Fresh work on the mathematics of bicycles in motion • Hacker News Board

Re: Fresh work on the mathematics of bicycles in motion

#41

Post by [deleted] » Wed, Jul 20, 2016, 7:51 PM UTC

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…

[deleted]

Re: Fresh work on the mathematics of bicycles in motion

#42

Post by HCIdivision17 » Wed, Jul 20, 2016, 7:52 PM UTC

_Wintermute wrote: post #30

HCIdivision17 wrote: post #16

Earlier quoted context omitted.

It's wildly unintuitive, so don't feel bad. When I was first learning to ride a motorcycle with the MSF, I damn neared dumped the practice bike a few times trying to manhandle it. You'll really quickly internalize push-left-go-left. And it turns out to work great on regular bikes, too. (But it's terrifyingly more responsive - I actually can't relax pedaling a bicycle because of the fear of how easy it is to flip the…

> And it turns out to work great on regular bikes, too Well yes, seeing as that's how you steer a bicycle. As a keen cyclist it annoys me when people (especially coaches) start harping on about countersteering being an additional technique you should learn, when it's what everyone has been doing intuitively since they first learned to ride a bike.

Don't take it personally - I was always just a terrible rider when I was young; I meant that in a mildly sarcastic way. I never really figured out how to properly steer until I got a motorcycle, and that just about ruined my feeling of force in the other way. Put me on a bike and in 15 feet I'll accidentally steer so hard you'd think I was dodging semis / saw a hundred dollar bill on the pavement. (I assume as a kid I just always manhandled the bike so hard I never noticed. Always standing on the pedals and pumping them like I was running, wobbling the bike's center of gravity the whole way.)

Re: Fresh work on the mathematics of bicycles in motion

#43

Post by Someone » Wed, Jul 20, 2016, 7:54 PM UTC

abakker wrote: post #20

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…

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

Re: Fresh work on the mathematics of bicycles in motion

#44

Post by upofadown » Wed, Jul 20, 2016, 7:59 PM UTC

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?

You don't have to countersteer to turn on a bike.

When you are riding straight you are using a combination of balance and handlebar position to adjust the angle of the bike so it is directly between you and the ground. If you fail to do this you fall over. So to turn without countersteer just stop doing anything and start to fall over. When you reach your desired angle of bank then turn the handlebars in the direction you are falling just enough so the acceleration from turning exactly counteracts the force that is causing you to fall. You are now in a continuous turn and you didn't countersteer at all.

If you don't want to have to wait to fall or want to turn in a particular direction you will end up turning the handlebars in the opposite direction for a time. But that is just you continuing to adjust the angle of the bike to a desired angle like you do continuously all the time you are riding the bike. You haven't done anything different or counter intuitive. I personally don't consider "countersteer" to be a thing.

Re: Fresh work on the mathematics of bicycles in motion

#45

Post by sliverstorm » Wed, Jul 20, 2016, 8:03 PM UTC

artimaeis wrote: post #11

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'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 with your body.

Re: Fresh work on the mathematics of bicycles in motion

#46

Post by sliverstorm » Wed, Jul 20, 2016, 8:05 PM UTC

HCIdivision17 wrote: post #16

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?

It's wildly unintuitive, so don't feel bad. When I was first learning to ride a motorcycle with the MSF, I damn neared dumped the practice bike a few times trying to manhandle it. You'll really quickly internalize push-left-go-left. And it turns out to work great on regular bikes, too. (But it's terrifyingly more responsive - I actually can't relax pedaling a bicycle because of the fear of how easy it is to flip the…

What really made it intuitive for me was watching video of moto gp bikes gently "folding" into a turn.

Re: Fresh work on the mathematics of bicycles in motion

#47

Post by dahart » Wed, Jul 20, 2016, 8:10 PM UTC

upofadown wrote: post #44

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?

You don't have to countersteer to turn on a bike. When you are riding straight you are using a combination of balance and handlebar position to adjust the angle of the bike so it is directly between you and the ground. If you fail to do this you fall over. So to turn without countersteer just stop doing anything and start to fall over. When you reach your desired angle of bank then turn the handlebars in the directio…

> I personally don't consider "countersteer" to be a thing.

It sounds like you've never ridden a motorcycle? Most safety courses on motorcycles teach counter-steering, precisely because it is a thing and failure to understand it can compromise your ability to recover from a bad situation.

On a motorcycle going fast, you counter-steer continuously. If you make a slow right turn on a freeway, you can turn for 30 seconds by only pushing forward on the right handle.

I'm pretty sure you always counter-steer even on a bike, it's just very hard to notice, especially going slow. We don't think about it. It's not really a choice though, there's only one way to turn without leaning, you don't get to pick counter-steering or not.

You should definitely try it on a bicycle while going fast. Once you consciously turn your handlebars right and end up steering right no matter what you do, it becomes really clear.

Re: Fresh work on the mathematics of bicycles in motion

#48

Post by icc97 » Wed, Jul 20, 2016, 8:10 PM UTC

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.

Re: Fresh work on the mathematics of bicycles in motion

#49

Post by sliverstorm » Wed, Jul 20, 2016, 8:12 PM UTC

sdkjfwiluf wrote: post #3

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 ?

I think negative trail works pretty much the same way as positive trail; I think the question is, does a bike with zero trail work. I'm guessing it can be done, but experience with various motorcycles (which have a wide range of rake) suggest trail is desirable for other reasons too.

Re: Fresh work on the mathematics of bicycles in motion

#50

Post by dahart » Wed, Jul 20, 2016, 8:14 PM UTC

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?

Try doing it consciously! It's very fun & informative. Try not to lean, and do some experimenting while you're riding fast. The faster you go, the more noticeable the effect is. You can push forward on the right side, and it will immediately put you and your bike into a right lean. Hold your hand pushing slightly on the right side to continue turning right. The handlebars will push back a little and try to straighten out.

Many people that ride bikes never know about counter-steering, unless they ride motorcycles too. So, you're not alone. I didn't know about it on a bike until I learned riding motorcycles.