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Why Lifters or tall plates?

post #1 of 34
Thread Starter 
What are the advantages of standing taller on lifters or very thick plates? Marker tries to push the idea of some kind of leverage, but they do not explain what leverage (leverage suggests a point of support about which the leveraging action can be developed). Modern skis are narrow at the waste and I do not think they mean to reduce the problem of edge holding. (I do not see how lifters help putting a ski on its edge). On modern shorter skis the fore/aft balance is more critical so the lifters do not help here either.
I do not remember hitting the snow with my boots. If I don't fun carve/body carve with huge edge angles why endanger my knees even more than needed? The more I angulate the more I feel it. Another hoax?
post #2 of 34
Angulation is the main benefit. Simple physics that the higher off the snow you are the more you can angulate with the same effort, thus increasing edge power and thus tighter turns, deeper carves etc.

But if you don't want that then don't buy them.
post #3 of 34
Lifters also help prevent "boot-out" or when you are severely angled to the snow your boots won't touch the snow and cause you to fall. You saw it several times in the Olympics.
post #4 of 34
They look cool, in a KISS or Elton kind of way.

<FONT COLOR="#800080" SIZE="1">[ February 27, 2002 10:24 AM: Message edited 1 time, by milesb ]</font>
post #5 of 34
I ski a Stockli Laser SC in a 188 cm.
This ski does two things really well.
One, it skis like a GS and two, it turns a 17 m radius. Now, with that combination, I was "booting out" at very high speeds with steep turn angles. I mounted another pair this winter with a Vist Carver plate. I'm now 50+ mm off the deck and haven't booted once this season. Believe me, booting out is as pleasurable as pre-releasing from a binding. Plates may not be that necessary for GS's (unless you're trying to dampen the ski), but on carving or slalom skis, I would look into it. Good Luck!
post #6 of 34
Thread Starter 
I never questioned the issue of booting-out.
(Please read my first post)
What I do doubt is the so-called lever effect. People keep repeating this (some book writers too) and go so far as to suggest "basic laws of physics" without naming them or at least explaining what those laws are (a more serious response would be welcome).
Can anybody be more specific?
Lito mentioned booting-out in fun carving. Good. Ron LeMaster, the only one that I know of, ventured deeper into the area and covered the issue of ankle protection, but wisely said nothing about the lever action. At the same time, he forgot to extend his discussion to the knee protection. Here the problem is opposite. If you angulate with your knee, not only with hips, you tend to strain the knee. You simply put your knee in bending in the direction that the knee does not like. (If you use inclination only, your knees are safe). No wonder knee injuries happen more often these days.
Let's go back to basic mechanics of balancing the centrifugal force by inclination and angulation. Would you angulate better if you were taller? Or on stilts? Please be specific.
Wouldn't you question what Lisa Feinberg Densmore, for example, writes about leveraging? I quote:
"Because lifters increase your stand-heights off the snow, they not only help prevent boot out, but also give you more leverage over your edge. You can transfer more power to the edge, resulting in better edge grip." Lisa did not bother to elaborate. Can you? Please use mechanics if possible.
post #7 of 34
Since we all know that a longer stick under a rock will give you more leverage to lift it than a shorter stick will, I think we have all assumed that a taller lifter acts as a similar lever. It certainly *feels* as if there is more leverage over the ski. Many coaches and racers will be suprised if this is all an illusion. The FIS will be too since they put down rules about this lift precisely because they feel that the increased leverage also is more dangerous since leverage works two ways.

Will be interesting in hearing more about the physics of this.
post #8 of 34
there's lots of gimmicks out there, i just recently saw some dude w/ magnetic skis. but lifter plates are not a gimmick, bert. i imagine you have no problems holding a 50 lb bag of dog food, but if you put said 50 lb bag of dog food on a 10 ft pole you'd be hard pressed to hold it up straight, and if it got even slightly off center i'd be very impressed if you were able to maintain control over it. it's leverage. adding a lifter plate increases the amount of pressure your weight can put on an edge. it creates a higher center of gravity. if i had a physics textbook handy i could quote you the theorems....

of course, there are trade-offs. the higher you are off your skis the farther your body has to travel to shift from edge to edge (this extra movement, or need for it, is what is translated to increased pressure on your edges), and many complain about losing the 'feel' of their skis in variable snow w/ too much lift. i've also heard that too much lift will increase the risk of injury, the reason for which i'm just a little hazy on... my mind isn't bending around that idea too well at this late hour.

edit: if your skis get knocked around, hit a rut, a rock, etc - the lever would be reversed.... too much lift might make it a lot easier to tweak your knee. phew...now i can go to sleep.

<FONT COLOR="#800080" SIZE="1">[ February 27, 2002 10:06 PM: Message edited 2 times, by Auxcrinier ]</font>
post #9 of 34
A quick bit of internet research has yielded the following (p.s. this is my first time trying to add an image so sorry if it is a butchery):

"Because of the aggressive carving nature of shaped skis a skier can lean over a lot further thus increasing the edge pressure & the ski carves better. What happens if there is no Riser Plate is the tendency for the boot to touch the snow.

The Riser Plate allows more "edging" to occur before 'boot out' happens.
The major reason for a Riser Plate is one of simple physics and leverage. The higher the boot is off the snow (skis edge) the greater the pressure on the edge for the same angulation. The illustrations below show this effect.

The distance the Knee has moved in A is less than in B.
Less movement of the Knee provides the same edging effect when a Riser Plate is used."


http--www.vikinglodge.com.au-ProductPages-TuneGear-TuningPics-Riser.gif
post #10 of 34
post #11 of 34
Rock, do you mean:



S
post #12 of 34
I'm on the leverage kick. I was skeptical of the lifter thing. Years back lifters were the way to go, then the industry came back and put you as close to the ski as possible, then they figures out some lift was benificial.
I still was not sold but at the time I had two pair of identical GS racing skis (K2 GS Race 208cm). I put lifters on one pair and I could not believe the difference in performance. The ski was actually quicker edge to edge. The leverage difference actualy did something. It is not BS, it is done for a reason. The skis react quicker. If it was all bull pucky I doubt you would see racers with double stacks. A standard binding lift is around 14mm. A racing plate is around 14mm, you see people putting 28-30mm of lift under thier binding, refered to as a "Condo" or "Double Stack". I have only skied one pair of skis like this (P50) and I got so much darned powerout of that ski it was incredible.

I cannot give you the numbers or scientific data to back up my claims. I can only tell you my experiece, sensations and the differecnes I physically felt.

Lifters work and serve a purpouse, period.

<FONT COLOR="#800080" SIZE="1">[ February 28, 2002 12:52 PM: Message edited 1 time, by Argus ]</font>
post #13 of 34
Thread Starter 
I appreciate your response. A skech would be helpful.
How can I post a picture here? I tried to copy, paste a word document and it did not work. Any tricks needed? Am I doing something wrong? Other ideas?
post #14 of 34
Bert,
You need to have the image on the internet, then link to it to be able to post it here, so go to somewhere like webphotos.com upload the image, and then link to it using the image button when you're posting the reply.


Hope this helps,


S
post #15 of 34
I find it difficult to ski on hard snow without risers now. I have a pair of Bandit XX (74mm waist) with a pair of Salomon S900s with plastic Salomon lifters (12mm I believe) and I can still boot out on groomed runs. With a GS race ski with a waist around 63mm I don't think it would be possible to carve without some kind of lift, your boot would be smacking the snow constantly.
post #16 of 34
Hey WTFH, thanks for helping out with that image. It really says it all very simply don't you think? Bert, I hope this puts your doubts to bed.
post #17 of 34
Some really valuable information here, but of course there is the added benefit of the extra couple of cm's of height when spading in the lift queue.
post #18 of 34
Now that i have skied plated bindings i will never ski a flat binding ever again, and actually i dont think i will ever ski on a pair of skis that dont have some type of race lifter on them. The salomon poweraxe race sl plate gives the ski not only the standard 55mm of lift but if makes the ski so easy to ski on because it dampens it so much, you just get the pure spring out of the ski without it getting all bouncy on you. My GS plate on my gs skis is just sick, but it is so heavy that i wouldnt want to use it for free skiing. I think that even if i was buying a midfat that didnt have an integrated binding system that i would look into what kinds of race plates you can buy for it just because they make carving so much smoother, and you get the advantage of the extra leverage, and the ability to use large angles. Next season i think im scraping my 5mm FIS lifters under my heels and plating my bindings with a Salomon AXE+ lifter on top of the race plates. I think ill be around 65mm then, well over the FIS limit but ill be hauling @ss... and its not too big of a deal because in USCSA they dont check skis until you get to the nationals i think... I'll have the 5mm ones around just in case.
Later
GREG
post #19 of 34
Its interesting going back and forth between my skis with high lifters, and some with none. I miss the leverage of the lifters when I'm not on them, but I also feel less removed from the ski when I'm right on top of them. I was completely sold on nothing but lifters for the last few years, now I'm enjoying both skis with and without them.

--------------

Gear:
2000 SonicCare Electric Toothbrush
1999 Fiskars U.S.A. Office Stapler
2000 GBC Docuseal 30 Laminator
2002 Tragor Bronzed Fingernail Clippers
2000 Kurzweil K25000 Music Workstation
1999 Scotch 1/2"x450" Transparent Tape
Oh yeah . . . and a dozen pairs of skis.
post #20 of 34
<BLOCKQUOTE>quote:</font><HR>Originally posted by Todd M.:
...now I'm enjoying both skis with and without them.
<HR></BLOCKQUOTE>


So Todd, are you telling us you are a swinger

post #21 of 34
Heh! No such luck, pretty boring standard married lifestyle here!
post #22 of 34
There is another reason to have lifters. They smooth out the ride. Most of the lifters have the effect of absorbing shock and vibration. Skiers with bad knees often report less knee stress with plates. I have used plates for 10 years. Most of my skis use about 65mm total lift (10mm over FIS max).

An aside on knee angulation. There is no such thing. Point your leg straight and push medially and laterally. If you have a good knee it will not flex. The key to skiing these radical combinations is to have hip angulation and knee flexion. It is also vital not to "a-frame."
post #23 of 34
Thread Starter 
was trying to "borrow" and post some pictures from LeMaster's book on the subject. I am not a relative of Bill Gates' so I failed miserably.
(For those of you who have the book, please look at Figures 9.1 through 9.17., chapter: Edging the Ski).
First about the picture from down under. I do not see how it can explain anything. (Thank you for posting it though). It does not show the reaction force from the snow onto the ski. What are the yellow lines supposed to represent? A lever to work must have a fulcrum to develop any leverage. Where is it? What forces are leveraged there? Can you answer those questions based on the picture posted? I can not.
Not having a sketch to help me state my point more specifically, I will have to use many words to describe rather than state what I think so please bear with me. I will ask you to make your own free-hand sketches:
Sketch a tipped skater (not a skier) on ice, as viewed from behind the skater. A horizontal line = ice surface. Another line at, say, 45 deg to the ice surface = line of action of the reaction force onto the skate and, at the same time, the axis of symmetry of the skate. This view is intended to show the real thickness if the blade. Let the blade thickness be represented by the thickness of the 45deg. line. Put a skate boot on the blade (a tilted rectangle centered on the 45deg. line sitting on top of the blade). For now let's assume that the skater is neither ankle-angulating nor knee-angulating. Somewhere within the boot and on the 45deg. line mark the location of the ankle.
Add the location of the knee on the same 45deg. line but higher, above the boot. For simplicity imagine that the skater turns on the one skate only (in a minute it will be the dominant outside ski).
There are three external forces acting on the skater: (1) the gravity force through the center of the skater's mass directed vertically down, (2) the centrifugal force through the same mass center directed horizontally and towards the outside of the turn, (3) the reaction force with which ice acts on the blade at the point where the blade contacts the ice. Draw these three arrows. For equilibrium to exist, the vector sum of forces (1) and (2) must be equal in value and opposite in sense to the reaction force, and must act along the same line as the reaction force (in this case, along the 45deg.line)- this is the condition of equilibrium. Therefore, if you want to mark the location of the center of mass, put a dot somewhere higher than the knee mark but on the same 45deg. line.
A few conclusions can be drawn from this picture:
A)The reaction force acting on the blade compresses the bones of the leg, compresses the ankle and the knee (We should have sketched the hip joint and the upper leg bone, but it would be somewhat painful for me to describe how to construct the picture; let's just say that the hip joint would end up very close to the 45deg line and not far away from the mass center. The upper leg bone, because of its shape, would undergo some bending, mostly its upper portion at the hip)
B)The ankle is not in bending
C)The knee is not in bending
D)The skater has no problem holding the edge

Now the skater decides to increase the blade angle from 45deg. to, say, 60deg. by angulating with his ankle and knee.
Sketch a construction arc with its center at the blade-ice point of contact and of a radius equal to the distance between the blade-ice contact point and the ankle joint. Mark the new ankle location on this arc and towards the center of the turn. From the new ankle joint location make a construction arc whose radius is equal to the distance between the ankle and the knee and mark the new knee location on this arc. Do not change, for simplicity only, the location of the mass center. Join with construction lines the blade-ice contact point (not changed) with the new ankle mark and the new ankle mark with the new knee mark. The reaction force is still on the 45deg. line. Sketch two parallel line segments perpendicular to the original 45deg. line through the new ankle mark and the new knee mark. The lengths of these segments if multiplied by the reaction force, represent the bending moment action that the ankle and the knee are exposed to. You could add a few parallel segments between the ankle and the knee to illustrate the bending of the lower leg bones, if you want to. The longer the segments, the greater the bending moment. Now the skater's muscles must hold the angles if he wants to hold the blade angles. If the segment lengths are short or approach 0, the bending moments are negligible or approach 0, and the skier's muscles do not have to hold the ankle and knee angles, as it was in the case of no angulation. I hope I explained what I mean by bone/joint bending. Usually the bones can take a lot of abuse, unlike the joints.

Let's get back to skiing. A skier turns on his outside leg, no angulation for now. Replace the blade with a ski whose width at the waist is much greater than the blade's width. Make a new sketch showing the ski cross-section (a rectangle) instead of the skate blade, with a boot (a rectangle) on it, at a 45deg. to the snow (a horizontal line) angle. First, the case of soft snow (an extreme case).
On deep snow the ski sinks so that the contact with the snow covers the whole width of the ski base and we can assume that the resultant reaction force is perpendicular to the ski base and on a line close to or exactly on the line of symmetry of the ski cross-section. Draw this line of symmetry and mark the location of the ankle and the knee (no angulation) on this line. Add an arrow representing the reaction force (on the same line at 45deg). Is there a difference between the ski on soft snow and the skate blade on ice if you do not angulate? No, and there is no bending action on the joints. And no problem with holding the ski edge. Your muscles do not have to hold the joint angles because there are no joint angles. If, in addition to inclination, you angulate, you move your joints to the inside of the turn, create the angles (that your muscles have to hold), load your joints with bending moments the same way as the skater does. Would a riser change anything here? Nothing, as long as the reaction force is close to or exactly on the line of symmetry of the ski cross-section. Your sketch can be helpful here; increase the thickness of your ski cross-section to simulate a riser. All you will see is the reaction force moving deeper into the snow, no angles changing.
Now the case of iced/hard-packed snow (opposite extreme case).
Sketch a ski at 45deg.to the horizontal (snow). This line represents now the line of symmetry of the ski cross-section. Put a boot on the ski and mark the ankle and knee locations. To make things simpler let's disregard the possibility of ankle angulation for now (let's say your boot will not allow any) and focus on the knee angulation. The assumption of no ankle angle allows us to mark both the ankle and the knee joints on the 45deg. line (line of symmetry). The new thing here is the reaction force. On hard slopes we are dealing with practically a point contact of the ski with the snow. If you do not angulate at all, the reaction force can be assumed to be perpendicular to the ski base while passing through the sharp corner of the ski edge. (And, of course, its line of action must pass through the CM point.) If you angulate, the reaction force line, while passing through the edge and CM, is not perpendicular to the ski base. This is a very important point.
Let's say you angulate. To sketch the reaction force draw its line of action. Make a straight line that passes through the corner of the ski edge, and misses both the ankle mark and the knee mark but passes between both marks. Put an arrow pointing to the ski edge. You have the reaction force. (This reaction force is, of course, equal to the vector sum of the gravity force and the centrifugal force). The distances of the joint marks from the line of the reaction force, if multiplied by the reaction force, would represent the bending moments on both joints. (The greater the distances, the greater the moments.)
Please note that the ankle bending moment wants to reduce the edge angle while the knee bending moment wants to increase the edge angle. In order to hold the edge angle your muscles must work. If you are on wide-waisted powder ski, (sketch a wider rectangle representing the powder ski cross-section) the reaction force line will pass further away from the ankle joint and closer to the knee joint, perhaps through the knee (this would mean no knee bending) or even would end up on the inside of the knee. The wider the ski, the more you have to work your muscles to hold the edge angle on hard snow. Will a riser help with the wide skis? Yes, it will. Again simulate it by increasing the thickness of the ski into the snow. The reaction force will move towards the outside of the turn. The more non-perpendicular to the base the reaction force is, the more help you will get. Depending on how high the riser is, (stilts?) you can move the reaction force so that it passes through the ankle joint or even further so that the reaction force is on the outside of the ankle. You may gain a lot as far as the ankle goes. But take a look at the knee bending moment that you will create. Fortunately, the skis for hard slopes are narrow at the waist. Theoretically, you can manipulate the location of the all-important reaction force by fooling around with the riser heights. But the knee will remind you of its existence.
If I had a problem of holding the edge on wide skis on a hard slope, I would try to support better the ankle joint with my boots rather than overdo the lifter heights.
This is how I think the lifters are supposed to work. I wish binding manufacturers were honest enough to tell us about the pros and cons before we decide what to buy (if we had a choice), rather than publish silly glossy brochures about enigmatic lever actions that are more confusing than explanatory.
I hope I haven't bored you to death.
Regards.
post #24 of 34
Hey - not bored, just cut and pasting it for future referance! Nice work!
post #25 of 34
How lifters work article on Stockli web page. Author Ed Green.
http://www.stockli.com/asked/lifters.htm
post #26 of 34
Thread Starter 
Hi Fish Racer,
May I quote you?
"An aside on knee angulation. There is no such thing. Point your leg straight and push medially and laterally. If you have a good knee it will not flex. The key to skiing these radical combinations is to have hip angulation and knee flexion. It is also vital not to "a-frame.""
Remember Martina Ertl? She is not old knews. Didn't she knee angulate? If you do not, you must compensate for it somwhere else. At the hips? At the ankles?
Regards.
post #27 of 34
Fish is right - the knee simply does not flex laterally, and you would not want it too! We used to talk alot about knee angulation, what we were seeing and talking about though was the femur rotating in the hip socket, and the knee pushing fowards.
post #28 of 34
Thread Starter 
You are right. The knee angulation it done by means of femur. But it is commonly called the knee angulation to differentiate it from the hip angulation involving the upper body angle (from pelvis up). It feels differently and is generated differently. If I bend my knees while standing on the floor I can create the the so-called knee angle (and I do not rotatate my feet at the same time. I disagree on this issue with R.Mark Elling who is great) to stand on the edges of my feet without emplying the upper body angle.It is another degree of freedom that can be used and is used to control things. I can superimpose the so-called hip angle onto the knee angle quite independently. I am sure not only me. I am old. Martina is not.
post #29 of 34
Question for fish racer or anyone else.
"vital not to A-frame"
I've been working on dropping my inside knee to avoid just that very thing. An instructor that I know told me I was A-framing and that it is bad but he did'nt explain why it was bad.
Any thoughts?
post #30 of 34
Review the recent Olympics - there were A-Frame turns happening in Gold Medal winning runs in all alpine disciplines. In general we are more situated to handle sudden terrain/snow changes if our skis are not on opposing edges, but stepping out onto an opposing edge is a very powerful and fast way of changing your line and moving immediately from high edge angle to high edge angle. There is nothing "wrong" with it at all, and you are right to ask "why" when told not to do this. Its ineffecient to be doing it all the time, and tougher on your joints to be constantly putting your skis in opposition to each other, but it is a powerful and invaluable tool that is deployed by the worlds best skiers as needed.

Ah . . . dogmatic thinking, its everywhere isn't it?
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