New website app that tells you how fast you can ride for a given turn on the street - Page 9 - KawiForums - Kawasaki Motorcycle Forums
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post #81 of 108 (permalink) Old 01-07-2013, 01:25 AM
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Quote:
Originally Posted by noamkrief View Post
Thank for your comment.
Any single track vehicle, motorcycle, bicycle etc will have the exact same lean angle per given radius and speed.

This concept is difficult for most to understand.
Lean angle is "the angle at which the force of gravity which is trying to pull you down is exactly offset by the centrifugal force being generated."

Represented by: lean angle = arctan(v^2/g*r)
v = velocity in m/s
g = 9.81 m/s^2
r = radius in meters

So, no. Mass of rider + bike, wheelbase, C.G. height has no effect on the relationship between radius, speed, and lean angle.

The easiest way I can explain this is the following:
When you travel in an airplane and the airplane turns, your cup of water is not spilling over. The water is perfectly level in the glass even though the plane is banking.

Now imagine a Cessna 172 flying at 140mph banking at 30 degrees
Now imagine a Boeing 747 flying at 140mph banking at 30 degrees

Will both fly the same radius arc? If you answered yes - you are right.

A Harley, a bicycle, and an Ninja zx6r are all going into a 200 foot radius turn at 50mph.
THEY WILL ALL LEAN 39.95 DEGREES to negotiate that turn. Period.


The data on my app is very accurate. For a given lean you have selected (your comfort level lean) it will show you at what speed each corner will yield for your given lean angle.


williamr - would you like to argue highschool physics with me? Have you discovered an amendment to the laws of circular motions formula that adds in parameters for mass?


oh SHIT, bitches!
b
bet ya didn't see that coming?

this fuckin guy.. i like him already.

even tho i totally shot his app down.. points gained back.



Quote:
Originally Posted by strat1701 View Post
Well the app itself is cool, and obviously the guy knows something about math/physics but real world application with it, no. Not to mention liabilities.

And someone beat me to it, the last thing I look at when I'm in a turn on the street or track is my speedo or anything in the gauge cluster. I'm looking at the apex/exit.
this.
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Originally Posted by RacinJason44 View Post
Yeah, I'm looking at your drawing and I see the differences. It makes sense.
sev is gettin jiggy with the math too!


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post #82 of 108 (permalink) Old 01-07-2013, 01:45 AM
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Reminds me of my dynamics class I was taking in college. Good math stuff.


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post #83 of 108 (permalink) Old 01-07-2013, 09:52 AM
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Quote:
Originally Posted by RacinJason44 View Post
Weebel, I am not at all convinced that lower CoG contributes to reduced lean angle at speed. I think your misunderstanding of physics may make it seem that way.

Also, cruisers have a lower CoG than sportbikes.


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CoG def affects it. Lean angle is proportional to your moment of inertia about the center of radius of the turn. By lowering your CoG you make this moment of inertia smaller. This difference is way smaller than pulling yourself down AND inside the radius of the turn though.

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post #84 of 108 (permalink) Old 01-07-2013, 10:13 AM
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Quote:
Originally Posted by whitehendrix View Post


oh SHIT, bitches!
b
bet ya didn't see that coming?

this fuckin guy.. i like him already.

even tho i totally shot his app down.. points gained back.
When did you turn into a sucker for incorrect physics?
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post #85 of 108 (permalink) Old 01-08-2013, 12:39 AM
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Did Jason really say that the centrifugal force of the wheels effects how far the bike leans? I'm hoping he was just quoting the OP.

I also like how Sev went all nerd math to say the exact same thing I did. At least it makes sense in my head lol. Deosnt really matter I quess if the outcome is the same. I just know how and why things work, that math is beyond me at present.

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post #86 of 108 (permalink) Old 01-08-2013, 02:19 AM
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Quote:
Originally Posted by weebel View Post
Did Jason really say that the centrifugal force of the wheels effects how far the bike leans? I'm hoping he was just quoting the OP.

I also like how Sev went all nerd math to say the exact same thing I did. At least it makes sense in my head lol. Deosnt really matter I quess if the outcome is the same. I just know how and why things work, that math is beyond me at present.
If you can't teach it you don't know it.

Also, the one time I went "all nerd math" (nice backhanded insult) it wasn't to say the same as you, it actually expressed the exact opposite of what you were saying and included the necessary forumulas to prove my statements. But have fun on your merry-go-round. Car physics do not apply wholesale to bikes no matter how much you want them too.

Of course I'm generalizing from a single example here, but everyone does that. At least I do.



Last edited by Sev; 01-08-2013 at 06:34 AM.
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post #87 of 108 (permalink) Old 01-08-2013, 02:25 AM
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I was bored at the spot one night just messing around, I was dragging my crash cage on the ground at about 10-15 mph. I have my idle cranked up so I'm not using the throttle..

In the first video you can see my body position was on top of the bike..


In the second video I am in a more classic body position and my idle is set at the same rpm it was in the first video, in this video my front tire washes out.. Same speed, same bike, same surface, different body position..


Looks to me like I have more lean angle in the first video but the video is crappy so I can't say for sure..

To me this kinda puts the poo poo stamp on the app..lol
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post #88 of 108 (permalink) Old 01-08-2013, 02:29 AM
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And how can you guys even have this argument without ever once bringing up centripetal force? lol I didn't read most of the thread but I did do a word search.
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post #89 of 108 (permalink) Old 01-08-2013, 02:32 AM
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Quote:
Originally Posted by weebel View Post
Did Jason really say that the centrifugal force of the wheels effects how far the bike leans? I'm hoping he was just quoting the OP.

I also like how Sev went all nerd math to say the exact same thing I did. At least it makes sense in my head lol. Deosnt really matter I quess if the outcome is the same. I just know how and why things work, that math is beyond me at present.
No Weebel Hawkings, I didn't say that.


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post #90 of 108 (permalink) Old 01-08-2013, 02:45 AM
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So Sev, looking at your drawing again, if you use the line drawn between the higher CoG point and the tire contact patch and slide the CoG down that line nothing will change, correct? Given the same speed and radius the lean angle of the bike should stay the same.


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