Automatic Bicycle Transmission

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Sketchy sketch of project

Check it out!! We are on hackaday!! [[1]] Link to our Youtube Video made during our demo: http://www.youtube.com/watch?v=KFmDDD-pwwc [[2]]

Contents

Team Members

Andrew Toth, Jenna MacCarley, Peter McHale, Nicolas Mellis

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Project Description

Cars use an automatic transmission to most effectively change the gear ratio to accommodate driving conditions, without driver interaction. Motorcycles use a clutch and sequential gearbox to accomplish the same thing. Bicycles have no need for a clutch, but also require the rider to change gears themselves.

What if the bike changed gears for you, so you (the rider) can focus on keeping your cadence and go up, down, and around as quickly as possible?

Using magnets and hall-effect sensors, we intend to keep the rider's cadence at 80RPM (a number that is generally agreed upon in avid cyclist groups :: Source: Robert Abramson, CMU Cycling Club) and shifting gears when that cadence drops below 60RPM (and shifting to a lower gear to return closer to 80RPM) or if the cadence rises above 100RPM, shifting up to return to a preferred cadence. Servos are used to automate the gear shifts.

This has been attached to a 2012 Jamis Aurora bicycle, and could be a drop-in attachment to other bicycles with a few adjustments.

Other features that were scrapped in favor of demoing a working implementation within a week include:




Worklog

Sunday
*Begin machining the servo mounts
Monday
*Continue machining the servo mounts
*Test whether a servo has enough torque to pull the shift cable
Tuesday
*Mount the magnets to the wheel and pedals/crankshaft
*Mount magnets to the back wheel.
*Test the Hall-effect sensors to ensure they work as expected
*Machine additional mounts for more servos with intent to 
 combine the servos mechanically in parallel to share 
 torque load between multiple servos
Wednesday
*Debug Hall-effect sensors
*Test the combination of multiple sensors/actuators 
 connected simulataneously
*Making permanent connections between things on a protoboard
Thursday
*More system debugging
*System Integration
*Definition of System constants

Media

Hackaday: http://hackaday.com/2013/01/18/building-an-automatic-bicycle-transmission-in-a-week/ Youtube of Demo: http://www.youtube.com/watch?v=KFmDDD-pwwc


Files

Fritzing & Arduino code: https://www.dropbox.com/sh/skt3uydbxyfz927/iu0U3UM_RM

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