How Bikes Steer Themselves

A well designed bicycle traveling at the right speed will steer itself, no rider required. Reporting in the journal Science, Andy Ruina, Jim Papadopoulos and colleagues investigated what physical forces are required for self-steering and found that there is more than one way to build a bike.

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IRA FLATOW, host:

Up next now, Flora Lichtman is here. Hi, Flora.

FLORA LICHTMAN: Hi, Ira.

FLATOW: You got a digital Video Pick of the Week?

LICHTMAN: Yeah, and I have no segue...

(Soundbite of laughter)

LICHTMAN: ...from our last segment.

(Soundbite of laughter)

FLATOW: It's a yes. It's been gloom and doom hour this hour.

LICHTMAN: We'll just brighten it up. Bright as the...

FLATOW: It's springtime.

LICHTMAN: It's springtime.

FLATOW: And a fancy turns toward...

LICHTMAN: Bicycles.

FLATOW: Bicycles.

LICHTMAN: This week, scientists a few them, Andy Ruina and Jim Papadopoulos among them published a paper in Science about this kind of amazing thing that I didn't know bicycles can do. Bicycles, if it's well designed - so not my old clunker but a good bike, moving at a certain speed will steer itself without a rider.

FLATOW: You mean, if you let it go, give it a little push...

LICHTMAN: Give it a little push you can try this at home...

FLATOW: Yes.

LICHTMAN: If you don't care about how...

(Soundbite of laughter)

LICHTMAN: What can happen to your bicycle. At - you know, for some amount of time, it will it'll sort of start to fall, and then the wheel will turn and it'll pop back up. It just it seems like magic. It will steer itself and stay balanced.

FLATOW: And scientists have been wondering for years, maybe in their spare time because a lot of...

LICHTMAN: Very few have really devoted their lives to this...

FLATOW: A lot of them ride bicycles, right?

LICHTMAN: Yes. And actually, people haven't been wondering, because they thought the case was closed. They thought there are these two physical forces, one is called gyroscopic torque and it's, sort of, you can see it when you spin a top or a gyroscope.

FLATOW: Remember those toys with the strings? You all - I know our listeners remember that.

LICHTMAN: I know. I remember after Ira showed me a video of one this morning.

(Soundbite of laughter)

FLATOW: Too young to have played with a gyroscope. Oh, and...

LICHTMAN: That's one force. And another is called caster trail. And everyone thought these were necessary. These were the physical forces that were keeping that bike up by itself. And what these guys found out was that they're not necessary. You can build a bicycle that doesn't have gyroscopic torque at work and doesn't have trail at work, and it still steers itself. And you might be saying, well...

FLATOW: I'm just saying, you know, it's another myth of science, you know?

LICHTMAN: Yeah.

FLATOW: Why certain - we know the old thing about why bumblebees fly and all that. We thought we knew...

LICHTMAN: Right.

FLATOW: ...but not necessarily true.

LICHTMAN: Right. It is another myth of science. And if you're a really serious bike enthusiast like these guys that I talked to who are really serious bike enthusiasts...

FLATOW: I could see that.

LICHTMAN: They were very excited about it. You know, this is big news. But I think there's also in this study some tips relevant to anyone who rides a bike.

FLATOW: Such as?

LICHTMAN: Well, I was - I learned that, you know, we think about learning to ride a bicycle as something that's kind of hard, or at least I did.

FLATOW: Right.

LICHTMAN: And part of it is kind of getting out of the way of the machine that can balance itself. So...

FLATOW: Let the machine do its thing.

LICHTMAN: Let it do its thing. That's what they said that, you know, you can really think about it differently. In fact, actually, Andy Ruina, we were talking about this, and I was like, you know, when I was seven, I learned. And he was like, seven? You're a little bit of a late bloomer, Flora. I was teaching my kids at age three to ride two-wheelers.

FLATOW: I would have to agree with...

LICHTMAN: I know. I took a poll in the office.

(Soundbite of laughter)

LICHTMAN: And I'm not sure about that.

FLATOW: And so, in our Video Pick of the Week, you could see Flora out there on her bike and some SCIENCE FRIDAY staff members there.

LICHTMAN: Katherine Wells and Aleszu Bajak were also bike riding with me this week.

FLATOW: And a beautiful day, and you showed us how the mythology of this happens and the possible other explanations, and a really interesting tiny little bike that they designed, right?

LICHTMAN: Yeah. And this really weird-looking bike. Maybe this will be the bike of the future.

FLATOW: The bike of the future. Maybe you could see it right now. It's up on our website on our SCIENCE FRIDAY Video Pick of the Week up there on the left side. And Flora in her bike helmet.

LICHTMAN: Very nerdy.

FLATOW: And she makes a cameo appearance at the end of this one. You don't want to miss that for all you Flora Lichtman fans. I know there are lots of them out there.

LICHTMAN: Oh, Ira.

FLATOW: Thank you, Flora.

LICHTMAN: Thanks, Ira.

FLATOW: That's about all the time we have for today.

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