The inspiration for this meeting came from a bike touring trip I took in May/June of 2025, from Vancouver, Canada to San Diego, California. (To see photos and read about the trip: https://birdfruit.wordpress.com.)
I started the meeting by asking participants to draw a bicycle from memory. You might found it’s harder than you think. Give it a try.
After the group sketched and shared their drawings, we looked at this project by Gianluca Gimini: https://twistedsifter.com/2016/04/artist-asks-people-to-draw-bicycle-from-memory-and-renders-results/
As I was preparing for this meeting, I had the thought that most of us don’t really understand how a bicycle works. It’s a bit of magic that, at least for me, feels like a miracle. The goal of this meeting was to try to understand how the chainring (one of the front gears), the chain, and the cog (one of the back gears) work together to move us down the road.
We started by watching this video with a notice/wonder:
Some things the group noticed:
- The pink pompom on the front moves slower that the blue one on back wheel
- Foot is moving slower, back wheel is moving faster.
- For every revolution of the pink, the blue is in a different place on the circle.
- Some things they wondered:
- In the chainring, the work I’m doing is moving the chain. In the cog, the work that the chain is doing is moving the wheel.
Some things we wondered:
- How many revolutions in the back per revolutions in the front?
- What is the ratio of the lowest gear and the highest gear? At its easiest, does it ever get to 1:1?
- If you change the gears, is there a way to match the revolutions so that they move in sync?
- How long does it take to make a complete revolution?
We then did a slow reveal with this diagram and tried to predict which side was a low gear and which was a high gear.
This is the completed diagram.
Then we checked to see how well we understand what is happening.
I shared some information about one of my bikes.
And bike gearing in general:
Questions we investigated:
How many different gears are there on this bike? Are all the combinations unique?
Imagine starting to ride this bike from a stop, starting with the lowest (easiest) gear and shifting through all the gears in order from easiest to hardest as you accelerate. What would the shifting pattern be?
Resources:
Artist Asks People to Draw a Bicycle from Memory and Renders the Results
Chainring and cog – Marin Museum of Bicycling – A video I took when I visited the museum
Browse cassette toothcount and step data | kstoerz.com chainline tools
Joe Breeze | Marin Museum of Bicycling and Mountain Bike Hall of Fame – One of the originators of mountain bikes and a really great guy
https://birdfruit.wordpress.com/ – My blog with posts about the Pacific Coast Bike trip
Bikes! (Google Slides for the meeting)
