what holds a bike up?

[alex.s]

Link to original page on YouTube.

[Joshorilla]

Wrong. It's magic.



EDIT: Ok, not magic, but this is also a nice demonstration of how countersteering works.

[choneofakind]

That's not a demonstration of countersteering Josh. That's a demonstration showing the effects of angular momentum and torque.

Cool video alex. This is a fun experiment to do on your own as well.

[oblivion007]

Actually that plays a partial role in the dynamics of motorcycle stability.

Even if you have zero angular momentum, i.e, the effects you see in the video would not occur (this has been constructed before) bicycles are still very stable and then so are motorcycles. I'm looking up the article right now.

e:\ Here's a similar experiment, not as rigorous as the article/experiment I once found. The counter rotating wheel is of the same mass distribution and rotates opposite to the one in contact with the ground. Thus they have the same angular momentum's but opposite in direction, so a net angular momentum of zero. The fact that this was shown on a bicycle is pretty important as compared to that of a motorcycle because I would expect it to be difficult to remove the angular momentum of the crank shaft.

http://www2.eng.cam.ac.uk/~hemh/gyrobike.htm

[Joshorilla]

Originally Posted by choneofakind

That's not a demonstration of countersteering Josh. That's a demonstration showing the effects of angular momentum and torque.

Cool video alex. This is a fun experiment to do on your own as well.

I was always lead to believe the torque from the wheel when travelling in a forward momentum and when the force from the steering is applied to that system it causes the torque to lean the wheel?

[choneofakind]

Check out this thread:
http://www.ninjette.org/forums/showthread.php?t=100922

Basically, when you lean over, your center of mass is off to one side, and your normal force is at an angle other than 90 degrees. That means that the horizontal component of your normal force is the centripetal force that causes you to turn. The "centrifugal" force felt by the center of mass is large enough that the bike does not just fall inward towards the ground. Counter steering the opposite way brings the wheels back under the center of mass, and ends the turn.

[alex.s]

chode is wrong on several counts.

first of all, a normal vector is a unit vector (vector whose magnitude is 1) perpendicular to a surface. there would be no "horizontal" component of a normal force because force along a normal vector would be by definition perpendicular to the surface it's applied to.

secondly, picture instead of a wheel, a 10 sided star. the star itself has no mass but at each point there is a small weight. now spin the star. imagine its rotating on the x axis. each weight is trying to go straight but is pulled down along the axis of rotation by the connection to the star. now rotate the wheel around the Y axis to the left like you would steer a bike... what happens to each point? they still want to go straight. so what is straight when that axis is rotated? "straight" becomes leaning to the right. so the wheel trys to rotate clockwise around the Z axis. this is how you can steer while you are in a wheelie or in the air. when the wheel is in contact with the ground the combination left rotation on Y axis and right rotation on Z axis cause the wheel to pull the bottom of the bike away from the projected CG causing the entire bike to lean... as you lean over and stop applying rotational force on the Y axis, the bike naturally stabilizes from the forks trail

[choneofakind]

Normal was the wrong word. Sorry, I'm using ninjette as a quick distraction from my circuits hw. My brain is frazzled.

I'm backing out of this discussion for a while. Thanks for the good video alex.

[alex.s]

oh man... OWNED!

ignore homework. entertain me chode.

[choneofakind]

No, you're right. I don't think well in terms of angular momentum when I'm tired. I was thinking of a free body diagram of a leaned over bike (and used wrong terminology while doing so ) instead of thinking about what caused the bike to lean in the first place.

I'm not above admitting when I'm thinking of the wrong situation completely.

[Joshorilla]

So, I was right saying this is how counter steering works?

**** classical sciences, it's all about computer science, technically not a science, but if you went up to Dr Dre and told him he's not a real doctor he'll **** yo' ass up.

Anyway, I've discovered the hugs bisson, you can stop with your death machine france.

[choneofakind]

Josh that just made my evening.

There's always going to need to be people who are good at classical sciences. You can't just write a program to model something for you if you don't know how it works in the first place.

[alex.s]

if the pope doesn't believe in the higgs boson, how can he have mass?!?!

[CC Cowboy]

The Wheels on the train go round and round

Round and round

Round and round

The Wheels on the train go round and round

All through the town

The Engine on the train goes chug chug chug

Chug chug chug chug

The Engine on the train goes chug chug chug

All through the town



Smoke from the train goes puff puff puff

Puff puff puff

Smoke from the train goes puff puff puff

All through the town



The conductor on the train goes All aboard

All aboard all aboard

The conductor on the train goes All aboard

All through the town



The Wheels on the train go round and round

Round and round

Round and round

The Wheels on the train go round and round

All through the town

[Jono]

^^^
What he said!



Hahahahahahaha

[Motofool]

Originally Posted by Joshorilla

I was always lead to believe the torque from the wheel when travelling in a forward momentum and when the force from the steering is applied to that system it causes the torque to lean the wheel?

You were always lead to believe the right thing:

http://en.wikipedia.org/wiki/Precession

[dfox]

yay highschool physics! angular momentum is fun!

Originally Posted by Joshorilla

So, I was right saying this is how counter steering works?

there's a lot more to steering than just angular momentum and simple free body diagrams. You get into camber thrust and other things.

there's also a lot more to keeping a bike upright than angular momentum, rake has a role in it as well.

too much to start talking about in a thread... there's a few good articles online if you're good at searching.