# Homework Help: What can I investigate regarding the mechanics of bikes?

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1. Dec 5, 2018

### SwizzFizzicks

<< Multiple threads on the same subject merged, Thread moved to the schoolwork forums, and the OP has been reminded to show more effort on their own schoolwork questions >>

I want an investigation/research that is simple to experiment practically (I don't have fancy equipment. My main piece of equipment is my bike), but also complex enough that I can explore "theoretically" (meaning I can well beyond introductory mechanics principles). Can anybody list some ideas?

I know this is an open-minded question, but I just need ideas to get me started because coming up with an idea is excruciatingly difficult.

Thanks

Last edited by a moderator: Dec 6, 2018
2. Dec 5, 2018

### PeterO

How about the effect of gears on maximum speed you can attain on a hill. Using various known gradients (up and down (and flat)) see what the maximum speed you can attain in each gear and thus see if you can find conditions for optimum speed. A fixed wheel bike would be good for the down grades, so that you don't merely roll off to the same maximum speed in every gear. Perhaps you need to restrict to flat and up-hill.

3. Dec 5, 2018

### Staff: Mentor

You can also answer the classical question: why does it work? In other words, what force will be needed to overcome the angular momentum in dependency of speed? What is it's (plus yours) drag coefficient, what it's friction (in dependency of tire pressure)? How long does it take to break?

I think on a bike (or bicycle?) you can explore almost the entire classical mechanics.

4. Dec 5, 2018

### Staff: Mentor

Welcome to the PF.

Your Profile page says that you are currently in high school. Is this a school assignment, or just a personal interest?

What kind of bike do you have? Road bike or MTB? What gearset / groupset are you running? What is your biking background? How many miles a week do you typically ride? Is the terrain mostly flat or mostly hilly where you ride? Do you clip in your biking shoes, use toe straps on the pedals, or just pedal on top of the pedals with regular shoes?

Also, do you have any background in electronics yet? Have you built any circuits (if so, what?)? Have you done any projects with a Raspberry Pi or similar microcontroller yet? What is your mechanical background? Do you have access to your school's machine shop? Does it have a CNC or 3-D printer that you can use to build things to use in your bike experiments?

Answers to all those questions will help us figure out some suggestions for experiments.

My current MTB ride (before the silly sidestand came off):

Last edited: Dec 5, 2018
5. Dec 5, 2018

### jrmichler

An excellent book to read that will very likely give you some ideas is: Bicycling Science, Third Edition, by David Gordon Wilson. Be sure to get the third edition because it has a lot more information than the previous editions.

Another book is Bicycles & Tricycles, An Elementary Treatise on Their Design and Construction, by Archibald Sharp. This book has many different ideas that have been tried, plus some of the physics.

Both of these books are still in print. Both are good reading for a person with the interests that you indicate.

6. Dec 6, 2018

### OmCheeto

Along with the bicycle, you can analyze body mechanics. You are after all, the bicycle's engine.
Back when I was at university, I once went to the gymnasium, and found that I could leg press 600 lbs.
Since I only weigh 150 lbs, what would be my new maximum velocity if I were able to utilize 600 vs 150 lbs of force?

7. Dec 6, 2018

### SwizzFizzicks

I'm in high school, and I'm doing an Extended Essay for IB? I only have 1 bicycle and no fancy tools or measurement equipment, so it has be a pretty simple experiment, but complex enough that I can write 4000 words (lol, so many words xD) on it. What variables can I consider vs. stability of a bike?

P.S. I have a standard mountain bike (don't know the specific specs/model tbh)

This research essay/project is due in 10 days, and I'm pretty desperate lol.

8. Dec 6, 2018

9. Dec 6, 2018

### Staff: Mentor

Multiple threads merged. Please do not create multiple threads on the same topic. Also, you never replied to all of the questions and suggestions in your first thread (the start of this combined thread). But you finally posted a few details in your second thread, which is of some help. It is concerning that you have not shown any effort on your part so far, though...

10. Dec 6, 2018

### Klystron

If you're still stuck on the assignment and haven't developed your stability theory, here's a project from childhood (meaning no ):

Convert your bike for sound. Cheapest way is to find stiff but flexible small strips that can be clipped or attached to parts of the wheel (spokes perhaps) to strike the frame each revolution with enough noise you can hear to reach the mic on your phone. Collect sound data over several runs and process it with free apps you locate online or already in your phone/computer.

You should choose your variables depending on your measurements; what you are measuring. If your bike has a speedometer, compare sound data to speed? Record and match "peak speed" (if speedometer records highest speed each trip) to peak amplitude of the sound wave record of that trip. Also, record your bike estimated speed each trip. Graph and compare your data for each trip.

With no equipment you could compare sound from the front wheel to the rear. Do the sound files differ? On straight paths or turns?

[Compare sound graphs to your graphs by marking the time; say, on a flat known bike path Find position1 and position2 with phone keeping time. Many sound graphs have logarithmic vertical axis but time axis should allow you to roughly compare data. I'll leave any additional media such as pictures to you.]

Label everything neatly and include proper references in your essay (hint: the Wright brothers worked in and owned a bicycle shop...)

11. Dec 6, 2018

### SwizzFizzicks

Sounds (no pun intended) incredibly intriguing! Thanks. May I ask what is the significance of an experiment such as this.

12. Dec 6, 2018

### SwizzFizzicks

Sorry, I'm new to the forums :P
Will be more wary next time! Thanks for informing me.

13. Dec 6, 2018

### SwizzFizzicks

I don't quite understand. Can you elaborate more please? What do you mean by "overcoming the angular momentum in dependency of speed?" What's drag coefficient? And what do you mean by "break"? Do you mean "brake"? I'm thoroughly confused lol.

14. Dec 6, 2018

### SwizzFizzicks

Wait... So are you suggesting how does exerting force on the pedals while you're sitting on the bike vs. sitting on the bike without exerting any force on the pedals?

15. Dec 6, 2018

### SwizzFizzicks

Would this experiment work with 1 bike? If so, explain ?

16. Dec 7, 2018

### Klystron

Significance of sound includes a real world (ontological) model of Doppler effect in one atmosphere (1atm), a sound example of principles of relativity. Meaning learning about sound helps learn physics.

Does a person you pass hear (the sound) of your bike the same as the rider hears the sound or (records a sound-wave)?

Say you ring a bike bell continuously (please don't!) or play music or a whistle as you pass?

Last edited: Dec 7, 2018
17. Dec 7, 2018

### Staff: Mentor

Torque keeps the bike from falling over. The turning wheels provide stability, but how much?
I know it as $c_W$ value. It's air resistance. Wikipedia is has more details.
Sorry, yes, that was a mistake. Of course I meant brake.

18. Dec 7, 2018

### OmCheeto

Not much of a bicycle if there's no force on the pedals. I would call that, at the most, "art".