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Bicycles Baffle Scientists

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Old 09-22-11 | 03:01 PM
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Bicycles Baffle Scientists

Check this out:
Bicycles have been around since the early 19th century, and its basic design has actually changed relatively little for almost 200 years. You always had two wheels, a frame to connect them and a handlebar for steering, and you required a person completely devoid of shame to ride on it.

At the very least, you'd think that the guy who invented the damn thing knew what he was doing, but after more than a century of research, science has been forced to conclude that he was probably some kind of sorcerer. The first bicycles were invented, not through any kind of scientific procedure, but by dumb old trial and error. Even modern bike design schools admit that it's not engineering or computer knowledge that make a good bike designer, but instead "intuition and experience."

So, what happens when you ask scientists exactly what makes a bicycle stable? Or what keeps it going? Or how people ride them? Well, odds are they'll either nervously tell you that they have cookies in the oven and run out on you, or if they're honest, they'll give you a pretty big shrug. In fact, top bike researchers admit that, even though some people have come up with equations on how to ride a bike or how they think bikes work, those equations are pretty much fancy icing on top of a cake of cluelessness. One Cornell researcher even says that absolutely nobody has ever come to an intuitive understanding of what makes a bicycle do its thing.

For ages, scientists assumed that the gyroscopic effect (the force that keeps a spinning top from falling over) was the key for a bike's balance. But nope! In the '70s, a scientist disproved that theory.

So then, scientists thought that the principal factor for a bike's stability was something called the caster effect, or trail (something to do with the front wheel's angle away from the frame). But just this year, top bikeologists from Cornell and other universities formed an angry scientific mob, then torched and pitchforked that theory as well. They did this by building a goofy-looking bike that has no gyroscopic effect and no trail, but manages to stay upright nonetheless.

So scientists are essentially back at square one, as things such as steering geometry and the physics of stability are all going back to the drawing board. At least you can be secure in the knowledge that the humiliation you feel when you ride a bike is akin to the humiliation science feels when it's asked how a bike stays up.

Read more: 8 Simple Questions You Won't Believe Science Can't Answer | Cracked.com https://www.cracked.com/article_19442...#ixzz1YiWujZO0
I had learned the "gyroscopic effect" kept bicycles upright, but check out the science experiment video which counteracts that, and trail/caster.
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Old 09-22-11 | 03:02 PM
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Someone has been reading cracked
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Old 09-22-11 | 03:04 PM
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^ Yes, but there are linky's there to apparently actual scientifical articles.
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Old 09-22-11 | 03:35 PM
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Absolutely Unbelieveable!!!

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Old 09-22-11 | 03:49 PM
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I love Cracked.... except Gladstone. :-)
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Old 09-22-11 | 03:53 PM
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This effect predates bicycles. Coins have been rolling upright for millenia.
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Old 09-22-11 | 03:58 PM
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^ Makes sense.

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Old 09-22-11 | 05:57 PM
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It's been known for some time that gyroscopic effect is not important at all for stability. Then there's this more recent project.
https://www.scientificamerican.com/ar...lf-stable-bike
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Old 09-22-11 | 06:04 PM
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Originally Posted by Caretaker
This effect predates bicycles. Coins have been rolling upright for millenia.
Yap.



KeS
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Old 09-22-11 | 06:13 PM
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Originally Posted by kevin_stevens
Yap.



KeS
...that coin is from a time when the phrase "keep the change" became commonplace.
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Old 09-22-11 | 06:19 PM
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^ Looks like a time trial coin.
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Old 09-22-11 | 06:26 PM
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****ing bicycles, how do they work?

Um...

dumb old trial and error
and

intuition and experience
is how science works too. Now here's a video, and a spoof of that video, for all the science-haters:



Last edited by shawmutt; 09-22-11 at 06:30 PM. Reason: found clean version of the dirty songs
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Old 09-22-11 | 08:30 PM
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I figured it out when trying to ride wheelies and it's not that complicated. In order to not tip over to the right either you or the weight of the front end has to steer right in order to bring the bike back under your center of gravity. Leaning left means steering left. It even says something to this effect on a Wikipedia bicycle page. The reason this was important to understand is that it is the opposite when riding a wheelie. Falling right requires shifting the weight of the front wheel left. Very counter intutive to someone that has been cyclling for a long time.

Anyway, those folks at cracked are a bunch of a-holes. They grab some little snippet of information and run with it. As I've said Wikipedia already describes how a bike stays up. I read cracked when I'm bored at work and I don't know how many times I've caught them saying dumb crap that is just plain wrong.
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Old 09-22-11 | 08:36 PM
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"A bicycle stays upright while moving forward by being steered so as to keep its center of mass over the wheels.[13] This steering is usually provided by the rider, but under certain conditions may be provided by the bicycle itself."
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Old 09-22-11 | 08:45 PM
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Originally Posted by biknbrian
"A bicycle stays upright while moving forward by being steered so as to keep its center of mass over the wheels.[13] This steering is usually provided by the rider, but under certain conditions may be provided by the bicycle itself."
Err, that steering correction is ALWAYS provided by the bicycle. Try riding a bike with no rake and no trail and you won't get very far relying on just rider feedback.
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Old 09-23-11 | 10:51 AM
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Ride a recumbent and you will know what keeps a bike upright.
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Old 09-23-11 | 11:55 AM
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Why does the title of this thread make me think of Fox News or the New York Post?
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Old 09-26-11 | 08:38 AM
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Originally Posted by Dan The Man
Err, that steering correction is ALWAYS provided by the bicycle. Try riding a bike with no rake and no trail and you won't get very far relying on just rider feedback.

A bike was designed by MIT students that had no trail and had it's gyroscopic forces neutralized and, when pushed, still stayed up and steered to stany up by itself. I read this through a link on Ecovelo a while back, and unfortunately can;t find this link right now. If I find it, I'll post it.
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Old 09-26-11 | 12:55 PM
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Originally Posted by Hippiebrian
A bike was designed by MIT students that had no trail and had it's gyroscopic forces neutralized and, when pushed, still stayed up and steered to stany up by itself. I read this through a link on Ecovelo a while back, and unfortunately can;t find this link right now. If I find it, I'll post it.
Yes but it is still not balancing through rider feedback. In fact it had no rider. The fallacy of the original article in this thread was that they saw a bike that balanced without rake and trail and therefore concluded that no other bike balances using rake or trail either. But it's Cracked, so they have an excuse for being stupid.

The MIT bike does the same thing as a normal bike does to steer, just instead of using the weight of the bicycle and rider to turn the front wheel during a lean, it uses an extended weight hanging ahead of the front wheel. Same result, different mechanism. It doesn't preclude the normal function of a normal bike.
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Old 09-26-11 | 01:00 PM
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Originally Posted by ahsposo
Why does the title of this thread make me think of Fox News or the New York Post?
Because it's not loaded with inuendo and lies?
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Old 09-26-11 | 01:31 PM
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Who actually thought the gyroscopic effect had anything to do with balancing a bike ? That would make track stands impossible.
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Old 09-26-11 | 02:33 PM
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Originally Posted by Dan The Man
The MIT bike does the same thing as a normal bike does to steer, just instead of using the weight of the bicycle and rider to turn the front wheel during a lean, it uses an extended weight hanging ahead of the front wheel. Same result, different mechanism. It doesn't preclude the normal function of a normal bike.
That's proabaly a very good way to show what really does hold up a bike. A slight lean results in a turn into the lean which puts the bike back underneath the center of gravity. With a weight hanging out in front it would be obvious what was happening, but I'm sure it could be done with geometry or the nomal weight of front end components like handle bars that extend forward of the pivot point. As far a rider control goes, riding a bike with no rake and trail and no forward handle bar extension would probably be a lot like riding a razor scooter, possible but with no inherent stablity.
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Old 09-26-11 | 07:52 PM
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It may be useful to think about how a unicycle stays up. Not much gyroscopic effect in this case. The cyclist is providing 100% of the effort required to keep center of mass over *one* wheel. Unicycles are fun because it's a 360 degree problem, not just side-to-side. I used to be able to ride a unicycle, but after all this analysis I don't think I could do it again ;-)
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Old 09-26-11 | 07:59 PM
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Inertia. The secret ingredient in balancing a bicycle.
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Originally Posted by Bjforrestal
I don't care if you are on a unicycle, as long as you're not using a motor to get places you get props from me. We're here to support each other. Share ideas, and motivate one another to actually keep doing it.
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