The Coolest Commercial, Check it out, it's awsome! Options

I think they did this video on a slanted floor. Mainly because the wheels going up hill and something else that looked fishy.

[anthony]

Did you guys read the article? They said the wheels were weighted on the inside of the tire so all they needed was the little nudge to roll uphill.

[Zeke]

I'm with Jeroen. That muffler or cat sure rolled alot of revolutions. And I couldn't stop the thing in the right places, but each tire would knock the next 1/2 the distance of travel, not to mention the inertia lost due to friction of the rubber meeting while travleing in opposite directions.

Jeroen and I are just a couple of spoil sports. (IMG:style_emoticons/default/blink.gif) <_<

[EdwardBlume]

Nice.

[Curvie Roadlover]

All in all a very cool commercial, and I could see how the tires rolled uphill if they were weighted on the inside, but, I have to agree with Milt. That muffler rolls about 2 revolutions too many.

[Jeff Krieger]

I could only watch a few seconds of the ad but I don't see how anything could roll uphill starting from a stop no matter how it's weighted. As I understand it, the only way a rolling tire can roll uphill is by converting its kinetic energy into potential energy and if it has no kinetic energy to start, it's not going to start rolling uphill no matter how it's weighted. The center of mass of the tire is going to try to get to the place of least potential energy.

[Russ K]

Jeff.. you're exactly right.. but thats exactly why the tires apppear to roll uphill. If a large point mass (larger than the wheel and tire itself) is initially at the top of the tire, it's highly unstable. the slightest bump will cause the tire to turn and lower the center of mass (and potential energy) of the system. It just looks funny 'cause you're used to the center of mass of a tire+wheel being at the hub. You'll notice none of the tires on the incline spin more that 180 degrees. (in fact they dont even make 180, if you think about it)

..sorry i didnt mean for that to turn into a mechanics lecture.

[bander]

The tires rolling uphill is cool, (IMG:style_emoticons/default/clap56.gif) and after reading the article and discussing it, we understand how it works. But, the casual TV viewer won't. The tires rolling uphill will discredit the entire ad. 99% of the viewers will say "cool but fake". :toilet:

[Zeke]

Dont forget that there could be some funny weight/balance tricks done to the tires.

Hello?

[SirAndy]

but thats exactly why the tires apppear to roll uphill. If a large point mass (larger than the wheel and tire itself) is initially at the top of the tire, it's highly unstable. the slightest bump will cause the tire to turn and lower the center of mass (and potential energy) of the system. It just looks funny 'cause you're used to the center of mass of a tire+wheel being at the hub. You'll notice none of the tires on the incline spin more that 180 degrees. (in fact they dont even make 180, if you think about it)

Russ is exactly right. It needs to be balanced VERY carefully. large mass at the TOP of the tire. the smallest push will make that mass go down and the tire will move uphill just enough to touch the next and get it going. i do agree that it looks fake unless you know how they did it ...

[Curvie Roadlover]

Yeah, but what got that muffler to roll so many times?

[SirAndy]

Yeah, but what got that muffler to roll so many times?

just looked at the video again. watch the tires carefully. you can see how they "accelerate" once tipped. the weight mounted to the top kicks in. the second tire, wiggles a bit back and forth after it hits the third. that's because the weight is now on the bottom and rocks the tire a bit back and forth.

the muffler is the same :-) there's a weight inside. look closely at the movement of the muffler. you can see that it is NOT rolling at a consistent speed. it "wobbles" as the weight inside comes up to the OT again. (what's OT "Oberer Totpunkt" in english?). aha, looked it up, it's TDC (top dead center).

also, watch the background and the wood-floor. they set it up in a large warehouse. the floor looks continues. the back is not a wall but just white screen panels placed with a offset and back-lighting. the whole set looks continues and genuine to me.
amazing!

Andy

[SirAndy]

ok, time to dig out my physics degree and explain how the tire thing works. (Alfred (or jeff k. as he calls himself these days) will love this!).

1. is the ramp
2. is the tire
3. is the weight inside the tire. important, the weight has to be more or eaqual to the weight of the tire itself. i'll come back to that in just a sec.
4. the force vector for the weight, going straight down.
5. the force vector for the tire. trying to roll down the ramp. (also tries to go down, but we don't want to make it too complicated, do we)
6. the lenght of which the tire is going to move "uphill"
7. the point where it will come to rest

and here is how it works:
first, you need to get away from the obvious, a tire moving up a ramp on his own. you need to look behind that and "visualize" what is actually going on. (Alfred, still with me?).
to prefectly balance the tire on the ramp, the weight has to be placed with an offset to the tire's TDC that is eaqual to the angle of the ramp. (actually, not exactly because we also have some friction of the tire to the ramp). this will hold the tire in place. if the weight was less than the weight of the tire, the tire would be able to "spin" the weight around the TDC and the tire would roll down or the placement of the weight would have to be so far to the right that the amount traveled upwards would be insignificant.

now any additional force (like something hitting from the left) will make the setup unstable. the weight will start moving STRAIGHT DOWN. but because it is attached to the tire, this will result in a clockwise rotation of the tire. the weight actually still goes down, while the tire moves up on the ramp. the tire will stop moving when the weight comes as close to the ramp as possible (point 7). by then the tire will have traveled the distance of 6. up the ramp.

everybody still with me?

Andy

[SirAndy]

the muffler is the same :-) there's a weight inside.

we actually all know that effect very well.
it's the same physics that apply to the flywheel on a engine.

no flywheel or very light flywheel, as soon as you cut of the force (get off the gas), the engine will stop spinning immideately.
heavy flywheel, and the engine will keep on going and slowly wind down.

weight in the muffler will kepp it spinning (for a while),
no weight in muffler, it'll only spin once or so and come to a rest.

Andy

[jonwatts]

You guys gotta remember that this was for a commercial in the U.K. where they don't have any technology to do this with computers. Remember this is the same country that gave us Dr. Who.

(flame suit on)

Dr. WHo! LOL! (IMG:style_emoticons/default/mueba.gif)

YET another great commercial.

http://www.adforum.com/affiliates/EvS/003/...97&TDI=VDez8str

[Jeff Krieger]

Oops! This solution is wrong. Check out my later post for the correct solution.

***************************************

Ok, Andy, I'm no physicist so you can correct me where I'm wrong.

Let the tire sit just at the bottom of a ramp which has a positive slope. If
the tire's center of mass is a distance r from the tire's center and the
center of mass is located at the top dead center point on the tire, then
it's height (y) above ground is given by y = r*[1+cos(a)] + r*a*sinb. Here
"a" is the angle formed between the vertical axis and the tire's (point)
center of mass. 12 o clock ---> 0 rads and 3 oclock ---> pi/2 rads etc. "b"
is the angle that the ramp makes with the horizontal axis.

Since the tire's mass (m) and the acceleration due to gravity (g) are both
constant, the critical points of the tire's potential energy (mgh) equation
are determined completely by the
the height of the tire's center of mass above the ground h = y =
r*[1+cos(a)] + r*a*sinb. For fixed r and b, dy/da = r*sinb - r*sin(a). The
critical numbers occur when r*sinb = r*sin(a), when a = b or a = [pi - b].
When the ramp makes an angle of b with the ground, the first critical number
occurs at an angle of a = b. You can verify that a = b produces a local
maximum. Therefore the tire has its maximum potential energy when a = b and
as the tire rolls further up the ramp its PE decreases until the angle a =
[pi - b] when it reaches a local minimum.

Here is a graph for y = r*[1+cos(a)] + r*a*sinb for the specific case when r
= 10 and b = pi/3. (In this graph x = a).

(IMG:http://persweb.direct.ca/aschwenk/PE.jpg)

[Curvie Roadlover]

Since the tire's mass (m) and the acceleration due to gravity (g) are both
constant, the critical points of the tire's potential energy (mgh) equation
are determined completely by the
the height of the tire's center of mass above the ground h = y =
r*[1+cos(a)] + r*a*sinb. For fixed r and b, dy/da = r*sinb - r*sin(a). The
critical numbers occur when r*sinb = r*sin(a), when a = b or a = [pi - b].
When the ramp makes an angle of b with the ground, the first critical number
occurs at an angle of a = b. You can verify that a = b produces a local
maximum. Therefore the tire has its maximum potential energy when a = b and
as the tire rolls further up the ramp its PE decreases until the angle a =
[pi - b] when it reaches a local minimum.

Here is a graph for y = r*[1+cos(a)] + r*a*sinb for the specific case when r
= 10 and b = pi/3. (In this graph x = a).

(IMG:http://persweb.direct.ca/aschwenk/PE.jpg)

I was just gonna say that.

[SirAndy]

Ok, Andy, I'm no physicist so you can correct me where I'm wrong.

Alfred, (IMG:style_emoticons/default/rolleyes.gif)

you forgot to mention what your point is (IMG:style_emoticons/default/wink.gif)

i can see that you came to the conclusion that, if the tire's center of mass is not at the center of the tire but at the top (in a slight angle, because it has to be stable ON the ramp), it will in fact roll UP the ramp a bit when pushed slightly towards the top of the ramp.
nice graph, btw. most of us have moved on from DOS about 15 years ago,
but still nice (it says STUDENT EDITION in the lower right corner!) ...
just imagine the quality of that graph at 1280 x 1024 x 32 ...

Andy