Would gyroscopic force have anything to do with making it easier to balance on a bicycle when it’s moving rather than standing still? If so, then wouldn’t it be harder to steer the faster you go?
Yes and yes. Just not much harder.
On a related note - do you have to counter-steer bicycles? I can’t imagine why you would not, but I don’t recall anyone every talking about it.
Imagine how hard it would be to steer if you didn’t have the leverage of the handlebars to do the work for you…
IIRC, it’s not gyroscopic force that keeps a bicycle up. It’s a combination of the rider constantly making minute steering adjustments and Newton’s First Law of Motion that keeps him up.
First, if you have a bike at rest, it’s easy for it to fall over. If you’re on the bike trying to balance it without moving forward or backward, you’ll find it very difficult. There’s only two points resting on the ground (kickstands being passe nowadays), so over it’ll eventually go. Get off the bike and try to balance it. Even with a good balance, it’ll fall again.
But you may notice something as it falls: the front wheel twists a little. That’s because the front fork tube is not perpendicular to the ground, but slightly tilted back. So the resting point on the front tire changes as the entire bike is angled to one side or the other. If you slowly lower your bike to the ground, you’ll see the entire fork turn in the same direction; i.e., if you lower it to the left, the front wheel will turn to the left.
Now on to a moving bike, say at 10 mph. As evidenced when trying to balance while on the bike, it will start to fall over. But here’s where the tilted fork tube and Newton’s 1st Law come in. As you fall (say, to the left), the front wheel turns to the left. The bike will then start to turn to the left as it falls. But the bike’s momentum is vectored to straight ahead. This causes most of the force causing the bike to fall to be cancelled; just a tiny bit extra is required by the rider (in the form of minute steering adjustment) to keep the bike going completely straight.
AWB, sorry, but I think you may be a bit confused. Newton’s first law would also apply that the bike, once at rest, does not want to move.
The reason that it’s easier to balance on a moving bicycle is because of our good friend “angular momentum”. Spinning wheels have it, while stationary wheels do not.
this harkens back to the physics class demo where you sat in a rotating chair and held that bicycle in your outstrarms. When the wheel was not spinning, it was easy to change it’s orientation (relation to floor). When the wheel was spinning, however, angular momentum is around and it MUST be conserved! Trying to change the wheel’s orientation resulted in an opposite direction spin on the rotating chair. This is the same for bike tires. When the spin, they are “resistant” to any directional change - due to the momentum being conserved. this includes tipping and turning.
Incidentally, when moving forward, the standard direction for the angular momentum (right hand rule) is out of the center of the tire, perpendicular to the tire, to the left side of the bicycle.
To change the orientation of the tire (to turn) requires a great deal of force (long handlebars - more torque). The result of the conservation of momentum is the bike LEANING “into” the turn.
Go figure.
Conservatively,
Spritle
I think what AWB is trying to say is that a moving bike will stabilize itself without any input from the rider. Push a bike up to a decent speed (10-15 MPH) then release it with no rider, it will go more or less in a straight line until it slows down and spirals to a stop (or hits something :eek: ). This was the cool thing to do when I was a kid.
In my opinion (as a cyclist for several years) the main thing that holds a bike up is the rider steering into the direction the bike is falling. Watch someone riding very slowly and they have to swerve back and forth drastically to prevent the bike from tipping over. As you speed up these motions become so small as to be unnoticeable. By modifing this you can stand still on a bike. Turn the wheel to the right and if you start to fall right pedal forward slightly if you start to fall left roll back slightly. In effect moving the bike under your center of gravity.
I am sure the gyroscopic force of the wheels plays some part in keeping the bike upright but the force is small enough that any affect on making harder to steer would be unnoticeable. On the other hand racing motorcycles strive for low wheel weights because at high speeds (well over 100 MPH) it is very difficult to turn, but the wheel weights are <WAG> 100 times as much and moving 10-20 times faster </WAG>
Road racing style bikes (with very light wheels) are much harder to ride slowly. I don’t know if this is due to the lighter wheels or sharper steering angles, but probably a combination of both.
You do have to counter-steer bicycles but it is such a small motion that you would never notice it.