Why does a bike turn
- Thread starter MajBach
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I'll bet that you use both hands any time that you are not consciously thinking about it.
Of course that would be impossible to know since once you think about it, you are no longer not thinking about it.
It is the natural thing to do, and using both hands would give more precise control.
Of course that would be impossible to know since once you think about it, you are no longer not thinking about it.
It is the natural thing to do, and using both hands would give more precise control.
wheatonFJR
...
I use the inside hand on hard turns so my hands don't work against each other in the turn.
N4HHE
Well-known member
No, not that at all. The reason it is important to know what is happening is that many riders get hurt or killed in emergency avoidance situations when they yank the handlebars as if it was a steering wheel. That serves to throw the rider from the bike directly into that which one desired to avoid.The reason we think so little about the physics of steering is because it has no importance whatsoever in the outcome. Most of us physically learned how to ride a 2 wheeler before we even learned to add and subtract, so clearly an understanding of "how" it happens is not very important. Once you have learned through muscle memory what inputs are required, and what the outcome will be, there is no good reason to waste neurons deliberating over the physics that occur in between, unless of course you just enjoy cogitating.
Huh? You guys are scaring me. Didn't you ride bikes as a kid?
Not sure how one hand is fighting the other one when you push the inside bar and at the same time pull the outside one, obviously with some degree of control. I don't think yanking the steering wheel of a car works all that well either.
Not sure how one hand is fighting the other one when you push the inside bar and at the same time pull the outside one, obviously with some degree of control. I don't think yanking the steering wheel of a car works all that well either.
NTXFJR
Well-known member
The typical fork assy is rigid enough to overcome those imbalances which forces both forks to move at the same rate with each other. With a rigid enough assembly, one heavy enough spring and damper assy. on one side or the other would work just as well. In a balanced fork assy there is less induced drag on the bushings which act to keep the fork sliders lined up.
bigjohnsd
2021 BMW R1250GSA
NEPRT Bound I think
MajBach
Well-known member
I agree. And even in my never-ending but always dwindling thirst for knowledge, I do find it intriguing to understand how bees fly and why the toilet flushes clockwise. But in this instance, I'm more interested in establishing credibility to someone that has authored a highly recommended read within the biking community. If he has this one wrong, maybe some of the other other stuff that goes beyond letting the bike do its own thing is also wrong.
MajBach
Well-known member
I'm happy to read all these opinions. Surprisingly none have really shared my initial train of thought of why I felt this explanation is inaccurate. I envisioned the forces involved on a unicycle, or a motorcycle with solid steel rims or a quater rolled across the table the inevitable leans over and spirals inward. Certainly in the latter two examples, there aren't dissimilar radii that cause a differential turn but there is still lean.
MajBach
Well-known member
That article somewhat validates what I was implying. The author states that 40 years ago, bike tires were round (meaning cross-sectionally symmetrical) which would have the result of the contact patch not changing in shape regardless of how much lean there is.
The turning has nothing to do with the cross-sectional profile of the tire or the contact patch shape. That's a total fabrication.
On a racing bicycle the tires are as narrow as possible and have essentially no cross section, and they are inflated to extremely high pressures so that they offer the least possible rolling resistance, and so thee is very little squish, yet they turn just the same as a motorcycle.
Now... the real question is: Would a stationary motorcycle on a conveyor belt turn with no forward momentum?
On a racing bicycle the tires are as narrow as possible and have essentially no cross section, and they are inflated to extremely high pressures so that they offer the least possible rolling resistance, and so thee is very little squish, yet they turn just the same as a motorcycle.
Now... the real question is: Would a stationary motorcycle on a conveyor belt turn with no forward momentum?
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rushes
Well-known member
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NTXFJR
Well-known member
ionbeam
2 FUN
Search this term: +airplane +conveyor one of the threads this turns up should have about a 1,000 pages and is often referenced when there is no consensus on very simple things. Call it a Forum custom.How could it not be stationary if it has no forward momentum?
NTXFJR
Well-known member
Ah! I should have know Mr, Fred had some interlaced humor in there somewhere!
MajBach
Well-known member
On reconsideration, that does make sense. A steel ingot in the shape of a styrofoam cup would essentially have no contact patch yet it would still roll a circular path.
I think your hypothetical is genius! The answer to it would surely result in an answer to my post title. Im inclined to believe the bike would flop on its side.
wil780
Member
I'm not sure if you regard the topic of this thread as a simple thing, or if you're referring only to the +airplane +conveyor thread.
If it's the former, then it's simple only in a very restricted way. Of course, the front tire can generate a sideways force only if it is slipping sideways, although even that is too difficult for many journalists to understand. That's why there's so much nonsense on the subject in the motorcycle press and in books about riding.
If you broaden the question slightly, to "what forces cause the tire to reach and maintain the right slip angle for the corner", then it becomes an immensely complicated subject. The standard reference text, "Motorcycle Dynamics" by Vittore Cossalter, goes on for well over 300 pages. More recently a couple research groups in engineering departments at reputable universities have been constructing and testing models based on that text, and finding it incomplete. Their papers have been published in very prestigious journals, and the topic was recently selected by the British science newsmagazine "New Scientist" as one of the hottest areas of science. Other universities are establishing research programs on the topic and trying to recruit staff. It is not a simple subject.
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forehead slap
How does anything have NO forward momentum if it is NOT stationary?
How does anything have NO forward momentum if it is NOT stationary?
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ionbeam
2 FUN
MajBacH can't solve the conundrum of how a motorcycle goes around corners.
Form a hypothesis.
Devise a test.
Run the test while making observations or if relevant, taking measurements.
Think about the action and reaction from the test. Observe and repeat as necessary.
Mentally put it together.
Achieve enlightenment.
Form a hypothesis.
Devise a test.
Run the test while making observations or if relevant, taking measurements.
Think about the action and reaction from the test. Observe and repeat as necessary.
Mentally put it together.
Achieve enlightenment.
NTXFJR
Well-known member
Dammit Fred, I'm out of likes todayl! Can you take a rain check until tomorrow??
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