
The force vectors on a skateboard during an Ollie - aatish
http://www.wired.com/2014/10/skateboard-physics-empzeal/
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lbotos
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)

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weaksauce
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

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cobalt
Well Rodney Mullen invented almost all of the tricks. (Including the more
famous ones like the kickflip and such)

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bch
Witness: [https://www.youtube.com/watch?v=uEm-
wjPkegE](https://www.youtube.com/watch?v=uEm-wjPkegE)

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ivan_ah
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/)

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thret
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.

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mbenjaminsmith
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.

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thret
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 :)

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

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frozenport
Well tracking software has been around for a while. I did something like this
for a highschool project...

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adwf
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.

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subdane
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!

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snowwrestler
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.

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Too
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.

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tjradcliffe
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.

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Terr_
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.

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chrisdone
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. :)

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chrissnell
> 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.

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doorhammer
> 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.

I think this is why a lot of people get injured as they get older. You just
don't realize how much less time you're putting into something you used to be
able to do really well, then you try something that used to be easy with less
flexibility and bam. problems, heh.

I ran an obstacle course recently after having not done it in awhile. I was
actually pretty surprised at how coordinated I still was (I'm 31, so I don't
have all the issues I could yet), but I felt the tightness during and was
sooooo sore the next day

I really need to start doing consistent balance drills and flexibility
training

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rosser
_I really need to start doing consistent balance drills and flexibility
training_

If that's your aim, I can't recommend a regular yoga practice highly enough.

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doorhammer
This seems absurdly obvious now that you've mentioned it :)

I'll have to seriously look into that

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Animats
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.)

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anonfunction
> 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.

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seestheday
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.

