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Old October 21st, 2011, 07:01 PM   #20
Armadillo
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Join Date: Apr 2008
Location: Chicago, Near the Lake
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Default What the angles mean - Understanding why DA45 is slower

I find it amazing how so many so called experts, even those with championship skills pontificate about what are the design & performance advantages or disadvantages of a given plate (or class of plates), without ever explaining WHY? Terms like "stability and "squirrely" do not give much indication of what is really happening with the plate dynamics, and why/how performance is affected.

For example, the number one potential design advantage "feature" of the DA45 plate, especially those that place the front axle very near to right below the center of the pivot ball, is that the pivot carries nearly ALL the skaters weight, and very little gets onto the cushions.

With most shallower action skates, no matter how loose you set the action with them in your hands, once you step into those skates and place your weight on them, the compression of the cushions get an immediate kick upward to a higher level. This means that the force needed to work the action also goes higher as well.

The flip side of this aspect of the DA45 geometry is that at the neutral position, it offers LESS available leverage to compress the cushions and initiate the turning action. However, because the DA45 gives the LEAST amount of skater-weight cushion pre-compression, this lack of leverage is not so big of an issue, and once the axle begins to swing away from being almost directly below the pivot pin, the plates available turning leverage for cushion compression and axle swing ramps up quickly.

In addition to this effect, we also have the fact that the DA45 action geometry produces further axle swing with less plate lean. As to this "feature", the analogy with cars is more like a race car having a steering setup that goes from full left to full right with only 180 degrees of steering wheel rotation.

So knowing how these aspects of the DA45 plate's design function, the question remains as to how favorably do they impact the needs of a quad speed skater. Well, those of us who skate speed know that ALL the best speed skater skate LOW -- VERY LOW. Most coaches emphasize this as being the number one requirement for improving your speed -- get lower! Why this is so critical is that the width of your power stroke is limited by how far your hips are away from the floor. The more horizontal you can get your stroke the longer and stronger your stroke can be.

So, knowing that the maximum horizontal power stroke is going to give you the most speed, how do the DA45 plate's features described above impact a skater with their leg going very horizontal and trying to keep all four wheels down? Well, the first concern is the that the ankle must be bending considerably at the peak of the power stroke in order to optimally keep all the wheels equally pressed down onto the floor while negotiating the arc of the turn.

Do the DA45's "features" actually facilitate this process, or do they compromise this process. In my view they perform poorly compared to a less steep action plate (lower kingpin angle). When your ankle is at the maximum bend point while your leg is also in the maximum horizontal position, the DA45 is demanding that you DO NOT lean it over too much as you steer the arc of the curve. It is also reacting with maximum leverage against minimally compressed cushions, which means as you try to deliver the peak push of your power to the floor, you have to really work hard to avoid over-leaning the plate. This means you are trying to keep your ankle LESS BENT over when the leg wants it to bend MORE.

A shallower action (steep kingpin) plate works much better than a DA45 plate at this point in the stroke cycle. It allows the ankle to lean more while still maintaining the proper arc of the curve. This allows the power stroke to go further outward, In addition, for any given amount of ankle twitch, the shallower action produces less turn deviation to take you off your desired track. The better level of cushion leverage and greater level cushion compression developed with the shallower action (steep kingpin) plates, at the peak push point of a power stroke, also makes it a lot easier, as max power is being applied, to maintain the precision needed for sustaining the proper direction of your skate without as much mis-steering or over steering of the plate.

As to the longer plate being better for speed, there is more to think about than just your left-right turning/balance. There is also front-back balance and how it affects your roll. It is easier to maintain proper front-back balance to keep your weight evenly distributed across all four wheels on a longer wheel base. In addition, when you do deviate from your optimum front-back balance point, which inevitably will happen at different stages in the cycle of completing a lap, the longer wheelbase plate will steal less rolling energy as these front-back balance errors occur.

These are not the only reasons that the DA45 will rarely be the choice of elite speed skaters, but they are the main reasons.

-Armadillo

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