Harb Carver question

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Re: Harb Carver question

Postby kirtland » Fri Apr 01, 2011 9:08 am

Matt,
You say:
If I tip inlines/carvers just a little I argue that they turn very little. There is no sidecut radius of a carver.


You are right, there is no side cut on carvers. And I cannot give you a technical explanation of why they turn, when they are tipped. But if you can't tell from the videos that they turn by tipping. You will just have to try them. You will find, that what they do react to, is tipping. In fact, if I pull my free foot up too quickly during the turn, to tighten the radius, I cannot keep up with them. They are heading back up the hill, while the rest of me is still going down the hill, and the pavement hurts. They react very much like skis to carving movements. They are not forgiving, because they don't drift, and there is no tail or tip, so the fore and aft balance range is narrower. Consequently they teach good habits. I don't have the courage to go very fast on them, so I stick to a moderate slopes, and make sure the rocks are off the road and any cracks in the pavement are small.
You can go to Jay Peterson's Site SkierSynergy (He is one of the Harb Ski System Coaches) and see more Harb Carver Videos Here: http://www.skiersynergy.com/cms/home-sk ... rving.html
You will have to register to sign in, but it is free. They are under the SynergyTube videos.
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Re: Harb Carver question

Postby SkierSynergy » Fri Apr 01, 2011 6:30 pm

Hi Kirtland. I just rolled out the SynergyTube this last week. It has a growing list of PMTS/ Harb Carver videos. Many are already available in other parts of the site, such as blog articles. The "Tube" allows you to see/browse/search just the videos alone. So, you can see many of the Harb Carver videos on the site's Products => Harb Carver page without having to register. Very soon, registered users will be able to submit their own contributions in actual uploads or videos links from some other source. One purpose of the SynergyTube is to have all PMTS related videos from around the web (no matter the source) all in one place that is categorized and easily accessible.
SkierSynergy.com -- comprehensive services for the girlfriends of skiers
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Re: Harb Carver question

Postby kirtland » Fri Apr 01, 2011 11:35 pm

Jay,
I took some time tonight to see what you had on the Synergy Tube site. That is a great job, well organized and easy to use. Thanks. Everybody else you need to check this out.
http://www.skiersynergy.com/cms/home-sk ... ories.html

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Re: Harb Carver question

Postby Matt » Sat Apr 02, 2011 6:15 am

cheesehead wrote:
rwd wrote:
Matt wrote:No, they turn by steering the front wheel. The tipping is for balance.

f you are moving at speed and turn the bars to the left the bike will quickly lean right and then turn right after you return the bars to neutral position. ...

Turning the wheel to the left tips the bike to the right and turns it to the right. You can maintain the tipping with EITHER keeping the front wheel pointed to the outside of the turn, or maintaining the tipping with your body (or both). But releasing the wheel will reduce the tipping and stop the turn.

The front wheel turning to the outside is very much like counteracting.

(also, if you don't counterbalance you could lean too far into the turn and skid out or worse).

It seems to me that the PMTS opponents would learn a lot by trying out these movements on a motorcycle.


I don´t like the analogies with motorcycles. You don´t use CB, in fact the racers are hanging on the inside which is the opposite of CB.
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Re: Harb Carver question

Postby cheesehead » Sat Apr 02, 2011 7:17 am

Matt wrote: ....I don´t like the analogies with motorcycles. You don´t use CB, in fact the racers are hanging on the inside which is the opposite of CB.


I am certainly no motorcycle expert. I am talking about what you can do as a beginning motorcycle rider. What the racers do is fairly extreme and is not necessary to do to feel and/or demonstrate what I am talking about.

In a motorcycle turn, you tip the bike if you are going more than 20 miles an hour. The start of any motorcycle turn starts with the tipping (sound familiar?)

Once the bike is tipped, your body can stay "upright in relation to the bike" -- that is, perpendicular to the axis of the wheel (or perpendicular to the surface of the seat). Or you can tip the bike and keep your body "upright in relation to the earth" -- that is, perpendicular to the ground. I would call this counterbalancing because your body is closer to the outside of the turn than keeping your body upright in relation to the bike (which is tipping to the inside of the turn).

I found the counterbalanced position much more stable than not counterbalancing with the body. (Sound familiar?) You don't have to tip the bike all the way to the ground like the racers do in order to experience this.

The best conditions to experience this are curves at highway speed like on winding country roads. Turns in town (too slow) or on the interstate (too gradual) don't really work like this.

When I first learned about PMTS a couple of years ago and tried it out, I immediately realized, "oh yeah, this is just like riding a motorcycle." This made a whole lot more sense to me than my one lesson of PSIA where they taught me to wedge and spin around a pole plant.

The tipping phenomenon was something I was taught in a basic motorcycle licensing class. Why many ski instructors haven't figured out what any pimply-faced teenager with a dirtbike knows is a mystery.
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Re: Harb Carver question

Postby Matt » Sat Apr 02, 2011 1:18 pm

cheesehead wrote:
Matt wrote: ....I don´t like the analogies with motorcycles. You don´t use CB, in fact the racers are hanging on the inside which is the opposite of CB.


The start of any motorcycle turn starts with the tipping (sound familiar?)

Well, if you start off from going straight down the road how do you start the tipping?

In skiing you can start the tipping by just tipping the skis and reducing pressure on the inside ski. Riding a bike is like skiing on one ski. To turn left on a bike you need to steer right in order to tip the bike to the left, and then after that you can steer to the left.

To me biking is more inclination than CB, not at all PMTS. Agreed that there is a natural tendency to use CB on a bike in order not to get close to the ground, but from a performance point of view it does not work at all IMO.
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Re: Harb Carver question

Postby nickia » Sat Apr 02, 2011 9:36 pm

Is the Pro model in-stock anywhere?
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Re: Harb Carver question

Postby polecat » Mon Apr 04, 2011 3:53 pm

Matt,

I can't tell you what's going on with you on your inline skates. As we often say around here, post video and we can all analyze it together.

I can tell you that when I tip my inline skates they turn.

Before the invention of Harb Carvers, inline skates where the ticket for dryland training. They still work just great. The Carvers just work better.

The inline exercises are still posted on the HSS website.


Here's a sequence image from the HSS inline exercise on linked one-foot turns:

Image

The skater turns right when the skate's tipped right and left when the skate's tipped left. There can be no interaction between the skates (except through the kinetic chain) because the other skate isn't even touching the ground. The other skate is completely lifted, doing the phantom when it's inside and "anti-phantom" when it's outside, just like on skis.



pc.
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Re: Harb Carver question

Postby Matt » Mon Apr 04, 2011 10:40 pm

polecat wrote:Matt,

I can't tell you what's going on with you on your inline skates. As we often say around here, post video and we can all analyze it together.


Polecat, I have been inline skating since 1993 and I have worn down a pile of of wheels and bearing. I can tip my skates untill they scrape the ground. I know how to turn, its just that I don't know what I am actually doing, and judging from this thread not many other understand what is actually going on either. I'm interested in this from a theoretical point of view.

The fact that I can tip my skates in one direction and turn the other tells me that there must be something else going on.
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Re: Harb Carver question

Postby Max_501 » Tue Apr 05, 2011 1:29 pm

Matt wrote:The fact that I can tip my skates in one direction and turn the other tells me that there must be something else going on.


Why would you tip in one direction but turn in the other?
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Re: Harb Carver question

Postby GregM » Tue Apr 05, 2011 7:09 pm

Hi Matt,

I think I can offer some explanations. The wheel in the cross section is not round but more of an ellipsoid form. The contact patch for the non-tilted wheel under pressure has an ellipsoid symmetrical shape. The contact patch of the tilted wheel has asymmetrical triangular - ellipsoid shape. When the wheel is rolling it would go on the path of least resistance which for the asymmetrical patch leads to turning in the direction of tipping the wheel. The contact patch shape depends on the tipping angle so the more you tip the more turning is going on.
This is true for both inline skates and Harb Carvers. The main difference is that Carvers have asymmetrical wheel disposition -- two wheels in the back and one in the front on each side. This leads to a higher pressure applied to the front wheel and therefore much higher elastic deformation of the front wheel. This is even more exaggerated for the Pro model where the front wheel is of a smaller size (and is probably of a softer material) than the rear wheels. The difference between the contact patch shape / elastic deformation level leads to the front / rear wheels traveling on a different path and to a much sharper turn radius for Carvers compared to inlines. The second major Carvers feature is that on the Carvers you apply muscle force to tip them vs. on inlines you apply force to keep them vertical. In this sense they are the opposites of each other and that's why Carvers simulate skiing muscle effort patterns while inlines do not.

The design of the inlines you've posted make sense as well because for the skating movement pattern it is great when the skate goes on a slight curve to the outside after the push.
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Re: Harb Carver question

Postby Matt » Wed Apr 06, 2011 6:12 am

Max_501 wrote:
Matt wrote:The fact that I can tip my skates in one direction and turn the other tells me that there must be something else going on.


Why would you tip in one direction but turn in the other?


In the name of science :) Just out of theoretical interest.
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Re: Harb Carver question

Postby Matt » Wed Apr 06, 2011 6:17 am

GregM wrote:Hi Matt,

I think I can offer some explanations. The wheel in the cross section is not round but more of an ellipsoid form. The contact patch for the non-tilted wheel under pressure has an ellipsoid symmetrical shape. The contact patch of the tilted wheel has asymmetrical triangular - ellipsoid shape. When the wheel is rolling it would go on the path of least resistance which for the asymmetrical patch leads to turning in the direction of tipping the wheel. The contact patch shape depends on the tipping angle so the more you tip the more turning is going on.
This is true for both inline skates and Harb Carvers. The main difference is that Carvers have asymmetrical wheel disposition -- two wheels in the back and one in the front on each side. This leads to a higher pressure applied to the front wheel and therefore much higher elastic deformation of the front wheel. This is even more exaggerated for the Pro model where the front wheel is of a smaller size (and is probably of a softer material) than the rear wheels. The difference between the contact patch shape / elastic deformation level leads to the front / rear wheels traveling on a different path and to a much sharper turn radius for Carvers compared to inlines. The second major Carvers feature is that on the Carvers you apply muscle force to tip them vs. on inlines you apply force to keep them vertical. In this sense they are the opposites of each other and that's why Carvers simulate skiing muscle effort patterns while inlines do not.

The design of the inlines you've posted make sense as well because for the skating movement pattern it is great when the skate goes on a slight curve to the outside after the push.


Greg, the effects you are talking about are camber thrust and slip and that was discussed earlier in the thread.
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Re: Harb Carver question

Postby h.harb » Thu Apr 07, 2011 3:56 am

On Harb Carvers we tip the same direction as we turn. On a motorcycle you point in the opposite direction you turn. Many of the reasons for this occurance are as stated in this thread and rubber compound deflection and wheel shape.
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Re: Harb Carver question

Postby cheesehead » Thu Apr 07, 2011 7:11 am

h.harb wrote:On Harb Carvers we tip the same direction as we turn. On a motorcycle you point in the opposite direction you turn. ..


I don't know if we are talking about the same thing. On a motorcycle you tip the bike to the inside of the turn by pointing. It is the same tipping direction as on skis or carvers. The tipping is created by turning the wheel to the outside of the turn. That feels to me like counteracting but I am not sure the physics are exactly the same. And as I said, many riders use counterbalancing as well.

I don't mean to say that they are exactly the same thing, there are things that are obviously different. If the analogy doesn't work for you, then just forget it.
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