Engineers of Tomorrow, Today

Last time we spoke CalSol had just began its new semester along with a bevy of new goals. I’m happy to report that we are well on our way to achieving those!

Kids visiting CalSol's Solar Powered Radio

I’d like to thank everyone involved with Engineering 4 Kids (E4K). This was an event held last weekend in which a number of elementary schools from the Berkeley area brought 4th-6th graders to Berkeley to show them all the cool things that you can do with Science, Technology, Engineering and Mathematics. This year E4K drew in 350 students and a lot of cool demonstrations from the student groups here on campus. Unfortunately due to issues with the weather, CalSol was unable to bring out one of our solar cars to show off, but with a solar powered radio, and some sample composites and plenty of pictures you can bet we had plenty of the kids swarming around our table with questions aplenty. We hope that a few of those kids came away from E4K with a thirst for even more engineering! You can bet CalSol will be at E4K again next year!

If We Had Cylinders, We’d Be Banging On All of Them

High fives were had all around as CalSol’s Motor team recently submitted its final project proposal for the Big Ideas at Berkeley Grant Competition. But it was not long before we were back with our noses to the grindstone.

The CalSol Motor subteam (nicknamed “Rotors in Motion”) was born out of the challenges the team had getting our motor to run consistently leading up to the World Solar Challenge. While we were ultimately successful in coaxing our motor to run smoothly, the performance was still suboptimal. That, and the conviction of Professor Dennis Lieu that we could create a better machine ourselves, gave birth to our mission to design and build a new solar vehicle motor from the ground up. Specifically, we hope to introduce transverse flux technology to the solar racing community, which has hitherto relied almost entirely on a narrow selection of axial flux motors.

Permanent Magnets on the Rotor above, Coils on the Stator Below
Opening Our NGM SC M-150 Axial Flux Motor

While more difficult to construct, transverse flux motors innately have about twice the energy density of axial flux motors. This means that for the same power output, a transverse flux motor can be about half the size of an axial flux motor. In addition to saving weight on the motor itself, this allows for a slimmer rear suspension and wheel fairing, which are indispensible attributes in a solar racer.

Impulse’s New Canopy

After six weeks of preparation and work, shell team has successfully made a new canopy for Impulse. The current plastic canopy added unnecessary weight and deflected when we opened it, so we wanted a new canopy made mostly of composite materials with a windshield for vision. Due to the high strength-to-weight ratio of composites, we were able to make a new canopy that is not only lighter, but also stiffer. Our first concern was that we wanted the outside of the canopy to be as smooth as possible for improved aerodynamics. Therefore, we couldn’t use our current plug, because this would only allow for a smooth interior. Instead, we performed a fiberglass layup to create a female mold of the canopy using the pre-existing plug, and from this we were able to perform a composites layup. The result? A smooth, light, strong (and pretty) carbon fiber canopy. The project was difficult, and we made lots of initial mistakes, but we learned from them, and it was a great experience for both old and new members to perform a successful, large-scale composites layup.

We’ll be forming the windshield and integrating the new canopy with Impulse soon, and then we’ll get Impulse repainted in preparation for ASC!


Linear Technology in a Time of Need

Last week, we were working on improving our Battery Monitoring System, and ran into a few problems. High voltage went a few places that it wasn’t supposed to, and we were left with several boards in less-than-perfect working condition. The damaged boards were manufactured by Linear Technology, and were used to individually monitor each battery cell module in our battery box. Each board would read the voltage of a dozen modules and constantly balance them to prevent overcharging or undercharging any cells. Our car has 35 battery modules, each of them at a nominal 3.6V. After working on the problems for several days, we came to the conclusion that we really needed new boards. The problems were severe enough that we had neither the time nor the materials in-house to repair our damaged boards.

At this point it was Wednesday night, and we really wanted to get Impulse running by Friday. We were swiftly running out of time. In desperation, I reached out to my contact at Linear Technology to see if he could secure new boards for us at such short notice. He called me up Thursday morning telling me that he had the boards, and I could come and get them. I drove down from Berkeley to Linear’s headquarters, picked up the replacement boards, drove back to Berkeley, and installed the brand new boards in our car. A few short hours later, we were once again able to monitor and balance all of our battery cells. Thanks to the great people at Linear, our battery system is operational and working better than ever before.

People’s Car and People’s University

CalSol drove down with Impulse to the Volkswagen Electronics Research Lab today to give an end-of-year presentation on what we have learned, how much we have grown, how far we have come, and where we are heading next.  We’d like to thank everyone at the ERL for being there, supporting us, and inspiring us to dream big.  Additionally, we’d like to give a special thanks to Matt Montgomery for handling all of the logistical details of today; it was an amazing  meeting and CalSol had a blast!  With that said, we look forward to the continuing collaboration between People’s Car and People’s University…and GO BEARS!

A Belated Thank-You to SunPower

On August 19th of last year, literally days before the car shipped off across the Pacific Ocean, SunPower courteously invited us to an ice cream social event they were having at Richmond their office to wish Impulse bon voyage.  We were very honored to be there and extremely surprised to be welcomed by nearly 200 SunPower employees with some overwhelming enthusiasm (which we really loved)!

Sign all the things!

Well,  CalSol has been signing a lot of paperwork, but there are also a lot of signs and decals that Star Link Co. had generously donated to us for the World Solar Challenge.  These include decals, magnetic signs, window signs, and banners for Impulse and the convoy.  Some of these decals were required by the WSC and were realized relatively last-minute, so if it were not for Star Link, we would have not been able to rayce!