Motorcycle steering range of motion

[Johnny_L.A]

What Karen Lingel has to say.

What is a gyroscope and how does its stabilizing power work? A gyroscope is just something spinning. A spinning object has angular momentum, whose magnitude is dependent on the speed of rotation, the mass of the object, and the distribution of that mass with respect to the axis of rotation. Angular momentum, like its homely cousin linear momentum, is conserved. For our purposes this means that once a gyroscope gets lined up in a certain way, it wants to stay lined up. That, in short, is how gyroscopic stabilization works.

Tp which a reader replied (in part):

Professor Klein’s particular interest is bicycles, and among many fascinating bikes that he has built are several that remove any gyroscopic effect from the wheels (each wheel has a duplicate wheel mounted above it, turning in the opposite direction).

To which Ms. Lingel replied:

So, let’s all get up-to-date with this hot-off-the-press research, which was only published in . . . huh . . . 1970. That is distressing, because my primary physics education took place in the 1980’s. Of course, you’d expect news of breakthrough research to take 10 years or more to reach a podunk school like my alma mater, the University of Illinois at Urbana-Champaign . . . um, wait, you’re saying this UIUC professor in mechanical engineering knew all along and we never got wind of it in the physics department? Man, we really should have invited a wider circle of people to our weekly wine-and-cheese.

Of course “trail” is what happens when you have “rake”, which is described in the link I posted before.

[Bindlestiff]

This discussion seems to be going on in several threads.

A bicycle in motion is balanced primarily by the rider’s input to the handlebars. If the rider presses forward on the right bar (counter-clockwise torque), the front wheel is steered to the left forcing the bottom of the tires to the left. There is nothing to force the rest of the bike and rider to the left so inertia causes them to go straight. With the majority of the bike and rider going straight and the contact patches of the tires going left the bike has no choice but to lean to the right. To restore balance, the tires must be brought back to their position under the bike. This is accomplished with rearward pressure on the right bar (clockwise torque). This is an on-going, dynamic process.

When a bike with positive trail is leaned to the right, gravity applies clockwise torque, which, if the bike is moving, tends to restore balance. The greater the trail, the greater the clockwise torque - increased stability. Because of this effect of trail it is possible to ride no-handed by shifting one’s body weight.

In executing a turn on a bike, a rider initiates the turn by applying torque to the steering (handlebars) in a direction opposite the direction of the turn. This causes the bike to lean in the direction of the turn. Throughout the turn torque is constantly applied to the steering by a combination of trail’s effect and rider input. Finishing the turn entails applying torque to the steering in the direction of the turn to bring the tires back under the bike.

During the turning the vector sum of gravity and inertia (centrifugal force) must pass through the contact patches of the tires or the bike will spin out or high-side depending on the direction of error.

The gyroscopic effect is neglibible, as noted in the example of the razor scooter.

Steering a bike (bicycle or motorcycle) at ANY speed is counter steering if the only thing tuching the ground is the tires. The “crossover” point is only perceptual. If you try it in a parking lot at walking speeds, you will find that you still initiate a right turn by turning the fork to the left. Once you have induced lean this way, you have to put right-turn pressure on the bars to limit the tendency to turn right.

Let me recap; a rider initiates a right turn by pressing the handlebars so as to turn the front wheel to the left. This induces a right lean which is needed for turning right and keeping the vector sum of gravity and centrifugal force passing through the contact patch of the tires. To STOP turning right it is necessary to steer the tires back under the bike. This requires applying pressure to the bars so as to turn the front wheel to the right.

Try changing lanes one-handed. Do it at moderate speed (around 30 mph) with no traffic. Work into it slowly. Pay careful attention to the pressures you apply with that hand.

BTW: Karen Lingel got the polarity of trail backwards. If the pivot axis contacts the ground AHEAD fo the center of the contact patch, that is POSITIVE trail. You can go to the Harley-Davidson web site and find the page where they show specs for various models and they have between 4 and 6 inches all positive.

For and interesting explanation of rake and trail see www.paintbros.com