# Physics EE (Extended Essay) on Bicycle Stability

Hello! I'm new to the Physics forums so I'm not too sure if this is the right place. But hopefully it is :)
Anyway, I'm currently an IB student studying Physics at higher level and decided that I was going to do my EE (extended essay), which is about 4000 words, on physics.

Since I really wanted to do something related to stability, with help from my supervisor I decided to look into the stability of a bicycles. Anyway, I need help with deciding a few things to ensure I have enough content to write about for 4000 words as well as to be able to score high on my EE.

I'm investigating on two independent variables, two factors that affect how stable a bicycle is by measuring probably how much time it can stand upright without falling to one side. Nevertheless, I was wondering whether studying the stability of a bike with a rider on it or "rider-less" is better. The thing is that I think that studying the stability of a bike with a rider on it would be better as there are more factors that can be varied compared to rider-less, however, I feel like there is human error as we cannot ensure that certain variables will remain constant throughout all the trials (I hope you are getting my point).

Also, I need help deciding on what factors I should vary (I need 2 factors) so as to make my EE interesting and not such a straight forward answer. Here are some of the factors that I'm thinking of:

With rider: pressure of air in the wheels, weight distribution, height of the seat and/or handle, distance between handle and seat, distance between hands on handle, weight of rider (probably won't use this), distance between feet, fork angle.

Rider-less: pressure of air in the wheels, height of seat and/or handle, distance between handle and seat, angle of the seat?, fork angle

^^please feel free to add to the list, I'm trying to make it so the factors are not so "direct" but must still be measurable

Thanks for taking the time to read my threat, I'm open to any suggestions!! :)

berkeman
Mentor
Welcome to the PF.
how stable a bicycle is by measuring probably how much time it can stand upright without falling to one side.
I'm pretty sure you mean "when rolling", not "when standing". Bikes fall over if they are not moving.

I'd vote for doing the analysis with a typical rider on the bike, since that is how they are used, and is the most important time for them to be stable. There have been some previous PF threads on the stability of bikes and motorcycles -- I will do a quick search to see if I can find a few to link to for you...

manu101
berkeman
Mentor

manu101
jedishrfu
Mentor
Here's a Sciam article on it too:

https://www.scientificamerican.com/article/the-bicycle-problem-that-nearly-broke-mathematics/

Be aware that this is not a trivial problem and that folks have been arguing over it for years. Its akin to how the Stradivarius violin got its hauntingly beautiful sound.

Sometimes I wonder how classical physics was able to evolve and yet not have a good understanding of this phenomena. Einstein used to ride around on a bike a lot and apparently never considered it.

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jrmichler
Mentor
Get a copy of Bicycling Science Third Edition by David Gordon Wilson, and read Chapter 8: Steering and Balancing. Forty seven pages of everything you are looking for, and much more.

manu101 and berkeman
Get a copy of Bicycling Science Third Edition by David Gordon Wilson, and read Chapter 8: Steering and Balancing. Forty seven pages of everything you are looking for, and much more.