Blackstone Flat-Bottom V Thread

[Mimizk 114]

Thank you Afftondad,

Now I'm thinking as here,

1) Spinner dresser roughen surface of grinding wheel. It will affect finished surface of edge bottom.

2) Smoothness of the steel much affect gliding ability. This is just a common sense of skate science especially speed skate world.

3) In smoothness order, ROH>BFD>FBV dressing. The condition of BFD spinner is better than FBV's spinner from this view point.

4) It's so difficult to say difference of each FBV spinners by explanation. If we want to explain it subjectively, just we have to use it.

[AfftonDad 88]

Thank you Afftondad,

Now I'm thinking as here,

1) Spinner dresser roughen surface of grinding wheel. It will affect finished surface of edge bottom.

2) Smoothness of the steel much affect gliding ability. This is just a common sense of skate science especially speed skate world.

3) In smoothness order, ROH>BFD>FBV dressing. The condition of BFD spinner is better than FBV's spinner from this view point.

4) It's so difficult to say difference of each FBV spinners by explanation. If we want to explain it subjectively, just we have to use it.

However, it is not difficult to objectively say which spinner has more/less bite if you hold one of the numbers constant. The following would be objectively true...

70/50 72/50 75/50 80/50 82/50 85/50 88/50 90/50 92/50 95/50 98/50 100/50

<- Less Bite More Bite ->

Also The following would be objectively true...

90/50 90/75 90/1(00)

<- Less Bite More Bite->

Having just checked the full size spinners available in order to type the above, I see that Blackstone is in fact moving towards what I had hoped for; namely, a bunch of flat widths within a single edge depth. However, they are doing it for the 50 depth instead of 75. I have mini spinners and unfortunately, it doesn't look like they are doing it (yet) for the mini spinners. Plus, I have more 75 depth than 50 depth. Oh well.

I have not observed any roughness (in the edges as you state) due to FBV however, I sharpen my own skates. I would agree with Jimmy that if this is being observed it is due to the person doing the sharpening. I do agree however, that due to the differences in how a single point dresser applies it's dressing relative to how a spinner applies it's dressing, that FBV will be slightly less smooth than ROH LONGITUDINALLY (length wise along the blade). But in my opinion that shouldn't impact speed significantly since 1) those imperfections are longitudinal and 2) very, very slight. Someone earlier in this thread did some measurements with some very precise laboratory equipment and posted the results. The imperfections were very small. I think the most this will do is sometimes cause faint visible lines that run down the length of the blade. The difference between the types of dressings is that a single point quill maps itself onto the wheel in sort of a "1D/2D" manner where as the spinner maps itself onto the wheel in sort of a "2D/3D" manner.

[Mimizk 114]

Yesterday I had an icetime. The 90/50 was so good for recent soft ice!

This is the reason why I want to choose FBV rather than BFD. BFD is 5kinds. FBV is 23kinds. There is a huge difference between BFD X8 and X7. BFD is hard to choose instead of ice condition.

Afftondad,

I want to say. To say only "bite" factor, definitely we can get some answer relatively easily. I agree with your thinking. It's better to decide edge depth number at first. Of course there are some numbers and factors which make "bite" without this number. Edge depth, /50, /75, /1(100) are just one of those. But we are thinking that probably edge depth is the greatest number of making it. If chose edge depth, after we just choose suitable front number.

But people don't say exactly thing for choosing "glide". For example what is the best number for glide in these spinners, 100/50, 100/75 and 100/1? This question seeing glide from viewpoint of edge depth. Another, what is the best number for glide in these spinners, 80/ 75, 90/75 and 100/75? This question seeing glide ability from a viewpoint of bottom width to touch with the ice.

And also, I've been thinking for long time that it's helpful if Blackstone write spinners' edge angles without the 2 numbers.

Edited August 9, 2015 by Mimizk

[flip12 714]

I think it might be more helpful to shift the discussion from glide to drag. They're essentially inverses of each other, but the difference is, drag is something you can model physically, while glide is just what it feels like to have less drag.

Unless I'm picturing the scenario wrongly, isn't there less drag on narrower steel than wider steel (if everything else about the sharpening is held constant). I'm thinking anecdotally: Micron V2 steel attempted to replicate the decreased drag on speed skaters' steel, which is narrower than hockey steel. The greater width for hockey and figure skater steel being desirable for better spontaneous turning.

[AfftonDad 88]

I'm a electrical (software) engineer and it's been a long time since my core statics and dynamics courses, so this really isn't my area of expertise, but I think what you are suggesting might not be 100% correct. The physics of a sliding object, and in particular a skate, would be very complex to model. It would be (and probably has been) a good thesis project for a mechanical engineering or physics graduate student. The general equation for sliding friction is F = uN, where u is the coefficient of friction and N is the normal (downward) force exhibited and F is the resulting frictional force. You can see that there is no component in the equation that has anything to do with the surface areas in contact. Now this equation holds true only for non-deformable objects and we all know that ice IS deformable. So as the ice becomes less accurately modeled as something that is hard and more as something that is deformable, the general equation becomes less true and the surface areas begin to come in to play.

Now what would cause the ice to deform? Well the ice is able to melt at the point of blade contact due to the amount of pressure applied. The more pressure applied, the more it melts. The pressure applied IS a function of how much surface area there is in contact Think in terms of pressure in PSI, pounds per square inch, and it becomes obvious that the amount of pressure applied will be the amount you weigh divided by the surface area over which it is distributed. This means that as the surface area in contact is increased, the ice deforms less and the original equation once again becomes closer to being "correct". While this increased surface area does in fact increase the area over which you would have to calculate drag, the effect of drag becomes less and less significant. If I were going to try to push a car on ice, I would have much more success pushing a car that was sitting on a large hard flat platform than one that was sitting on four legs. That's why we put spikes on shoes for walking on ice.

So the long and short of it is, you generally want to increase surface area in contact with the ice to increase glide (reduce drag). This of course decreases bite though. The current hockey skate blade width of .110 inches is what has been empirically over time settled on as the "sweet spot" in this trade off for hockey. This incidentally is why FBV works. The whole point of it is that the FBV will sink in to (deform) the ice less than a ROH will. I think what Blackstone is saying about "decreasing the flat width increases the glide", is due to the fact that as the flat is decreased in width the blade becomes less able to deform (sink into) the ice, therefore increasing the glide.

As I said, not my area of expertise though... anyone with some real expertise in physics, please feel free to correct my amateurish mistakes in reasoning.

[flip12 714]

I've only had very basic physics as well, and that's certainly not adequate to explain what's going on. I'm pretty sure I have a faulty model in my head, but I'd love for it to be corrected.

To complicate matters further, the traditional explanation of pressure creating the liquid layer that makes skating possible has been challenged by resent surface science research (summary article from NYTimes: Explaining Ice: The Answers Are Slippery), though researchers have been unable to reach a consensus on what phenomenon actually is responsible. Still, whatever the nature of ice actually is, it probably doesn't change much in the physical modeling of how to interact with that slippery layer on skates.

My thought, with regards to the FBV producing less drag when the flat is wider is that it's actually an effect from the other factor--the depth of the bite. (I think we're on the same page-ish there.) Even if making the blade's flat wider were to increase drag (as my intuition tells me, though it is only an intuition), it might not do so nearly as much as the correlated adjustment of bite angle and bite depth would. I guess the way to check this would be to test the different settings by holding the first or the second number constant. If the depth is kept the same and the bite angle is changed or the bite angle is kept the same and the depth and width of the flat are changed, what is the effect on blade drag?

With FBV's particular shape, I can't see how to separate the effect of a wider flat from the other changes that automatically come with it.

[AfftonDad 88]

Yeah, I had already read that article before. Although I don't claim to fully understand it, I don't necessarily buy it. And I think that his view is still an isolated view compared to the conventional physics reasoning about why things slide on ice. I don't really think ice in itself is that slippery. It's my opinion that ice that is dry and has been sitting over night is less slippery than ice that has just been resurfaced and is not fully frozen yet. This is further supported by the observation we have all had that a puck sliding on wet ice slides very well while it is hydroplaning on top of the layer of water. But after is submarines into the water (deforms the surface it is sliding on) the other drag forces come into play and it comes suddenly to a dead stop. Also after a rink has been skated on, it is much less slippery than when it is fresh. The ice/snow is no less ice than the hard ice it is sitting on. if ice is "just slippery" as he states, the snow should be just as slippery as the hard ice. I think the snow just can be deformed much more easily than the hard fresh ice can, which causes the friction/drag factors to be a much greater contributor.

My experience is that you can touch a very dry piece of ice with your skin and for an instant or two it can feel sticky and almost rough, until a moment later when the heat (and perhaps pressure) of your skin melts it and causes a layer of water to form. Similarly, walking across a sheet of ice that is dry in street shoes is much easier than walking across a sheet of ice that has just been resurfaced and is still wet. In my opinion, it's all about the layer of water. And incidentally, that layer or water can be at the microscopic or molecular level (in other words not visible).

I agree with you that with a wider flat (and with edge depth and blade width constant) that the edge becomes sharper and therefore more easily causes the blade to cut into the ice. A blade that is "running deeper" in the ice is going to have more drag than a blade that is sitting on top of the ice. However, I think a true model for a skate blade has (although it is much more complicated than this simplistic view) a component for friction that goes up as surface area increases and a component that goes down as surface area increases. Furthermore, I think the rate at which they each increase/decrease is probably exponentially related to surface area such that at extremely narrow blade widths one is very large and one is very small and they flip significance at the other extreme. I think the effects are also very much directional. In other words the reason we have blades that are much longer than they are wide (and why speed skate blades are much longer than hockey skate blades), is because that's the direction we want to travel. If we made blades very wide we would gain a huge ability to slide side to side, but what hockey player (other than a goalie perhaps) would trade the ability to push off for the ability to easily slide from side to side? I think this directional aspect of things is also what makes the actual size of the WIDTH of the flat to be in fact insignificant to how "fast" you go. Because you are not really changing either one of the components (the one that increases with surface area or the one that decreases with surface area) very much in the direction that you care about for speed (longitudinally).

I think the bottom line on FBV is it works because ROH allowed you to sink into the ice an unnecessarily large amount. FBV allows you to sink into the ice less.

Edited August 10, 2015 by AfftonDad

[AfftonDad 88]

Here is another thing which supports my argument that less surface area doesn't always = less friction. Think of the action of pushing with a skate. You angle the skate such that the skate is on a single edge (if you pushed with the skate flat you wouldn't get much of a push). At the instant you start pushing with that skate, it has the absolute least surface area in contact with the ice of any time during skating (except when it is in the air during recovery). During this time of least surface area in contact with the ice, the frictional forces are at their absolute highest, allowing you to exert the maximum possible pushing force.

[RHINO61 1]

I was just able to try the fbv cut I went from 5/8 roh to 90/50 fbv and I really like it the change was easy to get used to and I noticed that I could glide better, get more speed and less tired, I think I will be sticking with it and maybe try the 90/75.

[hockeydad3 51]

Hello,

let us talk about the reasons for a pattern similar to fishskin with scales. It is very hard for me to reduce the pattern on the bottom of the blade after grinding the skates of my three boys. I use a X0-2 and there is no big difference between the orange and ruby grinding wheels.It is better when i use fineshine-oil but i was never able to produce a mirror-finish. In my opinion the pattern is caused by vibrations due to imbalances of the grinding wheel, the wheel-holder and/or the driving-belt.

What do you think? And what can i do against this phenomenon ?

[DEATHTRON 19]

How is your final slow pass(es) looking? Could be a myriad of other things as well.

Zach

[mnpucker 33]

I had a similar problem when I first started using my X02. Turned out I needed to apply more pressure on my passes. More pressure eliminated it for me.

[Davetronz 109]

A bit more pressure. A bit slower, more consistent passes. Check to see if your spinners are gunking up with any residue from the wheel. Ensure your spinner caps are hand-tight and not too loose. All of those have been things that have caused issues like that in the past.

[hockeydad3 51]

Now a picture of a goalieblade without fineshine.

[Davetronz 109]

Yeah, that's not too nice. Is that an attempt after the feedback you've received from us above?

To me, if you're doing the right pressure, the right speed, a slow, consistent final pass, you shouldn't have this issue unless your spinner is worn or not dressing properly, or there's a stone issue.

It also looks like you might be getting a bit of burning/overheating - but it's hard to tell from the picture.

Is your spinner "spinning" when you're dressing. Or is it stuck on a spot that has maybe worn down?

[hockeydad3 51]

It´s a picture before. The spinner is spinning and not worn. The pattern gets smaller when i reduce speed and pressure and use fineshine. I can feel the vibrations getting stronger in comparison from an empty wheelholder the wheelholder with the upper nut and a wheelholder with a grinding wheel. Burns can happen if the speed is to low. When i use fineshine the black line on the wheel is not consistent.Could this mean that the wheel is not dressed equally ?

[Davetronz 109]

You mean the line on the wheel kind of waves up and down vertically as you spin the wheel with your hand or as it spins down after turning off power?

Typically, whenever I've had this problem, my spinner has been worn, and it seems to happen more frequently with our FBV spinners as opposed to ROH.

It's also happened when I've had a wheel that hasn't been formed/manufactured properly - but those were cheaper wheels from a non-OEM source.

[hockeydad3 51]

The black line changes horizontally. One third of the circumference of the wheel has a black line fading on the beginning and the end and one third has almost no line.

Edited August 19, 2015 by hockeydad3

[sticktime 12]

Is there a difference in in the end result if you use fbv or bfd? I know that it's blackstone and blade masters versions.

Also, I did try the bfd in a 1/2 equivalent, think it was x6? Not sure. But, what I noticed, apart from the INSANE ice that you get, is that the first 2 or 3 steps when you quick start or really trying g to dig in to get going if just gliding seem to be slippery, as in my skates were sliding out. I'm wondering if I went with the 3/8 equivemt of the bfd if that would grip more AND have the same great glide?

And would this hold the same for blacktone's version.

Edited August 19, 2015 by sticktime

[AfftonDad 88]

I would have to guess that the only way that you could get that fineshine line coming and going as it goes around the wheel like that would be that the wheel "sticks out" more in one part than it does in another. I would think that could be caused by 1) the hole in the wheel being slightly off center OR 2) the wheel being "not true" (out of round). Either one of those cases should be taken care of once you dress enough off a new wheel to get it to "true". A third case would be if there is some periodic mechanical movement or wobble in the machine (in sync with the rotation of the wheel). I don't know where that would come from but that would be a pretty significant problem. If it is, I don't think it would be a "wobble" or a "non-perpendicularity" because in addition to the line getting fainter and darker, if it were a wobble, I would think it would also move up and down relative to the top and bottom of the wheel (which your picture doesn't seem to indicate is occurring). Rather, it would be a translational thing that would cause the wheel to move in and out as it goes around (while still staying perpendicular/level).

I've had out of round (or perhaps hole off center) wheels before that I have had to dress more than normal to get rather large vibrations to go away. Whenever I put a new wheel on my X-01, I try to minimize the vibrations from the start. I first put it on and if its smooth, good. If not, I rotate it 180 degrees. If vibration improves over the original then I use the new position. if not or if there is still too much, then I try the +/- 90 degree positions. I use whichever of the four positions produces the least vibration. Then I dress it until the remaining vibrations go away.

If your problem remains after a lot of "meat" has been taken off of the wheel (enough to ensure that it is true), then I would think it is either technique OR some mechanical issue with the machine. However, I don't see how technique could produce that line fading like that. The wheel is moving way too fast and not in sync with anything you are doing to produce a symptom like that.

EDIT: I would think you would be able to check that theory about the wheel moving in and out by putting a skate in the holder just barely touching the runner and then rotate the wheel slowly by hand, checking to see if the space between the runner changes (it's going to be very slight). This wouldn't test for something that might be occurring only when the sharpener is "under load" though. But if you did observe it happening, then that would at least tell you something. You of course should see a bigger gap where the line is faint and a smaller gap where the line is dark.

Edited August 20, 2015 by AfftonDad

[Davetronz 109]

That's an odd pattern on your stone...

It's not rubbing on anything anywhere while spinning?

Even with wobble or an uneven stone, at the speed that it spins, you'd assume that your pressure would be contacting different points at the wheel as it rotates to "blend" that pattern in.

I haven't looked back in time to see if this has been answered, but have you asked Blackstone about it or shown them the pattern?

[AfftonDad 88]

Now that I think about it, the specs of the X-01 say that it spins at something less than 5500RPM (that's a "no load" speed). If I were to guess, I might guess that it spins at about 2/3rds the no load speed... that would put it at around 3666 RPM. That would mean in the approximate one second pass that I do, there would be around 61 fish scale marks on a blade... On a typical blade that would put them about 0.47 centimeters apart. That sounds about right. I think the reason a slow final pass will reduce the apparent fish scale is that if your 1 second pass becomes something like a five second pass, the space between the marks becomes less than a millimeter, making them much less noticeable.

That's an odd pattern on your stone...

It's not rubbing on anything anywhere while spinning?

Even with wobble or an uneven stone, at the speed that it spins, you'd assume that your pressure would be contacting different points at the wheel as it rotates to "blend" that pattern in.

I haven't looked back in time to see if this has been answered, but have you asked Blackstone about it or shown them the pattern?

Most of the force is applied across (x-direction) not in (z-direction). Also I think that the approximate 61 times a second that the wheel would bump you back out would effectively keep you from moving it in against the "low spots". I just don't think the relatively small pressure applied inward would be enough to modulate in the z direction that quickly.

Edited August 20, 2015 by AfftonDad

[chiefs17 2]

I can feel the vibrations getting stronger in comparison from an empty wheelholder the wheelholder with the upper nut and a wheelholder with a grinding wheel.

You have discovered the poorly machined wheel arbor that Blackstone refuses to acknowledge. In your experiment you are adding mass with every piece you add to the wheelholder/arbor (upper nut, and grinding wheel), this exacerbates the problem.

I had the same issue with my X-01 when I first purchased it. My machine would vibrate and dance off the bench if I let it. I took the wheel arbor off and the machine was so quiet that I couldn't believe it, that's when I knew the arbor was bad. I even sent the wheel arbor back to BS and got a replacement arbor, same issue. Talked to Steve and told him of the problem, he insisted the wheel arbor has to be good because it was done on a CNC. No, that just makes them all the same. If the center hole is machined off-center, like I discovered, then it will vibrate.

I had a machinist where I work put the wheel arbor in his very expensive precision lathe, then show me the runout with a dial indicator. It was about .015" of runout, that's a lot when something is spinning at 5500rpm. So I then had the machinist clean up the entire part, resurfacing the face that the grinding wheel sits on and also centerbore the center hole of the arbor referenced from the round part of the arbor that the center of the grinding wheel sits on (hope that makes sense).

I now have to use shim stock between the motor shaft and wheel arbor, but that's fine by me. My machine runs much smoother now. and I have far less problems with finish.

I only wish I took a video of the problem and solution so that I could post it somewhere for everyone to see, but I didn't.

Here's something everyone can try. Take your grinding wheel off and turn the machine on. It won't sound much different. Then take the wheel arbor off, remember there are 2 set screws in that hole. Turn the machine on and listen to how quiet it is.

[AfftonDad 88]

You have discovered the poorly machined wheel arbor that Blackstone refuses to acknowledge. In your experiment you are adding mass with every piece you add to the wheelholder/arbor (upper nut, and grinding wheel), this exacerbates the problem.

Since the arbor center hole being not centered wouldn't make the wheel be off center (directly), what do you think causes the "bouncing" between the skate runner and the wheel?... The entire machine vibrating back and forth, the movement back and forth of the shaft (within the tolerance of the bearings) or some of both? If it is the entire machine that is moving, bolting it down might help some (mine is bolted down). I wonder if the issue would manifest with greater amplitude with an X-02 since it is not direct drive?

That makes sense as to why I have to do my rotating the wheel process when installing a new wheel. I'm essentially finding the spot where the imperfections in the mass of the wheel are 180 degrees out of phase with the imperfections of the arbor.

Your statement that "CNC will ensure that they are all made the same way" must not be entirely true, because your description of the amount of vibration you originally had is way more than I have even when I haven't tuned the wheel to the arbor.

Edited August 20, 2015 by AfftonDad

[AfftonDad 88]

If you had some way to add mass to the arbor, you could potentially balance it, similar to how you balance a ceiling fan or a car wheel/tire.

I guess you could try to balance the arbor by putting weights on the arbor without a wheel (with tape?) near the outside and moving them around the circumference until you find the minimum vibration. Then take the weights off and go 180 degrees from the spot where the weights were and begin to carefully drill out material until the vibration went away. Not as good a solution as a better machined arbor, but it might help.

Edited August 20, 2015 by AfftonDad