# Title Team Members TA Documents Sponsor
53 Multistage coil gun part 2
Area Award: Teamwork and Collaboration
Alejandro Esteban Otero
Changkun Li
Theodore Culbertson
Jackson Lenz design_document0.pdf
Our project is a continuation of the coil gun project that was started by Jonathan Dagdagan, Shashvat Nanavati, and Yohan Ko in 2013. They were able to build a three stage coilgun and fire it successfully, but the project still had several issues that need to be addressed. To begin with, the SCR cannot handle the voltage put across them during firing. We must find a way to reduce the stress on the SCR, or they will have to be replaced after every firing. We have thought about implementing an isolation transformer to achieve this goal. In order to reduce the current stress of the SCRs we would study the behavior of the circuit when adding SCRs in parallel for each transformer.

To increase the speed of the projectile and prevent the SCRs from blowing up we would include a diode and a resistance in parallel with the coils so that the energy stored in the inductor is dissipated quickly. We also intend to add several features to improve usability, including displays to show the speed of the projectile and charge of the capacitors.

Once the coil gun can be test fired reliably, we will do simulations and collect data to maximize the velocity of the projectile by altering placement of the coils and timing of the triggers.

Electronic Automatic Transmission for Bicycle

Tianqi Liu, Ruijie Qi, Xingkai Zhou

Featured Project

Tianqi Liu(tliu51)

Ruijie Qi(rqi2)

Xingkai Zhou(xzhou40)

Sometimes bikers might not which gear is the optimal one to select. Bicycle changes gears by pulling or releasing a steel cable mechanically. We could potentially automate gear changing by hooking up a servo motor to the gear cable. We could calculate the optimal gear under current condition by using several sensors: two hall effect sensors, one sensing cadence from the paddle and the other one sensing the overall speed from the wheel, we could also use pressure sensors on the paddle to determine how hard the biker is paddling. With these sensors, it would be sufficient enough for use detect different terrains since the biker tend to go slower and pedal slower for uphill or go faster and pedal faster for downhill. With all these information from the sensors, we could definitely find out the optimal gear electronically. We plan to take care of the shifting of rear derailleur, if we have more time we may consider modifying the front as well.

Besides shifting automatically, we plan to add a manual mode to our project as well. With manual mode activated, the rider could override the automatic system and select the gear on its own.

We found out another group did electronic bicycle shifting in Spring 2016, but they didn't have a automatic function and didn't have the sensor set-up like ours. Commercially, both SRAM and SHIMANO have electronic shifting products, but these products integrate the servo motor inside the derailleurs, and they have a price tag over $1000. Only professionals or rich enthusiasts can have a hand on them. As our system could potentially serve as an add-on device to all bicycles with gears, it would be much cheaper.

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