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Fresh work on the mathematics of bicycles in motion

nature.com

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Re: Fresh work on the mathematics of bicycles in motion

#71

Post by SapphireSun »

ethanbond wrote: post #34
mc32 wrote: post #32

Earlier quoted context omitted.

I was under the impression there is a speed at which countersteering becomes apparent and at low speeds it either is minimal or doesn't happen?

It doesn't just happen – you do it. I've never really considered it in the context of a bicycle, but it's the way to turn a motorcycle at any speed above 5mph or so. You'll hear non-riders say that you steer a motorcycle by leaning... Quite the opposite. You steer a motorcycle by steering away from the turn, which causes the bike to fall into the turn. It's the turn that makes you lean, not vice versa. Motorcycles ha…

Can vouch for this. I was very surprised when, after many years of bicycling, I went to motorcycle school and they taught us this principle. It was insanely cool that it worked.

Re: Fresh work on the mathematics of bicycles in motion

#72

Post by upofadown »

dahart wrote: post #55
upofadown wrote: post #52

Earlier quoted context omitted.

>there's only one way to turn without leaning I generated an argument that refutes that statement in the post you are responding to. I am not arguing that the effect does not exist, only that it isn't interesting and is not worthy of a special term to describe it. FWIW I ride motorcycles on a regular basis... I oppose the discussion on countersteering in the regular motorcycle training curriculum because it suggests…

You actually described counter-steering, even though you might disagree. ;) You said that I can lean right to start a right turn, then turn the handlebars into the turn as soon as you want to stop decreasing the turning radius. That is part of counter-steering. Turn the handlebars right to begin turning the bike left -- that can and does include slowing down an increasing right turn until it's at a constant turning r…

>and it's important to know in order to stay safe?

I disagree with that. Before someone learns to turn a cycle, motorized or not, they have to learn to not fall over. So we tell them that they have to turn towards the direction they are falling. Once they master not falling then in practice there is nothing more to teach. They can easily generalize to adjusting the bike to any lean angle because the required motion of the handlebars is exactly the same. If we don't tell them about countersteering they will have no idea they are doing something different for steep turns vs shallow turns. They just have to establish a greater angle sometimes.

Back in the day prospective pilots were taught by having someone show them how to move the controls for each possible manoeuvre. These days the prospective pilot is first taught what the effects of the controls are. After that they are entirely responsible for achieving the required aircraft attitude using that knowledge. They are told to roll the aircraft to turn. They are not told that they have move the stick to the right for a while and then centre it even though that is something that would not produce a continuous turn in a car.

Re: Fresh work on the mathematics of bicycles in motion

#73

Post by etcet »

willis77 wrote: post #51
icc97 wrote: post #48

If nothing else I find it quite fascinating how some bikes are easier to ride without holding the handle bars than others. I can balance much better on my 1998 Specialized Stumpjumper mountain bike (comfortable for minutes without hands) than I can on my 1998 Cannondale R900 racing bike (max 5 seconds without hand). But for my colleague - he finds it much easier to balance his racing bike. As the article suggest - th…

Some bikes that are hard to ride no-handed have "notched"/"indexed" headsets that are to blame. Small indentations in the headset prevent minor corrections from actually turning the wheel, making it hard to let go of the bars. http://www.sheldonbrown.com/headsets.html#troubleshooting (see section on "Indexed Steering")

Thank you so much. My bike has been exhibiting this behavior but I just assumed the headset was designed to 'clip' into place. Looks like I need to see the mechanic.

Re: Fresh work on the mathematics of bicycles in motion

#74

Post by tome »

no_flags wrote: post #9

Avid cyclist, but I have no idea what this is talking about: "...the phenomenon of 'countersteering', whereby the rider can steer to the left only by first briefly torquing the handlebars to the right, allowing the bike to fall into a leftward lean." Am I just doing this subconsciously?

I can't help wondering if everyone who has replied to you has mixed up cause and effect. My explanation would be:

"To turn left you need to lean to the left. Leaning to the left momentarily forces the handlebars to turn the right."

This describes an equivalent outcome to the quotation from the article but implication about what is cause and what is effect is quite different.

Re: Fresh work on the mathematics of bicycles in motion

#75

Post by mmf »

Meegul wrote: post #5
mmf wrote: post #4

How complex can it be? If you have a bare minimum background in basic physics and control theory, and a bicycle in your hands, the qualitative reasons for balance and stability will jump at you in under 10 minutes...

Alright then, what are the reasons for bicycles being balanced? If it's not anything related to gyroscopic effects, then what is it?

Ok, I guess I could have provided more info. Do this if you own a bicycle: hold it by the saddle perfectly straight, front of the bike forward. Make it lean on the left (no forward movement). Look at the handle, it steers left. When you're moving this means that when you lean left there will be a torque, due to your circular path you'll be following, that will try to make the bike lean right.

Bend left -> torque to the right, bend right -> torque to the left. Here you have the basic ingredient for stability: the one torqueless angle is the bike going straight perfectly vertical wrt the ground, while any perturbation leads to a torque in the opposite direction.

I felt it was basic stuff maybe it's not?

Re: Fresh work on the mathematics of bicycles in motion

#76

Post by mmf »

dang wrote: post #7
mmf wrote: post #4

How complex can it be? If you have a bare minimum background in basic physics and control theory, and a bicycle in your hands, the qualitative reasons for balance and stability will jump at you in under 10 minutes...

Please don't post unsubstantive dismissals of others' work to HN. If you know more than the rest of us, it would be good to post an informative comment that teaches the reader something. If you don't want to do that, it's fine to post nothing.

If you feel that something is trivial and potentially wasting other people's time by means of wasting pixels, I think it's fine to speak up. (Explaining why something is trivial may not be that effective, in general).

I was clearly wrong in that many people disagreed and found this to be an interesting and nontrivial subject.

Re: Fresh work on the mathematics of bicycles in motion

#77

Post by rukuu001 »

Bognar wrote: post #23
SamBam wrote: post #19

Earlier quoted context omitted.

It seems that they are saying you have to steer right in order to initiate a left lean. But how do they account for steering with no hands? I can steer pretty well without hands. It seems as if I must be able to initiate the left lean without pushing the handlebars right. So why couldn't I also do this when not riding without hands?

I can ride pretty well without hands as well. When I heard about counter-steering a long time back I paid closer attention to what I was doing while riding hands-free. Turns out that I was doing a weird little bodily flick motion in to get the wheel pointing to the opposite direction of the turn before I started leaning into the turn. Pay attention to yourself next time you ride and you might be surprised.

Yes, I discovered my weird hip tilt when I was using a bad seat. It was then that I realised I barely used my hands to steer at all (sharp turns excepted)

Re: Fresh work on the mathematics of bicycles in motion

#78

Post by [deleted] »

Bognar wrote: post #23
SamBam wrote: post #19

Earlier quoted context omitted.

It seems that they are saying you have to steer right in order to initiate a left lean. But how do they account for steering with no hands? I can steer pretty well without hands. It seems as if I must be able to initiate the left lean without pushing the handlebars right. So why couldn't I also do this when not riding without hands?

I can ride pretty well without hands as well. When I heard about counter-steering a long time back I paid closer attention to what I was doing while riding hands-free. Turns out that I was doing a weird little bodily flick motion in to get the wheel pointing to the opposite direction of the turn before I started leaning into the turn. Pay attention to yourself next time you ride and you might be surprised.

[deleted]

Re: Fresh work on the mathematics of bicycles in motion

#79

Post by dahart »

upofadown wrote: post #72
dahart wrote: post #55

Earlier quoted context omitted.

You actually described counter-steering, even though you might disagree. ;) You said that I can lean right to start a right turn, then turn the handlebars into the turn as soon as you want to stop decreasing the turning radius. That is part of counter-steering. Turn the handlebars right to begin turning the bike left -- that can and does include slowing down an increasing right turn until it's at a constant turning r…

>and it's important to know in order to stay safe? I disagree with that. Before someone learns to turn a cycle, motorized or not, they have to learn to not fall over. So we tell them that they have to turn towards the direction they are falling. Once they master not falling then in practice there is nothing more to teach. They can easily generalize to adjusting the bike to any lean angle because the required motion o…

It's not my opinion that learning counter-steering is a safety issue, there's a reason that practically all motorcycle safety courses teach it, and that reason is outlined in the Hurt Report on motorcycle safety.

https://en.m.wikipedia.org/wiki/Hurt_Report

"28. Motorcycle riders in these accidents showed significant collision avoidance problems. Most riders would overbrake and skid the rear wheel, and underbrake the front wheel greatly reducing collision avoidance deceleration. The ability to countersteer and swerve was essentially absent."

Wikipedia's article on counter-steering with respect to motorcycle safety begins with:

"Even more so than on a bicycle, deliberately countersteering is essential for safe motorcycle riding"

https://en.m.wikipedia.org/wiki/Countersteering#Motorcycles

You're free to argue against it using logic and analogies to pilot training, but both safety data and public opinion don't seem to agree. I would counter that pilots are most definitely taught that pushing forward (up) on the yoke causes the plane to dive (go down), that is somewhat analogous to counter-steering. They are also taught that turning left causes a left roll.

But this didn't answer my question either - counter-steering is so-called because you steer counter to the direction of turn, which is true. Even if it weren't a safety issue, why would it be inappropriate to name it? It is a thing that's different in some ways from other types of steering; we should have a name for that. We have names for everything.

Re: Fresh work on the mathematics of bicycles in motion

#80

Post by CydeWeys »

sliverstorm wrote: post #45
artimaeis wrote: post #11

Earlier quoted context omitted.

I've never noticed this on bicycles, but I also haven't ridden anything but a stationary in 5+ years now! But this is very noticeable in motorcycles. Most riders don't really think about the torque they're applying to the handlebars, but when you lean into a turn you're definitely applying that torque to the handlebars. You're kind of putting the side of the wheel to the ground in the process, and the only way to put…

I don't know why it's so much more important in motorcycles- even riders who have ridden bikes for many years like myself benefit from pointed instruction in "press right to go right". Perhaps because the rake is so much greater, it's not a natural, immediate carryover from bicycles. Or perhaps because the motorcycle is much heavier, handlebar input becomes all the more important, relative to a bicycle you can steer…

It's that the motorcycle is much heavier. You need to countersteer first to get the wheels out from under the center of mass of the motorcycle, in order to initiate the lean in the opposite direction. A bicycle is much lighter so you muscle it around more solely by moving your body, which significantly outmasses the bike.
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