I'm disappointed by many of the comments. They are critical nit picking. What is suggested by this video is that a whole new technological bicycle may come of Arend Schwab's work. A bicycle with greater stability due to electronic stabilization. A safer safety bike. A fall resistant bike that would lower the number of people injured on bikes. I think it is great work, I applaud this work and look forward to seeing future prototypes.
wow! It was a real pleasure to be disabused of my misconceptions so convincingly. I am going to watch this a few times to catch a couple of points that went by me too fast to absorb. The remarkable thing about bicycles (I still believe) is how readily they plug into human beings innate abilities.
Sorry to be so off topic but does anybody know a trick to log back into an instagram account? I stupidly lost my account password. I love any tips you can offer me
@Kyng Gregory I really appreciate your reply. I got to the site thru google and Im trying it out now. Seems to take a while so I will reply here later with my results.
Impressive speech! In an era in which science is devoted to come up with theories and explanations on the creation of our universe, simple everyday classic physics phenomena such as the stability of a bicycle remain unclarified.
It's even more amazing that you can put a child on such a magical device and it will eventually learn to control it, do tricks on it all without understanding what it's doing. The human mind is astounding.
I'm really glad there are people out there like this gentleman. I'm way not detail oriented enough for this type of work and it's good there are people out there like him. I'm, generally, more focused on not getting killed by a car.
I have heard a quote: that the bike was the pinnacle of man's enginneering and all the rest of technology has been downhill from that. If you think about most everything else has increased pollution and dependency of some sort or another.
@@kcfish4862 are you referring to its production makes pollution ? It does, but when you think a well made bike can last probably 50 plus years of constant use , I'd see it pretty good use compared to a car. Unfortunately our cities are designed around cars, not people, pedestrians or cyclist to commute.
@@recyclespinning9839 not only that but also the production of bicycle is also depending on something else be it the frame, gearbox hub, etc. While not as much as things like cars etc, it's nevertheless a pretty rude claim to just say that everything else is a downhill in terms of engineering and has more dependency, I mean just look at how you even typed that comment in the first place.
@@kcfish4862 I mean down hill in terms of pollution . I'm a bit biased on cars. I like sports cars , but realize that we basically have become a "car culture" . Its like car manufactures rule the world. I mean we fight wars for oil to fuel them..
@@recyclespinning9839 Well I too agree on the car part, don't mean to look down on bike since they make a single human so much more efficient at traveling, mainly it was that I don't think it deserves the title of pinnacle of man's engineering, and that there are definitely other things that creates less pollution/dependency.
Who edits these TED videos? . Most times the videos cut to the presenter whilst he's talking about something on the screen behind, so we miss what he's talking about! Happens on a lot of Ted videos nowadays
It's because these are TEDx events, not TED. These events are conducted by people outside of TED licensed to conduct the event. The part of the name after TEDx gives idea on who conducted it. And also these people are in charge of recording and editing these videos too.
Assistant Professor vs. Mechanical Engineer: The picture at 9:14 shows positive caster. The device in action has positive caster. There is no demonstration of the device working with no caster. If his argument about tipping masses was correct, a stationary bicycle would turn toward the fall. This does not occur in the demonstration at 4:11. Bicycles self stabilize because of the caster effect and the rounded rubber tire. As the bike falls, the contact patch moves toward the side wall, and friction helps to turn the wheel toward the fall. Metal, "pizza cutter" type wheels would rely completely on the caster effect.
Any time Mr. Sibert. I'll bring the graph paper and the screen grabs. I'm out of whiskey at the moment, so let me know ahead of time so I can pop down to the shops.
The stationary bike falling does provoke a steering effect, but if you just let the bike fall, you can't see it in time. I've just tried it with my own bike. Hold the bike upright with the steering straight and lean it over. The steering will turn into the lean every time. The caster is what does it, and I agree that his "no caster" model does in fact have some positive caster.
I've been riding two wheels for over 45 years and your reasoning is just common sense to me. Stability is a function of inertia, variable caster angle, and contact patch area/friction. It's the relationship of these three things that determine stability. If you look at any one aspect while ignoring the others - of course it'll make you wonder. The delta must be close to zero sum. You vary the caster effect, either by making it 0 or increasing it too much like a chopper, stability will decrease. Increase or decrease friction too much, (like riding on ice or having a front tire so flat that the contact patch affects caster and inertia, stability decreases. Increase or decrease inertia and caster will need to vary to maintain zero sum. For example, we increase inertia during high speed cornering. To overcome this we have to decrease caster to offset the inertia. This is done by leaning forward and literally steering away from the lean - the opposite of a low speed turn. Their experiments were done by limiting both inertia and speed. The rear steer bike worked well at low speed. Increase speed beyond the limits that the caster can be varied and during a turn the caster will cause the back end to swing around, increasing friction of the contact patch and inertia will cause the rider to endo in a straight line until friction overcomes inertia. Ouch.
I am really surprised there is no mention of wheel camber, especially given that the speaker is a professer of applied mechanics. A single wheel rolling on it's own shows the same tendency to steer in the direction it is tilted. When a wheel that is rolling in a straight line is tilted it exerts a thrust in the same direction at the contact patch because the tilted wheel wants to follow a circular path. In effect the rolling wheel automatically moves the contact point to be under the center of gravity. This is the same principle behind a band saw blade or flat belt tracking on a crowned pulley, and also what makes a car with misaligned wheels pull to one direction. Gyroscopic effect is negligible to nonexistent, and has been debunked, caster effect is negligible but makes steering from the handlebars more stable. I find the idea of one wheel 'falling faster' than the other highly dubious without supporting evidence. I have a front wheel drive recumbent bike with almost zero trail/caster that will toss you onto the ground if you try to steer only with the handlebars. Instead you have to lean into a turn even at low speed and the handlebars just let you damp the oscillation or turn more agressively. ...Steering on a bicycle can be accomplished almost exclusively with camber thrust. I'm not well versed on unicycles but I tend to guess that the statement holds true for those as well.
Mark McCormack The camber is the mechanism how bicycles turn corners. But to make a bicycle "SELF-STABLE", you need: at least two wheels aligned straight in the rolling direction, and only one but not all wheels that can steer left and right freely. Besides, if the road friction is negligibly small (like on well polished smooth floor), even negative casterring is fine. But if the friction is relatively big (like on muddy road), you need positive casterring or at least zero casterring to achieve self-stability.
+Mark McCormack Very good comment, sir! I've been trying to find resources to understand that and counter steering properly (most stuff online if full of guessing and no physical or mathematical explanations whatsoever) and this video and comment are gold! Of course this also mean they left me even more confused than before... hehehe Tbh the only part I disliked about it was when you said "the tilted wheel wants to follow a circular path", like it has a will of its own. I did not quite understand this point because of it. Care to elaborate? I can imagine why this happens on a bicycle, but not really on a wheel by itself. Thanks!
The tire acts like a rolling cone when the axis is off parallel with the road surface, following a circular path, but the inertia of the wheel acts in the tangent, so the forces oppose eachother and move the wheel back to horizontal. Or if the inertia isn't strong enough, the wheel spirals inward until it falls over.
Not huge on all this physics stuff but your problems comes from a difference in steering. A motorcycle or bike with 2 wheels that are rear wheel drive you counter steer push left go left push right go right. A front wheel drive bike not fun to steer tried it with my e bike and switched to a rear wheel drive motor. Also no sure if your recumbent is 2 or 3 wheels. If its 3 wheels you really are gonna have a bad time with single front wheel drive. Front wheel drive can only be done right with 3 wheels when the front 2 wheels drive in unison.
The rear wheel imposes the trailing castor effect as well, as the rear wheel follows the path of the front wheel. Essentially, the front wheel replicates the pivot point of a castor wheel. The key to balancing is to alter the position for the center of gravity to match the angular path of travel - alter the center of gravity to move in the direction of a desired turn, and match the turn of the wheel in proportion to the momentum and direction of an off-center center of gravity.
Excellent,not only bicycles but for future vehicles,enclosed motorcycles.Designing safer,more stable motorcycles and other narrow track vehicles is a win win for all of us.
So, it's still the caster effect. When you look at a bicycle tire in cross section it is circular. The center line of the steering axis is in line with the center of the contact patch however, as the bike leans to one side the contact patch moves to that side but the steering axis leans with the bike and so the contact patch and steering axis are no longer aligned. If the bike leans to the left the contact patch moves left of the steering axis creating a caster effect not in the line of the movement of the bike (y axis) but in the line of the lean of the bike (x axis) . This causes the steering to turn into the lean. The caster effect is in the x axis and not the y axis. Make a bike with tires that have a cross section of zero (a thin sheet of metal for example) and you will see that it is unstable. You can experience this by riding with no hands. Take a mountian bike with wide tires, ride it with no hands, then switch to very thin road tires. It will be much more difficult to ride hands free. Maybe the upward trend in accidents is due to a trend in narrower tires? Maybe a return to wider tires would help.
It doesn't sound like they considered the fact that a tilted wheel will apply a turning and stabilizing force, regardless of trail, mass distribution, and gyroscopic effects. Lose the bike all together and slowly roll a wheel by itself, it's stable. As it tilts into a fall, it rolls on its radius and applies a turning motion correcting the fall.
Hi Timothy: Andy Ruina here, I am in and made some of the clips in the video above. And I have worked for years with Arend Schwab, the speaker in the video. Your explanation for bike stability, that it is like the stability of a rolling wheel, was one of the prominent theories of bicycle stability in the 1800s. And it lives today. And it is a big part of what motivated our theory and experiments. So, no only did we consider the self-stability of a rolling wheel, our work was explicitly intended to show that this effect was not key. It is relevant, but not key. By the way, that stability of a lone rolling wheel IS completely dependent on gyroscopic effects. That a rolling wheel steers left as falls left is entirely a gyroscopic effect. And that effect is there on a bicycle. And it is important for bicycle self-stability. But for a bicycle, unlike for a rolling wheel, that effect is not needed for self-stability. That is really one of the two original points in the video above. The other of the two points is that trail is also not necessary. The whole point of the video, corresponding to the title of the Science paper which it is describing, is that Neither Trail Nor Gyroscopic Effects Are Needed For Bicycle Self Stability. This is to distinguish the bicycle from a rolling wheel, in which gyroscopic effects are needed for self-stability.
hello sir, I have strated to get very interested in this subject. When you talk about a lone rolling wheel relying on gyroscopic effects , do you mean gyroscopic precession? From what I have understood, it takes effect when the wheel actualy leans to one side. If so, why does a wheel rolling in circles and having a fixed angle to the road not go straight? hope you respond
I didn't intend to say that gyroscopic effects don't exist. I believe there are other small forces that are also involved based on the geometry of a wheel/tire and where the contact patch is applied and the CG and resultant forces. How involved would depend greatly on the details of each application. I agree that gyroscopic effects play a big part on single wheel stability. I think the situation i'm thinking of is a rolling coin as it falls. It will rotate around its radius even though the angular momentum is very small.
The problem with all of these things is people trying to find "which effect makes bicycles stable", when there's many effects which all contribute, to varying degrees depending on design, speed, and lean angle. If, at a given speed and lean angle, all of the forces on the steering add up to turn towards the fall, the bike is stable. If they add up to turn it away, it is unstable. Just because you can build a bike that works without trail doesn't mean that trail isn't the main contributor to stability on a conventional bike. If you take a normal bike, and give it negative trail without increasing some other stabilizing factors, you're going to have a bad time.
But you can take a normal bike with rake and trail; and easily make it unstable by adding mass to the steering mechanism, behind the tyre contact point.
The facts for bike self-stabilizing: 1.gyro effect destabilizes, but it's negligible for normal speeds of a road bike 2.both articulated parts are inverted pendulums =>CG are always above contact line =>mass distribution is negligible here too (for normal wheelbase) 3.any bike geometry stabilizes as long as it reacts by steering IN DIRECTION of accidental lean (any learner is told to do) 4.classic geometry is the most stable, but it can't help handicap who must stay away from any machinery operating. 5. B.S. can be presented with professor's style.
Why is the bike stable? So simple question, so simple answer. Gyroscopic effect is ever present and is one of the reasons the bike will stay upright when moving. Second one is the overall mass of the bike. When pushed, pulled, thrown etc., any object has the tendency to move in the desired direction until it has no energy to continue further. Third reason is that at least one wheel is free steering in the steering head to compensate external forces (irregularities of pavement, winddrag and so on) by aligning the steering wheel into the direction of the movement. Front vs. rear steering wheel and positive/no/negative trail. This determines the level of sensitivity with which u will steer the the wheel. Rear wheel steering is really sensitive as mentioned in the video (steering while going backwards in a car). Similar to that is negative or no trail while steering the front wheel. The less sensitive is positive trail, i.e. chopper with extra long front forks (this one will feel the most stable in the stright line) Due to this sensitivity we mainly use positive trail to ensure the best steering abilities of the bike. Btw have you ever rode a motorcycle? Do you know what is countersteering? Do you know and understand weight distribution between front nad rear wheel?
+Aaron L You made a mistake thinking I did not undestand the video. Fact is I just do not agree with more than a half of it. From a third view it almost seems like a fundraiser video in the first place
I don't get the confusion because it is so simple. Looking at the wheel as a tall, skinny donut, with a tire that is round in cross section, it is obvious that the furthest part of the tire from the center of the axle is the center of the tire as you look down on it. To either side of this longest diameter, there are shorter and shorter paths around the tire due to the shortening distances from the tire contact point center to the axle center as you move away from the wheel maximum diameter. For a left turn where the tire contact patch extends from the bottom center of the tire toward the left side of the tire, if we define the other edge of the patch as maybe an inch left of the longest diameter then that edge is traveling a shorter distance. So the tire will move along a circle whose length is the distance around the tire at the center of the patch ( halfway between the longest distance around the tire and the shorter distance of the left edge of the tire contact patch). Thus the front wheel circles to the left while the rear wheel follows. This flexes the spokes to the right, creating a pressure toward the left which pulls the tire back toward the furthest diameter thus the bike rights itself.
I read that the increase in accidents of elderly people in The Netherlands is due to the increase in electric bikes. And from personal bicycle experience, falls are the result of interacting with the environment: hitting a hole being my least favorite. A more stable bike doesn't help with that, maybe a flying bike would. ;-)
Maybe I am wrong but I believe I have always understood from looking at bicycle frame design that the angle of the head tube/steerer tube, was a huge determining factor in the stability of a bicycle and also on how quickly or slowly it can be steered. The first safety bikes such as the Wright brothers build had a fairly relaxed head tube angle which in turn made it easier to keep the bike going straight. Somewhere along the evolution of frame building and I am not sure on this point that certain frames had the head tube angle steepened. I know on most of my road bikes which I have models from the 60s thru 2015 the head tube angles are different than my mt. bike frames which for obvious reason are designed to turn or maneuver quicker. I would think if you did the push the bike and let go test the modern road bike would out-distance the modern mt. bike. I am not sure this gentleman explained that, maybe he did but I am not tech-smart enough to know if he did. Lots of factors for people falling over on bikes nowadays besides stability, cell-phones, lack of skill, not paying attention, riding an E-bike faster than they are capable of handling it. Just my humble opinion, have a nice day.
Centrifugal force -- velocity holds the wheels upright. When the bike loses velocity it starts to tip. When it tips, it increases velocity, and the increased velocity returns the bike to stability. Like an airplane that stalls, falls, increases speed, and regains lift.
Is not the rear wheel also a castor that lies behind the steering axis? In fact, with the experimental design in which the tiny front wheel's contact point was moved slightly ahead of the steering axis, did not the tiny rear wheel's contact point remain behind the steering point[it castors still]. So a conventional bicycle actually has two castors - both trailing the steering point! The steering point always leads two in-line castors . Essentially the steering axis 'pulls' two in-line castors with a differential in castor contact points with respect to the distance to the steering axis - which sets the condition for auto steer into the fall.
I would like to see an explanation of why a bicycle or motorcycle is more stable under power and less stable under braking. I think that it is related to any theory of bicycle stability.
Interesting problem. Could it be caused by the difference in diameter of the front tyre contact surface when the tyre starts to tilt and the contact surface is not the middle of the tyre but rather shifted either left or right ? The tyre will roll partially on it's sidewall where it's diameter is smaller, and therefore it's speed lower, compared to the middle of the tyre resulting in a difference in speed between the faster outside (middle) and slower inside (left or right depending on direction of fall) of the contact surface area of the tyre forcing the front tyre to steer into the fall (path of less resistance). The following weight of the bike wants to continue its movement forward (not the direction the tyre is steering into) and will increase friction (grip) on the faster outside contact surface area (middle) of the front tyre causing it to turn in the opposite direction of the fall ?
12:45 The reason for the instability of the bicycle being pushed in reverse is not an inherent rear-wheel-steering problem as implied. It's because you were using a front-wheel-steering-stable bicycle in a direction for which the steering was not designed. I'm sure your trailing-wheel penny-farthing design wouldn't fare very well if you pushed it with the small wheel forward!
Is it conceivable that, once the public began to accept something akin to the self-stable rear wheel steering bike, it could provide a more stable ride for those prone to falling? How actually maneuverable is such a machine? Could it make quick avoidance maneuvers? Could a box be put on the back?
I think he only gives half the explanation. Once the bike begins to tip and turn, the inertia of the bike and rider wants to keep the bike moving along the original vector, so as the bike turns and tips a little, the inertia induces a small force righting it. That's my theory anyway. :P As for the gyroscopic effect, it has to be negligible (when there is an actual rider on the bike), as the mass of the wheels is so small and the wheels rotate relatively slowly. On a heavier motorcycle, I suspect this effect is much more prevalent.
This isnt right, keith code figured it, watch twist of the wrist 2. they are stable because the forward inertia pushes the bicycle forward while any instability moves the contact patch under the falling weight, the inertia from the forward motion then pushes against the high side of the bike turning it the other way. the bigger the movement in the contact patch the more turning force is exerted which is why on a motorcycle pushing forward on the right handle bar turns the bike right even though the wheel is trying to turn left, the wider contact patch creates more friction, tipping the front over. once the front is falling the forward interia againt the high side of the bike turns the wheel the opposite way. i'm not a physicist but ive ridden a motorcycle on a pennys worth of contact patch and from a practical standpoint, the bars always track to the most stable point. with cruise control you can place a bike into full lean with a penny sized contact patch between both tires and the bike will be stable without any rider input; or rider if youve seen the motorcycles winning races without riders on them in the motogp. furthermore that same bike at full lean with no rider input is stable to essentially any disruptions, from sand to poor road conditions, the only thing that will make it fall over is an input on the bars that prevents the contact patch from tracking to the center of mass
Why Bicycle stays upward while running? The answer is pretty easy. The pull of Gravity is Defeated by Velocity. Explanation: As we all know that there is gravity that always pulling everything downward. The Bicycle driver as riding on a bike the gravity pulls the driver at right and left side causing unstable position. To balance the bike, the driver has to move the steering sidewards but it is not enough to make the bike balanced. So the biggest option the driver do, is to have velocity to counter the pulling gravity. Thus the bike balances because the velocity force cannot overcome by the pulling force of gravity. Example, a single bike tire, turn it on upward position. the tire could stand balanced upward while on run. Remove the velocity, the tire will fall down because the gravity force will be greater than the force of velocity.
+Romy Nacido The reason that a tire will stay upright is because of the gyro effect, when it starts to tilt the tire turns into the tilt just like a bike in that way it stays upright. :)
Few years later and this video is even less accurate. He never said why safety/regular bike works the way it does, neither why we all use it for our happiness. The funny thing is he presents 2 bikes with different design (highly impractical and inefficient form many points of view), yet, in the end, thar electric toy bike has the same safety/regular bike geometry we all use. No, there won't any revolution in bike design. It happened in the second part of 19th century. I am pretty sure there is nothing new to add to make the bike design any more efficient and practical. Yes, better materials, better suspension, better tyres etc. will make it better but there will not be any radical change of design. Especially not these "theoretical" bikes. I am pretty sure I got a bit further in understanding why the safety/regular bike works. Video is in progress, right now. Just some food for thought - positive trail, contact patch, angle and position of the head tube, two wheels ;-)
5:4 I did it with bike wheel &got opposite results Indeed, upper part of rolling wheel has most horizontal component of momentum &its conservation reacts against lean or steering move (motorbike racers have appropriate counter-steering reflexive jerk before steady phase of turning). In normal riding negligible disturbing gyro affect is canceled by classic bike geometry that is only stabilizing factor. Schwab should've learnt Wikipedia article first.
HI currishev: Andy Ruina here, friend and colleague of Schwabb who made the video. I am even in some of the video clips. I was also the Masters Thesis advisor of Andrew Dressel, the main author and moderator of the Wikipedia page on bicycle stability. Yes, the wikipedia article on bicycle stability is VERY GOOD and informative. The Wikipedia page has most things right, as best I have seen. And I don't think you will find any disagreement in the Wikepedia page on bicycle stability with what Arend Schwab says in the video. If you glance through the various papers and appendices on Schwab's or my www pages you will see that the work presented in the video above is not casual dabbling, but pays lots of respect to the 150 years of thoughts and researches on bicycle stability.
If u are right, I don't understand English then. My understanding of bike stability is self-coherent and consistent with my grasp on classical mechanics, So, further non-specific talk is pointless unless u can cite wrong part in the Wikipedia article ("..most things right.." is not everything right in plain English) with yo arguments.
Dear currishev: Please tell me what about the Schwabb video you think is in contradiction with the Wikipedia article on bicycle stability. If you are specific I will try to give a specific answer.
reread my first comment: it can't be more specific as it gets: I noted moment and content of contradiction with my wheel test and article's claim (I agree with) about negligible gyro effect on bike stability. I don't see point in the conversation when one writes just for sake of writing,. Bye.
Hi currishev: In response to your Dec 12, 2014 post. I'd like to think I am not just writing for the sake of writing. I reread your post from Dec 8, 2013 and do not find it clear enough to respond to. But I am not complaining about that. I would like to write in a way that is clarifying for you if I can. My central claims, which I would like a chance to defend or explain, are: 1) Arend Schwab's talk is probably correct in almost every detail, and 2) The Schwab talk probably agrees with the Wikipedia article in almost every detail. Schwab and the main wiki author, Andrew Dressel, know each other and know pretty much what each other know. So if there is apparent disagreement between them I guess they would both like to know that and have things clarified. So might you humor me and try to explain yourself again?
Did I miss something or did he never actually confirm why a bicycle is stable? Gyro? Nope. Trail? Nope. So wtf is it? I always figured “path of least resistance” was part of it, but that wasn’t even included in the talk.
Yes, he never did. In fact, the electronically stabilized bike at the end of a video is the so called safety bike - classic conception. That is the funniest part of the whole video.
yep; if you take your hands off of the handle bars and just push the right handle bar away from you (and them let go), the wheel will turn left, you will start to fall right and then (without you touching the handle bars) the wheel will turn right.
I'm not an expert but I think the method of propulsion has no influence on the physics of a vehicle with 2 wheels in tandem. So bicycle or motorcycle, same deal.
Peter is right, it's governed by the same principal. Centripetal force is exerted on the wheels and pushes you inwards (towards the center point of the turn). However, without a counter force, you would just fall straight down or be thrown in towards the center. This is where centrifugal force comes into play. Centrifugal force is a fictitious force caused by a non-inertial reference frame. This force is what makes it feel like something is pushing you when you turn in a car.
Very interesting. But as a basic design for a stable two wheel vehicle the bicycle seems to have found its optimal configuration nearly 150 years ago. That's why the bicyle has stayed essentially the same despite great technical innovations in material science and computer design. So the conclusion should have been not innovation using non-passive steering methods "let's add some motors and a processing unit because we can", but "If it ain't broke don't fix it!"
Sensory organs such as the eyes and inner ear (as Timothy Green has said) receive signals about our bodies' position, the brain processes the information and sends signals to our muscles to correct imbalances. When walking our arms play a role too, have you noticed how they naturally move at the same time as the opposite leg? In other animals the tail also helps with balance.
All of this makes sense except for at 8:31. By adding additional wheels you do not nullify angular momentum, you double it. Angular momentum toward the rear of the bike has the same effect as it does in the other direction.
eyesyc You clearly don't understand angular momentum. The mass of the rotating wheel travels along the same plane as the mass of the bike frame, And they are rigidly connected. Regardless of the wheels direction of rotation, it's still moving along the same plane. The energy needed to deflect mass from this plane is angular momentum. For example, The front wheel has a rotational mass of say one pound, it's rotating at 100 revolutions per minute. at the given mass, moving at the given speed of rotation, it will take a specific amount of energy to deflect that mass by the one degree from the plane described. Regardless of what direction it is spinning. Spinning another wheel in the opposite direction does NOT cancel out anything.
eyesyc What you have described is torque. Then you threw in some unrelated terms that you found on Google. I remain unimpressed. And YES... Please do give me a full vector analysis. Seriously... I'm looking forward to it. Here's a prediction... You will avoid my challenge to provide it, then change the subject in order to avoid the shame of having been caught bluffing.
Hi JustSomeGuy: Your comment is echoed in several places on the www. And it reflects a common misconception about angular momentum. Too common. The misconception is even in a video put out by NASA in which an astronaut tries to explain angular momentum using rotating CD players. Here is the misconception. In your mistaken view, and the mistaken view of many others, angular momentum is a positive scalar, like mass. If I have some and you have some and we get together we have more. But this is not so. Angular momentum is a vector. If I have some pointing left and you have some pointing right and we get together, they cancel. And this is the way it is with the wheels on the bike above in the video. The propagation of this false conception, that angular momentum is a scalar and not a vector, is in part due to a common overly simplified expalanation of a gyroscope. That overly simplified description is this: A spinning object resists rotation. The more correct statement is that: A spinning object, if torqued about an axis perpendicular to the spin axis, turns about the axis perpendicular to the first two. And the direction of this turn depends on the direction of the spin. Hence the cancellation if two spinning wheels are mounted to the same part of the bicycle frame. I realize this is hard to understand. No-one I have met, and this includes lots of people with PhD's and me as well, really has a deep intuitive feel for angular momentum in 3D. It is so, well, three-dimensional. And picturing things in 3D is hard for our human brains. None-the-less, we understand some things. Enough to know, say, that gyro effects cancel when you have counter-spinning wheels. But we also know enough to know that these things are hard to understand. So your being confused about this is well within the realm of the normal.
Can someone get me more information, especially visual material about the rear wheel steered bikes? I don't quite get how they work and am yet to find further material. About the rest of the Talk: Thank you very much for making the effort. I don't get all the shittalk of mostly English-Natives who complain about the teaching skills. It seems that they want to have teachers who make it easy not Scientists who understand a lot. I think that goes back to a client mentality in a privatised educational system where good students are not expected to be capable of dealing with science without some sort of Entertainment. I am not used to speak a lot of English myself so I have a lot of respect for making it understandable and am thankful for showing the principles.
Since I was in a hurry, I skimmed through this, but he said that gyro and angular momentum wasn’t the reason but they are factors, then what is the reason it says up ? Many factors ?
"Why don't we fall off of bicycles?" would be correct grammar if that's what you mean. A better question however, is why is this guy wearing a MasterCard as a nametag?
When one doesn't have the answer it is easy to spend much time explaining. Why a moving bicycle stands up is never explained. The road forces on the bicycle are responsible as I explain in my short video, "Bicycle Stability 101.
Hi Calvin, Andy Ruina here, a co-author of Schwabb on the video above. I even made, and am in, some of the clips in the video above. For the record, in case anyone reads these comments, I have spent some time trying to understand your theory of bicycle balance. So have several other bicycle experts. And you have yet to write anything that we can evaluate as right or wrong. That is, your claims are, so far, too vague to even be wrong. You haven't described an experiment that could, in principle if you were wrong, falsify your explanation. Without such it is hard to know if you are saying anything. For those who don't know Calvin, his theory is something about tire forces and torques from the ground reaction. But that something is something he can't describe well enough, yet, for those of us who think in terms of experiments and equations, to understand.
Andy Ruina Hi Andy, thank you for your critical comments. They have helped refine my understanding as has the TMS design. In my experience, it is not possible to explain anything to an expert, nor is it possible for an expert to learn. Your paper and press release picked up by pop sci mags present the case that only such experts can understand why a bike remains upright in motion. I believe, anyone with curiosity and a little technical aptitude can grasp the specific mechanism detailed in my video "bicycle steering 101."
I am sorry Calvin but i must agree with Andy here. Your video consists of simply stating some things the bike must do to steer. Yet it doesn't explain how any of this works physically. You mentioned some sort of friction, but you don't go further on this topic. I imagine if it was due to friction i would have to feel the influence of a tire change onto the steering at least in some way. Yet my bikes feel relatively similar with different tyre types and on different ground types. In conclusion that cannot be the point. What i do feel on the other hand is Mass changes on front or rear parts of the bike. If I add lots of weight in my Lowriders my bike gets unstable. If I add it on the rear it is more difficult to steer at higher speeds. I guess one could also conclude that this is due to the effects of inertia, but then it would have to work the same added to the front. I am no expert, yet i do get the points of the paper and think that there is something to it, but i am quite certain that what you are explaining makes not sense at all. If you are certain about your point it would be really nice of you to design some experiment to show it. Like in case of your friction argument you could maybe glue sandpaper to tires to increase the friction on their sides and thus show the influence onto the steering ...?
Unicycles aren't self-stable, but the process of operating them involves the same idea of moving the tyre contact point to be in line with the resultant of gravitational, acceleration and centripetal force vectors.
I like how he shows virtually no proof and not even a hint of mathematics. It's all conceptual physics without force or energy vectors to help illustrate. I further appreciate how little thought is given to the visual examples in the form of props. Yes, a cone stand for the gyroscope is too much to ask even though it comes free with every gyroscope I have ever seen. He knows that to be an effective demonstrator he must use no more complex items than can fit in his fanny pack when he buys them at the airport gift shop AFTER landing, on the way to the TED Talk. I like it.
He explained nothing. All he did was disprove some popular theories. Clearly there is a negative mechanical feedback loop at work in conventional bicycles. It has nothing to do with the rider because conventional bicycles are inherently stable without them. The fact is, the negative feedback mechanism which keeps a moving bicycle upright is still a mystery. Amazing, but true.
Yeah, I wasn't highly interested in the subject, but I couldn't finish the video cause I kept tuning out due to his tone and pace. Would hate to have him as a professor in college.
this man should not be a teacher. he has no understanding how to explain things clearly. and i say this even though i understand why bicycle dont fall. a second thing he said is that the trail isnt needed for balance. thats like saying eating bananas isnt needed to feel full. yes, but if i eat bananas every day then the bananas are whats keeping me full. in bicycles the trail DOES add balance, and it doesnt mean anything he built a bicycle without a trail
I'm disappointed by many of the comments. They are critical nit picking. What is suggested by this video is that a whole new technological bicycle may come of Arend Schwab's work. A bicycle with greater stability due to electronic stabilization. A safer safety bike. A fall resistant bike that would lower the number of people injured on bikes. I think it is great work, I applaud this work and look forward to seeing future prototypes.
This is the only guy that I have actually understood. Good job for explaining it so clearly!
He did not explain it.
wow! It was a real pleasure to be disabused of my misconceptions so convincingly. I am going to watch this a few times to catch a couple of points that went by me too fast to absorb. The remarkable thing about bicycles (I still believe) is how readily they plug into human beings innate abilities.
The bicycle is the most efficient machine ever devised.
Sorry to be so off topic but does anybody know a trick to log back into an instagram account?
I stupidly lost my account password. I love any tips you can offer me
@Kamari Kai instablaster =)
@Kyng Gregory I really appreciate your reply. I got to the site thru google and Im trying it out now.
Seems to take a while so I will reply here later with my results.
@Kyng Gregory it did the trick and I finally got access to my account again. I am so happy!
Thank you so much, you saved my account !
Impressive speech! In an era in which science is devoted to come up with theories and explanations on the creation of our universe, simple everyday classic physics phenomena such as the stability of a bicycle remain unclarified.
It's even more amazing that you can put a child on such a magical device and it will eventually learn to control it, do tricks on it all without understanding what it's doing. The human mind is astounding.
Being a cyclist; first time got to know such eyes opening scientific input from Arneb !!! Kudos 👍👍👍
I'm really glad there are people out there like this gentleman. I'm way not detail oriented enough for this type of work and it's good there are people out there like him. I'm, generally, more focused on not getting killed by a car.
I have heard a quote: that the bike was the pinnacle of man's enginneering and all the rest of technology has been downhill from that. If you think about most everything else has increased pollution and dependency of some sort or another.
as if the production of the bike itself isn't one
@@kcfish4862 are you referring to its production makes pollution ?
It does, but when you think a well made bike can last probably 50 plus years of constant use , I'd see it pretty good use compared to a car. Unfortunately our cities are designed around cars, not people, pedestrians or cyclist to commute.
@@recyclespinning9839 not only that but also the production of bicycle is also depending on something else be it the frame, gearbox hub, etc. While not as much as things like cars etc, it's nevertheless a pretty rude claim to just say that everything else is a downhill in terms of engineering and has more dependency, I mean just look at how you even typed that comment in the first place.
@@kcfish4862 I mean down hill in terms of pollution . I'm a bit biased on cars. I like sports cars , but realize that we basically have become a "car culture" . Its like car manufactures rule the world. I mean we fight wars for oil to fuel them..
@@recyclespinning9839 Well I too agree on the car part, don't mean to look down on bike since they make a single human so much more efficient at traveling, mainly it was that I don't think it deserves the title of pinnacle of man's engineering, and that there are definitely other things that creates less pollution/dependency.
Excellent review of bicycle stability and what the future could hold in improvements.
Bicycles are by their very nature stable. Been riding since 1968 and I have never lost control due to stability issues.
Who edits these TED videos?
.
Most times the videos cut to the presenter whilst he's talking about something on the screen behind, so we miss what he's talking about!
Happens on a lot of Ted videos nowadays
Maybe because of copyright issues
It's because these are TEDx events, not TED.
These events are conducted by people outside of TED licensed to conduct the event. The part of the name after TEDx gives idea on who conducted it. And also these people are in charge of recording and editing these videos too.
@@prince.r wowww, it happens with Ted videos too though
Assistant Professor vs. Mechanical Engineer:
The picture at 9:14 shows positive caster. The device in action has positive caster. There is no demonstration of the device working with no caster. If his argument about tipping masses was correct, a stationary bicycle would turn toward the fall. This does not occur in the demonstration at 4:11. Bicycles self stabilize because of the caster effect and the rounded rubber tire. As the bike falls, the contact patch moves toward the side wall, and friction helps to turn the wheel toward the fall. Metal, "pizza cutter" type wheels would rely completely on the caster effect.
Any time Mr. Sibert. I'll bring the graph paper and the screen grabs. I'm out of whiskey at the moment, so let me know ahead of time so I can pop down to the shops.
The stationary bike falling does provoke a steering effect, but if you just let the bike fall, you can't see it in time. I've just tried it with my own bike. Hold the bike upright with the steering straight and lean it over. The steering will turn into the lean every time. The caster is what does it, and I agree that his "no caster" model does in fact have some positive caster.
I've been riding two wheels for over 45 years and your reasoning is just common sense to me. Stability is a function of inertia, variable caster angle, and contact patch area/friction. It's the relationship of these three things that determine stability. If you look at any one aspect while ignoring the others - of course it'll make you wonder. The delta must be close to zero sum. You vary the caster effect, either by making it 0 or increasing it too much like a chopper, stability will decrease. Increase or decrease friction too much, (like riding on ice or having a front tire so flat that the contact patch affects caster and inertia, stability decreases. Increase or decrease inertia and caster will need to vary to maintain zero sum. For example, we increase inertia during high speed cornering. To overcome this we have to decrease caster to offset the inertia. This is done by leaning forward and literally steering away from the lean - the opposite of a low speed turn.
Their experiments were done by limiting both inertia and speed. The rear steer bike worked well at low speed. Increase speed beyond the limits that the caster can be varied and during a turn the caster will cause the back end to swing around, increasing friction of the contact patch and inertia will cause the rider to endo in a straight line until friction overcomes inertia. Ouch.
I used to think that the chief reason for the stability of bicycles was the gyroscopic effect of the fast rotating wheels. Not any longer! Thank you.
I am really surprised there is no mention of wheel camber, especially given that the speaker is a professer of applied mechanics.
A single wheel rolling on it's own shows the same tendency to steer in the direction it is tilted. When a wheel that is rolling in a straight line is tilted it exerts a thrust in the same direction at the contact patch because the tilted wheel wants to follow a circular path. In effect the rolling wheel automatically moves the contact point to be under the center of gravity. This is the same principle behind a band saw blade or flat belt tracking on a crowned pulley, and also what makes a car with misaligned wheels pull to one direction.
Gyroscopic effect is negligible to nonexistent, and has been debunked, caster effect is negligible but makes steering from the handlebars more stable. I find the idea of one wheel 'falling faster' than the other highly dubious without supporting evidence.
I have a front wheel drive recumbent bike with almost zero trail/caster that will toss you onto the ground if you try to steer only with the handlebars. Instead you have to lean into a turn even at low speed and the handlebars just let you damp the oscillation or turn more agressively. ...Steering on a bicycle can be accomplished almost exclusively with camber thrust. I'm not well versed on unicycles but I tend to guess that the statement holds true for those as well.
Mark McCormack The camber is the mechanism how bicycles turn corners.
But to make a bicycle "SELF-STABLE", you need: at least two wheels aligned straight in the rolling direction, and only one but not all wheels that can steer left and right freely. Besides, if the road friction is negligibly small (like on well polished smooth floor), even negative casterring is fine. But if the friction is relatively big (like on muddy road), you need positive casterring or at least zero casterring to achieve self-stability.
+Mark McCormack Very good comment, sir!
I've been trying to find resources to understand that and counter steering properly (most stuff online if full of guessing and no physical or mathematical explanations whatsoever) and this video and comment are gold! Of course this also mean they left me even more confused than before... hehehe
Tbh the only part I disliked about it was when you said "the tilted wheel wants to follow a circular path", like it has a will of its own. I did not quite understand this point because of it. Care to elaborate? I can imagine why this happens on a bicycle, but not really on a wheel by itself.
Thanks!
The tire acts like a rolling cone when the axis is off parallel with the road surface, following a circular path, but the inertia of the wheel acts in the tangent, so the forces oppose eachother and move the wheel back to horizontal. Or if the inertia isn't strong enough, the wheel spirals inward until it falls over.
Not huge on all this physics stuff but your problems comes from a difference in steering. A motorcycle or bike with 2 wheels that are rear wheel drive you counter steer push left go left push right go right. A front wheel drive bike not fun to steer tried it with my e bike and switched to a rear wheel drive motor. Also no sure if your recumbent is 2 or 3 wheels. If its 3 wheels you really are gonna have a bad time with single front wheel drive. Front wheel drive can only be done right with 3 wheels when the front 2 wheels drive in unison.
That's a fair point, much like the stability of a train on tracks. 👍
You are awesome :D
Much thanks for your very cool, fun and useful work.
All humans should be able to follow such amazing lines of work like this...
The rear wheel imposes the trailing castor effect as well, as the rear wheel follows the path of the front wheel. Essentially, the front wheel replicates the pivot point of a castor wheel.
The key to balancing is to alter the position for the center of gravity to match the angular path of travel - alter the center of gravity to move in the direction of a desired turn, and match the turn of the wheel in proportion to the momentum and direction of an off-center center of gravity.
amazing insight of bicycle dynamic! So many new ideas in an old machine.
Good speech,now I understand how bikes balances when we ride them.
Excellent,not only bicycles but for future vehicles,enclosed motorcycles.Designing safer,more stable motorcycles and other narrow track vehicles is a win win for all of us.
So, it's still the caster effect.
When you look at a bicycle tire in cross section it is circular. The center line of the steering axis is in line with the center of the contact patch however, as the bike leans to one side the contact patch moves to that side but the steering axis leans with the bike and so the contact patch and steering axis are no longer aligned. If the bike leans to the left the contact patch moves left of the steering axis creating a caster effect not in the line of the movement of the bike (y axis) but in the line of the lean of the bike (x axis) . This causes the steering to turn into the lean. The caster effect is in the x axis and not the y axis. Make a bike with tires that have a cross section of zero (a thin sheet of metal for example) and you will see that it is unstable. You can experience this by riding with no hands. Take a mountian bike with wide tires, ride it with no hands, then switch to very thin road tires. It will be much more difficult to ride hands free. Maybe the upward trend in accidents is due to a trend in narrower tires? Maybe a return to wider tires would help.
Brilliant - very informative and completely turned around my understanding of bicycle mechanics
He explained nothing.
Nicely explained ! Thank you !
Bicycle design was perfected by the late 1800s. Just look at that scene in Butch Cassidy and the Sundance kid. :)
The best mass/gyro/trail interaction. That would be an interesting problem to solve for AI/Neural network.
I think this is a really well done and clear talk.
So what was its conclusion?
It doesn't sound like they considered the fact that a tilted wheel will apply a turning and stabilizing force, regardless of trail, mass distribution, and gyroscopic effects. Lose the bike all together and slowly roll a wheel by itself, it's stable. As it tilts into a fall, it rolls on its radius and applies a turning motion correcting the fall.
Hi Timothy:
Andy Ruina here, I am in and made some of the clips in the video above. And I have worked for years with Arend Schwab, the speaker in the video.
Your explanation for bike stability, that it is like the stability of a rolling wheel, was one of the prominent theories of bicycle stability in the 1800s. And it lives today. And it is a big part of what motivated our theory and experiments. So, no only did we consider the self-stability of a rolling wheel, our work was explicitly intended to show that this effect was not key. It is relevant, but not key.
By the way, that stability of a lone rolling wheel IS completely dependent on gyroscopic effects. That a rolling wheel steers left as falls left is entirely a gyroscopic effect. And that effect is there on a bicycle. And it is important for bicycle self-stability. But for a bicycle, unlike for a rolling wheel, that effect is not needed for self-stability. That is really one of the two original points in the video above.
The other of the two points is that trail is also not necessary.
The whole point of the video, corresponding to the title of the Science paper which it is describing, is that Neither Trail Nor Gyroscopic Effects Are Needed For Bicycle Self Stability. This is to distinguish the bicycle from a rolling wheel, in which gyroscopic effects are needed for self-stability.
A wheel rolling by itself does have gyroscopic effects!
hello sir, I have strated to get very interested in this subject. When you talk about a lone rolling wheel relying on gyroscopic effects , do you mean gyroscopic precession? From what I have understood, it takes effect when the wheel actualy leans to one side. If so, why does a wheel rolling in circles and having a fixed angle to the road not go straight? hope you respond
I didn't intend to say that gyroscopic effects don't exist. I believe there are other small forces that are also involved based on the geometry of a wheel/tire and where the contact patch is applied and the CG and resultant forces. How involved would depend greatly on the details of each application. I agree that gyroscopic effects play a big part on single wheel stability. I think the situation i'm thinking of is a rolling coin as it falls. It will rotate around its radius even though the angular momentum is very small.
I think this is more of a car matter than a bike matter. I believe the tilt is factored in trail
A very good explanation. Thank you.
The problem with all of these things is people trying to find "which effect makes bicycles stable", when there's many effects which all contribute, to varying degrees depending on design, speed, and lean angle. If, at a given speed and lean angle, all of the forces on the steering add up to turn towards the fall, the bike is stable. If they add up to turn it away, it is unstable.
Just because you can build a bike that works without trail doesn't mean that trail isn't the main contributor to stability on a conventional bike. If you take a normal bike, and give it negative trail without increasing some other stabilizing factors, you're going to have a bad time.
But you can take a normal bike with rake and trail; and easily make it unstable by adding mass to the steering mechanism, behind the tyre contact point.
wow a lecture discussing fork rake and trail...awesome and pithy
The facts for bike self-stabilizing:
1.gyro effect destabilizes, but it's negligible for normal speeds of a road bike
2.both articulated parts are inverted pendulums =>CG are always above contact line =>mass distribution is negligible here too (for normal wheelbase)
3.any bike geometry stabilizes as long as it reacts by steering IN DIRECTION of accidental lean (any learner is told to do)
4.classic geometry is the most stable, but it can't help handicap who must stay away from any machinery operating.
5. B.S. can be presented with professor's style.
Stable rear wheel steering is very interesting for a velomobile or recummbrant bicycle! You gould get rid if the long chain.
Anyone here read a paper called "Stability analysis for the Whipple bicycle dynamics"? It's a very interesting work about the topic.
Why is the bike stable? So simple question, so simple answer.
Gyroscopic effect is ever present and is one of the reasons the bike will stay upright when moving. Second one is the overall mass of the bike. When pushed, pulled, thrown etc., any object has the tendency to move in the desired direction until it has no energy to continue further. Third reason is that at least one wheel is free steering in the steering head to compensate external forces (irregularities of pavement, winddrag and so on) by aligning the steering wheel into the direction of the movement.
Front vs. rear steering wheel and positive/no/negative trail. This determines the level of sensitivity with which u will steer the the wheel. Rear wheel steering is really sensitive as mentioned in the video (steering while going backwards in a car). Similar to that is negative or no trail while steering the front wheel. The less sensitive is positive trail, i.e. chopper with extra long front forks (this one will feel the most stable in the stright line) Due to this sensitivity we mainly use positive trail to ensure the best steering abilities of the bike.
Btw have you ever rode a motorcycle? Do you know what is countersteering? Do you know and understand weight distribution between front nad rear wheel?
+Krejza82 Why are you saying any of this without having watched the video? 9:40
+Aaron L You made a mistake thinking I did not undestand the video. Fact is I just do not agree with more than a half of it. From a third view it almost seems like a fundraiser video in the first place
Nope. You missed much of the point of the video. Bicycle geometry determines stability, NOT angular momentum of its wheels.
Fascinating
he has mentioned a book named Theorie des Kreisels, where can I find a pdf of that book in English?
I basically want that derivation he talks about
I don't get the confusion because it is so simple. Looking at the wheel as a tall, skinny donut, with a tire that is round in cross section, it is obvious that the furthest part of the tire from the center of the axle is the center of the tire as you look down on it. To either side of this longest diameter, there are shorter and shorter paths around the tire due to the shortening distances from the tire contact point center to the axle center as you move away from the wheel maximum diameter. For a left turn where the tire contact patch extends from the bottom center of the tire toward the left side of the tire, if we define the other edge of the patch as maybe an inch left of the longest diameter then that edge is traveling a shorter distance. So the tire will move along a circle whose length is the distance around the tire at the center of the patch ( halfway between the longest distance around the tire and the shorter distance of the left edge of the tire contact patch). Thus the front wheel circles to the left while the rear wheel follows. This flexes the spokes to the right, creating a pressure toward the left which pulls the tire back toward the furthest diameter thus the bike rights itself.
I read that the increase in accidents of elderly people in The Netherlands is due to the increase in electric bikes. And from personal bicycle experience, falls are the result of interacting with the environment: hitting a hole being my least favorite. A more stable bike doesn't help with that, maybe a flying bike would. ;-)
I'm curious, why would electric bikes increase accidents? Because it allows them to go faster?
@@caiofernando Exactly.
velocity plus symmetrical weight distribution from handle to handle. seems way simplier than what he explains
Maybe I am wrong but I believe I have always understood from looking at bicycle frame design that the angle of the head tube/steerer tube, was a huge determining factor in the stability of a bicycle and also on how quickly or slowly it can be steered. The first safety bikes such as the Wright brothers build had a fairly relaxed head tube angle which in turn made it easier to keep the bike going straight. Somewhere along the evolution of frame building and I am not sure on this point that certain frames had the head tube angle steepened. I know on most of my road bikes which I have models from the 60s thru 2015 the head tube angles are different than my mt. bike frames which for obvious reason are designed to turn or maneuver quicker. I would think if you did the push the bike and let go test the modern road bike would out-distance the modern mt. bike. I am not sure this gentleman explained that, maybe he did but I am not tech-smart enough to know if he did. Lots of factors for people falling over on bikes nowadays besides stability, cell-phones, lack of skill, not paying attention, riding an E-bike faster than they are capable of handling it. Just my humble opinion, have a nice day.
Centrifugal force -- velocity holds the wheels upright. When the bike loses velocity it starts to tip. When it tips, it increases velocity, and the increased velocity returns the bike to stability. Like an airplane that stalls, falls, increases speed, and regains lift.
No
Is not the rear wheel also a castor that lies behind the steering axis? In fact, with the experimental design in which the tiny front wheel's contact point was moved slightly ahead of the steering axis, did not the tiny rear wheel's contact point remain behind the steering point[it castors still]. So a conventional bicycle actually has two castors - both trailing the steering point! The steering point always leads two in-line castors . Essentially the steering axis 'pulls' two in-line castors with a differential in castor contact points with respect to the distance to the steering axis - which sets the condition for auto steer into the fall.
Sorry for incorrect spellings: Arend ☺️
Eye Opening Bicycles
I would like to see an explanation of why a bicycle or motorcycle is more stable under power and less stable under braking. I think that it is related to any theory of bicycle stability.
I have one. Are you interested?
Nice! Fortunately only necessary for nerds to understand and enjoy. Lego bike is toooo cool!
Interesting problem. Could it be caused by the difference in diameter of the front tyre contact surface when the tyre starts to tilt and the contact surface is not the middle of the tyre but rather shifted either left or right ? The tyre will roll partially on it's sidewall where it's diameter is smaller, and therefore it's speed lower, compared to the middle of the tyre resulting in a difference in speed between the faster outside (middle) and slower inside (left or right depending on direction of fall) of the contact surface area of the tyre forcing the front tyre to steer into the fall (path of less resistance). The following weight of the bike wants to continue its movement forward (not the direction the tyre is steering into) and will increase friction (grip) on the faster outside contact surface area (middle) of the front tyre causing it to turn in the opposite direction of the fall ?
0:09 "long known but still amazing" - so, the meaning is that when u come to know the logic behind things, the amaze they once had gets lost right??
i am a bit confused. so, is the stability of bicycle fully known, or is only one more parameter is explored in detail???
12:45 The reason for the instability of the bicycle being pushed in reverse is not an inherent rear-wheel-steering problem as implied. It's because you were using a front-wheel-steering-stable bicycle in a direction for which the steering was not designed. I'm sure your trailing-wheel penny-farthing design wouldn't fare very well if you pushed it with the small wheel forward!
So really it's about the centre of mass and dynamically altering it so the bicycle falls into the turn?
Is it conceivable that, once the public began to accept something akin to the self-stable rear wheel steering bike, it could provide a more stable ride for those prone to falling? How actually maneuverable is such a machine? Could it make quick avoidance maneuvers? Could a box be put on the back?
I think he only gives half the explanation. Once the bike begins to tip and turn, the inertia of the bike and rider wants to keep the bike moving along the original vector, so as the bike turns and tips a little, the inertia induces a small force righting it. That's my theory anyway. :P
As for the gyroscopic effect, it has to be negligible (when there is an actual rider on the bike), as the mass of the wheels is so small and the wheels rotate relatively slowly. On a heavier motorcycle, I suspect this effect is much more prevalent.
You're correct .
Jan 2021 and we honestly still don't know how they work .
This isnt right, keith code figured it, watch twist of the wrist 2. they are stable because the forward inertia pushes the bicycle forward while any instability moves the contact patch under the falling weight, the inertia from the forward motion then pushes against the high side of the bike turning it the other way. the bigger the movement in the contact patch the more turning force is exerted which is why on a motorcycle pushing forward on the right handle bar turns the bike right even though the wheel is trying to turn left, the wider contact patch creates more friction, tipping the front over. once the front is falling the forward interia againt the high side of the bike turns the wheel the opposite way. i'm not a physicist but ive ridden a motorcycle on a pennys worth of contact patch and from a practical standpoint, the bars always track to the most stable point. with cruise control you can place a bike into full lean with a penny sized contact patch between both tires and the bike will be stable without any rider input; or rider if youve seen the motorcycles winning races without riders on them in the motogp. furthermore that same bike at full lean with no rider input is stable to essentially any disruptions, from sand to poor road conditions, the only thing that will make it fall over is an input on the bars that prevents the contact patch from tracking to the center of mass
that's amazing. I think this needs to be visualized in an animated way.
Why Bicycle stays upward while running? The answer is pretty easy. The pull of Gravity is Defeated by Velocity. Explanation: As we all know that there is gravity that always pulling everything downward. The Bicycle driver as riding on a bike the gravity pulls the driver at right and left side causing unstable position. To balance the bike, the driver has to move the steering sidewards but it is not enough to make the bike balanced. So the biggest option the driver do, is to have velocity to counter the pulling gravity. Thus the bike balances because the velocity force cannot overcome by the pulling force of gravity. Example, a single bike tire, turn it on upward position. the tire could stand balanced upward while on run. Remove the velocity, the tire will fall down because the gravity force will be greater than the force of velocity.
Nope that's not it.
+Romy Nacido The reason that a tire will stay upright is because of the gyro effect, when it starts to tilt the tire turns into the tilt just like a bike in that way it stays upright. :)
Funny😂😂r u being serious? Velocity force?
Few years later and this video is even less accurate.
He never said why safety/regular bike works the way it does, neither why we all use it for our happiness. The funny thing is he presents 2 bikes with different design (highly impractical and inefficient form many points of view), yet, in the end, thar electric toy bike has the same safety/regular bike geometry we all use.
No, there won't any revolution in bike design. It happened in the second part of 19th century. I am pretty sure there is nothing new to add to make the bike design any more efficient and practical. Yes, better materials, better suspension, better tyres etc. will make it better but there will not be any radical change of design. Especially not these "theoretical" bikes.
I am pretty sure I got a bit further in understanding why the safety/regular bike works. Video is in progress, right now.
Just some food for thought - positive trail, contact patch, angle and position of the head tube, two wheels ;-)
5:4 I did it with bike wheel &got opposite results
Indeed, upper part of rolling wheel has most horizontal component of momentum &its conservation reacts against lean or steering move (motorbike racers have appropriate counter-steering reflexive jerk before steady phase of turning). In normal riding negligible disturbing gyro affect is canceled by classic bike geometry that is only stabilizing factor.
Schwab should've learnt Wikipedia article first.
HI currishev:
Andy Ruina here, friend and colleague of Schwabb who made the video. I am even in some of the video clips. I was also the Masters Thesis advisor of Andrew Dressel,
the main author and moderator of the Wikipedia page on bicycle stability.
Yes, the wikipedia article on bicycle stability is VERY GOOD and informative. The Wikipedia page has most things right, as best I have seen. And I don't think you will find any disagreement in the Wikepedia page on bicycle stability with what Arend Schwab says in the video.
If you glance through the various papers and appendices on Schwab's or my www pages you will see that the work presented in the video above is not casual dabbling, but pays lots of respect to the 150 years of thoughts and researches on bicycle stability.
If u are right, I don't understand English then.
My understanding of bike stability is self-coherent and consistent with my grasp on classical mechanics, So, further non-specific talk is pointless unless u can cite wrong part in the Wikipedia article ("..most things right.." is not everything right in plain English) with yo arguments.
Dear currishev:
Please tell me what about the Schwabb video you think is in contradiction with the Wikipedia article on bicycle stability. If you are specific I will try to give a specific answer.
reread my first comment: it can't be more specific as it gets: I noted moment and content of contradiction with my wheel test and article's claim (I agree with) about negligible gyro effect on bike stability.
I don't see point in the conversation when one writes just for sake of writing,. Bye.
Hi currishev:
In response to your Dec 12, 2014 post.
I'd like to think I am not just writing for the sake of writing. I reread your post from Dec 8, 2013 and do not find it clear enough to respond to. But I am not complaining about that. I would like to write in a way that is clarifying for you if I can. My central claims, which I would like a chance to defend or explain, are: 1) Arend Schwab's talk is probably correct in almost every detail, and 2) The Schwab talk probably agrees with the Wikipedia article in almost every detail. Schwab and the main wiki author, Andrew Dressel, know each other and know pretty much what each other know. So if there is apparent disagreement between them I guess they would both like to know that and have things clarified.
So might you humor me and try to explain yourself again?
Did I miss something or did he never actually confirm why a bicycle is stable? Gyro? Nope. Trail? Nope. So wtf is it? I always figured “path of least resistance” was part of it, but that wasn’t even included in the talk.
Yes, he never did. In fact, the electronically stabilized bike at the end of a video is the so called safety bike - classic conception. That is the funniest part of the whole video.
If you let drive a bicycle exactly straight, and then you steer to the left (with a remote control), it will fall to the right. Correct?
yep; if you take your hands off of the handle bars and just push the right handle bar away from you (and them let go), the wheel will turn left, you will start to fall right and then (without you touching the handle bars) the wheel will turn right.
Why did he even mention older people? For what reason do they suffer single vehicle accidents? He didn't answer the question of why they stay upright.
I don't think no one knows at this moment.
Isn't the possibility of doing a trackstand already the proof that Gyroscopic effects aren't necessary for stabilization?
What about motorbikes? I was told it was the centrifugal force of the wheels that keep it upright around corners
I'm not an expert but I think the method of propulsion has no influence on the physics of a vehicle with 2 wheels in tandem. So bicycle or motorcycle, same deal.
Peter is right, it's governed by the same principal. Centripetal force is exerted on the wheels and pushes you inwards (towards the center point of the turn). However, without a counter force, you would just fall straight down or be thrown in towards the center. This is where centrifugal force comes into play. Centrifugal force is a fictitious force caused by a non-inertial reference frame. This force is what makes it feel like something is pushing you when you turn in a car.
very inspiring
Very interesting. But as a basic design for a stable two wheel vehicle the bicycle seems to have found its optimal configuration nearly 150 years ago. That's why the bicyle has stayed essentially the same despite great technical innovations in material science and computer design. So the conclusion should have been not innovation using non-passive steering methods "let's add some motors and a processing unit because we can", but "If it ain't broke don't fix it!"
Do humans have a gyroscope inside our bodies to keep it from falling?
Is that a serious question?
***** Um honda did it. Asimo
Zhonguoria The inner ear is where most of the magic is.
Sensory organs such as the eyes and inner ear (as Timothy Green has said) receive signals about our bodies' position, the brain processes the information and sends signals to our muscles to correct imbalances. When walking our arms play a role too, have you noticed how they naturally move at the same time as the opposite leg? In other animals the tail also helps with balance.
Not exactly.
Caster is the magic word
trail and gyro are not needed for stability, I built one !
Inverted Pendulum Effect.
I ride a Flatland bmx, zero rack! No caster.
All of this makes sense except for at 8:31. By adding additional wheels you do not nullify angular momentum, you double it. Angular momentum toward the rear of the bike has the same effect as it does in the other direction.
eyesyc
You clearly don't understand angular momentum. The mass of the rotating wheel travels along the same plane as the mass of the bike frame, And they are rigidly connected. Regardless of the wheels direction of rotation, it's still moving along the same plane. The energy needed to deflect mass from this plane is angular momentum. For example, The front wheel has a rotational mass of say one pound, it's rotating at 100 revolutions per minute. at the given mass, moving at the given speed of rotation, it will take a specific amount of energy to deflect that mass by the one degree from the plane described. Regardless of what direction it is spinning. Spinning another wheel in the opposite direction does NOT cancel out anything.
eyesyc
What you have described is torque. Then you threw in some unrelated terms that you found on Google. I remain unimpressed.
And YES... Please do give me a full vector analysis. Seriously... I'm looking forward to it.
Here's a prediction... You will avoid my challenge to provide it, then change the subject in order to avoid the shame of having been caught bluffing.
eyesyc
As predicted.
Hi JustSomeGuy:
Your comment is echoed in several places on the www. And it reflects a common misconception about angular momentum. Too common. The misconception is even in a video put out by NASA in which an astronaut tries
to explain angular momentum using rotating CD players. Here is the misconception. In your mistaken view, and the mistaken view of many others, angular momentum is a positive scalar, like mass. If I have some and you have some and we get together we have more.
But this is not so. Angular momentum is a vector. If I have some pointing left and you have some pointing right and we get together, they cancel. And this is the way it is with the wheels on the bike above in the video.
The propagation of this false conception, that angular momentum is a scalar and not a vector, is in part due to a common overly simplified expalanation of a gyroscope. That overly simplified description is this: A spinning object resists rotation.
The more correct statement is that: A spinning object, if torqued about an axis perpendicular to the spin axis, turns about the axis perpendicular to the first two.
And the direction of this turn depends on the direction of the spin. Hence the cancellation if two spinning wheels are mounted to the same part of the bicycle frame.
I realize this is hard to understand. No-one I have met, and this includes lots of people with PhD's and me as well, really has a deep intuitive feel for angular momentum in 3D. It is so, well, three-dimensional. And picturing things in 3D is hard for our human brains. None-the-less, we understand some things. Enough to know, say, that gyro effects cancel when you have counter-spinning wheels.
But we also know enough to know that these things are hard to understand. So your being confused about this is well within the realm of the normal.
Andy Ruina
What you've done here is called straw man argument. It in no way addresses what I said.
Science of bicycles, so dutch :p
All these engineers trying to build the simplest machine that is self stable, hula hoops work just fine
Josh Hula hoops aren't rideable
A Germ probably can : )
However, good explanation.
A bicycle in motion... is an inverted pendulum. Why is that so hard to understand?.
I always thought they are stable because steering slightly lifts the bicycle
I watched this whole thing, and I wish I hadn't.
yeah man he didn't say the reason he just complained about the wrong answers and i just wasted 17 min of my life:/
You're both heading for hydrant rollover : )
Can someone get me more information, especially visual material about the rear wheel steered bikes? I don't quite get how they work and am yet to find further material.
About the rest of the Talk: Thank you very much for making the effort. I don't get all the shittalk of mostly English-Natives who complain about the teaching skills. It seems that they want to have teachers who make it easy not Scientists who understand a lot. I think that goes back to a client mentality in a privatised educational system where good students are not expected to be capable of dealing with science without some sort of Entertainment.
I am not used to speak a lot of English myself so I have a lot of respect for making it understandable and am thankful for showing the principles.
Since I was in a hurry, I skimmed through this, but he said that gyro and angular momentum wasn’t the reason but they are factors, then what is the reason it says up ? Many factors ?
Nicolas Maggio We don't know exactly and that is the most interesting thing.
"Why don't we fall off of bicycles?" would be correct grammar if that's what you mean. A better question however, is why is this guy wearing a MasterCard as a nametag?
I think it has the TEDx logo on it not the MasterCard logo.
Why bicycles do not fall? Because we aint fucking stupid
Gravity
Only some bikes can balamce themselves. A lot of Chinese bikes cannot.
When one doesn't have the answer it is easy to spend much time explaining. Why a moving bicycle stands up is never explained. The road forces on the bicycle are responsible as I explain in my short video, "Bicycle Stability 101.
Hi Calvin, Andy Ruina here, a co-author of Schwabb on the video above. I even made, and am in, some of the clips in the video above. For the record, in case anyone reads these comments, I have spent some time trying to understand your theory of bicycle balance. So have several other bicycle experts. And you have yet to write anything that we can evaluate as right or wrong. That is, your claims are, so far, too vague to even be wrong. You haven't described an experiment that could, in principle if you were wrong, falsify your explanation. Without such it is hard to know if you are saying anything.
For those who don't know Calvin, his theory is something about tire forces and torques from the ground reaction. But that something is something he can't describe well enough, yet, for those of us who think in terms of experiments and equations, to understand.
Andy Ruina Hi Andy, thank you for your critical comments. They have helped refine my understanding as has the TMS design. In my experience, it is not possible to explain anything to an expert, nor is it possible for an expert to learn. Your paper and press release picked up by pop sci mags present the case that only such experts can understand why a bike remains upright in motion. I believe, anyone with curiosity and a little technical aptitude can grasp the specific mechanism detailed in my video "bicycle steering 101."
I am sorry Calvin but i must agree with Andy here. Your video consists of simply stating some things the bike must do to steer. Yet it doesn't explain how any of this works physically. You mentioned some sort of friction, but you don't go further on this topic. I imagine if it was due to friction i would have to feel the influence of a tire change onto the steering at least in some way. Yet my bikes feel relatively similar with different tyre types and on different ground types. In conclusion that cannot be the point. What i do feel on the other hand is Mass changes on front or rear parts of the bike. If I add lots of weight in my Lowriders my bike gets unstable. If I add it on the rear it is more difficult to steer at higher speeds. I guess one could also conclude that this is due to the effects of inertia, but then it would have to work the same added to the front.
I am no expert, yet i do get the points of the paper and think that there is something to it, but i am quite certain that what you are explaining makes not sense at all.
If you are certain about your point it would be really nice of you to design some experiment to show it. Like in case of your friction argument you could maybe glue sandpaper to tires to increase the friction on their sides and thus show the influence onto the steering ...?
So...unicycles????
labradoodleandpalz Unicycles fall down ..unicycles fall down every day. We're talking about self-stability!
wiskifrac you just need more practice
Nyctophobia Ahah you got me
Unicycles aren't self-stable, but the process of operating them involves the same idea of moving the tyre contact point to be in line with the resultant of gravitational, acceleration and centripetal force vectors.
his gyroscope test failed.
I like how he shows virtually no proof and not even a hint of mathematics. It's all conceptual physics without force or energy vectors to help illustrate.
I further appreciate how little thought is given to the visual examples in the form of props. Yes, a cone stand for the gyroscope is too much to ask even though it comes free with every gyroscope I have ever seen.
He knows that to be an effective demonstrator he must use no more complex items than can fit in his fanny pack when he buys them at the airport gift shop AFTER landing, on the way to the TED Talk.
I like it.
Feathering Walthamstone nerd
It is a Dutch professor living in the Netherlands. I doubt he came with an airplane to Delft...
@Jon-William Murphy Energy is a scalar quantity
If you want math i recommend reading the paper "Stability analysis for the Whipple bicycle dynamics".
He explained nothing. All he did was disprove some popular theories.
Clearly there is a negative mechanical feedback loop at work in conventional bicycles. It has nothing to do with the rider because conventional bicycles are inherently stable without them.
The fact is, the negative feedback mechanism which keeps a moving bicycle upright is still a mystery. Amazing, but true.
Read a paper called "Stability analysis for the Whipple bicycle dynamics". I think it has a very nice approach to this issue
pff next time use a broomstick , easier to balanse anyway and its bigger.
0 Trail
it is same like walking and standing in one leg ....inretia is the answer , it minimize the fallen in one side
thats just false and its a shame people write things without understanding them. please, if u dont know things then dont mislead others
This guy has to pick up his pace. His mechanical way of speaking is distracting me from the subject matter.
Yeah, I wasn't highly interested in the subject, but I couldn't finish the video cause I kept tuning out due to his tone and pace. Would hate to have him as a professor in college.
Same here, stopped after 6 minutes!
Just go on to settings near captions at the bottom of the screen and turn the speed up.
this guy is living in 3017
Watch it @ 2x speed. Fixed.
It's called a ghosty because a ghost is riding it. Problem solved. 👻
So.. why bicycles do not fall? He explains only the past wrong approaches..
wiskifrac On TH-cam, there are videos about this from both Minute Physics and Smarter Every Day.
TRiG.
Thanks mate
Older people can't steer into the fall? Rubbish.
Did this guy really pronounce the ‘p’ in pneumatic? Lmfao
this man should not be a teacher. he has no understanding how to explain things clearly. and i say this even though i understand why bicycle dont fall. a second thing he said is that the trail isnt needed for balance. thats like saying eating bananas isnt needed to feel full. yes, but if i eat bananas every day then the bananas are whats keeping me full. in bicycles the trail DOES add balance, and it doesnt mean anything he built a bicycle without a trail