Three Electric Cars for under $100: A STEM NOVA Project

I had the great honor of working with the boys of Troop 414, about thirty of them ages 11 to 18. The night had been set aside to introduce the boys to new STEM Nova program the boy scouts of America have rolled out.  The award program enables scouts to “Be Prepared” in a world of global economies, exponential technological growth, and unprecedented access to information.

I had the help of Dean Petrella of RoPro Designs to come up with an activity that not only announced the award program but also helped the boys begin to earn one of the STEM Nova awards.  Awards vary with age groups.  Cub scouts can earn four NOVA Awards (Science Everywhere, Tech Talk, Swing!, and 1-2-3-Go!) and a SuperNova (Dr. Luis W. Alvarez). Webelos can earn a SuperNova named for Dr. Charles Townes.  Venture Scouts (Venture crews are co-ed high school aged) can earn Launch!, PowerUp, Hang On!, Numbers Don’t Lie Nova Awards and the SuperNovas Awards named for Dr. Sally Wright, the Wright Brothers, and Dr. Albert Einstein.  The boy scouts can earn Shoot!, Start Your Engines, Whoosh!, and Designed to Crunch with Super Nova awards entitled Dr. Bernard Harris and Thomas Edison.

Dean and I decided, with the help of some of the boys that serve as the Leadership Council for the troop, to focus on the “Start Your Engines” Award and tackle the task to “Design and build a working model vehicle (not from a kit) that is powered by battery, wind or solar.” The task had to be something they could test and redesign and extend into an independent activity.

I love an engineer’s mind, particularly when it is combined with a MacGyver like practicality to use what is at hand.  The scout committee gave me a budget of $100 from which I needed to make a prototype car and have the supplies on hand for three patrols to build a car during the 45 minute patrol time of a meeting.  Dean and I broke the task done to its simplest elements:  the body, the wheels, the motor, the power source, and switches.   We decided on a shoe box for the body and ran into a local cub scout leader who managed a nearby DSW Shoes.  Woot – car bodies checked off and we still had our full budget.

The next decision was wheels.  Part of patrol work is to create a job for each kid.  It is frustrating to be part of any group project in which there is only enough work for two or four hands alongside fourteen or sixteen idle hands.  We decided to use cardboard for the wheels, enabling at least one scout to measure and cut out the front and back wheels.  The end goal was to have their patrol’s car complete a ten foot course. Engineering and math became part of maximizing their supplies to make their tires as large as possible, as well as measuring and cutting them to the same size.  They would soon discover that a one cardboard thick wheel was not stable, and problem solving was needed  to double up the wheels with some glue. A shout out to Pizza Joe’s for the donation of pizza boxes.  Woot – tires checked off and we still had our full budget.

The power source we decided on was a battery operated car. Dean met me at Hobbytown and we scoured the shelves for the right motor and matched it with a 4 AA battery pack as well as a dowel rod we could use as the axle wheels not attached to the motor. The motor we found was the 4-Speed Crank Axle manufactured by Tamiya.  For twelve dollars, this amazing little electric motor and gear box lets you build gear ratios from 126 to 1 to 5402 to 1.  We build the motor with the smallest gear ratio, more than adequate for our project.

The time consuming part of the preparation was assembling the motors.  Ideally, I would have liked for each patrol leader to put one together, and if I had it to do over again, I would have asked that a portion of the Patrol Leader meeting had been spent assembling motors.  It would have given them a chance to discuss with their patrols the gear ratios options and why they chose what they did. Fortunately, one of the patrol leaders happens to be my son, and he volunteered to assemble all four motors.

As we looked at the motor attached to the body and the battery pack sitting beside, we saw an opportunity to let the kids discover a little about electrical circuitry. We created “leads” (pieces of paperclips) soldered onto the end of the connecting wires to allow the students to create their own switch from tin foil and electrical tape. This configuration also allowed them to experiment with polarity and make their rear wheel drive electric card into front wheel drive electric card. Supplies of tin foil to be gently crumbled into a switch and electrical tape were added to the patrol project supply box.

Batteries became the last piece we needed to assemble.  We decided to again create a job for a pair of hands and grabbed a multimeter to measure battery voltage along with the vast supply of used AA batteries that have become assembled in our house.  Final budget numbers, thanks to so many volunteer labor and donated supplies, were under $80.

The troop meeting, after opening ceremonies and announcements, included an introduction to the STEM Nova Awards and our focus on the Start Your Engines Award.  I have a screen, laptop and projector at our disposal and so used a PowerPoint to communicate quickly with images the topics we discussed.  We spent a little time on energy sources in the United States and one of the major problems confronting the development of electric cars – the battery.   Our prototype was demonstrated and work began.

Two of our handyman scout leaders took up residence at a designated workbench for the meeting.   They explained the multimeter, how it worked, and the voltage needed for the motors to work.  Another worked with kids who were using a utility knife to cut slots for the wheels in the shoebox. Several of the parent leaders remarked how each scout approached their small task with great diligence.   The evening ended with a few commercials for Tesla Roadsters and Pulse Motors with a heads up to what engineers are doing with electric car technology today.

Success is not necessary for learning, but it’s nice to experience.  Honestly, we could have used another 15 minutes.  Two of the patrols got their cars working, but neither car drove strait enough to cross the finish line. Given the extra time, each car would have been working and kids would have had the chance to make modifications to the original design.

I passed out a worksheet (none were yet available online) for interested kids to complete the reward, which included redesigning the electric cars. I’ll keep you up to date on how many finish!