7 ms·

The force vectors on a skateboard during an Ollie

194 points by aatish 12y ago

Terr_ 12y ago
It looks like the skater drags his shoes against the "lip" of the skateboard to get a bit more "forward" direction on takeoff, pulling it upwards.
- rosser 12y ago
  We are dragging the shoe on our forward foot, but it's against the "grip tape" (made from crushed glass in a bed of adhesive). The force of friction from the shoe sliding forward against the grip tape is, in conjunction with the upward force from striking the tail of the board against the ground, sufficient to lift the board. Coordinating those two motions is the essence of an ollie.
- chrisdone 12y ago
  Ollie is the hardest thing to learn in skateboarding. It took me and my friends a long time. I think it's hard to explain it, so it's hard to teach. It's rather that the initial smack or pop of the tail against the floor makes the board fly upward, which you can reproduce by just by stamping on the tail of your board. That was my first insight. You can do a standing Ollie with one foot: stamp it and as the board starts going up you shove your same foot to the right to stabilize it. After mastering that, a two-foot Ollie was just a matter of practice. Also, the longer you delay putting any downward force in the nose, the more air you get. I feel like I should make a video of a standing single foot Ollie, as two feet complicate demonstration, I think. The moving forward of the foot isn't for adding more forward velocity, a standing Ollie can get really high and land in the same place. A moving Ollie relies on your existing velocity, which should be pretty high. I've not skated for about 10 years, but I got a board recently to see if I still had it. Ollie'ing is like riding a bike, never forget how to do it. :)
  - chrissnell 12y ago
    > I've not skated for about 10 years, but I got a board recently to see if I still had it. Ollie'ing is like riding a bike, never forget how to do it. :) It's tough for me. I skated nearly every day of high school and not much since then. I got on a board a few months back and it was like starting all over again. The biggest difference that I noticed was my diminishing flexibility. I need to start managing that--my wife, a physical therapist, says that lack of flexibility in our 30's and 40's is highly correlated with likelihood of falls when we are elderly.
    - deleted 12y ago
      [deleted]
    - chrisdone 12y ago
      Good on you! I noticed I was initially afraid to just get moving on the thing. What about the skateboard falls? Partly why I stopped street skating was all the falls and ankle kinks. I still feel like I need to stage a fall on this new board just to break the ice. :-)
    - akbar501 12y ago
      > The biggest difference that I noticed was my diminishing flexibility. This is definitely the biggest change I've noticed. There is no way I could skate now like I did in college and high school as my body simply won't allow it. Also important is that I doubt I'd recover from a nasty fall like I did when I was younger. Lastly, even if I could physically move like I did before, the mental concern about the cost of a bad fall / breaking a bone / pulling a ligament / etc. would prevent me from landing any type of trick beyond the basics. One of my friends who skated with me a lot in college used to like saying that the biggest factor in pulling off a trick is "thinking that you're going to".
      - tomsthumb 12y ago
        > There is no way I could skate now like I did in college and high school as my body simply won't allow it. With some work you probably could. You'd be surprised by how many "older" dudes (40+) absolutely crush it at the climbing gym. It takes a damn lot of strength and flexibility for them to be able to do that.
  - jere 12y ago
    >It's rather that the initial smack or pop of the tail against the floor makes the board fly upward, which you can reproduce by just by stamping on the tail of your board. That was my first insight. I see this repeated over and over. Maybe I'm misinterpreting your comment, thought I've definitely seen it elsewhere such as this comment on the article: >It actually looks like he "bounces" the board while starting the ollie, which provides a portion of the initial upwards velocity of the board. Think about that for a moment. This is patently absurd. It's like trying to get several feet of air by crouching down and hitting the ground with a hammer. The collision is too elastic. I think the confusion might arise because a really strong smack of the ground by the tail coincides with more torque (torque, right?). Of course, you can easily ollie if your tail hangs over nothing at all; it's probably even easier because you can rotate further. IMHO, Terr's guess is exactly right. You get all the lift from pushing down the nose / dragging across the grip tape.
    - pacaro 12y ago
      > IMHO, Terr's guess is exactly right. You get all the lift from pushing down the nose / dragging across the grip tape. This is clearly not the case. The front foot guides the board, stops it rotating backwards, and is necessary to land the ollie, but it doesn't help get the board into the air. The back foot pushes down (HARD) on the tail, the entire board rotates about the back axle until the tail hits the ground. At this point the front truck (which has significant weight (relative to the rest of the board)) is moving up and the rear truck is stationary, the momentum of the entire system is now up - the skater now (simply!) has to lift the rear foot at about the same speed as the tail lifts off the ground, and use the front foot to stop the board from over rotating back.
    - pbhjpbhj 12y ago
      >Think about that for a moment. This is patently absurd. It's like trying to get several feet of air by crouching down and hitting the ground with a hammer. The collision is too elastic. // It's not at all like hitting the ground with a hammer [but hammers will bounce on concrete FWIW and even flip end over]. It's more akin to a see-saw that isn't fixed down. If the force at the back of the board is sufficient to overcome the weight of the board pulling it down at the front then the board will rotate lifting the front. Once the back of the board hits the floor there is a new pivot point, the rear tip of the board (https://www.youtube.com/watch?feature=player_embedded&v=339k4XEvbxY#t=4 https://www.youtube.com/watch?feature=player_embedded&v=339k...). Now the board is rotating - in the clip - anticlockwise. But the front foot prevents this rotation and provides a further pivot. You can do this experiment to demonstrate that a pivoted plank can jump. Take a ruler, place it on top of a rounded pen - this setup mimicking the rear wheel of a skateboard. Hit the ruler down at the short end and you'll see it flip up (it might take some practice!). Indeed the whole ruler, if it's short enough, might flip and continue rotating such that the long end goes up and over the short end - but this is because you don't have a front foot pushing that part down. Replacing the foot with your hand - as a barrier above the ruler preventing this continued rotation - leads to the ollie being imitated. The ruler jumps up with nothing other than a swift hit on the short end furthest from the pivot. ( ) hand imitates ( ) front foot ( ) ( ) ( ) ( ) ( ) hit ( ) down --------------------------------- O pivot, eg pen
  - ap22213 12y ago
    I wouldn't say it's the hardest, but it's definitely the first hard step. I learned to ollie in the summer of 1987. It had taken me and my brother about 6 months to figure it out. The hardest part was training our brains to be ok with it. Once we landed a few, it was then fairly simple. But, it was the landing that was most difficult. We intuitively understood the motion and forces required, but we resisted letting our back foot follow through. By 1989, we were able to do bike racks, picnic tables (with appropriate ramp angle), garbage cans. And, we eventually figured out the kick flip, which was the second hardest trick to learn (at first). Now, the 360 flip to handrail grind - that's a freaking hard trick that requires some guts to let oneself do. And, it's one of those tricks that requires a good video camera nearby to establish proof.
  - brc 12y ago
    Big moment in my childhood was learning to 'pop an ollie'. From that moment on, you could separate yourself from others with these seemingly impossible standing jumps up kerbs and over obstacles. I didn't ever really get much higher than maybe a foot on my best day, but it was great fun. Now I feel like finding a board just to see if I can. Sadly my Powell Peralta was lost with my Lego in some parental clean out while I was out being an adult that had flown the nest. I'd gladly trade my school photos and stupid artwork that was saved to get those back again.
- bronson 12y ago
  The "a-ha" moment for me was concentrating on driving my rear foot into the ground. No matter how you jump or drag your front foot, if you don't get a good solid "pop" on the tail, nothing happens. Felt weird at first but now it seems like it couldn't be any other way. (where "now" is 10 years ago, when I last ollied anything... wtf)
- agumonkey 12y ago
  It helps but it's not necessary. It's a game of shifting centers of rotation.[1] Kick the backend :: upward tilted lift, center : ~back wheels. Quickly slow the frontend :: upward tilted lift, center : ~front wheels. [1] it requires suppleness in choreography, that's why any kid can do it, they're swift; the window of execution for both steps are very tiny. And they ask you to uncouple your mind, your feet and your center of gravity. Mind altering leap of faith it is.
- swimfar 12y ago
  I always thought this was the most logical explanation. Look at how high people can ollie,[1]. This wouldn't be possible if it they were just changing the axis of rotation. And this video here shows the skaters clearly pulling the board up with the grip tape/front lip [2]. Sliding your foot along the board is one of the basic steps for olling. [1] http://www.youtube.com/watch?v=IYE-ZaXbzUg http://www.youtube.com/watch?v=IYE-ZaXbzUg [2] http://www.youtube.com/watch?v=339k4XEvbxY http://www.youtube.com/watch?v=339k4XEvbxY
  - fedlarm 12y ago
    Yes the Griptape is an essential part to make high ollies consistently. However ollie's are possible to do without griptape as well. Just a lot harder because you'll have a lot less control. The harder you slam down the tail of the board the more friction you get, the easier it is to pull the board up/forward.
lbotos 12y ago
If you like this and you haven't seen 1000fps flatland tricks: https://www.youtube.com/watch?v=aHrn3-Cb3iM https://www.youtube.com/watch?v=aHrn3-Cb3iM
- iaw 12y ago
  I hadn't seen that. It really emphasizes how much precision of timing/movement is required in order to pull off a trick.
- weaksauce 12y ago
  I was a decent skateboarder in my day but these tricks are an order of magnitude harder than anything that was happening in my day/era... the exception was rodney mullen. he was the only pro doing anything like that
  - cobalt 12y ago
    Well Rodney Mullen invented almost all of the tricks. (Including the more famous ones like the kickflip and such)
    - bch 12y ago
      Witness: https://www.youtube.com/watch?v=uEm-wjPkegE https://www.youtube.com/watch?v=uEm-wjPkegE
  - lloeki 12y ago
    I really dig what Killian Martin is doing in that regard: pushing limits, applied to an artsy end. [0]: https://www.youtube.com/watch?v=D_h-7Kp87OE https://www.youtube.com/watch?v=D_h-7Kp87OE [1]: https://www.youtube.com/watch?v=cbSbbY5ibas https://www.youtube.com/watch?v=cbSbbY5ibas
- aboodman 12y ago
  Also: http://vimeo.com/1340684 http://vimeo.com/1340684
adwf 12y ago
I'm less impressed by the skateboarding tricks and more impressed by the physics software that can derive all this from a video.
- frozenport 12y ago
  Well tracking software has been around for a while. I did something like this for a highschool project...
  - adwf 12y ago
    I guess it's just something I'd never seen before, impressive at first sight! I did all my physics quite a few years ago and don't remember video analysis like this, although I guess it wasn't really my focus anyway.
- iaw 12y ago
  The simple Ollie in that video is no where near as impressive as the tricks performed in the video lbotos posted (top comment currently). Unfortunately, I get the feeling the tracking software would have a hard time with any component of movement that isn't coplanar (including rotation).
- ap22213 12y ago
  Skateboarding is an incredibly fun sport. You should give it a try.
- Too 12y ago
  There's no advanced physics software required to get the data in the video, he's just plotting the second derivative of a line he got by tracing the center of the wheel. F is proportional to a :)
ivan_ah 12y ago
I really like the overlay of physics information in the video. It is so much easier to explain to students what acceleration is by showing it rather than asking students to imagine "the second derivative of the position function r(t)=(x(t),y(t))." Check out the software they used: http://www.cabrillo.edu/~dbrown/tracker/ http://www.cabrillo.edu/~dbrown/tracker/
subdane 12y ago
I never got any good ollies in high school. Watching the vids and reading the article I think I realized something I never understood. It looks like most of the skater's upward body acceleration is coming from using the the _left_ leg, with the right foot going along for the ride (and smacking the tail down). I always tried to get the major jumping lift from my right leg, while also somehow smacking the tail at the same time. I think I've always had it backwards!
- snowwrestler 12y ago
  The highest ollies come from jumping with both legs, and using the ankle of the foot on the tail (right if you're regular-footed) to flick the tail down and pop the board. It's basically a two-foot jump; the hard part is getting the board to stay with your feet.
  - Too 12y ago
    Jumping on a bike is also basically a two-foot jump, where you pull the whole bike up after yourself using the handlebars. There is no special "pull up the front first and then push forward" as many people believe. The initial jerk is just to get the handle bars above the COG so that you can actually lift the bike from there and to put your pedals above the balance point of the rear wheel so you can push down hard for the actual jump. This might seem strange at first but when you think of it, apart from the legs what parts of the body have enough force to jump yourself that high, it's not like you can magically jump higher just because you are standing on some weird contraption. On a bike you do get some help from preloading the tyres to give you a bit of bounce but that's minor compared to the rest of the movement.
Animats 12y ago
The motion capture shown is kind of limited. The wheels are tracked, but not the CG of the rider. Also, the video doesn't show the beginning of the ollie. It looks like, in this one, the rider did this entirely by loading up the springs in the trucks to get a bounce, rather than dragging the tail of the board. It's a good physical simulation problem. Now that Gazebo has a real physics engine (by Mike Sherman from Stanford) rather than ones from video games, it should be possible to do an ollie in a robot simulation. (The game-type physics engines use an impulse/constraint model for contacts, which is unrealistic when you have a collision followed by sliding.)
- anonfunction 12y ago
  > by loading up the springs in the trucks to get a bounce There are no springs in skateboard trucks. The force comes from pushing down on the tail and then shifting your front foot up the nose.
  - seestheday 12y ago
    There are bushings which will provide a small amount of spring, but your general points stands that the force comes from pushing down on the tail and shifting the front foot up to the nose to pull the skateboard up.
- aatish 12y ago
  No, it doesn't make sense to track the center of mass of the skateboarder here. If you're interested specifically in the forces on skateboard, you want to track the center of mass on the skateboard. If you include the skateboarder in your system and track the new modified center of mass, you will only see the effect of gravity, being the only remaining external force.
  - seestheday 12y ago
    Tracking the centre of mass of the skateboarder would give you an idea of how to get additional height on your ollie. Essentially sucking up your legs, bending at the waist and throwing your arms down will allow you to clear higher obstacles.
tjradcliffe 12y ago
You don't actually need any fancy software to see what's going on if you've mastered the fine art of free body diagrams: http://www.tjradcliffe.com/?p=1374 http://www.tjradcliffe.com/?p=1374 (not related to skateboards, but those damned wobbly suitcases). And the advantage of simple free body diagrams is they are amenable to relatively simple models, frequently involving simple harmonic motion: http://www.tjradcliffe.com/?p=1410 http://www.tjradcliffe.com/?p=1410 These are teachable skills, and while it's great we have software to help us out, I'm a sufficiently aged crustacean to see the value in learning to do these sorts of analyses formally, by observation and inference.
thret 12y ago
For anyone trying to learn how to do an ollie for the first time, the one thing that really helped me was this: do it on grass. I spent ages on concrete, and it is a lot harder. On grass the board doesn't roll and you don't get hurt if you fall. A bit like learning to walk on your hands - start in a shallow pool. Once you get comfortable with the motion translating it to a different surface is not that hard.
- mbenjaminsmith 12y ago
  Yeah, that's how I did it. Grass is helpful until you can get the board to come up close to level and land on it. For some reason it took me much longer to learn how to drop in on a ramp. I built an 8-foot ramp in high school (no vertical) and it took me ages (weeks, IIRC) to drop in without immediately planting a foot and running or falling down the ramp. When I finally nailed it I was so happy. Damn, I miss skateboarding.
  - thret 12y ago
    I remember the first time I dropped in too. It is another one of those things where if you don't commit all the way, you fail. Once you get it you have it for life. I think having my friends get it first helped me with that one! I'm impressed you built a ramp! Luckily there was a nice new outdoor skateboard park near my friend's house, we didn't have to build anything :)
- ratsimihah 12y ago
  Doesn't grass absorb most of the pop, though?
  - thret 12y ago
    You may be thinking of longer grass? It is just important that the board doesn't move forwards or backwards while you are practicing.

194 points by aatish 12y ago

Terr_ 12y ago

It looks like the skater drags his shoes against the "lip" of the skateboard to get a bit more "forward" direction on takeoff, pulling it upwards.

rosser 12y ago
We are dragging the shoe on our forward foot, but it's against the "grip tape" (made from crushed glass in a bed of adhesive). The force of friction from the shoe sliding forward against the grip tape is, in conjunction with the upward force from striking the tail of the board against the ground, sufficient to lift the board. Coordinating those two motions is the essence of an ollie.
chrisdone 12y ago
Ollie is the hardest thing to learn in skateboarding. It took me and my friends a long time. I think it's hard to explain it, so it's hard to teach. It's rather that the initial smack or pop of the tail against the floor makes the board fly upward, which you can reproduce by just by stamping on the tail of your board. That was my first insight. You can do a standing Ollie with one foot: stamp it and as the board starts going up you shove your same foot to the right to stabilize it. After mastering that, a two-foot Ollie was just a matter of practice. Also, the longer you delay putting any downward force in the nose, the more air you get. I feel like I should make a video of a standing single foot Ollie, as two feet complicate demonstration, I think. The moving forward of the foot isn't for adding more forward velocity, a standing Ollie can get really high and land in the same place. A moving Ollie relies on your existing velocity, which should be pretty high. I've not skated for about 10 years, but I got a board recently to see if I still had it. Ollie'ing is like riding a bike, never forget how to do it. :)
- chrissnell 12y ago
  > I've not skated for about 10 years, but I got a board recently to see if I still had it. Ollie'ing is like riding a bike, never forget how to do it. :) It's tough for me. I skated nearly every day of high school and not much since then. I got on a board a few months back and it was like starting all over again. The biggest difference that I noticed was my diminishing flexibility. I need to start managing that--my wife, a physical therapist, says that lack of flexibility in our 30's and 40's is highly correlated with likelihood of falls when we are elderly.
  - deleted 12y ago
    [deleted]
  - chrisdone 12y ago
    Good on you! I noticed I was initially afraid to just get moving on the thing. What about the skateboard falls? Partly why I stopped street skating was all the falls and ankle kinks. I still feel like I need to stage a fall on this new board just to break the ice. :-)
  - akbar501 12y ago
    > The biggest difference that I noticed was my diminishing flexibility. This is definitely the biggest change I've noticed. There is no way I could skate now like I did in college and high school as my body simply won't allow it. Also important is that I doubt I'd recover from a nasty fall like I did when I was younger. Lastly, even if I could physically move like I did before, the mental concern about the cost of a bad fall / breaking a bone / pulling a ligament / etc. would prevent me from landing any type of trick beyond the basics. One of my friends who skated with me a lot in college used to like saying that the biggest factor in pulling off a trick is "thinking that you're going to".
    - tomsthumb 12y ago
      > There is no way I could skate now like I did in college and high school as my body simply won't allow it. With some work you probably could. You'd be surprised by how many "older" dudes (40+) absolutely crush it at the climbing gym. It takes a damn lot of strength and flexibility for them to be able to do that.
- jere 12y ago
  >It's rather that the initial smack or pop of the tail against the floor makes the board fly upward, which you can reproduce by just by stamping on the tail of your board. That was my first insight. I see this repeated over and over. Maybe I'm misinterpreting your comment, thought I've definitely seen it elsewhere such as this comment on the article: >It actually looks like he "bounces" the board while starting the ollie, which provides a portion of the initial upwards velocity of the board. Think about that for a moment. This is patently absurd. It's like trying to get several feet of air by crouching down and hitting the ground with a hammer. The collision is too elastic. I think the confusion might arise because a really strong smack of the ground by the tail coincides with more torque (torque, right?). Of course, you can easily ollie if your tail hangs over nothing at all; it's probably even easier because you can rotate further. IMHO, Terr's guess is exactly right. You get all the lift from pushing down the nose / dragging across the grip tape.
  - pacaro 12y ago
    > IMHO, Terr's guess is exactly right. You get all the lift from pushing down the nose / dragging across the grip tape. This is clearly not the case. The front foot guides the board, stops it rotating backwards, and is necessary to land the ollie, but it doesn't help get the board into the air. The back foot pushes down (HARD) on the tail, the entire board rotates about the back axle until the tail hits the ground. At this point the front truck (which has significant weight (relative to the rest of the board)) is moving up and the rear truck is stationary, the momentum of the entire system is now up - the skater now (simply!) has to lift the rear foot at about the same speed as the tail lifts off the ground, and use the front foot to stop the board from over rotating back.
  - pbhjpbhj 12y ago
    >Think about that for a moment. This is patently absurd. It's like trying to get several feet of air by crouching down and hitting the ground with a hammer. The collision is too elastic. // It's not at all like hitting the ground with a hammer [but hammers will bounce on concrete FWIW and even flip end over]. It's more akin to a see-saw that isn't fixed down. If the force at the back of the board is sufficient to overcome the weight of the board pulling it down at the front then the board will rotate lifting the front. Once the back of the board hits the floor there is a new pivot point, the rear tip of the board (https://www.youtube.com/watch?feature=player_embedded&v=339k4XEvbxY#t=4 https://www.youtube.com/watch?feature=player_embedded&v=339k...). Now the board is rotating - in the clip - anticlockwise. But the front foot prevents this rotation and provides a further pivot. You can do this experiment to demonstrate that a pivoted plank can jump. Take a ruler, place it on top of a rounded pen - this setup mimicking the rear wheel of a skateboard. Hit the ruler down at the short end and you'll see it flip up (it might take some practice!). Indeed the whole ruler, if it's short enough, might flip and continue rotating such that the long end goes up and over the short end - but this is because you don't have a front foot pushing that part down. Replacing the foot with your hand - as a barrier above the ruler preventing this continued rotation - leads to the ollie being imitated. The ruler jumps up with nothing other than a swift hit on the short end furthest from the pivot. ( ) hand imitates ( ) front foot ( ) ( ) ( ) ( ) ( ) hit ( ) down --------------------------------- O pivot, eg pen
- ap22213 12y ago
  I wouldn't say it's the hardest, but it's definitely the first hard step. I learned to ollie in the summer of 1987. It had taken me and my brother about 6 months to figure it out. The hardest part was training our brains to be ok with it. Once we landed a few, it was then fairly simple. But, it was the landing that was most difficult. We intuitively understood the motion and forces required, but we resisted letting our back foot follow through. By 1989, we were able to do bike racks, picnic tables (with appropriate ramp angle), garbage cans. And, we eventually figured out the kick flip, which was the second hardest trick to learn (at first). Now, the 360 flip to handrail grind - that's a freaking hard trick that requires some guts to let oneself do. And, it's one of those tricks that requires a good video camera nearby to establish proof.
- brc 12y ago
  Big moment in my childhood was learning to 'pop an ollie'. From that moment on, you could separate yourself from others with these seemingly impossible standing jumps up kerbs and over obstacles. I didn't ever really get much higher than maybe a foot on my best day, but it was great fun. Now I feel like finding a board just to see if I can. Sadly my Powell Peralta was lost with my Lego in some parental clean out while I was out being an adult that had flown the nest. I'd gladly trade my school photos and stupid artwork that was saved to get those back again.
bronson 12y ago
The "a-ha" moment for me was concentrating on driving my rear foot into the ground. No matter how you jump or drag your front foot, if you don't get a good solid "pop" on the tail, nothing happens. Felt weird at first but now it seems like it couldn't be any other way. (where "now" is 10 years ago, when I last ollied anything... wtf)
agumonkey 12y ago
It helps but it's not necessary. It's a game of shifting centers of rotation.[1] Kick the backend :: upward tilted lift, center : ~back wheels. Quickly slow the frontend :: upward tilted lift, center : ~front wheels. [1] it requires suppleness in choreography, that's why any kid can do it, they're swift; the window of execution for both steps are very tiny. And they ask you to uncouple your mind, your feet and your center of gravity. Mind altering leap of faith it is.
swimfar 12y ago
I always thought this was the most logical explanation. Look at how high people can ollie,[1]. This wouldn't be possible if it they were just changing the axis of rotation. And this video here shows the skaters clearly pulling the board up with the grip tape/front lip [2]. Sliding your foot along the board is one of the basic steps for olling. [1] http://www.youtube.com/watch?v=IYE-ZaXbzUg http://www.youtube.com/watch?v=IYE-ZaXbzUg [2] http://www.youtube.com/watch?v=339k4XEvbxY http://www.youtube.com/watch?v=339k4XEvbxY
- fedlarm 12y ago
  Yes the Griptape is an essential part to make high ollies consistently. However ollie's are possible to do without griptape as well. Just a lot harder because you'll have a lot less control. The harder you slam down the tail of the board the more friction you get, the easier it is to pull the board up/forward.

lbotos 12y ago

If you like this and you haven't seen 1000fps flatland tricks: https://www.youtube.com/watch?v=aHrn3-Cb3iM https://www.youtube.com/watch?v=aHrn3-Cb3iM

iaw 12y ago
I hadn't seen that. It really emphasizes how much precision of timing/movement is required in order to pull off a trick.
weaksauce 12y ago
I was a decent skateboarder in my day but these tricks are an order of magnitude harder than anything that was happening in my day/era... the exception was rodney mullen. he was the only pro doing anything like that
- cobalt 12y ago
  Well Rodney Mullen invented almost all of the tricks. (Including the more famous ones like the kickflip and such)
  - bch 12y ago
    Witness: https://www.youtube.com/watch?v=uEm-wjPkegE https://www.youtube.com/watch?v=uEm-wjPkegE
- lloeki 12y ago
  I really dig what Killian Martin is doing in that regard: pushing limits, applied to an artsy end. [0]: https://www.youtube.com/watch?v=D_h-7Kp87OE https://www.youtube.com/watch?v=D_h-7Kp87OE [1]: https://www.youtube.com/watch?v=cbSbbY5ibas https://www.youtube.com/watch?v=cbSbbY5ibas
aboodman 12y ago
Also: http://vimeo.com/1340684 http://vimeo.com/1340684

adwf 12y ago

I'm less impressed by the skateboarding tricks and more impressed by the physics software that can derive all this from a video.

frozenport 12y ago
Well tracking software has been around for a while. I did something like this for a highschool project...
- adwf 12y ago
  I guess it's just something I'd never seen before, impressive at first sight! I did all my physics quite a few years ago and don't remember video analysis like this, although I guess it wasn't really my focus anyway.
iaw 12y ago
The simple Ollie in that video is no where near as impressive as the tricks performed in the video lbotos posted (top comment currently). Unfortunately, I get the feeling the tracking software would have a hard time with any component of movement that isn't coplanar (including rotation).
ap22213 12y ago
Skateboarding is an incredibly fun sport. You should give it a try.
Too 12y ago
There's no advanced physics software required to get the data in the video, he's just plotting the second derivative of a line he got by tracing the center of the wheel. F is proportional to a :)

ivan_ah 12y ago

I really like the overlay of physics information in the video. It is so much easier to explain to students what acceleration is by showing it rather than asking students to imagine "the second derivative of the position function r(t)=(x(t),y(t))." Check out the software they used: http://www.cabrillo.edu/~dbrown/tracker/ http://www.cabrillo.edu/~dbrown/tracker/

subdane 12y ago

I never got any good ollies in high school. Watching the vids and reading the article I think I realized something I never understood. It looks like most of the skater's upward body acceleration is coming from using the the _left_ leg, with the right foot going along for the ride (and smacking the tail down). I always tried to get the major jumping lift from my right leg, while also somehow smacking the tail at the same time. I think I've always had it backwards!

snowwrestler 12y ago
The highest ollies come from jumping with both legs, and using the ankle of the foot on the tail (right if you're regular-footed) to flick the tail down and pop the board. It's basically a two-foot jump; the hard part is getting the board to stay with your feet.
- Too 12y ago
  Jumping on a bike is also basically a two-foot jump, where you pull the whole bike up after yourself using the handlebars. There is no special "pull up the front first and then push forward" as many people believe. The initial jerk is just to get the handle bars above the COG so that you can actually lift the bike from there and to put your pedals above the balance point of the rear wheel so you can push down hard for the actual jump. This might seem strange at first but when you think of it, apart from the legs what parts of the body have enough force to jump yourself that high, it's not like you can magically jump higher just because you are standing on some weird contraption. On a bike you do get some help from preloading the tyres to give you a bit of bounce but that's minor compared to the rest of the movement.

Animats 12y ago

The motion capture shown is kind of limited. The wheels are tracked, but not the CG of the rider. Also, the video doesn't show the beginning of the ollie. It looks like, in this one, the rider did this entirely by loading up the springs in the trucks to get a bounce, rather than dragging the tail of the board. It's a good physical simulation problem. Now that Gazebo has a real physics engine (by Mike Sherman from Stanford) rather than ones from video games, it should be possible to do an ollie in a robot simulation. (The game-type physics engines use an impulse/constraint model for contacts, which is unrealistic when you have a collision followed by sliding.)

anonfunction 12y ago
> by loading up the springs in the trucks to get a bounce There are no springs in skateboard trucks. The force comes from pushing down on the tail and then shifting your front foot up the nose.
- seestheday 12y ago
  There are bushings which will provide a small amount of spring, but your general points stands that the force comes from pushing down on the tail and shifting the front foot up to the nose to pull the skateboard up.
aatish 12y ago
No, it doesn't make sense to track the center of mass of the skateboarder here. If you're interested specifically in the forces on skateboard, you want to track the center of mass on the skateboard. If you include the skateboarder in your system and track the new modified center of mass, you will only see the effect of gravity, being the only remaining external force.
- seestheday 12y ago
  Tracking the centre of mass of the skateboarder would give you an idea of how to get additional height on your ollie. Essentially sucking up your legs, bending at the waist and throwing your arms down will allow you to clear higher obstacles.

tjradcliffe 12y ago

You don't actually need any fancy software to see what's going on if you've mastered the fine art of free body diagrams: http://www.tjradcliffe.com/?p=1374 http://www.tjradcliffe.com/?p=1374 (not related to skateboards, but those damned wobbly suitcases). And the advantage of simple free body diagrams is they are amenable to relatively simple models, frequently involving simple harmonic motion: http://www.tjradcliffe.com/?p=1410 http://www.tjradcliffe.com/?p=1410 These are teachable skills, and while it's great we have software to help us out, I'm a sufficiently aged crustacean to see the value in learning to do these sorts of analyses formally, by observation and inference.

thret 12y ago

For anyone trying to learn how to do an ollie for the first time, the one thing that really helped me was this: do it on grass. I spent ages on concrete, and it is a lot harder. On grass the board doesn't roll and you don't get hurt if you fall. A bit like learning to walk on your hands - start in a shallow pool. Once you get comfortable with the motion translating it to a different surface is not that hard.

mbenjaminsmith 12y ago
Yeah, that's how I did it. Grass is helpful until you can get the board to come up close to level and land on it. For some reason it took me much longer to learn how to drop in on a ramp. I built an 8-foot ramp in high school (no vertical) and it took me ages (weeks, IIRC) to drop in without immediately planting a foot and running or falling down the ramp. When I finally nailed it I was so happy. Damn, I miss skateboarding.
- thret 12y ago
  I remember the first time I dropped in too. It is another one of those things where if you don't commit all the way, you fail. Once you get it you have it for life. I think having my friends get it first helped me with that one! I'm impressed you built a ramp! Luckily there was a nice new outdoor skateboard park near my friend's house, we didn't have to build anything :)
ratsimihah 12y ago
Doesn't grass absorb most of the pop, though?
- thret 12y ago
  You may be thinking of longer grass? It is just important that the board doesn't move forwards or backwards while you are practicing.