
Fresh work on the mathematics of bicycles in motion - maximz
http://www.nature.com/news/the-bicycle-problem-that-nearly-broke-mathematics-1.20281
======
no_flags
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?

~~~
Luc
Yes!

This PDF explains it very well, with illustrations, on the last page:

[http://bicycle.tudelft.nl/schwab/Bicycle/DO-07-3-2bicycles.p...](http://bicycle.tudelft.nl/schwab/Bicycle/DO-07-3-2bicycles.pdf)

"Practically nobody is conscious of the fact that they must steer briefly to
the left ion order to make a right-hand turn. But this is not so strange,
because the swerve is very small (approximately 3 degrees) and happens very
quickly – 0.5 seconds. The wet tire tracks from cycling experiments reveal
that we all do this. Apparently we learn this unconsciously when we learn to
ride a bike."

~~~
SamBam
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?

~~~
Bognar
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.

~~~
peterwwillis
Yep. If you try to just lean right immediately, the bike will just.... fall
over, because the wheel stayed straight.

The momentum from the flick your body creates begins to turn the wheel a small
amount, and the forward momentum of the bike in combination with the lean
keeps the wheel turned right. By contrast, if you flicked the bike/wheel but
did not lean, the wheel would simply straighten itself again.

Even for automobiles this stuff is very simple suspension + steering
mechanics. Due to how their suspension & steering components are designed, and
assuming they are aligned properly, a car will always follow the road. If the
road leans + curves, so does their steering.

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maaaats
> _...an ambitious effort that would investigate everything from the strength
> of wheels..._

My master touched this. Used AI to find spoke patterns.
[http://master.matsemann.com](http://master.matsemann.com)

> _There were untested geometries out there that could transform bike design._

Better hardware and simulations makes it easier to test thousands of these,
possibly with the help of AI. I wonder if any drastically new designs will be
found in the feature, or if time will show the current design is the best.

~~~
fiftyacorn
Thats an interesting pattern - but the issue is how would you true a wheel
like that?

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icc97
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 - the hope is that this will provide better guidelines
for building bikes that are more stable.

The balance on my mountain bike definitely saved me from two near crashes of a
knock to my rear wheel by a u-turning car and being hit on the handle bars by
a wing mirror.

~~~
davidw
Peter Sagan showing how well some people can ride with no hands:
[https://streamable.com/2u94](https://streamable.com/2u94)

(From today's stage of the Tour de France)

~~~
theOnliest
And Ilnur Zakarin (also from today's stage) showing how others aren't as good!
Starting at about 2:00 in: [http://www.dailymotion.com/video/x4l18sa_flamme-
rouge-etape-...](http://www.dailymotion.com/video/x4l18sa_flamme-rouge-
etape-17-berne-finhaut-emosson-tour-de-france-2016_sport)

~~~
stedalus
To be fair to Zakarin, the finish is substantially steeper than the section
Peter was on, and he had just spent the 30 minutes on the rivet to get the
stage win.

------
sdkjfwiluf
what was the conclusion ? it's not gyroscopic effects because they still
balance with counter-rotating wheels, it's not trail because they can still
balance with negative trail. Is it some of each of these effects, if so how
much ? What else is involved ?

~~~
jessaustin
According to TFA (and to this avid cyclist it makes sense) it is the
combination of the two effects you mention and weight distribution. Novel
bikes can be constructed that tweak one of these inputs into an unsuitable
range and yet still balance, but I really doubt you could mess up all three
and still have a bicycle.

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abakker
OK - this is probably my ignorance talking, but why is it surprising that bike
are balanced? The pedals are basically shoulder width and staggered, which is
a very natural position for people to balance in as bipedal creatures? in
addition, while the bike is moving, won't the inertia tend to keep things
moving in the same direction?

This is all coupled by the fact that the rider is actively piloting and
adjusting the bike to keep it under control at all times. The bike seems like
it would balance to me because the control mechanisms are designed to keep
things balanced easily.

~~~
Someone
Bikes balance themselves; they don't need a rider to do it for them. Watch
[https://www.youtube.com/watch?v=oZAc5t2lkvo](https://www.youtube.com/watch?v=oZAc5t2lkvo)

~~~
HCIdivision17
I just want to note that this also happens on motorcycles. On a cold winter
day my bike dumped me off as I lost traction at a stop light. It started to
fall over, bumped its saddle bags, and before the tilt sensor could stall the
engine it righted itself in second gear and idled its way through the
intersection... with me literally running after it. It hit a curb and
eventually stalled upright.

Second most embarassing thing the bike ever did to me.

~~~
sohkamyung
Dare I ask what was the most embarrassing thing the bike did to you?...};-)

~~~
HCIdivision17
Oh that was at a stop light shortly after it started raining in a Texas
winter. I'm fully layered and geared up with leathers and full rain suit - I
can walk a bit like a robot and look 150 pounds heavier. So I pull up to the
light and just before I fully stop, my Dyna just ... slides out from under me.
It's rush hour, a busy intersection, and my bike just sorta falls over _in
place_ while I'm sitting on it. Nothing you can do can stop it once it slowly
starts properly tipping over, so it plonks onto the roll bars and bags (which
are wide and leather, thank god). I scramble to haul it back upright on this
oil slicked crowned lane, hop back on, and act like nothing at all happened.

------
sevenless
It might help if they program humanoid robots to ride bikes. The problem seems
to be hard to analyze because there's a person on the bike, and the way the
person moves with the bike is hard to track.

~~~
dskhatri
See Murata's Robots: [http://www.murata.com/en-
us/about/mboymgirl](http://www.murata.com/en-us/about/mboymgirl)

~~~
sevenless
That's cool, but the robot there needs a large gyro stabilizer disc to keep
balance. Not exactly the way we do it.

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bcook
Regarding countersteering & bicycles (and motorcycles), I better understood
the phenomenon by picturing a bar shoved horizontally through a basketball.

You can steer by either turning the basketball (horizontal plane) or leaning
the basketball (vertical plane). In the case of a motorcycle at speed, the
bike's effective turning radius is affected more by the lean than by how much
the handle-bars are turned. The handle-bars are more about controlling the
amount lean.

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dang
We changed this title to something less baity than the original (et tu,
Nature?). If someone suggests a better (more accurate and neutral) title, we
can change it again.

~~~
nitrogen
Pretty soon all of human language will consist of phrases like, "You won't
believe what happens when this one weird news aggregator changes a submission
title!" Is there some way we can try to reverse this trend outside of HN?

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mmf
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...

~~~
dang
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.

~~~
mmf
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.

