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Author Topic: Hey MSF Coaches! I Need a Picture of Something  (Read 258 times)

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Online jadziadax8

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Hey MSF Coaches! I Need a Picture of Something
« on: February 16, 2021, 01:10:57 PM »
When I took the ERC ages ago, I remember seeing a page where they talked about how the area of the contact patch affected the magnitude of the friction force. Does anyone here know what I'm talking about, and if so, could you share a pic of the page? It's for my physics class on Thursday. Thanks!
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Online Vulcanbill

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Re: Hey MSF Coaches! I Need a Picture of Something
« Reply #1 on: February 16, 2021, 02:09:25 PM »
I'm not an MSF coach but I play one on parking lots all the time...

This? or something like it?

https://www.msgroup.org/Tip.aspx?Num=219#:~:text=The%20idea%2C%20according%20to%20the,%2C%20and%20Reserve%20(unused).

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Online Skee

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Re: Hey MSF Coaches! I Need a Picture of Something
« Reply #2 on: February 16, 2021, 03:16:27 PM »
Or are you looking for something more like this?  The diagrams does not illustrate the change in contact patch size attributable to deformation and tire profile as the bike leans, but they get the point across. 

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we calculate the lean angle based on turning acceleration and coefficient of friction
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I have no familiarity with what's in MSF manual - I joined as a lifetime supporter circa 1974 - pretty sure that membership has expired. 

Just trying to be helpful.   (If I find the illustration showing the effect of tire profile on force, I'll post it later - still looking.)
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Online jadziadax8

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Re: Hey MSF Coaches! I Need a Picture of Something
« Reply #3 on: February 16, 2021, 05:00:02 PM »
Those are good, thank you. There are some good pics of how the contact patch changes with lean angle too.

I remember a formula showing how friction was proportional to the square of the area of the contact patch, which is what I also really wanted to know.
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Online Vulcanbill

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Re: Hey MSF Coaches! I Need a Picture of Something
« Reply #4 on: February 18, 2021, 07:59:41 PM »
42
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Offline jimmy

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Re: Hey MSF Coaches! I Need a Picture of Something
« Reply #5 on: February 19, 2021, 12:09:05 PM »
So I'm not that bright, let's put that out there right now.

I read that the surface area doesn't impact friction.

I read a bigger contact patch, then, doesn't increase friction.

Then I read that a pneumatic tire doesn't behave "normally" when it comes to friction.

So, is the weight transfer under acceleration or deceleration responsible for friction, rather than contact patch size?

https://www.stevemunden.com/friction.html

https://forums.superbikeschool.com/topic/3231-contact-patch-vs-grip/page/2/

Is this why going to the "dark side" works for those who like it?

 :crazy:

Online Skee

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Re: Hey MSF Coaches! I Need a Picture of Something
« Reply #6 on: February 19, 2021, 04:05:24 PM »
Au contraire, corner traction is a confounding dynamic not easily explained in a simple steady-state diagram.  And I think you understand that only too well from seat-of-the-pants experience.

The angular forces change with the contact patch as the bike leans further into a turn.  The sidewall of a pneumatic tire may start to flex in response to the deformation caused by the flattening of the contact patch. 
The ratio between the dynamic and static coefficients of friction may also change with the amount of tire deformation as the angel of lean increases, although I may be wrong about that. 

In other words, there's a whole lot of sh!t happening really fast.  And while I think I understand it, I don't think I'd want to attempt further discussion without beer and cigars.  You get that, I'm sure.

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Offline OHScot

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Re: Hey MSF Coaches! I Need a Picture of Something
« Reply #8 on: February 19, 2021, 05:10:52 PM »
When I lean that far I need to pick the bike up.  After I heal...


Bet the CF of the pavement is not that constant either.
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Re: Hey MSF Coaches! I Need a Picture of Something
« Reply #9 on: February 20, 2021, 08:35:29 AM »
I started digging a little deeper - came to realize I understand very little - it's more than I'll ever want to know!

Grip Vs Lean Angle

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Online Vulcanbill

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Re: Hey MSF Coaches! I Need a Picture of Something
« Reply #10 on: February 20, 2021, 09:55:34 AM »
I do not require a molecular understanding of what's going on under me.  I require a fairly in depth but general understanding of the concepts of traction dynamics.  It's great to know the math but the math is only every accurate for a given moment in time.  The factors involved change so rapidly and have immeasurable (arguably) consequences from every point on the timeline to the next that I wouldn't be able to grasp a fraction of it anyway.  I know what stuff tends to be slickery and under what circumstances...most of the time.  I have a pretty decent understanding of what circumstances other than the tire and the road affect traction.  I suppose that's a mis statement.  Nothing other than the tire and the road really matter but it's the stuff that influences the dynamics of that relationship that we need to process as quickly and as far in advance as possible. 

That's my calculated risk.  I guess my own stupidity needs to be factored in as a risk factor as well.  :) 
If a person's primary concern is increasing freedom, they should prepare for a reduction in average lifespan.  ---  Misanthropist

If you say "Gullible" real slow, it sounds like "Orange"

Offline jimmy

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Re: Hey MSF Coaches! I Need a Picture of Something
« Reply #11 on: February 20, 2021, 10:09:10 AM »
I started digging a little deeper - came to realize I understand very little - it's more than I'll ever want to know!

Grip Vs Lean Angle

CAMBER THRUST© Tony Foale 1985 -- 1997

Bicycle and motorcycle dynamics


I know, right?

I found two of the links you posted when I went down the rabbit hole the other day.

I knew, because my tire profile is not perfectly round, my contact patch increases with lean.

I figured that more contact patch = more traction.  But maybe no.

I am still confident about my own riding.  Those who ride slower than I are wasting an opportunity, and those who ride faster are maniacs.   8)

Online Skee

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Re: Hey MSF Coaches! I Need a Picture of Something
« Reply #12 on: February 20, 2021, 10:38:30 AM »
I do not require a molecular understanding of what's going on under me.  It's great to know the math but the math is only every accurate for a given moment in time. 

The converse is what appeals to me.  I never saw the benefit of pure math until a prof took me aside and showed me that acceleration can be understood as the second integral of the time-distance line equasion. 

I spent a lot of time riding my Wee thinking about what caused the head buffeting.  I came to the conclusion there was a low pressure pocket of air in the center of the windscreen that caused high pressure streams to roll around the outer edges (as evidenced by drops of condensation on humid days in the vcenter of the screen  that dried very slowly).  Never had the b@lls to cut a hole in the center of the screen to test it out.  Along comes kawasaki and they solve the problem on the 2019 Versys by putting a hole in the center of the screen.  And rain doesn't blow through it because of the low pressure pocket. 

I love thinking about stuff like this while I ride.  But I wouldn't use an equasion to pick a corner line either.

The factors involved change so rapidly and have immeasurable (arguably) consequences from every point on the timeline to the next that I wouldn't be able to grasp a fraction of it anyway. 

I know, right?  :banana:
The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt.    Bertrand Russell

"The fishermen know that the sea is dangerous and the storm terrible, but they have never found these dangers sufficient reason for remaining ashore."   Vincent van Gogh