17 ms·

Uncontrollability of a bricycle (2014) [video]

539 points by gballan 9y ago

gballan 9y ago
Paper is here: http://ruina.tam.cornell.edu/research/topics/bicycle_mechanics/overview.html http://ruina.tam.cornell.edu/research/topics/bicycle_mechani...
maaaats 9y ago
What you unconsciously do when turning, is to quickly turn it a bit in the other direction first in order to get the bicycle more to the other side of you, so you have a better balance point for the big turn. Not perfectly explained, sorry. But try this: Try following a straight marker on the road on your bike. It's very hard. When you start going too much to the right, you will find it impossible to actually nudge the bike back to the left, unless you accept that you have to go further to the right first. This also happens when driving close to a curb. It feels like it's sucking you in.
- Adirael 9y ago
  That's countersteering [1]. I find it very hard to explain but it's something that most people on a bicycle (at speed) or a motorcycle (again, at speed) do naturally. [1] https://en.wikipedia.org/wiki/Countersteering https://en.wikipedia.org/wiki/Countersteering
  - Moodles 9y ago
    I'm no physicist, but it seems the intuitive reason countersteering works is because when you turn, e.g. left, your center of mass also moves left because you need to lean left in order to turn. So if you turn left on your own this will move your center of mass left. And if you turn too sharply left your center of mass will be so far out that you will fall over. So turning right very quickly before turning left means that your center of mass suddenly shifts massively right, and therefore you get some extra time turning left while your center of mass is still busy shifting from right to left?
  - NLips 9y ago
    I'd like to especially highlight your 'at speed' point here. It's often claimed that _all_ steering on a bike requires countersteering, but that is false. Countersteering allows rapid change of direction, but if you're going in a straight line, then lean left and gently steer left (or just lean left and allowing the front wheel to steer itself), you _will_ go left, no countersteering required.
    - ozim 9y ago
      If you lean left, front wheel will "do" countersteering itself (same as noted). Since gyroscopic effect on bike is not so big and speed, mass is not bigger than rider it is not noticable. For motorbike you cannot just lean hence need for explicit countersteering because of much higher forces involved. So I think it is correct to say that countersteering is always required.
      - baud147258 9y ago
        > countersteering is always required Only on a motorbike.
        marodox 9y ago
        > If you lean left, front wheel will "do" countersteering itself The same applies to a bicycle.
        ioseph 9y ago
        > Only on a motorbike. Only above a certain speed, at low speeds countersteering will not work Similarly above a certain speed on a bicycle countersteering is the only way you can turn
        schoen 9y ago
        Some people seem to describe this difference as unconscious countersteering versus deliberate countersteering, that is, that the difference isn't really whether you're countersteering or not, but whether the countersteer is large enough that you have to do it "on purpose".
  - baud147258 9y ago
    On a bike, even at speed you can initiate a turn by simply leaning on the side.
    - marodox 9y ago
      The front wheel still kicks out in the opposite direction and counter steers for you due to the natural stabilizing properties of the bike
    - rplnt 9y ago
      Easiest way to try/prove this is ride without holding handlebars. You can turn corners easily. Limits (compared to regular turning) are your lowest speed is higher (where you'd lose balance without holding handlebars) and the fact your center of gravity and stability are messed up (can't turn as tightly). And self preservation of course.
      - baud147258 9y ago
        I've done a lot of riding without holding handlebars, so that's how I learned this. Another limits is that you've got a delay to reach the brakes, which can make it dangerous for others in addition to yourself. And I agree that having your center of gravity moved up really mess up your stability.
        maskros 9y ago
        Only if you've got a stupid racing bike with only hand brakes. Coaster/foot/back-pedal brakes are standard issue around these parts, and I wouldn't ever want to ride a bike without one.
        JoeAltmaier 9y ago
        Depends on how you ride. An adult in the US, you're on a road bike bent over the bars and going 15-20mph. Hands on the brakes at all times. I do a ride every summer with 20,000 like-minded people and if you see even one bike with coaster brakes all week its unusual.
  - rplnt 9y ago
    It's very easy to try. Go up to speed (20 km/h or so) and press on a handlebar, away from you. You will "turn" to that side even though the handlebars are moving in the opposite direction.
  - dahart 9y ago
    Counter steer happens at all speeds at all times on a two-wheel vehicle, it's just hard to notice at slow speeds, and confusing because you do steer right during the stable lean angle portion of a right turn, as depicted in the first image in that Wikipedia article. I think counter-steering is misunderstood since people assume it means that if you're turning right then your steering has to be left of center. But counter-steering is referring to the direction of change, the steering delta, not the absolute steering angle. You always steer in the opposite relative direction from what you'd do in a car. This is still true on a bicycle at 1mph.
  - arnarbi 9y ago
    Here's how I explained countersteering to myself: To turn left, I need to lean left. The easiest way to lean left is to pull the bottom of the bike, where the wheels touch the ground, to the right.
  - upofadown 9y ago
    Not fan of the term "countersteering". If you changed the mechanical direction that the handlebars rotated the front wheel I doubt anyone would bother to call it "prosteering". A better way to think about this is that bikes turn by banking. The method of controlling the angle of bank does not map in a simple way to the direction of turn.
    - NegativeLatency 9y ago
      Do you have a better single word or short phrase to describe it though?
      - upofadown 9y ago
        Well the aviation people, who also control vehicles that are controlled by banking, don't bother to come up with a special name. When teaching people to fly they first teach how the controls can be used to control the attitude of the vehicle (roll, pitch, yaw are the terms that are used). Then they start a whole new discussion of how various attitudes will affect where the vehicle will end up. Some things can't really be simplified (and perhaps shouldn't be).
    - dahart 9y ago
      > The method of controlling the angle of bank does not map in a simple way to the direction of turn. Sure it does! (Unless by "simple" you're ruling out derivatives). If your wheel angle is moving right, then your bank angle is increasing left (or IOW, your left turn is becoming sharper, left turn radius is decreasing). While your wheel angle is moving left, your bank angle is increasing right. Whenever you stop moving the wheel, your bank angle will stop changing and you will be in a constant radius turn. > I doubt anyone would bother to call it "prosteering". Not sure I understand this objection... there's no rule about symmetric or consistent prefixes. Lots of things called X have a counter-X (see also anti-X). Examples: counter-intuitive, counter-insurgency, counter-strike, counter-reformation, counter-current, etc. Counter-steering is differentiating from steering. But there's no need to differentiate normal steering from steering, so we don't normally prefix things with "pro", unless you're talking about someone who advocates for something. I think there are a few counter-examples to that in physics though. :) In motorcycle safety, it's rather important to call out the counter-intuitiveness of counter-steering. People's reflexes tend to do the wrong thing in tight situations where quick steering is needed. If you need to turn right very quickly and haven't learned counter-steering, you can injure yourself by trying to steer right, and many people have. It's pretty common for riders who haven't learned counter-steering to believe that leaning hard will be sufficient, and/or that body lean is as or more important than steering. But to turn very quickly, knowing about and being able to counter-steer is incredibly important.
  - skookumchuck 9y ago
    I used to ride a bike with no hands. I was still able to countersteer! If I leaned to the left, the bike would lean to the right, the steering wheel would go right, then I could lean to the right into the turn.
  - lisper 9y ago
    The best way I've found to experience this is to first learn to ride with no hands. This works best at speed. You actually steer by shifting your weight, but the easiest way to learn is is to grip the seat with your thighs and think about turning the bike by trying to turn the seat. Once you can stabilize a no-hands ride, try pushing on the handlebar with one finger. You will find the the bike turns in the opposite direction of what you would naively expect. The harder you push, the tighter the turn will be in the "wrong" direction.
- lmm 9y ago
  > Try following a straight marker on the road on your bike. It's very hard. When you start going too much to the right, you will find it impossible to actually nudge the bike back to the left, unless you accept that you have to go further to the right first. Not true - you just have to shift your weight to the left.
  - fwdpropaganda 9y ago
    > Not true - you just have to shift your weight to the left. Not true - because of conservation of momentum (in the perpendicular direction) if you shift you weight to the left the bicycle will lean to the right and the center of mass will remain unchanged. It's called countersteering, look it up.
    - marodox 9y ago
      I never thought I'd see people arguing against counter steering on HN, I left that up to youtube comments.
      - fwdpropaganda 9y ago
        On the contrary, it doesn't surprise me at all. Many people on HN are young and successful which often means they overestimate how confident they should be in subjects outside their area of expertise. It's not just simple mechanics either, it's everything. Didn't you see just yesterday that lunatic claiming that the "4-color map theory is bunk"? https://news.ycombinator.com/item?id=16862553 https://news.ycombinator.com/item?id=16862553
    - lmm 9y ago
      You look it up. Every article you'll find will point out that on a light vehicle like an bicycle you don't need to countersteer with the handlebars and can achieve the same effect by weight shifting. (Indeed the fact that it's possible to ride a bicycle without holding the handlebars at all should be all the proof that's necessary that one can navigate through weight shifting alone).
- trzmiel4 9y ago
  The explanation is that you need to balance out centrifugal force F=mv^2/r. "Sharp turn" has smaller radius, therefore much larger the force. By turning in the opposite direction first, you're making the turn much less sharp, increasing the radius and thus reducing the force.
- eezurr 9y ago
  I've wondered if following a painted line on a road with your bike is an example of Zen. The more I try to follow the line, the harder it is to stay on it. But when I stop trying/thinking about it, I have no problem staying on that line.
  - komali2 9y ago
    And if you don't take a moment to occasionally look up from the line to consider your surroundings, you might crash into an Uber.
    - Froyoh 9y ago
      Or a car
- tzs 9y ago
  > But try this: Try following a straight marker on the road on your bike. It's very hard. When you start going too much to the right, you will find it impossible to actually nudge the bike back to the left, unless you accept that you have to go further to the right first. This holds in general for any motion where velocity is a continuous function of time, doesn't it? Let f(t) be your deviation at time t perpendicular to the desired straight path, with positive to the right and negative to the left. If you are "going too much to the right" at time t, e.g., f'(t) > 0, then because f' is continuous there must be some interval around t such that f' > 0 at all points in the interval. That means that f is strictly increasing throughout that interval, e.g., "you have to go further to the right first".
- russdill 9y ago
  I've always thought of it like a plane, with the terms adverse yaw and adverse roll applying. The main difference is if your turn is uncoordinated, you fall over. Yaw is controlled via the handlebars. Roll is controlled via balance. Just turning the handlebars causes adverse roll in the other direction. If you are falling to the left, turning the wheel to the right causes an opposite roll and restores balance. Turning the handlebars the opposite way momentarily is a great way to start a turn because of the adverse roll that it causes.
kikoreis 9y ago
I don't watch Youtube, so it's hard to assess the point being made, but zero gravity implies no normal force and therefore friction. Bicycles need friction for both drive and steering, as I and many others have painfully experienced!
- aidos 9y ago
  Which is why you'll miss the point that "the bicycle is, for balance purposes, effectively in zero gravity". It's actually a really fascinating clip — though I suspect you're not going to watch it. For anyone else, you can start here to see it in action. https://youtu.be/rNQdSfgJDNM?t=1m https://youtu.be/rNQdSfgJDNM?t=1m The original video is only 3 minutes long.
- roryhughes 9y ago
  https://hooktube.com/watch?v=rNQdSfgJDNM https://hooktube.com/watch?v=rNQdSfgJDNM (youtube mirror site)
- deleted 9y ago
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- IshKebab 9y ago
  Maybe skip commenting on YouTube videos that you refuse to watch? I'm sure there must be a rule here about commenting without rtfa?
  - Jaruzel 9y ago
    Actually the rule (guideline) is the inverse: "Please don't insinuate that someone hasn't read an article. "Did you even read the article? It mentions that" can be shortened to "The article mentions that." " It's fine to comment without reading/viewing the submission, and I'm sure many of us do :) Although, I am curious as to why kikoreis doesn't use YouTube?
    - shawabawa3 9y ago
      > Please don't insinuate that someone hasn't read an article Sure, but if they explicitly say they haven't read it, then make a wrong assumption about it, surely you can call them out
ageofwant 9y ago
Title is misleading. A 'bricycle' in zero gravity is unsteerable
- nicky0 9y ago
  Surely is shows that a bricycle in earth gravity is unsteerable.
- donkeyd 9y ago
  Actually, I'm pretty sure it'll be unridable too. But you're right, the video isn't about that.
- IshKebab 9y ago
  A bricycle is a bicycle in zero gravity. Should be "a bicycle in zero gravity is unsteerable".
sohkamyung 9y ago
That clip (and the research paper) is from 2014. Should a year tag be added to the headline?
rurban 9y ago
Well, it IS perfectly ridable, but unsteerable. You need a straight road. Bicycles in space are still usable, as long as you just go ahead, e.g. as the jogger in Kubrick's 2001.
- jowsie 9y ago
  I feel like learning to steer it would be just as possible as learning to ride a bike you steer and pedal in reverse. You just need to get past your muscle memory.
  - pwinnski 9y ago
    It doesn't seem like you watched the whole video, where they explain the "why."
  - larkeith 9y ago
    Unless I'm misunderstanding the physics, it would be quite literally impossible, not a matter of learning - any attemp to steer results in the angle of the bike moving in the opposite direction an amount directly proportional to the change in direction, and with gravity being cancelled out by the spring (or in 0G), there is no way to rectify the tilt except by steering back to the original course. Technically, you can steer temporarily - if steering right by 20° tilts you to 45°, you can ride at 45° (actually, it's possible that a 45° turn would always relate to a 45° tilt - I'd need to think on it), however your allowed directions are determined entirely by your starting direction; if you started pointing South, there would be no possible way to move North, and would likely only be able to operate the bike in the 160° - 200° range, looking at the video.
    - jerf 9y ago
      I believe you are correct, based on the video. Mathematically, with the usual simplifications and restrictions we mean by that, the device can not be steered freely at all. Practically, if you were left in a room with the device alone for a while, you'd probably find some way to change its direction. My initial guess is to jerk it up as high as possible and then jerk it sideways and rebalance. It's pretty heavy, so this isn't going to work very well and will be very exhausting. However, I suspect the ultimate technique you'd settle on would work just as well if we locked the front wheel entirely so it couldn't be turned, so while you may be able to "direct" the device you would still arguably not be "steering" it.
ajuc 9y ago
First of all without gravity and weight wheels won't get grip on the road, so no matter if it's a bicycle, tricycle, or a regular car - you can't drive it in 0 gravity, it will just jump away from the road.
- IshKebab 9y ago
  Yes but ignoring that, or using magnetic wheels, you still can't steer it.
  - contravariant 9y ago
    If you have a force pushing it onto the road wouldn't that suffice to make it steerable?
    - cryptonector 9y ago
      You also need some way to counter the centripetal acceleration. The training wheels do that in the tricycle, and leaning does it in a bicycle, but you need gravity for leaning, so in zero g with magnetic wheels&track you could not steer a bike the normal way, and perhaps not at all, but you could steer a tricycle.
- sliken 9y ago
  Cars emit exhaust, that thrust however small could be used to move the car around. Granted not quickly.
  - cx_in_the_chat 9y ago
    Cars require oxygen to operate, there's no oxygen in space.
    - zuminator 9y ago
      Nobody said anything about "space." "Zero gravity" (or microgravity, anyway) doesn't imply a vacuum.
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dreen 9y ago
A bicycle on the moon on the other hand... now that would be fun
- larkeith 9y ago
  Or even better, an aerocycle - human-powered flight is almost impossible on Earth, but in 1/6 g you could do some very fun stuff. IIRC, Arthur C Clarke mentioned races of that sort of vehicle in one of his works, so credit to him.
  - djsumdog 9y ago
    In Kim Stanley Robinson Mars trilogy, one of the characters talks about being on one of Mars's moons, and how they had to be careful because a good running start could get you to escape velocity.
    - sesutton 9y ago
      The escape velocity of Deimos is only 20 km/h (~12 mph) but I'm not sure how well running would work in such low gravity.
  - bagacrap 9y ago
    Wouldn't that require a thicker atmosphere?
torrance 9y ago
This reminds me of the backwards brain bicycle a bit [1]. I get that the argument they’re making here is one of physics - but failing to ride a counterintuitive bike isn’t something that can just be ‘done’ without a lot of practice! [1] https://youtu.be/MFzDaBzBlL0 https://youtu.be/MFzDaBzBlL0
- maaaats 9y ago
  I have been trying to ride the other way on my fixie[0] lately. I think this is kinda the same. I know what I have to do, but instinctively it all gets wrong. I can kinda override it, but then my reactions are way too delayed. So here's hoping for it will click some day.. [0]: A fixie is a bike with no freewheel. So the pedals follow the back wheel, and the other way. So if I pedal backwards, the bike goes the other way.
  - stevehawk 9y ago
    huh.. I grew up on a fixie.. I wonder if 20 years later I would just pick it up again.. or 30 years later.. note to self knock up wife.. get child fixie bike.. take bike for self when kid is at school xD I'm sure the experiment will be worth the college debt.
    - mattstreet 9y ago
      I believe you can buy hubs that are single speed and then if you flip them are fixie, might be cheaper to put that on a cheap bike than having a kid...
      - piva00 9y ago
        Yup, they are called flip-flop hubs, quite common and a bunch of bikes come with them installed so you can always choose between singlespeed or fixed gear.
  - kaybe 9y ago
    The sport trick cycling has this in a lot of tricks. You might find some advice there if you want.
RunningRabbit 9y ago
Discovery Channels Mythbusters tested if one could cycle underwater, which failed too.
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amelius 9y ago
Reminded me of this great Smarter Every Day video: https://www.youtube.com/watch?v=MFzDaBzBlL0 https://www.youtube.com/watch?v=MFzDaBzBlL0 (both interesting and funny)
- rootlocus 9y ago
  This sounds very similar to the spinning dancer illusion [1] where your brain locks into a configuration where it can see it rotate in one way or the other, but you can't control when or which. [1] https://en.wikipedia.org/wiki/Spinning_Dancer https://en.wikipedia.org/wiki/Spinning_Dancer
  - loco5niner 9y ago
    I can control the direction. It kind of feels similar to 3D stereograms where the image just kind of 'snaps' into place, but in this case, she starts spinning the other direction. Kind of fun and quirky, and you really have to do it on purpose.
    - lenocinor 9y ago
      To provide a corroborating perspective on this, I learned to control this too, but it took a lot of practice to do it, and even now it's not 100% immediately effective for me.
      - loco5niner 9y ago
        Same here, not 100%. I actually just tried it on the spinning dancer, and the more I practiced, the better I got, but definitely not 100%. I bet I could get there with enough practice though.
michaelmcdonald 9y ago
Why is she not wearing any type of safety gear / a helmet?!
- jrootabega 9y ago
  Yep, your head will crack open from a four foot drop at any speed. And how about a helmet where the strap is actually clipped and tightened?
  - corobo 9y ago
    Hope they don't play any kind of sports in that sports room they're testing in then!
    - jrootabega 9y ago
      Bikes are risky in that sense. Your legs and arms can't mitigate a fall like they usually do. And testing an experimental bike with a bunch of extra metal to find out how it fails? Even worse. Besides, the point of the experiment is to test the bike. There's nothing gained by not wearing a helmet. You're also implying that those other sports wouldn't be better with helmets, which may not be true.
      - gerbilly 9y ago
        >Bikes are risky in that sense. Your legs and arms can't mitigate a fall like they usually do. The way to handle most falls if you can anticipate them is to jump straight up and off the bike. [1] https://www.youtube.com/watch?v=ZcCGDr9f1L8 https://www.youtube.com/watch?v=ZcCGDr9f1L8
  - recursive 9y ago
    > Yep, your head will crack open from a four foot drop at any speed. I highly doubt this. The amount of force required to crack a human head open seems to be much more than what you can generate in 4 feet of free-fall.
- 9y ago
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nightcracker 9y ago
Fascinating. This is the content I enjoy seeing most.
stinos 9y ago
Interesting read as wel, link in first answer etc: basically, the exact physics between why cycling even works, seem yet to be a bit unclear: https://bicycles.stackexchange.com/questions/4656/what-makes-a-bike-stay-upright-when-moving https://bicycles.stackexchange.com/questions/4656/what-makes...
- glaberficken 9y ago
  This is a very interesting video that debunks some common theories of how the bicycle balancing works, and also proposes some extra insights (although no definitive theory yet) https://m.youtube.com/watch?v=NcZCzr9ExKk https://m.youtube.com/watch?v=NcZCzr9ExKk Also see this one for extra footage of the Gyroless, "trail-less" TMS bicycle that still manages to balance itslef https://m.youtube.com/watch?v=LbeENKn5kZU https://m.youtube.com/watch?v=LbeENKn5kZU
gmueckl 9y ago
Can someone explain to me why the authors neglect to mention nutation and precession on a vehicle that consists of non-negligible spinning masses? I don't get it.
Moodles 9y ago
I suspect running will similarly be difficult in a low gravity environment: proper technique in running is basically falling forward and your legs moving to continually prevent it. Without gravity to fall forward, it's probably very hard to move efficiently.
- mabbo 9y ago
  A few scifi authors have talked about this idea. I forget which book/author[0], but one of remember suggested that children born on the moon had naturally developed what was called a "kangaroo run" that let them move quickly, that immigrants from Earth couldn't copy well at all. [0] One of you is about to tell me exactly the name and author now, aren't you?
  - Moodles 9y ago
    "kangaroo run" certainly seems like a good description of the running technique the Apollo astronauts used to move around.
  - cecilpl2 9y ago
    You are thinking of the Red/Green/Blue Mars series by Kim Stanley Robinson.
    - mabbo 9y ago
      That sounds about right. I loved the first two of those books.
- THE_PUN_STOPS 9y ago
  It’s not zero gravity but I recommend this video from an Apollo mission: https://m.youtube.com/watch?v=HKdwcLytloU https://m.youtube.com/watch?v=HKdwcLytloU
monkeynotes 9y ago
Really highlights how you have to throw a bike slightly into the opposite direction[0] to a turn in order to get it to turn. When she tries to do this in the zero-gravity mode the bike just rolls over in the opposite direction without being able to kick the front wheel into the turn. [0] https://www.youtube.com/watch?v=llRkf1fnNDM https://www.youtube.com/watch?v=llRkf1fnNDM
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tlb 9y ago
I suspect you can ride it with a hack: either raise your center of gravity (to get into bike mode) or lower it (to get into trike mode).
- Retric 9y ago
  Or simply turn at lower speeds/make less sharp turns as they still had some control. It would simply have made a less interesting video. Similarly with the zero gee pendulum keep going far enough and the end would move to the left as it's only so long. Then reverse the process to move the pendulum to an arbitrary position. Alternatively, use vastly slower motions and the friction with the arm will counteract tiny momentum changes.
grayhatter 9y ago
Am I the only one who thought throughout; "I could turn that thing, just drag your foot across the outer most wheel in the direction you want to turn." Let the friction, and unequal spinning speeds to the work. (The wheels can't be locked to each other, otherwise that would also cause the bricycle to be unable to turn, thus invalidating the whole experiment.)
- PeterisP 9y ago
  The wheels certainly can be locked to each other, that's how standard kid tricycles work - all it means that in turns some slipping/friction is inevitable.

539 points by gballan 9y ago

Paper is here: http://ruina.tam.cornell.edu/research/topics/bicycle_mechanics/overview.html http://ruina.tam.cornell.edu/research/topics/bicycle_mechani...

maaaats 9y ago

What you unconsciously do when turning, is to quickly turn it a bit in the other direction first in order to get the bicycle more to the other side of you, so you have a better balance point for the big turn. Not perfectly explained, sorry. But try this: Try following a straight marker on the road on your bike. It's very hard. When you start going too much to the right, you will find it impossible to actually nudge the bike back to the left, unless you accept that you have to go further to the right first. This also happens when driving close to a curb. It feels like it's sucking you in.

Adirael 9y ago
That's countersteering [1]. I find it very hard to explain but it's something that most people on a bicycle (at speed) or a motorcycle (again, at speed) do naturally. [1] https://en.wikipedia.org/wiki/Countersteering https://en.wikipedia.org/wiki/Countersteering
- Moodles 9y ago
  I'm no physicist, but it seems the intuitive reason countersteering works is because when you turn, e.g. left, your center of mass also moves left because you need to lean left in order to turn. So if you turn left on your own this will move your center of mass left. And if you turn too sharply left your center of mass will be so far out that you will fall over. So turning right very quickly before turning left means that your center of mass suddenly shifts massively right, and therefore you get some extra time turning left while your center of mass is still busy shifting from right to left?
- NLips 9y ago
  I'd like to especially highlight your 'at speed' point here. It's often claimed that _all_ steering on a bike requires countersteering, but that is false. Countersteering allows rapid change of direction, but if you're going in a straight line, then lean left and gently steer left (or just lean left and allowing the front wheel to steer itself), you _will_ go left, no countersteering required.
  - ozim 9y ago
    If you lean left, front wheel will "do" countersteering itself (same as noted). Since gyroscopic effect on bike is not so big and speed, mass is not bigger than rider it is not noticable. For motorbike you cannot just lean hence need for explicit countersteering because of much higher forces involved. So I think it is correct to say that countersteering is always required.
    - baud147258 9y ago
      > countersteering is always required Only on a motorbike.
      - marodox 9y ago
        > If you lean left, front wheel will "do" countersteering itself The same applies to a bicycle.
      - ioseph 9y ago
        > Only on a motorbike. Only above a certain speed, at low speeds countersteering will not work Similarly above a certain speed on a bicycle countersteering is the only way you can turn
        schoen 9y ago
        Some people seem to describe this difference as unconscious countersteering versus deliberate countersteering, that is, that the difference isn't really whether you're countersteering or not, but whether the countersteer is large enough that you have to do it "on purpose".
- baud147258 9y ago
  On a bike, even at speed you can initiate a turn by simply leaning on the side.
  - marodox 9y ago
    The front wheel still kicks out in the opposite direction and counter steers for you due to the natural stabilizing properties of the bike
  - rplnt 9y ago
    Easiest way to try/prove this is ride without holding handlebars. You can turn corners easily. Limits (compared to regular turning) are your lowest speed is higher (where you'd lose balance without holding handlebars) and the fact your center of gravity and stability are messed up (can't turn as tightly). And self preservation of course.
    - baud147258 9y ago
      I've done a lot of riding without holding handlebars, so that's how I learned this. Another limits is that you've got a delay to reach the brakes, which can make it dangerous for others in addition to yourself. And I agree that having your center of gravity moved up really mess up your stability.
      - maskros 9y ago
        Only if you've got a stupid racing bike with only hand brakes. Coaster/foot/back-pedal brakes are standard issue around these parts, and I wouldn't ever want to ride a bike without one.
        JoeAltmaier 9y ago
        Depends on how you ride. An adult in the US, you're on a road bike bent over the bars and going 15-20mph. Hands on the brakes at all times. I do a ride every summer with 20,000 like-minded people and if you see even one bike with coaster brakes all week its unusual.
- rplnt 9y ago
  It's very easy to try. Go up to speed (20 km/h or so) and press on a handlebar, away from you. You will "turn" to that side even though the handlebars are moving in the opposite direction.
- dahart 9y ago
  Counter steer happens at all speeds at all times on a two-wheel vehicle, it's just hard to notice at slow speeds, and confusing because you do steer right during the stable lean angle portion of a right turn, as depicted in the first image in that Wikipedia article. I think counter-steering is misunderstood since people assume it means that if you're turning right then your steering has to be left of center. But counter-steering is referring to the direction of change, the steering delta, not the absolute steering angle. You always steer in the opposite relative direction from what you'd do in a car. This is still true on a bicycle at 1mph.
- arnarbi 9y ago
  Here's how I explained countersteering to myself: To turn left, I need to lean left. The easiest way to lean left is to pull the bottom of the bike, where the wheels touch the ground, to the right.
- upofadown 9y ago
  Not fan of the term "countersteering". If you changed the mechanical direction that the handlebars rotated the front wheel I doubt anyone would bother to call it "prosteering". A better way to think about this is that bikes turn by banking. The method of controlling the angle of bank does not map in a simple way to the direction of turn.
  - NegativeLatency 9y ago
    Do you have a better single word or short phrase to describe it though?
    - upofadown 9y ago
      Well the aviation people, who also control vehicles that are controlled by banking, don't bother to come up with a special name. When teaching people to fly they first teach how the controls can be used to control the attitude of the vehicle (roll, pitch, yaw are the terms that are used). Then they start a whole new discussion of how various attitudes will affect where the vehicle will end up. Some things can't really be simplified (and perhaps shouldn't be).
  - dahart 9y ago
    > The method of controlling the angle of bank does not map in a simple way to the direction of turn. Sure it does! (Unless by "simple" you're ruling out derivatives). If your wheel angle is moving right, then your bank angle is increasing left (or IOW, your left turn is becoming sharper, left turn radius is decreasing). While your wheel angle is moving left, your bank angle is increasing right. Whenever you stop moving the wheel, your bank angle will stop changing and you will be in a constant radius turn. > I doubt anyone would bother to call it "prosteering". Not sure I understand this objection... there's no rule about symmetric or consistent prefixes. Lots of things called X have a counter-X (see also anti-X). Examples: counter-intuitive, counter-insurgency, counter-strike, counter-reformation, counter-current, etc. Counter-steering is differentiating from steering. But there's no need to differentiate normal steering from steering, so we don't normally prefix things with "pro", unless you're talking about someone who advocates for something. I think there are a few counter-examples to that in physics though. :) In motorcycle safety, it's rather important to call out the counter-intuitiveness of counter-steering. People's reflexes tend to do the wrong thing in tight situations where quick steering is needed. If you need to turn right very quickly and haven't learned counter-steering, you can injure yourself by trying to steer right, and many people have. It's pretty common for riders who haven't learned counter-steering to believe that leaning hard will be sufficient, and/or that body lean is as or more important than steering. But to turn very quickly, knowing about and being able to counter-steer is incredibly important.
- skookumchuck 9y ago
  I used to ride a bike with no hands. I was still able to countersteer! If I leaned to the left, the bike would lean to the right, the steering wheel would go right, then I could lean to the right into the turn.
- lisper 9y ago
  The best way I've found to experience this is to first learn to ride with no hands. This works best at speed. You actually steer by shifting your weight, but the easiest way to learn is is to grip the seat with your thighs and think about turning the bike by trying to turn the seat. Once you can stabilize a no-hands ride, try pushing on the handlebar with one finger. You will find the the bike turns in the opposite direction of what you would naively expect. The harder you push, the tighter the turn will be in the "wrong" direction.
lmm 9y ago
> Try following a straight marker on the road on your bike. It's very hard. When you start going too much to the right, you will find it impossible to actually nudge the bike back to the left, unless you accept that you have to go further to the right first. Not true - you just have to shift your weight to the left.
- fwdpropaganda 9y ago
  > Not true - you just have to shift your weight to the left. Not true - because of conservation of momentum (in the perpendicular direction) if you shift you weight to the left the bicycle will lean to the right and the center of mass will remain unchanged. It's called countersteering, look it up.
  - marodox 9y ago
    I never thought I'd see people arguing against counter steering on HN, I left that up to youtube comments.
    - fwdpropaganda 9y ago
      On the contrary, it doesn't surprise me at all. Many people on HN are young and successful which often means they overestimate how confident they should be in subjects outside their area of expertise. It's not just simple mechanics either, it's everything. Didn't you see just yesterday that lunatic claiming that the "4-color map theory is bunk"? https://news.ycombinator.com/item?id=16862553 https://news.ycombinator.com/item?id=16862553
  - lmm 9y ago
    You look it up. Every article you'll find will point out that on a light vehicle like an bicycle you don't need to countersteer with the handlebars and can achieve the same effect by weight shifting. (Indeed the fact that it's possible to ride a bicycle without holding the handlebars at all should be all the proof that's necessary that one can navigate through weight shifting alone).
trzmiel4 9y ago
The explanation is that you need to balance out centrifugal force F=mv^2/r. "Sharp turn" has smaller radius, therefore much larger the force. By turning in the opposite direction first, you're making the turn much less sharp, increasing the radius and thus reducing the force.
eezurr 9y ago
I've wondered if following a painted line on a road with your bike is an example of Zen. The more I try to follow the line, the harder it is to stay on it. But when I stop trying/thinking about it, I have no problem staying on that line.
- komali2 9y ago
  And if you don't take a moment to occasionally look up from the line to consider your surroundings, you might crash into an Uber.
  - Froyoh 9y ago
    Or a car
tzs 9y ago
> But try this: Try following a straight marker on the road on your bike. It's very hard. When you start going too much to the right, you will find it impossible to actually nudge the bike back to the left, unless you accept that you have to go further to the right first. This holds in general for any motion where velocity is a continuous function of time, doesn't it? Let f(t) be your deviation at time t perpendicular to the desired straight path, with positive to the right and negative to the left. If you are "going too much to the right" at time t, e.g., f'(t) > 0, then because f' is continuous there must be some interval around t such that f' > 0 at all points in the interval. That means that f is strictly increasing throughout that interval, e.g., "you have to go further to the right first".
russdill 9y ago
I've always thought of it like a plane, with the terms adverse yaw and adverse roll applying. The main difference is if your turn is uncoordinated, you fall over. Yaw is controlled via the handlebars. Roll is controlled via balance. Just turning the handlebars causes adverse roll in the other direction. If you are falling to the left, turning the wheel to the right causes an opposite roll and restores balance. Turning the handlebars the opposite way momentarily is a great way to start a turn because of the adverse roll that it causes.

kikoreis 9y ago

I don't watch Youtube, so it's hard to assess the point being made, but zero gravity implies no normal force and therefore friction. Bicycles need friction for both drive and steering, as I and many others have painfully experienced!

aidos 9y ago
Which is why you'll miss the point that "the bicycle is, for balance purposes, effectively in zero gravity". It's actually a really fascinating clip — though I suspect you're not going to watch it. For anyone else, you can start here to see it in action. https://youtu.be/rNQdSfgJDNM?t=1m https://youtu.be/rNQdSfgJDNM?t=1m The original video is only 3 minutes long.
roryhughes 9y ago
https://hooktube.com/watch?v=rNQdSfgJDNM https://hooktube.com/watch?v=rNQdSfgJDNM (youtube mirror site)
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IshKebab 9y ago
Maybe skip commenting on YouTube videos that you refuse to watch? I'm sure there must be a rule here about commenting without rtfa?
- Jaruzel 9y ago
  Actually the rule (guideline) is the inverse: "Please don't insinuate that someone hasn't read an article. "Did you even read the article? It mentions that" can be shortened to "The article mentions that." " It's fine to comment without reading/viewing the submission, and I'm sure many of us do :) Although, I am curious as to why kikoreis doesn't use YouTube?
  - shawabawa3 9y ago
    > Please don't insinuate that someone hasn't read an article Sure, but if they explicitly say they haven't read it, then make a wrong assumption about it, surely you can call them out

ageofwant 9y ago

Title is misleading. A 'bricycle' in zero gravity is unsteerable

nicky0 9y ago
Surely is shows that a bricycle in earth gravity is unsteerable.
donkeyd 9y ago
Actually, I'm pretty sure it'll be unridable too. But you're right, the video isn't about that.
IshKebab 9y ago
A bricycle is a bicycle in zero gravity. Should be "a bicycle in zero gravity is unsteerable".

sohkamyung 9y ago

That clip (and the research paper) is from 2014. Should a year tag be added to the headline?

rurban 9y ago

Well, it IS perfectly ridable, but unsteerable. You need a straight road. Bicycles in space are still usable, as long as you just go ahead, e.g. as the jogger in Kubrick's 2001.

jowsie 9y ago
I feel like learning to steer it would be just as possible as learning to ride a bike you steer and pedal in reverse. You just need to get past your muscle memory.
- pwinnski 9y ago
  It doesn't seem like you watched the whole video, where they explain the "why."
- larkeith 9y ago
  Unless I'm misunderstanding the physics, it would be quite literally impossible, not a matter of learning - any attemp to steer results in the angle of the bike moving in the opposite direction an amount directly proportional to the change in direction, and with gravity being cancelled out by the spring (or in 0G), there is no way to rectify the tilt except by steering back to the original course. Technically, you can steer temporarily - if steering right by 20° tilts you to 45°, you can ride at 45° (actually, it's possible that a 45° turn would always relate to a 45° tilt - I'd need to think on it), however your allowed directions are determined entirely by your starting direction; if you started pointing South, there would be no possible way to move North, and would likely only be able to operate the bike in the 160° - 200° range, looking at the video.
  - jerf 9y ago
    I believe you are correct, based on the video. Mathematically, with the usual simplifications and restrictions we mean by that, the device can not be steered freely at all. Practically, if you were left in a room with the device alone for a while, you'd probably find some way to change its direction. My initial guess is to jerk it up as high as possible and then jerk it sideways and rebalance. It's pretty heavy, so this isn't going to work very well and will be very exhausting. However, I suspect the ultimate technique you'd settle on would work just as well if we locked the front wheel entirely so it couldn't be turned, so while you may be able to "direct" the device you would still arguably not be "steering" it.

ajuc 9y ago

First of all without gravity and weight wheels won't get grip on the road, so no matter if it's a bicycle, tricycle, or a regular car - you can't drive it in 0 gravity, it will just jump away from the road.

IshKebab 9y ago
Yes but ignoring that, or using magnetic wheels, you still can't steer it.
- contravariant 9y ago
  If you have a force pushing it onto the road wouldn't that suffice to make it steerable?
  - cryptonector 9y ago
    You also need some way to counter the centripetal acceleration. The training wheels do that in the tricycle, and leaning does it in a bicycle, but you need gravity for leaning, so in zero g with magnetic wheels&track you could not steer a bike the normal way, and perhaps not at all, but you could steer a tricycle.
sliken 9y ago
Cars emit exhaust, that thrust however small could be used to move the car around. Granted not quickly.
- cx_in_the_chat 9y ago
  Cars require oxygen to operate, there's no oxygen in space.
  - zuminator 9y ago
    Nobody said anything about "space." "Zero gravity" (or microgravity, anyway) doesn't imply a vacuum.

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dreen 9y ago

A bicycle on the moon on the other hand... now that would be fun

larkeith 9y ago
Or even better, an aerocycle - human-powered flight is almost impossible on Earth, but in 1/6 g you could do some very fun stuff. IIRC, Arthur C Clarke mentioned races of that sort of vehicle in one of his works, so credit to him.
- djsumdog 9y ago
  In Kim Stanley Robinson Mars trilogy, one of the characters talks about being on one of Mars's moons, and how they had to be careful because a good running start could get you to escape velocity.
  - sesutton 9y ago
    The escape velocity of Deimos is only 20 km/h (~12 mph) but I'm not sure how well running would work in such low gravity.
- bagacrap 9y ago
  Wouldn't that require a thicker atmosphere?

torrance 9y ago

This reminds me of the backwards brain bicycle a bit [1]. I get that the argument they’re making here is one of physics - but failing to ride a counterintuitive bike isn’t something that can just be ‘done’ without a lot of practice! [1] https://youtu.be/MFzDaBzBlL0 https://youtu.be/MFzDaBzBlL0

maaaats 9y ago
I have been trying to ride the other way on my fixie[0] lately. I think this is kinda the same. I know what I have to do, but instinctively it all gets wrong. I can kinda override it, but then my reactions are way too delayed. So here's hoping for it will click some day.. [0]: A fixie is a bike with no freewheel. So the pedals follow the back wheel, and the other way. So if I pedal backwards, the bike goes the other way.
- stevehawk 9y ago
  huh.. I grew up on a fixie.. I wonder if 20 years later I would just pick it up again.. or 30 years later.. note to self knock up wife.. get child fixie bike.. take bike for self when kid is at school xD I'm sure the experiment will be worth the college debt.
  - mattstreet 9y ago
    I believe you can buy hubs that are single speed and then if you flip them are fixie, might be cheaper to put that on a cheap bike than having a kid...
    - piva00 9y ago
      Yup, they are called flip-flop hubs, quite common and a bunch of bikes come with them installed so you can always choose between singlespeed or fixed gear.
- kaybe 9y ago
  The sport trick cycling has this in a lot of tricks. You might find some advice there if you want.

RunningRabbit 9y ago

Discovery Channels Mythbusters tested if one could cycle underwater, which failed too.

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amelius 9y ago

Reminded me of this great Smarter Every Day video: https://www.youtube.com/watch?v=MFzDaBzBlL0 https://www.youtube.com/watch?v=MFzDaBzBlL0 (both interesting and funny)

rootlocus 9y ago
This sounds very similar to the spinning dancer illusion [1] where your brain locks into a configuration where it can see it rotate in one way or the other, but you can't control when or which. [1] https://en.wikipedia.org/wiki/Spinning_Dancer https://en.wikipedia.org/wiki/Spinning_Dancer
- loco5niner 9y ago
  I can control the direction. It kind of feels similar to 3D stereograms where the image just kind of 'snaps' into place, but in this case, she starts spinning the other direction. Kind of fun and quirky, and you really have to do it on purpose.
  - lenocinor 9y ago
    To provide a corroborating perspective on this, I learned to control this too, but it took a lot of practice to do it, and even now it's not 100% immediately effective for me.
    - loco5niner 9y ago
      Same here, not 100%. I actually just tried it on the spinning dancer, and the more I practiced, the better I got, but definitely not 100%. I bet I could get there with enough practice though.

michaelmcdonald 9y ago

Why is she not wearing any type of safety gear / a helmet?!

jrootabega 9y ago
Yep, your head will crack open from a four foot drop at any speed. And how about a helmet where the strap is actually clipped and tightened?
- corobo 9y ago
  Hope they don't play any kind of sports in that sports room they're testing in then!
  - jrootabega 9y ago
    Bikes are risky in that sense. Your legs and arms can't mitigate a fall like they usually do. And testing an experimental bike with a bunch of extra metal to find out how it fails? Even worse. Besides, the point of the experiment is to test the bike. There's nothing gained by not wearing a helmet. You're also implying that those other sports wouldn't be better with helmets, which may not be true.
    - gerbilly 9y ago
      >Bikes are risky in that sense. Your legs and arms can't mitigate a fall like they usually do. The way to handle most falls if you can anticipate them is to jump straight up and off the bike. [1] https://www.youtube.com/watch?v=ZcCGDr9f1L8 https://www.youtube.com/watch?v=ZcCGDr9f1L8
- recursive 9y ago
  > Yep, your head will crack open from a four foot drop at any speed. I highly doubt this. The amount of force required to crack a human head open seems to be much more than what you can generate in 4 feet of free-fall.
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nightcracker 9y ago

Fascinating. This is the content I enjoy seeing most.

stinos 9y ago

Interesting read as wel, link in first answer etc: basically, the exact physics between why cycling even works, seem yet to be a bit unclear: https://bicycles.stackexchange.com/questions/4656/what-makes-a-bike-stay-upright-when-moving https://bicycles.stackexchange.com/questions/4656/what-makes...

glaberficken 9y ago
This is a very interesting video that debunks some common theories of how the bicycle balancing works, and also proposes some extra insights (although no definitive theory yet) https://m.youtube.com/watch?v=NcZCzr9ExKk https://m.youtube.com/watch?v=NcZCzr9ExKk Also see this one for extra footage of the Gyroless, "trail-less" TMS bicycle that still manages to balance itslef https://m.youtube.com/watch?v=LbeENKn5kZU https://m.youtube.com/watch?v=LbeENKn5kZU

gmueckl 9y ago

Can someone explain to me why the authors neglect to mention nutation and precession on a vehicle that consists of non-negligible spinning masses? I don't get it.

Moodles 9y ago

I suspect running will similarly be difficult in a low gravity environment: proper technique in running is basically falling forward and your legs moving to continually prevent it. Without gravity to fall forward, it's probably very hard to move efficiently.

mabbo 9y ago
A few scifi authors have talked about this idea. I forget which book/author[0], but one of remember suggested that children born on the moon had naturally developed what was called a "kangaroo run" that let them move quickly, that immigrants from Earth couldn't copy well at all. [0] One of you is about to tell me exactly the name and author now, aren't you?
- Moodles 9y ago
  "kangaroo run" certainly seems like a good description of the running technique the Apollo astronauts used to move around.
- cecilpl2 9y ago
  You are thinking of the Red/Green/Blue Mars series by Kim Stanley Robinson.
  - mabbo 9y ago
    That sounds about right. I loved the first two of those books.
THE_PUN_STOPS 9y ago
It’s not zero gravity but I recommend this video from an Apollo mission: https://m.youtube.com/watch?v=HKdwcLytloU https://m.youtube.com/watch?v=HKdwcLytloU

monkeynotes 9y ago

Really highlights how you have to throw a bike slightly into the opposite direction[0] to a turn in order to get it to turn. When she tries to do this in the zero-gravity mode the bike just rolls over in the opposite direction without being able to kick the front wheel into the turn. [0] https://www.youtube.com/watch?v=llRkf1fnNDM https://www.youtube.com/watch?v=llRkf1fnNDM

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tlb 9y ago

I suspect you can ride it with a hack: either raise your center of gravity (to get into bike mode) or lower it (to get into trike mode).

Retric 9y ago
Or simply turn at lower speeds/make less sharp turns as they still had some control. It would simply have made a less interesting video. Similarly with the zero gee pendulum keep going far enough and the end would move to the left as it's only so long. Then reverse the process to move the pendulum to an arbitrary position. Alternatively, use vastly slower motions and the friction with the arm will counteract tiny momentum changes.

grayhatter 9y ago

Am I the only one who thought throughout; "I could turn that thing, just drag your foot across the outer most wheel in the direction you want to turn." Let the friction, and unequal spinning speeds to the work. (The wheels can't be locked to each other, otherwise that would also cause the bricycle to be unable to turn, thus invalidating the whole experiment.)

PeterisP 9y ago
The wheels certainly can be locked to each other, that's how standard kid tricycles work - all it means that in turns some slipping/friction is inevitable.