Hanging off on cruisers and "non" sport bikes?

[Thundurburd]

Originally Posted by Clint

At the moment I'm studying several programming languages and Microsoft development platforms in preparation for the most promising (read: only) job interview I've had to date, which happens in two hours. Wish me luck.

Good luck...

[leonidas]

Originally Posted by Thundurburd

Good luck...

Ditto.
Here's hopeing we hear some good news from you soon!

[Clint]

Thanks, guys. I'm sweating ice here.

[GeorgiaRoller]

Originally Posted by Clint

I'm a lifetime student who only knows enough to truly understand how much I don't know.

Clint, you complete me!

Knock'em dead on the interview. Take the cage not the bike.

[Rickster]

Originally Posted by Easy Rider

Well you see, that's not exactly true either because you aren't taking force VECTORS into account. The total force is likely to be about the same but it is applied in a different plane or vector.

If you have the proper lean, that is the proper placement of the center of mass, the forces will be applied to the contact patch in a way that will maximize the traction.

If the center of mass isn't leaned over far enough, part of those forces tries to push the bike and rider OVER and that portion of the force is NOT applied to the contact patch.

Too much lean and you low side. Not enough and you high side or run off the outside of the curve...... or both.

Well I'm just a poor dumb pipe fitter, and the toughest math problems I deal with can be solved using simple geometry, but I'm sure there is a formula that some math whiz has figured out that explains this down to a very finite number.

No offence meant, but I don't know what your background in math is, I do know that Clint's education includes quite a bit of math, so on subjects like this where I'm in over my head I usually will go with his calculations.

All that aside, I'm not quite sure you and I are talking about the same thing, my statement was directed at the amount of force that is applied to the tires, you seem to be talking about the force that is trying to push the rider off the bike, and well I understand that both of these things are connected , they are still quite different.

The force as it is applied to the tires involves all the weight of the rider & the bike together, it seems to me that the force you are talking about is just the force as it is applied to the weight of the rider.

I can see where there would be a slight (very slight) decrease in the amount of force applied to the rider if he were leaned over. because he would be slightly closer to the pivot point of the arc of the circle they are traveling, and therefor moving at a slower speed, the force that the rider feels would be significantly less leaned over because he would be being pressed into the seat rather than being pushed sideways if he were straight up & down.

But what I don't understand is how you feel that any of these forces can be separated so that they don't apply to the contact patch.

Best of luck Clint, go get em buddy.

[Easy Rider]

Originally Posted by Clint

Apparently you still don't believe the rest of us that shifting body weight doesn't change the dynamics of the system from the tire's perspective. We can't really have a conversation until you do.

I don't because it is not true.......or at least not usually.

If you shift body weight and then shift the bikes axis so that the total center of mass is unchanged, then sure, what you say is true. Unless you are shifting your but back and forth from one side of the seat to the other while going straight down the road, that NEVER happens.

When you and the bike are leaned over for a corner, the center of mass absolutley does change and the forces applied to the contact patch change. Until your understand that, we can't have an intelligent discussion.

[Easy Rider]

Originally Posted by Rickster

All that aside, I'm not quite sure you and I are talking about the same thing,

But what I don't understand is how you feel that any of these forces can be separated so that they don't apply to the contact patch.

This is getting WAY out of hand.

Clint said "the center of gravity doesn't change when you are leaned over".

I said " it really is center of mass and it absolutely DOES change when you are leaned over".

That's it; that's the whole discussion. All the rest is just smoke.

I never said anything about cornering forces not applying to the contact patch. I said that the forces applying to the contact patch CHANGE when you are leaned over, partly because the center of mass moves.......because it is true.

We've had this "discussion" before and it ended up in a draw of sorts that time too. I will try to remember not to take up the arguement again since it seems to be pointless.

[Clint]

You're really oversimplifying what I said, and that may be our point of contention.

[leonidas]

Originally Posted by Easy Rider

When you and the bike are leaned over for a corner, the center of mass absolutley does change and the forces applied to the contact patch change. Until your understand that, we can't have an intelligent discussion.

This sorta seems like it's between you two, but I'll throw this in anyway. I'm no scientist, nor did I stay at a Holiday Inn Express last night. This is just how it looks to me:
Hanging off the bike in a turn changes the center of gravity by lowering it,
and helping the bike to turn better. (I just read that in Motorcyclist Mag)
Turning also changes the piont on tire contact with the road (of couse),
and the type of pressure put on the "contact patch" into centrifugal force
rather than staight gravity.
The faster you turn, the more presure is put on the tire.

Here's some good reading:
Speed 101: Motorcycle Racing as Real-World Physics Lab | Edutopia

And here's something in responce to the original question:
(what was it again?
High-Performance Street Riding

[GeorgiaRoller]

Originally Posted by leonidas

Here's some good reading:
Speed 101: Motorcycle Racing as Real-World Physics Lab | Edutopia

Oooooooooh Pictures! Now I get it!

"Successful race riding is a lot like paying taxes: You want to push the rules as far as you can without breaking them."

Now that's a guy I can understand & respect all at the same time.

[Easy Rider]

Originally Posted by Clint

The CG of the entire system stays put regardless of the bike's lean angle, and therefore the lateral forces on the tire don't change.

Originally Posted by Clint

You're really oversimplifying what I said, and that may be our point of contention.

There it is......in all of it's naked glory.

I think the point of contention is the definition of "center of gravity".

[Easy Rider]

Originally Posted by leonidas

This sorta seems like it's between you two, but I'll throw this in anyway.

Thank you. Good reference!

"Gravity:The rider shifts weight into the turn
to help the motorcycle change direction and lower its center of gravity."

"The lean angle of the motorcycle shifts the center of gravity to the side,
causing the bike to turn, while the weight redistribution
lets the machine stay slightly more upright."

[Clint]

Rather than a little quote, which can easily be misinterpreted because it was written ambiguously, I'll submit to you a good discussion of the matter among real physicists (not journalists). Note the post following the diagram, which explains that the CG doesn't move laterally based on the weight shift of the rider, thought it may move up and down along the effective lean angle (which doesn't change anything).

All Things Motorcycle - Re: Hanging Off

[Thundurburd]

That's a good link. I consider the James Davis site the go to place for accurate info on the physics and dynamics of motorcycles. It can get very deep and difficult to understand at times though.

[Clint]

I know. I about choked on it.

[leonidas]

I was at the James R. Davis site while resaerching
this topic, but didn't post a link because I didn't
speak their language.
What the...?
"That is, 'mg' would remain 'mg' and 'mv^2/R' would still be 'mv^2/R'."

Wish I understood. A person can never stop learning.

[Clint]

mass, gravity, velocity (squared), turn radius

[leonidas]

Originally Posted by Clint

mass, gravity, velocity (squared), turn radius

ummmmmm....
Ok. I'm turning pure spectator from here on in this thread.

[Easy Rider]

Originally Posted by Clint

Note the post following the diagram, which explains that the CG doesn't move laterally based on the weight shift of the rider, thought it may move up and down along the effective lean angle (which doesn't change anything).

The center of mass moves.
You said it doesn't.
The reference you provided refutes your own statement.
Thank you.
Done.

[m50Joe]

Originally Posted by Clint

Sportbike tires actually increase area as lean is increased.

Wow, really?! So hanging off may not always be an improved situation?