, we are the bullets"

Makes no sense to me. Possibly he's just describing the external view as opposed to actions the skier takes. Bullets are not good absorbers. .What's your take away?

This guy is a former World Cup level skier and he was talking (in this case) about zipperline mogul skiing (I should have made that more clear).

I think he may have made the remark after seeing someone take a fairly wide line around any large moguls.

I guess my point is that he was using impact of the shovels in a deliberate way, sometimes referred to as "stuffing the tips".

Does that help? (especially within the context of Zipperline moguls)

Quote:
Originally Posted by The Engineer

Also, he looks exhausted just going around this circle, so he's not very efficient with it, unless there's just not that much energy that can be converted by that method.  If it must compare to the amount of energy dissipated while skiing down a steep slope, he should be ripping around that circle at 30 miles per hour without giving any more energy than he would use to ski down a mogul run.

I don't think he's trying to be efficient - he's trying to go around as fast as he can .  I can't fathom how you would expect him to go 30 mph on

a course that is essentially flat - what am I missing?

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Quote:
Originally Posted by The Engineer

Also, he looks exhausted just going around this circle, so he's not very efficient with it, unless there's just not that much energy that can be converted by that method.  If it must compare to the amount of energy dissipated while skiing down a steep slope, he should be ripping around that circle at 30 miles per hour without giving any more energy than he would use to ski down a mogul run.

I don't think he's trying to be efficient - he's trying to go around as fast as he can .  I can't fathom how you would expect him to go 30 mph on

a course that is essentially flat - what am I missing?

Well it does show how much energy is available from "pumping" on skis versus say going the same distance down a 25 degree pitch.  Add in some non-arced turns and friction more than negates pumping, especially if you are not really pumping hard on the back face, just extending to maintain pressure on the edges.

I get it.  He is saying that if pumping was the major factor, then the speed you could build up going around the pump track would be comparable to the amount of gravitational speed you could prevent by pumping going down moguls.  The fact that it is not shows that dissipative forces (friction and its kin) dominate.

There may be some merit to that.

So if I understand correctly, the claim is that the direct effect of pumping on the energy balance is minor, compared to the indirect effect of keeping your skis where they can generate the most energy dissipation (friction, deformation, etc) on the snow.

Of course, at a high level of competition, minor effects can mean the difference between winning and losing.

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Quote:
Originally Posted by Tog

"they are the ducks, we are the bullets"

Makes no sense to me. Possibly he's just describing the external view as opposed to actions the skier takes. Bullets are not good absorbers. .What's your take away?

@Tog
This guy is a former World Cup level skier and he was talking (in this case) about zipperline mogul skiing (I should have made that more clear).

I think he may have made the remark after seeing someone take a fairly wide line around any large moguls.

I guess my point is that he was using impact of the shovels in a deliberate way, sometimes referred to as "stuffing the tips".

Does that help? (especially within the context of Zipperline moguls)
Ok, so he's blasting the moguls with the tips and letting them absorb some of the impact. That requires commiting to the line and a certain speed- fast.
What else was suggested to get to that point?
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Originally Posted by mdf

I get it.  He is saying that if pumping was the major factor, then the speed you could build up going around the pump track would be comparable to the amount of gravitational speed you could prevent by pumping going down moguls.  ...

I would note he's going at a decent clip for the first 12 or so seconds, and the pump track is in terms of geometry peaky and tight, including a speed-killing corner.  To build a more speed-friendly track would have taken more time and work.  I'm not sure how much more speed you'd get from a snow pump track that's a bit more optimized, but for comparison on a bike it can make a huge difference, as much as 3x.  Plus technique-wise on the track in that video he would have wanted to double to really get going faster.

Those are all silly internet nits on my part.

The general rough rule of thumb is that in "expert" bumps speed control is roughly 50/50 absorption and turns.  I would assert this video more or less proves that out.  Tilt that pumptrack to make it a mellow blue and likewise I think the video shows easily that for a mellow blue that's been allowed to bump up, it's possible to control speed solely through absorption.

As a design and terrain point, I'd also note that non-optimized things can also be more fun.

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Originally Posted by Tog

Ok professor, but the student gives you an NA or F for the lack of analysis of Mosely's pumping vid. Platitudes do not an analysis make.

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I don't think he's trying to be efficient - he's trying to go around as fast as he can .  I can't fathom how you would expect him to go 30 mph on

a course that is essentially flat - what am I missing?

Ok guys, last one, then you'll have to think a little for yourselves.  If parametric pumping is a major player for speed control and friction is a minor player for mogul skiing than he should be able to whip around that course at 30 miles per hour with very little effort.  The fact that it's allot of effort means either parametric pumping is a minor contributor or he's pumping inefficiently.  If he's pumping efficiently, then this video proves that parametric pumping is a very minor player.  Without friction to dissipate energy all the potential energy of the skier (mass, gravity, height) must be dissipated in the legs over the length of a steep mogul run.  Energy is force over a distance.  The force is calculated based on the angle of the slope.  From this understanding we can quickly determine the speed he could obtain with the same forces applied while he's on a flat slope.  With those forces applied and friction a minor player, he'd be whipping around at great speeds in no time with little effort, because acceleration is force divided by mass.  In the downward slope the slowing forces would be in opposition to gravity giving a constant velocity, but on a flat slope with nothing to stop him he would just keep accelerating.  This video shows that friction is the major player, and we can stop thinking too much about angular momentum.  If he's pumping inefficiently with motion that's supposed to be the opposite to mogul skiing in the first place, then none of his motions are of particular interest and analyzing his hip movements or anything else has no useful application to learning mogul skiing.

Quote:
Originally Posted by mdf

I get it.  He is saying that if pumping was the major factor, then the speed you could build up going around the pump track would be comparable to the amount of gravitational speed you could prevent by pumping going down moguls.  The fact that it is not shows that dissipative forces (friction and its kin) dominate.

There may be some merit to that.

So if I understand correctly, the claim is that the direct effect of pumping on the energy balance is minor, compared to the indirect effect of keeping your skis where they can generate the most energy dissipation (friction, deformation, etc) on the snow.

Of course, at a high level of competition, minor effects can mean the difference between winning and losing.

Wow, I ranted too soon.  Thanks for getting it.

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Originally Posted by Ghost

Well it does show how much energy is available from "pumping" on skis versus say going the same distance down a 25 degree pitch.  Add in some non-arced turns and friction more than negates pumping, especially if you are not really pumping hard on the back face, just extending to maintain pressure on the edges.

And you got it too.  My faith in humanity is restored.

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Originally Posted by The Engineer

Ok guys, last one, then you'll have to think a little for yourselves.  If parametric pumping is a major player for speed control and friction is a minor player for mogul skiing than he should be able to whip around that course at 30 miles per hour with very little effort.  The fact that it's allot of effort means either parametric pumping is a minor contributor or he's pumping inefficiently.  If he's pumping efficiently, then this video proves that parametric pumping is a very minor player.  Without friction to dissipate energy all the potential energy of the skier (mass, gravity, height) must be dissipated in the legs over the length of a steep mogul run.  Energy is force over a distance.  The force is calculated based on the angle of the slope.  From this understanding we can quickly determine the speed he could obtain with the same forces applied while he's on a flat slope.  With those forces applied and friction a minor player, he'd be whipping around at great speeds in no time with little effort, because acceleration is force divided by mass.  In the downward slope the slowing forces would be in opposition to gravity giving a constant velocity, but on a flat slope with nothing to stop him he would just keep accelerating.  This video shows that friction is the major player, and we can stop thinking too much about angular momentum.  If he's pumping inefficiently with motion that's supposed to be the opposite to mogul skiing in the first place, then none of his motions are of particular interest and analyzing his hip movements or anything else has no useful application to learning mogul skiing.

I asked "what am I missing"  so I don't really understand where your reply is coming from...

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I asked "what am I missing"  so I don't really understand where your reply is coming from...

Most of that was aimed at Tog who doesn't seem to pass up any opportunity to give me a jab, well thought out or not.

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Originally Posted by Tog

Ok, so he's blasting the moguls with the tips and letting them absorb some of the impact. That requires commiting to the line and a certain speed- fast.
What else was suggested to get to that point?

The usual suspects:  hands in front, eyes 2-5 moguls down the line, hips stay directly down the hills, turning as well as A&E happen in the lower body.

I mentioned this in response to a post by @borntoski683 where he talked about touch and pressure.  For me personally (and in the right bumps / pitch / etc)

I sometimes need to remind myself to take a very direct line, which, as you noted, requires commitment to speed.  I found this usually only happens (for me)

on blue terrain and/or spring slush bumps or filled in bumps (ie powder day bumps)

Just to change the direction, some actual mogul skiing:

doc,  would you say Reilly is extending into the turn finish as he deflects of the mogul sidewall and then flex's/ retracts as soon as his feet crest the bump?

Nail

Quote:
Originally Posted by The Engineer

Ok guys, last one, then you'll have to think a little for yourselves.  If parametric pumping is a major player for speed control and friction is a minor player for mogul skiing than he should be able to whip around that course at 30 miles per hour with very little effort.  The fact that it's allot of effort means either parametric pumping is a minor contributor or he's pumping inefficiently.  If he's pumping efficiently, then this video proves that parametric pumping is a very minor player.  Without friction to dissipate energy all the potential energy of the skier (mass, gravity, height) must be dissipated in the legs over the length of a steep mogul run.  Energy is force over a distance.  The force is calculated based on the angle of the slope.  From this understanding we can quickly determine the speed he could obtain with the same forces applied while he's on a flat slope.  With those forces applied and friction a minor player, he'd be whipping around at great speeds in no time with little effort, because acceleration is force divided by mass.  In the downward slope the slowing forces would be in opposition to gravity giving a constant velocity, but on a flat slope with nothing to stop him he would just keep accelerating.  This video shows that friction is the major player, and we can stop thinking too much about angular momentum.  If he's pumping inefficiently with motion that's supposed to be the opposite to mogul skiing in the first place, then none of his motions are of particular interest and analyzing his hip movements or anything else has no useful application to learning mogul skiing.

Seems you are treating pumping and friction as two independent effects (for now I am assuming pumping in general, not limited to parametric)

Pumping, or rather anti-pumping, has a major effect, but primarily due to friction.

As I tried to explain in post http://www.epicski.com/t/39753/dan-dipiros-mogul-book/630#post_1874289 distributing the pressure can make you ski a flatter slope in practice.

With friction a flatter slope means less speed than a steeper one.

Very simple, Occam's razor?

I'm curious, what is your view on parametric oscillation in the context of bumps? when would you extend and flex? It is easy to apply to the half-pipe or swing example, but it is not the same as bumps.

Quote:
Originally Posted by Nailbender

doc,  would you say Reilly is extending into the turn finish as he deflects of the mogul sidewall and then flex's/ retracts as soon as his feet crest the bump?

Nail

Heres the thing @Nailbender

You largely talk about what is happening at turn finish and crest of mogul, while most people talk about frontside and backside,

so perhaps that is some of the disconnect.  I do see the deflection as you mention, as well as A and E.

When you say "extending into the turn finish", can you put that in relation to frontside / crest / backside / trough?

I'd say this is some pretty good skiing - those bumps are not small and he is carrying speed.

I also know that one thing he was working on this spring was range of motion, to allow him more "A"...

Some still grabs and text of how I see it:

Quote:
Originally Posted by The Engineer

. He's pretty clear that absorption (A&E) is about speed control/going slower.

I'm not contradicting this. Absorption and extension slows you down and I'm telling you why. It allows you to weight your skis on flat sections instead of steep sections, just like walking down stairs, just like Dan says in his book. Read my other posts, on this. The engineering analysis is very solid. Absorption by itself does nothing to slow you down; it only works in combination with extension.

I'm exhausted spelling out every little detail for unthoughtful challenges. This isn't a discussion, it's all posturing along with meaningless one liner zingers, while arguing with someone who has short term memory loss. Don't just read the last posts in a discussion.

I have to take a break, but I would like to point out the true highlights that made it worthwhile. Dan's reply. Cosmoliu and Liquidfeet's testimonial. Plunge's technical advice and Tball's heart rate. Thanks guys, and please enjoy direct line bump skiing if you're interested.

I just went back and read some old posts and I see we are on the same page. I haven't read the entire thread but I don't know why you talked about A&E being a minor effect, angular momentum, parametric oscillations etc. Not really necessary IMO.

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