A full PDF documentation has been uploaded:
Full Documentation - Download
Mechabike
Monday, May 5, 2014
Friday, May 2, 2014
Video update
Here is a video of the completed prototype (4th iteration).
A full document detailing the build will follow shortly.
A full document detailing the build will follow shortly.
Wednesday, April 30, 2014
Update - fine tuning the 4th iteration
After two days of rapid machining and assembly, we were able to get a working prototype.
The software was also fine-tuned such that the servos' angular rotations matched the gear ratios on the bike.
All that lies ahead is complete documentation of the project and logistical administration in preparation for the demo day.
The software was also fine-tuned such that the servos' angular rotations matched the gear ratios on the bike.
All that lies ahead is complete documentation of the project and logistical administration in preparation for the demo day.
Monday, April 28, 2014
Update - 4th prototype
Closing in on the deadline, we made a final effort to get a working prototype done.
At the suggestion of Wesley, we moved the clamp from the downtube to the seat-tube and ran a secondary pull cable from the servos to the normal gear shift cable. The cables were joined with a loop and clamp.
The result was a much smaller force on the servos, enough where they could reliably actuate the cable between 4 gears.
The front gear was also tested and we were able to shift reliably between both gears.
As the deadline closes, we will be machining the second set of clamps, finalizing the servo actuation mechanism, and fine-tuning the software.
At the suggestion of Wesley, we moved the clamp from the downtube to the seat-tube and ran a secondary pull cable from the servos to the normal gear shift cable. The cables were joined with a loop and clamp.
The result was a much smaller force on the servos, enough where they could reliably actuate the cable between 4 gears.
The front gear was also tested and we were able to shift reliably between both gears.
As the deadline closes, we will be machining the second set of clamps, finalizing the servo actuation mechanism, and fine-tuning the software.
Monday, April 21, 2014
Update - 3rd prototype
We re-designed the clamp with a design by Steven which utilizes two servos in mirror configuration. Bernard, Steven, Jason, and Wesley machined the new clamps over the course of 2 days to get them ready for rapid deployment (due to the looming deadline).
The clamp proved to be a success in many ways: the spatial footprint was much smaller; the dual servos yielded greater force on the cable; the clamp was able to be positioned in multiple places and configurations, resulting in a more modular design.
Even with the dual servos, new clamp, and a single ended design, the cables still did not actuate enough to shift a single gear.
The clamp proved to be a success in many ways: the spatial footprint was much smaller; the dual servos yielded greater force on the cable; the clamp was able to be positioned in multiple places and configurations, resulting in a more modular design.
Even with the dual servos, new clamp, and a single ended design, the cables still did not actuate enough to shift a single gear.
Tuesday, April 15, 2014
Update - 2nd prototype
The second iteration saw us replace the MG995 servo with a more powerful, and apparently more reliable, HD-1501MG. This yielded a 50% increase in torque.
Special thanks to the good people at Banana Robotics (bananarobotics.com) for helping us with the servos and getting them to us so quickly.
We also disengaged the gear shift cable from the shifters, resulting in a single-ended design where the cable terminated at the servo pin.
Overall, we we able to achieve greater actuation of the cable, but not enough as we still failed to shift the gears.
Special thanks to the good people at Banana Robotics (bananarobotics.com) for helping us with the servos and getting them to us so quickly.
We also disengaged the gear shift cable from the shifters, resulting in a single-ended design where the cable terminated at the servo pin.
Overall, we we able to achieve greater actuation of the cable, but not enough as we still failed to shift the gears.
Wednesday, April 9, 2014
Update - 1st prototype
Using a clamp designed by Jason, we were able to mount a single servo onto the bike. The cable was passed through a pin connected to the servo, and the rotational force of the servo was converted to tension on the gear shift cable.
Unfortunately, this design did not work due to lack of torque on the MG995 servo, and possibly resistance to bending from the cable.
Unfortunately, this design did not work due to lack of torque on the MG995 servo, and possibly resistance to bending from the cable.
Wednesday, February 26, 2014
Hello!
The purpose of this blog is to chronicle the planning, execution, testing, and refinement of a low-cost, automatic bicycle transmission system. The system is being developed as a course project for the Spring 2014 offering of Mechanical Engineering 102B at UC Berkeley (a.k.a. Mechatronics).
The mechatronic system has been approved by Professor Homayoon Kazerooni and is now in the planning stages.
The partial parts list (will be updated as project goes along):
The full parts list can be found in the documentation.
LAST UPDATED [05/09/14]
The mechatronic system has been approved by Professor Homayoon Kazerooni and is now in the planning stages.
The partial parts list (will be updated as project goes along):
The full parts list can be found in the documentation.
LAST UPDATED [05/09/14]
- 1x 14-speed bicycle
- 1x Arduino Pro Mini (5v, 16MHz, ATmega368)
- 2x Hall Sensor pre-fab units
- 1x 3.2" 5v LCD Display
- 1x LM7805 5v regulator
- 4x HD-1501MG servos
- 4x servo couplers
- 1x SPST Toggle Switch
- 8x AA batteries
- Aluminum 6061 stock
- Bowden cables
- Miscellaneous nuts and bolts
- Miscellaneous wiring and connectors
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