Your post scrip file (profile) sees to be built from the very limited amount of lines instead of curves. Not sure if the problem is in post scrip translation when I import it to CAD or low resolution of your post scrip code. Or is this tracing from your jiw saw cutting 

I am still puzzling where the main rocker ends and where spinning rocker start. Where is the centre of the blade profile and is main rocker somehow longer either side of the blade centre point. This is not so simple. Your tangent explanation solved one of my problems, but I am stuck again in the same problem than in the past. My profile arcs does have now smooth joints, but still lots of things is unclear.

Quote from: Query on October 04, 2024, 08:54:01 AM
With 2 rocker blades, you do not touch the toe pick while on the sweet spot.

This holds only if we accept your definition of a sweet spot (a sweet spot is defined as a spot in which the radius of curvature of the blade changes; a blade can have multiple sweet spots; a sweet spot does not depend on the position of the drag pick).  As we've discussed over many years now, there is no consensus on this definition.  You once cited ScarletSkater as an authoritative source, but I pointed out that they provided three different definitions of sweet spot, and you picked the one that agreed with yours.

ETA1:  According to you, with a Coronation Ace blade, after repeated sharpenings, you will need to trim the toepick to extend the service life.  But with an MK Pro blade, you won't need to.  This may make sense to you, but it doesn't to me.

ETA2:  You have created this confusing scenario (confusing even to you) in which some blades have one sweet spot and some blades have two (or more) sweet spots.  If the blade has only one sweet spot, that sweet spot is not correlated with the drag pick.  But if the blade has two sweet spots, the rear sweet spot is not correlated with the drag pick, but the front sweet spot is correlated with the drag pick (which contradicts your basic definition).  And you ask why this is so.  Again, perhaps you should revisit your definition.  Perhaps this confusion doesn't really exist and is an artifact of your own creation.

I noted in https://skatingforums.com/index.php?topic=8922.msg107565#msg107565 that the JW blades that have 3 rocker radius segments (and 2 sweet spots, by my definition as points where the rocker radius changes), the toepick touches when you are on the forward sweet spot.

With 2 rocker blades, you do not touch the toe pick while on the sweet spot.

This based on profiles at
https://scarletskater.wordpress.com/2017/06/01/choosing-figure-skating-blades/
and
https://scarletskater.wordpress.com/2017/06/02/blade-profiles/

I assume the blade doesn't sink far into the ice, so the sweet spot is horizontal when you are on it.

So - the forward sweet spot is only used for moves that use the toepick - e.g., scratch spins, 3-turns, etc.

Why is it there? I think you can feel (and hear) the toepick just as easily.

Consequences:

1. To retain this relationship, trim the toepick, or adjust the sweet spot position, when you sharpen your blades.
2. If you adjust the forward sweet spot position, to make it fall below the ball of your foot, you should also adjust the spin rocker radii, to scale them together.
3. You can never skate on the forward spin rocker segment. Exception: high jumps, because you sink into the ice.
4. Proper behavior of these blades is very sensitive to sharpening technique.

I'm still doing it for me.

Several CAD programs can input Postscript or PDF files (PDF files are easily derived from Postscript files - in fact I've done it.)

It turns out I made some algebraic errors in that code, concerning Toepick angles. I'm fixing that.

Also, looking at various photographs and tracings of blade profiles, it appears that all the blades I've looked at that have 3 rocker segments (i.e., 2 sweet spots in my terminology), when you rest on the forward sweet spot (which makes that spot horizontal), the drag pick touches.

So! It appears the forward sweet spot on such blades is specifically designed for scratch spins, and turns that engage the toe pick (like many people say to do in 3 turns). That is something I never understood before trying to write this code. (BTW I use 2 rocker segment blades, not 3 segment blades.)

I guess the back sweet spot is mostly designed for non-scratch spins?...

Thank you Query, I can see you have used lots of efforts to make your code. Unfortunately it seems it does not help me so much. Blade profiles which are in picture format are basically same as pencil tracings what I have from the different blades. Its not so easy to copy profiles by trying to overlay lines in CAD software. I can measure example radiuses of the blade with some accuracy, but not as accurately as I would like. Even bigger problem is define the point where radiuses changes. I will try to 3D print my own rocker radius gauge during the weekend. It uses ball bearings and measures radiuses from the edges of the blade, not from the hollow like Sid Broadbent tool does. Otherwise working principle is very similar. I hope it helps to measure profile radiuses more accurately so that I would have more clear overview from the different blades. If I can measure length of radiuses and radius it selves, rest is quite easy.

Attached file where you can see sketches where one is made with your instructions and using the Paramount skates profile data. In the next page you can see sketch where I have overlaid profile which I have made from the pencil tracing and profile which I made based on your instructions.

I will make 3D model from some blade profile as soon as I have time for that. It takes some time. I have planned to print also profiles kind a mirrored so that I have gauge what to put on top of blade profile to see if theory meets measured / informed profiles. 3D printer is super nice invention and gives me lots of opportunities to make what I need. 3D printed blade profile would be much more accurate template to make own blade than jig saw. You could use example wood router which follows this printed template. You will hear more about this later. At the moment I am focusing more to get 3D model / print from the one complete blade.

I've spent more time at this than I originally thought. I'm fixing some issues on that program right now:
1. I am creating a diagram that explains the input parameters.
2. I didn't take into account the width of the lines. In particular if I try to cut with a jig saw on the outside (rather than the center) of the printed lines, that would distort the shape, especially of the toe picks. Perhaps the suggested line width should be adjusted too.
3. I don't know how and if CAD programs deal with that - whether, when inputing Postscript, and/or images, they take that into account, when creating computer guided cutting and drilling instructions.
4. I can't afford AutoCAD, but there are free CAD programs I could play with that could maybe teach me how they are used. The ones I have looked up on the web so far can't take in postscript. But some of them might take in PDFs - and there are free tools to convert Postscript to PDF.
5. Likewise, a CAD program would need to take into account the width of the cutting tool. Again, I don't know if CAD programs take that into account.
6. I need an option to extend the cut lines at toepick corners, so I can cut them more accurately. And I don't know whether CAD programs do that either.
7. None of the tools I have found so far to convert Postscript to images correctly produce image more than 8.5"*11". So I scale down by a factor of two. Needs to be fixed. Or I need to print at a diagonal, and/or split the diagram in two, with clear marked points to tape the printed pages together. And/or to fix rotation, so the blade can be printed at a page diagonal. And/or, I produce my own scaled TIFF image, instead of Postscript.
8. I need to adjust the way lines at angles join together better. I though "butting" was best, because it is Postscript default but the corners look wrong.
9. I need to check that my pick angle calculations are right.
10. I need to add the rest of the runner to the diagram, and maybe produce one for the mounting chassis. And add countersunk mounting holes.

Some of these may be fixed within a few days. But learning about CAD programs will take longer. Sorry for the delay.

I have slightly expanded that

http://mgrunes.com/boots/ToKaitsu.zip

folder.


It now also contains:
DrawBlade.f90     My current attempt at a program to draw Postscript blade profile.
DrawBlade.txt      Parameter file for a sample run. My program can input this,
                          or prepare parameter files and outputs for any chosen dimensions
                          and toepick angles. I admit I haven't fully verified it is correct.
                          Note that this is not any particular blade, but was just a test run.
                          I used .5 factor scaling, because I haven't yet figured out how to make it work in landscape mode,
                          and couldn't fit the sample blade on an 8.5 by 11 inch page. But there are photocopiers that can
                          double the size of the output image. It is a text file.
DrawBlade.ps       The output postscript file. It is a somewhat human readable text file.
typescript            The program dialog that occurred while running that program. As you can see, it has text dialog,
                          not a graphical user interface.                         
DrawBlade.png     A PNG format image prepared from that, by an old version of Paintshop Pro. I selected 600 dpi
                           resolution, though paintshop can also do 1200 dpi.

Anyone know about Jerry's ISE Sabre Dance blades. They claim to copy MK Dance, at a much lower price.

https://figure8.ca/shop/index.php?route=product/product&product_id=2123

https://www.amazon.com/Figure-Skating-Blades-ISE-Sterling/dp/B07BNX8JCJ

I'm wondering about material composition, and whether they truly copy the rocker profile, toepick shape, and the slimline width at the bottom.

From these pictures
https://discountskatewear.com/mk-dance/?sku=SKU-1717-Blade%20to%20fit%20boot&utm_term=&utm_campaign=SO_Desktop&utm_source=google&utm_medium=cpc&gad_source=1

https://skatesus.com/product/mk-dance-figure-skating-blade/

I think the toe pick is a bit different.

I cannot find where I got the WilsonbladeRadius.JPG image. And it's probably somewhat out of date. Note that the position of the sweet spots is often changed by expert skate techs, to be close to underneath the ball of the foot. Not also that some people who say this are saying the entire spin rocker should be under the ball of the foot. There is no standardization of terminology or technique.

https://scarletskater.wordpress.com/2017/06/01/choosing-figure-skating-blades/
https://scarletskater.wordpress.com/2017/06/01/choosing-figure-skating-blades/
https://scarletskater.wordpress.com/2017/06/02/blade-profiles/

Note: these say many MK blades have 27" - not the 24" the image I found claimed.

https://figureskatingstore.com/blade-type-information/

https://ice-blog.riedellskates.com/know-toe-picks/ - says that spin rocker (what I call the sweet spot) should be slightly behind the ball of the foot. Many other people say it should be directly under, or slightly ahead of the ball.

https://www.afterness.com/skating/blade_rocker_measurements.html (Bill_s on this forum)

I've written a Fortran program that creates Postscript of the bottom profile of the blade, with toepick, but haven't tested it yet, cuz I need to get ghostscript running to see the output. It will take me a bit of time to fully debug it.

Perhaps you could extract the values your app needs from it, once I have it working.

What about the hardware that you have - what does it take and do? Can it cut, drill, and mill (making both sides of the cut piece the parallel to get a desired thickness near the edge) according to instructions? Is that common in machine shops?

Given that I want to play with many shapes, it might not make sense to go through you long distance.

I could get access to a machine shop on the Eastern shore of Maryland, by joining a club, but then I'd have to learn how to use it. Supposedly they offer lessons. But I'm not sure how much knowledge they a assume.

But I wonder whether a jig saw would be good enough...

And what about the idea of using a torch and hot oil to harden and temper steel (e.g., eventually 440C alloy)? Is it reasonably easy? Or would I need a blacksmith?