Command-line program for doing bicycle gearing calculations.
It prompts the user to enter the number of gears in the front and rear cassettes of the bicycle gearing. After that, the number of teeth on each gear is prompted.
The program then prints the resulting gear ratios, gear steps and velocities for all different front/rear gear combinations. Wheel size is assumed to be 700 mm in all calculations.
[user@fedora sprockets]$ fpm run
Project is up to date
hello from project sprockets,
a bicycle gearing calculator program.
Enter number of chainrings [front]: 2
Enter number of sprockets [rear]: 5
:: Chainrings [front] ::
Enter size for gear #1: 34
Enter size for gear #2: 50
:: Sprockets [rear] ::
Enter size for gear #1: 36
Enter size for gear #2: 30
Enter size for gear #3: 25
Enter size for gear #4: 21
Enter size for gear #5: 18
:: Gearing overview ::
Chainrings [front] 34-50
Sprockets [rear] 36-30-25-21-18
Theoretical # of gears 10
Max. gear ratio 1.06
Min. gear ratio .36
Progression 294.1 %
Chainring step % [min/avg/max] NaN / NaN / NaN
Sprocket step % [min/avg/max] 14.3 / 15.9 / 16.7
:: Gear step tables ::
:: Chainrings [front] ::
1 - 2
-47.1 %
:: Sprockets [rear] ::
1 - 2 2 - 3 3 - 4 4 - 5
16.7 % 16.7 % 16.0 % 14.3 %
:: Gear ratio table ::
F: Chainring [front], R: Sprocket [rear]
R #1 R #2 R #3 R #4 R #5
F #1 1.06 0.88 0.74 0.62 0.53
F #2 0.72 0.60 0.50 0.42 0.36
:: Gear vs. cadence [rpm] vs. speed [km/h] table ::
cadence
chainring sprocket 40 60 80 100 120
----------------------------------------------------------------
F #1 (34T) R #1 (36T) 5.0 7.5 10.0 12.5 15.0
F #1 (34T) R #2 (30T) 6.0 9.0 12.0 15.0 17.9
F #1 (34T) R #3 (25T) 7.2 10.8 14.4 17.9 21.5
F #1 (34T) R #4 (21T) 8.5 12.8 17.1 21.4 25.6
F #1 (34T) R #5 (18T) 10.0 15.0 19.9 24.9 29.9
-----------------------------------------------------------------
F #2 (50T) R #1 (36T) 7.3 11.0 14.7 18.3 22.0
F #2 (50T) R #2 (30T) 8.8 13.2 17.6 22.0 26.4
F #2 (50T) R #3 (25T) 10.6 15.8 21.1 26.4 31.7
F #2 (50T) R #4 (21T) 12.6 18.8 25.1 31.4 37.7
F #2 (50T) R #5 (18T) 14.7 22.0 29.3 36.7 44.0
-----------------------------------------------------------------
- Install FPM (Fortran Package
Manager) and copy it into your $PATH as
fpm. - Clone the git repository.
- Execute the command
fpm runinside the base directory of the repository.
This program was developed with GFortran and packaged with FPM.