# The Bicycle's Upright Mystery: Explained

• ishansaksena
In summary, this bicycle has wheels of the same size rotating in the opposite direction and it still manages to stay upright.

#### ishansaksena

Hi guys,

Why does a Bicycle stay upright ?
(It's not because of the gyroscopic forces applied by the wheels as shown by http://ruina.tam.cornell.edu/resear...ics/stablebicycle/StableBicyclev34Revised.pdf)

In short this bicycle has wheels of the same size rotating in the opposite direction thus countering the gyroscopic force but it still manages to stay upright.

There is more than one way this can be accomplished, but what the methods have in common is to steer the front wheel into the direction of lean sufficiently to correct the lean and return the bicycle back to vertical orientation (although the direction of the bike will have changed).

For a normal bicycle, this is done with "trail", the point of contact with the ground is behind the point where the pivot (steering) axis of the front wheel intercepts the ground. This results an inwards steering torque due to the upwards force from the pavement being applied "behind" the extended pivot axis.

Some research type bicycles don't use any "trail", and instead use a mass mounted above and in front of the front tire, so that the center of mass is in front of the pivot axis and above the rotational axis, which again results in the front tire steering into the direction of lean, but I don't know the details involved with this type of design.

I'm sorry if I wasn't clear, I already have a similar understanding of how it turns, my question is how it tends to stay upright when it's traveling in a straight line ( all the other sites say it's because of the gyroscopic effect which has now been proven wrong by http://ruina.tam.cornell.edu/resear...ics/stablebicycle/StableBicyclev34Revised.pdf )

Thanks,

ishansaksena said:
I already have a similar understanding of how it turns, my question is how it tends to stay upright when it's traveling in a straight line
To stay upright it makes slight turns.

ishansaksena said:
( all the other sites say it's because of the gyroscopic effect which has now been proven wrong )
Note that the gyroscopic effect is not supposed to keep the bike itself upright. Is just steers the wheel into the direction the bike falls over, so the bike straightens up again. The trail effect does the same. This wasn't proven wrong for normal bikes. It was just shown that the same steering effect can be achieved by other means, without trail and without gyroscopic effect.

Check out this thread where Andy Ruina, one of the authors, commented himself:

Last edited:
Thanks, that video was really helpful.

## 1. What is "The Bicycle's Upright Mystery"?

"The Bicycle's Upright Mystery" refers to the phenomenon of a bicycle remaining upright and balanced without the rider actively steering or pedaling. This has puzzled scientists for many years, as it goes against the laws of physics and common sense.

## 2. How is "The Bicycle's Upright Mystery" explained?

Through research and experiments, scientists have discovered that the key to the upright mystery lies in the bike's design and the rider's movements. A combination of factors such as the angle of the headtube, the gyroscopic effect of the wheels, and the rider's forward motion all contribute to keeping the bike balanced.

## 3. Why is understanding "The Bicycle's Upright Mystery" important?

Understanding this phenomenon has implications for bike design and stability, as well as for our understanding of physics and human movement. It also has practical applications for improving bike safety and stability.

## 4. Can anyone ride a bike without actively steering?

While some people may be able to ride a bike without actively steering, it is not recommended as it can be dangerous and requires a specific combination of factors to keep the bike balanced. It is always best to actively steer and control the bike while riding.

## 5. Is there still more research to be done on "The Bicycle's Upright Mystery"?

Yes, there is still ongoing research and debate among scientists about the exact mechanisms and factors involved in the upright mystery. The more we understand about this phenomenon, the better we can design and ride bicycles for optimal stability and safety.

• Classical Physics
Replies
4
Views
4K
• Other Physics Topics
Replies
69
Views
10K
• Other Physics Topics
Replies
2
Views
2K
• Mechanical Engineering
Replies
21
Views
27K
• Mechanical Engineering
Replies
2
Views
1K
• Introductory Physics Homework Help
Replies
3
Views
1K
• Classical Physics
Replies
2
Views
2K
• Other Physics Topics
Replies
9
Views
1K
• Engineering and Comp Sci Homework Help
Replies
1
Views
705
• Classical Physics
Replies
2
Views
2K