Mechanical Challenges

Mechanical challenges were mostly overcome with a bigger hammer or more air pressure for our grinder. We disassembled most of the vehicle we bought, and the students who built this car are quite good at this. We did come across big challenges mounting the electric motor in place of the gasoline one and we had to replace the tires, mount the solar panels, foot pedal, and windshield.

Mounting the motor

Motor Mounted

The previous gasoline motor weighed almost 90 pounds, and took up a lot of space. Our more compact electric motor needed to be mounted above the rear axel drive sprocket, so that it lined up and held the chain. Doing initial calculations, the person who knew most about sprockets and motors wanted to buy a planetary gear box that weighed 110 pounds and was 2' by 10" by 18". The class decided to just go with some sprockets and chain, and we figured out the ratio we wanted was 10:1. As the chain sizes get bigger, it's much harder to get that kind of a ratio. We went with chain size 40, which we were told by the lead mechanic would break in a second (which it never did). We then had to machine the new sprocket for the rear axel to get the four holes aligned with the mounting plate already on the axel. Once both the motor sprocket and the drive sprocket were mounted, the chain was put on. We tried driving the car, but the chain was so loose that the whole car jerked forward or backwards, and the chain skipped. The chain was also rubbing against a metal bar that was 1/4 of an inch near it.

Motor ChannelWe tensioned and fixed the rubbing at the same time. First we took the solid steel plate that the motor was bolted two and moved it forward a couple inches. We were then able to take a full chain link off. Then, we pushed the mounting plate farther away from the motor and the chain got taut. We then took a grinder and made a nice channel in the metal bar next to the sprocket so it wouldn't rub against it. Take a look at the image on the left for the channel that was grinded out.


Wheels & Differential

We bought a dune buggy. Dune buggies generally don't drive on streets. So we had to get different types of tires that were flatter and more street looking than the curved sand tires the vehicle came with. Another problem, and probably the largest problem of all, is that the vehicle has no differential on the rear drive axel. Since it's meant to work in sand, there is no need to have one, and is even detrimental to the vehicle if it does have one in sand. We didn't have the time, or even close to the knowledge of how to make our solid rear axel a differential. So when we turn it takes much more torque and amps than it does to just go forward, plus our back wheel burns rubber if we turn too sharply. Let's hope the CHP doesn't watch us closely as we turn!

No Div

Above: Our rear axel in is one solid bar going across. When our car turns sharply the tires skid and our car's tires will get worn out easily.

Above: A normal car's differential allows the wheels to turn at different speeds while still maintaining a constant speed forward.

Mounting the solar panels

AAfter getting over the challenge of figuring out how much solar power we needed, we decided to use the largest solar panels we had from previous solar cars. There were many suggestions on how to mount the panels, but the final solution was to mount them at the same angle and connect them so they are almost solid. They are also angled down so it reduces wind resistance. There is still a parachute effect between the windshield and solar panels, but we didn't have enough time to fix this.

Solar Panels Front MountSolar Panels Middle

There was also another challenge of how to secure the panels down to the car. Initially we were going to weld the panels down to the frame of the vehicle, but since the panel's frame is aluminum, and the roll-cage of dune buggy is steel, one side of the mounting tubes would have to be bolted. We then just decided to bolt the panels at an angle in the front and back, and then in the center it would be U bolted to the car's frame. The photos on the right demonstrate how the panels are bolted in the front, center and back.



To be street legal, we had to have a speedometer. Our teacher bought a speedometer that uses a magnet and a sensor. There was difficulty mounting the sensor as it was designed for a bicycle. We ended up gluing the magnet to the wheel well, and the sensor on the hydraulic brake tube. Check out the photo on the left to see it in detail.

Securing battery packs

Batteries with wire

Even though our Ni-Mh batteries aren’t as heavy as lead-acid, our batteries were flying everywhere when we used Velcro to strap them down. We eventually used wire to strap the battery packs down, and we may still encase them in a box or with some cloth. We also bought insulated nuts so that no terminal could touch you by the top, and then we used liquid electrical tape to ensure no contact would be made with foreign objects.

Gas Pedal?


Unlike the popular terminology, on an electric vehicle there is no "pushing the gas." Instead of using a physical connection to the motor, an electric car uses a potentiometer. We purchased a foot pedal that had a pot in it, and then we had the challenge of mounting it. The original vehicle had two identical pedals for braking and acceleration, but we couldn't salvage the old gas pedal so we had to saw and grind it out. We then took the potentiometer foot pedal and mounted it at a 45 degree angle upside down so it acted more like a conventional vehicle. The pedal is so well secured to the vehicle’s floor that it is held by a single, angled bolt.

The dune buggy also has a much different seating arrangement than your typical sedan. There really is no seat, your knees don't bend much when you sit down and reach for the pedals. Because of this, big people tend to cramp while sitting in the vehicle, and short people can't even touch the pedal. Also since the pedals are so close together and you can't move your feet easily, the solar car is two foot drive. This means you must have each foot on separate pedals all the time, requiring a disable switch on the brake so you can't press both at the same time. The car takes some time getting used to driving because of this.

Fixing up a floor model


We bought our dune buggy from Pep Boys in Van Nuys, CA. This specific car was sitting inside their shop and was a floor model for nearly 5 years. Because of that, parts of the car were destroyed or missing. For example the driver's seat belt was broken, and the shock holders in the front of the car were missing unusual-sized metric bolts. The gas motor was missing caps and wires, since we were never going to use it we didn't care. We ended up buying the car for almost 50% off since the manager wanted the thing gone; it was taking up too much space.

Foward & Reverse


Unlike a conventional car where you have gears that will put you into reverse, an electric car just has to have the polarity reversed. We purchased a reverse switch online that does just that, with four inputs that switch when you turn the handle 70 degrees. Since we have to use very heavy gauge wires, we decided that the closer to the motor the switch could go, the less resistance. We mounted the switch in-between the seats, so in order to turn it the driver will need to reach his left hand around his shoulder like he's scratching his back. Since you're going to have to look behind you when you turn anyways, we thought this was just fine.