Sweet spot position vs screw hole position

[Query]

When people change blades, they often re-use the same screw holes, so the positions of those screw holes relative to other blade features are among the most important distinguishing blade characteristics.

Most screw-mounted figure skating blades have 6 circular screw holes in the front mounting plate, used in the permanent mount. For this discussion I ignore the back mounting plate.

Based on a very small sample size, the point midway between the 2 middle holes is, approximately, vertically over top the sweet spot, on MK and Ultima blades, when they ship from the factory.

(For this discussion: A "sweet spot" is a point where rocker curvature changes.)

Has anyone else looked at this?

Thanks.

[Query]

Oh yes - is it true of all blade models that the front few inches are identical, regardless of blade length?

If not, how are other blade models scaled with length?

How much sense would that make?

[Bill_S]

Your question about scaling is a very good one. I don't have any answers though.  For me, it's a question that has arisen from the rocker experiment.

I did make a photo of the Jackson Synchro blades that I measured in Agnes' rocker radius thread http://skatingforums.com/index.php?topic=6925.0.

Measured from the rear of the blade (=0), the spin rocker was very evident at the 8" mark, and may have started between the 7" and 8" location. That places it somewhere in the upright stanchion area of this particular blade.



(Note to self - let's start measuring distance from the root of the toe pick instead of from the tail. It will make comparisons easier later on.)

I did note that these blades had a different hole pattern than you described. When I find time, I'll measure my Aces for rocker radii and determine the location of the transition between rockers.

This is a synchro blade and it's shorter than a freestyle blade. Here is a graphic showing tracings comparing the synchro with my Aces. The difference in length is 11/16" (0.69").

[Query]

Your comment that the hole pattern was different made me re-examine my blades.

Oh dear. Even within MK and Wilson blades (I think I threw away my old MK Dance and Wilson Coronation Ace blades , but I still have some old MK Club 2000 and Wilson Excel blades - though both are pretty old, so things may have changed, and I can't use their rocker profiles), the approximate positions of the sliding and 2 of the round holes are interchanged, and the hole spacing is not the same. On top of that, my MK and Wilson blades have rounded mounting plates (assuming that isn't a consequence of boot mounting), whereas my Ultima Matrix I Mounting plates are flat (though the front and rear plates are not co-planar).

It looks increasingly hard to compare blade shapes in a consistent manner. Clearly hole positions are too hard to correlate.

I think your idea of overlaying the toe picks is pretty good, though maybe that works well because neither of the blades you are using is meant for beginners, and both have almost exactly the same rocker profiles relative to those toe picks.

I'm fascinated that (your) Wilson Coronation Ace and Jackson Ultima Synchro blades are so similar in rocker profile. Of course, maybe your blades aren't new. Maybe your skate tech the profiles to be similar, as many skate techs do? (But I noticed earlier that my Ultima Matrix I runners for Dance, Synchro, and Supreme (freestyle) profiles were essentially identical, except for toe pick teeth and tail length.)

If I hold my printed rocker profiles against my blades, I can fairly easily fit the blade against the right radius profile. I can do that with both the main rocker (8' for my Ultima Supreme and Ultima Dance blades), and the spin rocker (about 1' for same). I suppose I could pick out precisely where they intercept (the sweet spot) if I printed the profiles on transparency material - but ink-jet-compatible transparency material packs are fairly expensive. I guess one way to do this is in software, after scanning the bottom of the blade into an image.

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I'm guessing, Bill_S, that you only have 10.5" blades, so it isn't easy for you to figure out how blade shapes vary with length.

[Bill_S]

I'm guessing, Bill_S, that you only have 10.5" blades, so it isn't easy for you to figure out how blade shapes vary with length.

That's true, both the Synchros (brand new) and the Aces ( older) are 10.5" blades. I've been wondering myself about rocker-shape differences between various sizes of the same blade model. That's an intriguing question.

[AgnesNitt]

Well, it would be interesting to compare blades of different sizes. Scaling the rocker up must require some math, but on the other hand, it could be scaled physically (if you have good data on foot sizes.)

[beginner skater]

Very interesting. The sweet spot is where the   blade will spin easily. Is there any evidence that this is where the rocker curvature changes?

[Query]

Some time ago, the sharpener at Riedell told me that the front part of the blades (i.e., rocker sizes and lengths) were independent of blade length on MK and Wilson blades - but I haven't verified that.

If you think of it, rocker length affects turning ability, spin point, and jump characteristics. Quite possibly, you want the scaling different for different moves.

What it boils down to is that if an adult coach likes a blade, and assumes that blade will perform the same for a small child, it probably won't be true.

Very interesting. The sweet spot is where the blade will spin easily. Is there any evidence that this is where the rocker curvature changes?

People don't all spin at the same point, and many people spin on different points for different types of spin. I like the sweet spot because it is a point I can sometimes feel.