I am doing a research project where I need inertial data of bicycle crashes. Currently, no open source data exists on this topic; so I tasked myself with getting the crash data myself. On Saturday, I went to my local recreational park and found a good lookin’ hill for me to roll my bike down. Now for actual crashes, there would be a human (weighing about 130 lbs) on top of the bicycle when the crash happens but to get the crash data we need to not injure someone. So, either I won’t use a mannequin, or I will.

But here is the thing: bicycle stability. See, bicycles are naturally stable. That means, when gravity tilts the bike in on direction, the front wheel will naturally turn in that direction to counter the instability; essentially causing the bike to be stable. Technically, there are 3 reasons to as why bikes are self-stable. The first is because the bike’s front wheel axis is in front of the point which the bike touches the ground:

The forcing acting on the wheel/ground creates a equal force on the wheel, causing the bike’s wheel to rotate the second it becomes unstable. Becuase then the force from the ground won’t be directly vertically up, it will be slightly off when it’s off balance; causing the front wheel to rotate.

The second way bicycles balance are because of how the handle bars are located on the bike. In bicycles, the handle bars are usually infront of the contact point to the ground. When the bike tilts, the weight from the handle bars causes the front wheel to rotate in the direction of tilt essentially “pulling” the bike under itself.

See bikes are essentially inverted pendulums.

Imagine trying to balance a broom stick on your hand. To get it to move forward, you can’t just simply move forward. Instead, you have to first move back a bit (causing the broom to fall forward) and then start walking with the broom.

This is the same concept in bicycles.

For more information, watch this video: Veritasium

The third reason why bikes are stable is because of gyroscopic precision from the spinning wheels. Basically, when the wheels are spinning at a certain speed the force applied to them from the imbalance is redirected 90 degrees causing the bike to self level. But this is a very small amount. Bikes are stable mostly because of the first 2 reasons.

And that’s it. Hope you enjoyed my catch up on my project.