K2 did it a long time ago. Head does it in their intelligence line. Using piezoelectric fibers to reduce vibration and in the case of Head supposedly stiffen the ski during exposure to heavy vibration.
Has anyone tried using piezoelectric fibers or have any experience using board(s) that are built with them?
http://www.advancedcerametrics.com/pages/pzt_fiber/
I don't know what all that crap means, but I figure one of ya engineer types might get it.
piezoelectric fibers
Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp
I remember the K2s. I believe the slogan was "when its blinkin' its thinkin'".
I believe most of the info on that page pertains to crystal orientation in regards to voltage generation and displacements in respect to an applied voltage. Displacements are usually quite small (10^-12). My only experience is using them to position AFM tips.
In terms of vibration/stiffening: if I remember correctly any material will appear to stiffen at high frequency. Not my area of expertise and I could be wrong.
I believe most of the info on that page pertains to crystal orientation in regards to voltage generation and displacements in respect to an applied voltage. Displacements are usually quite small (10^-12). My only experience is using them to position AFM tips.
In terms of vibration/stiffening: if I remember correctly any material will appear to stiffen at high frequency. Not my area of expertise and I could be wrong.
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Head Monkey
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I used to ride a K2 Electra 167. It was a nice board… I rode that thing into the ground. It delaminated multiple times and I kept getting it repaired just for grins. After that I rode many different boards before I started making my own. The Electra wasn’t even the best board in my quiver at that time. In my opinion, it was a gimmick. I don’t think it was the same technology as the fibers you linked to, though. I think they just used very small, localized piezos to blink the lights. The amount of force these fibers can generate is probably amazingly small. If it actually works as advertised, and actually stiffens the ski, how much does it stiffen it by? I’d bet < 1%. I’m sure they have some lab measurement that shows they dampen vibrations at a couple of specific frequencies in a ski in a controlled test. K2 had a cool graph that went along with the Electra. Does it matter when you ride? Can you even feel it? I doubt it, and I’d assert that I couldn’t tell on the Electra… I just liked the sidecut of that board at the time…
Everything I know about snowboard building, almost: MonkeyWiki, a guide to snowboard construction
Free open source ski and snowboard CADCAM: MonkeyCAM, snoCAD-X
Free open source ski and snowboard CADCAM: MonkeyCAM, snoCAD-X
doughboyshredder: what you're looking at are simply properties of certain types of piezoelectric materials; namely, the constants that reflect how well they transduce or convert mechanical to electrical energy and vice versa. For example, the d33 value tells you if you apply one volt along the polarization direction of the material (the first '3'), then the strain along that same direction (the second '3') will be 241x10^-12 meters for the hard piezo material. In other words, it will expand by 2.41 angstroms! Not a whole lot, but definitely enough if you want to move some sort of probe or tool attached to the end of a piezoelectric material with atomic resolution. The d31 value tells you how much it will expand along the direction normal (perpendicular) to the material's polarization direction. The negative number indicates that the material contracts, which makes sense because when the material stretches along one direction, it has to contract along some other direction by conservation. Note, the 'hard' vs. 'soft' has nothing to do with how physically hard or soft the material is. The classification tells whether the material requires high or low voltage. For example, it's quite obvious looking at the d-values that hard piezos require a lot of voltage to get them to move compared to the 'soft' material.
At my day job I work with piezos and other active materials, mostly for nano-resolution positioning in the case of piezos, like the AFM example that brewster mentioned. In fact, one of my group's projects is designing a 3-axis high-speed positioning stage for a custom-built AFM system. The stage uses small piezo-stack actuators -- layers of thin piezoelectric ceramic materials (~0.1mm thick) bonded together and wired in parallel. These stacks can deliver thousands of newtons of force at a few hundred volts DC.
But I agree with Mike -- the K2 system was simply a gimmick. Though it's true that you can vibrate a piezo material and generate some power, the power generation is only enough to drive a small LED, and the marketing people obviously went nuts at the sight of that...
I don't want to get into efficiencies and such, but simply put, it will be difficult to embed piezos into a ski and try to use the vibrational energy to power other piezo materials to control damping. But if you're interested, look into the literature on power harvesting using piezos to get more insight. Oh, did I mention that piezos are ceramics and mostly brittle, so don't strain them too much or they will break. So forget about making bump skis.
Rather than use the vibrational energy of the ski, one can simply use a power supply to drive the piezos. This has been explored extensively for active vibration control of many types of structures, such as aircraft wings, building supports, etc. And it does work in some cases provided the range of motion is reasonable. So why not do this for skis? Well, one issue is the power supply. It would require too big and bulky of a power supply to effectively drive the piezo. It's not trival to build a small and lightweight power supply that delivers a few hundred volts to control a piezo. And I haven't even mentioned the required current, which increases with the speed at which you try to control a piezo material by the very fact that the material is capacitive. In other words, it gets really power hungry if you want it to move fast, in the case of damping vibration.
Anyway, I think you're better off designing a good ski/board by exploiting the basic properties of materials and where you place them in a ski/board. Also, tools like finite element analysis can be used to optimize a design...
At my day job I work with piezos and other active materials, mostly for nano-resolution positioning in the case of piezos, like the AFM example that brewster mentioned. In fact, one of my group's projects is designing a 3-axis high-speed positioning stage for a custom-built AFM system. The stage uses small piezo-stack actuators -- layers of thin piezoelectric ceramic materials (~0.1mm thick) bonded together and wired in parallel. These stacks can deliver thousands of newtons of force at a few hundred volts DC.
But I agree with Mike -- the K2 system was simply a gimmick. Though it's true that you can vibrate a piezo material and generate some power, the power generation is only enough to drive a small LED, and the marketing people obviously went nuts at the sight of that...
I don't want to get into efficiencies and such, but simply put, it will be difficult to embed piezos into a ski and try to use the vibrational energy to power other piezo materials to control damping. But if you're interested, look into the literature on power harvesting using piezos to get more insight. Oh, did I mention that piezos are ceramics and mostly brittle, so don't strain them too much or they will break. So forget about making bump skis.
Rather than use the vibrational energy of the ski, one can simply use a power supply to drive the piezos. This has been explored extensively for active vibration control of many types of structures, such as aircraft wings, building supports, etc. And it does work in some cases provided the range of motion is reasonable. So why not do this for skis? Well, one issue is the power supply. It would require too big and bulky of a power supply to effectively drive the piezo. It's not trival to build a small and lightweight power supply that delivers a few hundred volts to control a piezo. And I haven't even mentioned the required current, which increases with the speed at which you try to control a piezo material by the very fact that the material is capacitive. In other words, it gets really power hungry if you want it to move fast, in the case of damping vibration.
Anyway, I think you're better off designing a good ski/board by exploiting the basic properties of materials and where you place them in a ski/board. Also, tools like finite element analysis can be used to optimize a design...
Off on a slight tangent... we use piezo for vibration and stress monitoring on things like bridges. Its been used before in ski's for monitoring vibration and other movements, but it would really be gimmicky for vibration dampening.
However, in robotics we use something called muscle wires - these are wires that expand and contract depending on the current passed through them..
So combine piezo sensors to a computer to send signals to braids of musclewire throughout a ski - even break it up between tip and tail.. now you have some RoboSki's!!
don't you dare steal that name.. lol
However, in robotics we use something called muscle wires - these are wires that expand and contract depending on the current passed through them..
So combine piezo sensors to a computer to send signals to braids of musclewire throughout a ski - even break it up between tip and tail.. now you have some RoboSki's!!
don't you dare steal that name.. lol
I used to be a lifeguard, but some blue kid got me fired.
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doughboyshredder
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BigKam thanks for the excellent explanation. I really appreciate it. Sounds like you have a fun job! I have no desire to build with any piezoelectric devices or fibers, I was just looking for confirmation of my thoughts that Heads snowboard design is pretty much a gimmick.
RoboGeek that wire sounds similar to what Head is claiming with intellifiber, except that they are generating the voltage from the fibers.
I think, after reading the previous responses that there is no way the piezoelectric fibers are actually generating enough electricity to stiffen the fibers in such a way that the ski / snowboard would perform differently.
I recently read a stunning review, and I can't imagine the fibers are contributing to the feel of the board as much as was claimed.
RoboGeek that wire sounds similar to what Head is claiming with intellifiber, except that they are generating the voltage from the fibers.
I think, after reading the previous responses that there is no way the piezoelectric fibers are actually generating enough electricity to stiffen the fibers in such a way that the ski / snowboard would perform differently.
I recently read a stunning review, and I can't imagine the fibers are contributing to the feel of the board as much as was claimed.
RoboGeek: several years ago I started working with the so-called 'muscle wires'. I played around with Nitinol (nickel-titanium alloy) shape memory alloy (SMA). The material is really interesting and used extensively in stents and wires for braces. As you mentioned, they are used in some robotics -- I recall the BEAM walker robot. My work with them was modeling their behavior and trying to control them for positioning. I even built a simple SMA rotatory actuator that can be used for a joint in a robot.
Back then I thought about embedding them into skis. At the time I came up with the idea of making a shape-changing ski, ultimately a self-adapting ski. You know, a ski that relaxes its side cut when you want to go fast, and then tightens up for the trees and bumps. Obviously it's still a dream, but I tried to create a couple prototypes. Unfortunately the prototypes were not made with the muscle wires -- still not enough research yet to figure out how to do it.
SMA is really interesting material. Most metals when you heat them expand, but not so much. SMAs on the other hand undergo a phase change (from martensite to austenite or vice versa) when they are heated/cooled, and the phase change causes the material to contract! Note, the contraction only occurs when one-way SMA is heated. The contraction is massive: up to 8% strain! For one-way SMA, after heating and then allowed to cool, the material does nothing and remains in its contacted state, but its elastic modulus drops significantly allowing it to be easily stretched under load. Then when heated again, it contracts and returns to its 'trained state'. This behavior is exploited to create stents where body temperature ensures the stent stays expanded. With an appropriate restoring force or 'preload', SMAs make great actuators, but they are slow so probably not worth it for vibration damping.
Using SMAs in skis may work, but there's the issue of power and how to insulate the material from the surrounding cold temperature. I think snow is cold -- at least 32F
. So it's basically an engineering problem, but it seems to me that it may work because of the amount of strain they can provide as well as their force output. But there are other issues too....
At some point I'll try to resurrect my shape-changing ski. But if anyone is interested in working on the concept I'm willing to chip in. Maybe two or more heads are better than one.
doughboyshredder: i think you're right --- those fibers aren't doing much. If they are, have them show you the data.
Back then I thought about embedding them into skis. At the time I came up with the idea of making a shape-changing ski, ultimately a self-adapting ski. You know, a ski that relaxes its side cut when you want to go fast, and then tightens up for the trees and bumps. Obviously it's still a dream, but I tried to create a couple prototypes. Unfortunately the prototypes were not made with the muscle wires -- still not enough research yet to figure out how to do it.
SMA is really interesting material. Most metals when you heat them expand, but not so much. SMAs on the other hand undergo a phase change (from martensite to austenite or vice versa) when they are heated/cooled, and the phase change causes the material to contract! Note, the contraction only occurs when one-way SMA is heated. The contraction is massive: up to 8% strain! For one-way SMA, after heating and then allowed to cool, the material does nothing and remains in its contacted state, but its elastic modulus drops significantly allowing it to be easily stretched under load. Then when heated again, it contracts and returns to its 'trained state'. This behavior is exploited to create stents where body temperature ensures the stent stays expanded. With an appropriate restoring force or 'preload', SMAs make great actuators, but they are slow so probably not worth it for vibration damping.
Using SMAs in skis may work, but there's the issue of power and how to insulate the material from the surrounding cold temperature. I think snow is cold -- at least 32F
. So it's basically an engineering problem, but it seems to me that it may work because of the amount of strain they can provide as well as their force output. But there are other issues too....At some point I'll try to resurrect my shape-changing ski. But if anyone is interested in working on the concept I'm willing to chip in. Maybe two or more heads are better than one.
doughboyshredder: i think you're right --- those fibers aren't doing much. If they are, have them show you the data.