Why is it easier to balance on a moving bike than a non-moving one (revisited)?

[lesizz]

Yes, TRAIL!

But why?

The real balance mechanism is the rider’s brain. The brain has built into it a feedback servo system that works in the background (subconscious). When walking, a person’s (or chihuahua’s) brain will sense via physical senses when the body starts a micro-tilt in one direction, and compensate by using the muscular to offset that tilt with a forced tilt in the opposite direction.

Same thing with riding a bike, except that the response mechanism is the steering. A micro-tilt in one direction will be compensated by the brain with a micro-steer to do an offsetting tilt in the opposite direction. This is why if your front wheel loses traction, you crash. Period. Unless you do a lightning-fast forced recovery. If you are following another bike and your front wheel touches the bike in front, you crash. Probably.

The reason a positive trail bike can’t be made to work by a human is that apparently our servo’s are equipped to work with negative trail but not with the commanding adjustment in the opposite polarity. A driveless bike controlled by a computer could be programmed to work with any trail you would wish.

[cochrane]

Link to the article.

[Musicat]

In spite of Karen’s article, the gyroscopic effect may be less important than is commonly thought:

On the other hand, it has also been shown that the gyroscopic effect of a bicycle’s wheel is all but cancelled out by the weight of the rider’s body as well as the force pushing down on the front handlebars. One ambitious engineer, Dr. Hugh Hunt of the University of Cambridge, built a bike with a second front wheel. Theoretically, if gyroscopes were all that had to do with balance, spinning the second wheel in the opposite direction of the first would cancel out the gyroscopic forces, and make the bike un-rideable. Yet no matter how fast the second wheel was spun, the bike performed exactly the same. This, he concluded, demonstrated that while gyroscopes are part of a bicycle’s movement, their effect on stability is small enough that it is overshadowed by the force of the rider’s weight and movement.

also:

Gyroscopic forces are not important for the stability of a bicycle…but they help us to control the bike when riding with no hands. More important than anything is “the trail”. The front wheel makes contact with the pavement at a point that lies behind the point where the steering axis intersects with the pavement - and the distance between these is called the trail.

[scr4]

@lesizz

The reason a positive trail bike can’t be made to work by a human is …

Do you have a cite for this? (That a positive trail bike cannot be ridden by a human?)

[watchwolf49]

I tried the right hand rule but I got my thumb caught in the spokes … Karen should have warned us about that …

[naita]

@scr4

Do you have a cite for this? (That a positive trail bike cannot be ridden by a human?)

Here’s a cite to the contrary:

The common view is that this self-steering is caused by gyroscopic precession of the front wheel, or by the wheel contact trailing like a caster behind the steer axis. We show that neither effect is necessary for self-stability.

http://science.sciencemag.org/content/332/6027/339

[snowthx]

I thought a bike could not stand on it’s own because it is two tired.

[standingwave]

Kinda related… From Smarter Every Day. What happens when the steering is reversed on a bicycle? Answer: It can’t be ridden. At least not easily and not until you’ve forgotten how to ride a normal bike:

The Backwards Brain Bicycle: The Backwards Brain Bicycle - Smarter Every Day 133 - YouTube

I don’t think I ever truly understood countersteering until I was riding street motorcycles.It was just something I always took for granted.

[Chronos]

Most bicycle riders don’t understand countersteering for the simple reason that it’s not something that you do on a bicycle at all. I’ve done the experiments to verify it.

[Irishman]

@lesizz

The reason a positive trail bike can’t be made to work by a human is that apparently our servo’s are equipped to work with negative trail but not with the commanding adjustment in the opposite polarity. A driveless bike controlled by a computer could be programmed to work with any trail you would wish.

People can learn to ride negative trail bikes. The difficulty is that they are inherently more unstable than positive trail. Trail is self-correcting. As you start to move in one direction (turn), the trail follows the turn automatically. A negative trail bike is like trying to balance a broom on your nose. People can do it, but it takes a lot of practice to learn how to counter the small imbalances.

Compare balancing a pencil on your finger to holding the pencil by the tip and letting it hang down. It hangs down straight automatically, but balancing requires you to shift your finger around to compensate for small disturbances. That’s positive vs negative trail.

Musicat, apparently you didn’t follow the link at the top of the column to the follow up report, which says the same thing you did.

Why is it easier to balance on a moving bike than a non-moving one (revisited)?

@standingwave

I don’t think I ever truly understood countersteering until I was riding street motorcycles.It was just something I always took for granted.

@Chronos

Most bicycle riders don’t understand countersteering for the simple reason that it’s not something that you do on a bicycle at all. I’ve done the experiments to verify it.

Yes, when riding a bicycle, the forces are small enough to be overcome by your steering. Motorcycles are much heavier and require countersteering.

However, you can find countersteering if you ride a bicycle with no hands.

Gyroscopic Forces by Jobst Brandt

[standingwave]

@Chronos

Most bicycle riders don’t understand countersteering for the simple reason that it’s not something that you do on a bicycle at all. I’ve done the experiments to verify it.

Agree to disagree.
You may not realize that you intuitively countersteer every time you enter a corner. However, once you are aware of this concept it’s much easier to control and perfect.
To initiate countersteering, momentarily turn away from the direction you’re turning. This increases the lean of the bicycle into the turn. This method allows for greater steering control and makes it easy to affect a change in direction during the turn.

Cornering Tips

[Chronos]

Again, I’ve done the experiment. I positioned my hands on the handlebars such that they could only push, not pull, and then I removed my left hand (so I was pushing only on the right bar, and hence rotating it only counterclockwise). Result, I turned left, just as someone who’d never heard of countersteering would expect.

[Dr.Strangelove]

How did you eliminate the effect from shifting your body’s weight? If you instinctively leaned into the turn and the handlebars pushed back slightly, you probably wouldn’t notice.

I’m tempted to install a rotary encoder on my bike’s steering and record some no-hands riding.

[Xema]

@Chronos

I turned left, just as someone who’d never heard of countersteering would expect.

It’s easy to mask countersteering if you want only small steering changes: the bicycle regularly tilts slightly from side to side, so you just wait until it tilts the way you want, and go with it.

But more pronounced direction changes require countersteering. If you push the right handlebar briskly forward, you will definitely lean left; you must then either do the opposite to continue along your former track, or accept the left lean (by turning the handlebars left) and watch yourself turn left.

[Xema]

Here’s Wiki on countersteering:

When countersteering to turn left, the following is performed:

A torque on the handlebars to the right is applied.
The front wheel will then rotate about the steering axis to the right and the tire will generate forces in the contact patch to the right.
The machine as a whole steers to the right
Because the forces in the contact patch are at ground level, this pulls the wheels "out from under" the bike to the right and causes it to lean to the left.
The rider, or in most cases the inherent stability of the bike, provides the steering torque necessary to rotate the front wheel back to the left and in the direction of the desired turn.
The bike begins a turn to the left.

While this appears to be a complex sequence of motions, it is performed by every child who rides a bicycle. The entire sequence goes largely unnoticed by most riders, which is why some assert that they do not do it.

The Wiki article includes this interesting quote:

@Wilbur Wright

I have asked dozens of bicycle riders how they turn to the left. I have never found a single person who stated all the facts correctly when first asked. They almost invariably said that to turn to the left, they turned the handlebar to the left and as a result made a turn to the left. But on further questioning them, some would agree that they first turned the handlebar a little to the right, and then as the machine inclined to the left, they turned the handlebar to the left and as a result made the circle, inclining inward.

[Chronos]

Pushing the right handlebar forward is turning the handlebars left.

[thelikesofdave]

It is because you can steer into a fall thereby keeping yourself upright.

The gyroscope effect is mumbojumbo

Here is a ski bike that proves the point:

Lenz Sport skibiking

[scr4]

@Chronos

Again, I’ve done the experiment. I positioned my hands on the handlebars such that they could only push, not pull, and then I removed my left hand (so I was pushing only on the right bar, and hence rotating it only counterclockwise). Result, I turned left, just as someone who’d never heard of countersteering would expect.

If you were going straight and balanced, then suddenly turned the steering wheel to the left, the front wheel goes to the left, the center of mass will end up on the right side of the wheels, and you will fall down to your right.

What you actually did was to wait till you were already leaning to the left, and then turn the handlebar to the left. You can then maintain balance through a left turn by varying the amount of left steering input.

Counter-steering is far more obvious on a recumbent bike, where the rider’s upper body is less mobile. It’s also very obvious on long-wheelbase bikes like tandem bikes. So it was very obvious on my tandem recumbent bike. But even then, it wasn’t something I did consciously. It’s an automatic reflex for anyone who knows how to ride a bicycle.

[Chronos]

If you’re going straight and suddenly turn the handlebars left, the result won’t be turning left or turning right. It’ll be that you fall down.

If you manage to recover from the fall, it’ll be by turning the other direction. In that sense, countersteering makes it necessary to steer the correct way. But steering the correct way doesn’t require countersteering.

[scr4]

@Chronos

If you manage to recover from the fall, it’ll be by turning the other direction. In that sense, countersteering makes it necessary to steer the correct way. But steering the correct way doesn’t require countersteering.

That is the correct way to steer a bicycle. You initiate a turn by creating a slight imbalance, so that you+bicycle are leaning towards the turn. It may not be a conscious or even visible amount of countersteer - often it’s done by just waiting for the imbalance to occur and letting it build up to the desired amount.