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Solar Model Cars Solar Model Cars By Bill Kuhl http://www.scienceguy.org

Solar Model Cars By Bill Kuhl

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Page 1: Solar Model Cars By Bill Kuhl

Solar Model CarsSolar Model Cars

By Bill Kuhl http://www.scienceguy.org

Page 2: Solar Model Cars By Bill Kuhl

Looking for more science projects on the Internet, I ran across ran across the Junior Solar Sprint Competition. I have been interested in alternative energy for a long time, so I decided I would build a solar powered model car.

EverythingHobby had two Tamiya solar panels and one motor. I purchased the motor and the ½ volt 1200 mah panel to start with thinking both panels were the same. I later purchased  the other panel which was 1.5 volts 400 mah, this would be good for experimenting with trade-offs between voltage and amperage.

Background

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For my next car I purchased the panel and motor specified for the Junior Solar Sprint Competition, in my first tests of running this car pictured above, the speed is at a jogging speed. This car was also an experiment in using bamboo to stiffen the thin plywood chassis. I also purchased a 10-pack of kit cars from Pitsco because the price is below $10 a car and I thought this would be good for a class this summer.  The solar cell is rather tiny so I used lower gearing to get the car to move, but it will work fine in bright sun. The model solar cars appear to be a good activity to learn about harnessing sunlight, electricity, electric motors, gearing, and construction ideas.

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The first car I built from Tamiya components I found in local hobby shop.

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The second car built using solar panel and motor specified in Junior Solar Sprint rules.

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Sun Zoon Lite car kit was the third car I built which is an inexpensive kit.

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Applications for Photovoltaic Solar Power

This large solar panel seen at the Minnesota State Fair was available for rent.

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Another smaller solar panel seen at Minnesota State Fair

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Calculator powered by small solar panel.

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Traffic signals sometimes use solar panel to charge battery power.

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Small solar panel recharges battery in garden light.

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Home with solar panels on the roof.

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Demonstrating Small Electric Motors

This demonstration electric motor leaves everything exposed to show how motor operates.

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Close-up of brushes and commutator in demonstration motor.

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Commutator and windings seen in Speed 400, a typical brushed electric motor.  Note: When looking for a motor for solar power, it helps to look at the start-up current requirements as some motors require more electricity to start than others. 

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Building First Solar Model Car

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This panel is ½ volt but 1200 mah.

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This Tamiya panel of the same physical size but is 1 ½ volts and 400 mah.

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1 ½ volt panel has more cells.

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No load voltage of 1 ½ volt panels reads 1.71 volts in bright sun.

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1200 mah .5volt panel displayed .56 volt in bright sun.

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Tamiya motor designed for solar panels.

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Lightweight wheels used for indoor radio control model airplanes, I selected the wheels on the left for my car.

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Brass eyelets are sandwiched between balsa for bearings.

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At this point motor was only sitting on top of the chassis, I will shim the motor to get good mesh between gears.

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View of chassis with car turned upside down, Popsicle sticks were used to stiffen rear of car where motor is mounted.

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Some of the craft beads used in bearing assembly.

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I used a spur gear from a RC car. The gear is glued to the side of the wheel.

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Tamiya panel came with a swivel mount that gave me ideato replicate this for larger panel on second solar car.

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Using Velcro makes it easy to change PV panels.

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Shimming the motor gave space between gears and it ran smoother.

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Junior Solar Sprint - specifies a certain solar panel and motor which I purchased from Solar World.

Building Second Solar Model Car

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Specified solar panel produces 3 volts @ 3 watts, dimensions are 4 ½” x 13”

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Motor comes with solar panel and it is the only motor allowed. The motor can not be modified in anyway either.

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The Accessory bag from Solar World includes 2 shafts, 4 wheels/tires, and 3 spur gear sizes.

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Craft beads I used for spacers .

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Bamboo skewers were used to strengthen the chassis of the car.

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As with my first solar car, I used brass eyelets sandwiched between balsa. These eyelets were the kind used with medium size radio control servos.

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Eyelet from RC servo used for bearing.

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Chassis turned upside down before I put layer of balsa on top of eyelets which completes the balsa sandwich.

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Motor running, gears must mesh easily for good performance.

The correct gearing is a trade off between quick enough acceleration and top speed. Small gear on motor shaft is the “pinion” and large gear is the “spur” gear.

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Solar panel in the horizontal position, adjusting the panel to match the angle of the sun will make a big difference in performance.

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Ping pong ball used for swivel. Straps were made plastic in a cottage cheese container.

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The underside of rear half of car shows reinforcement done with plywood and bamboo.

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After seeing the pivot on the Tamiya panel, I built my own swivel joint using a ping pong ball.

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Platform for panel made from Popsicle sticks and thin plywood. Velcro fastens the panel to the platform, the panel could easily be switched to another car. I like to design everything to be flexible if possible.

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Pitsco SunZoon Lite

I ordered the 10 pack of solar cars from Pitsco which are very reasonably priced. The car goes together easily but needs very bright sun to move the car.

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Pitsco SunZoon Lite kits are available in a 10-pack.

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Top side of the small solar panel. 

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As seen from the back, the solar panel is only .45 volt 400 mah. 

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I measured the voltage of the panel at .47 volt in strong sun. 

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Screw eyelets are used for bearings that are very quick to install.

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Side view of front axle and wheels

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Gears

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Gear font gave the specs of all the gears included, more gears than needed are included but might be useful for another project.

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Many gears are included but some are larger in diameter than the wheels which is a problem.

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I installed the 20-tooth pinion gear per the instructions but the car would only move in really bright sunlight. With the PV panel putting out less than ½ volt there is no power to spare. Spur gear 40-tooth.

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I installed the smaller 10-tooth pinion gear on the motor shaft but it does not match up with the spur gear, a modification would be needed.

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I flipped the car over and considered putting the motor in the rear but the solar cell could not rest on the motor because the wheels were in the way.

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Moving the motor in front of the spur gear will prop up the solar panel and gears mesh fine. The gear ratio is now 1:4 which gives the car more torque to move.

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Completed car, some of the wood chassis could be cut off making the car slightly lighter.

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