2. We made a prototype of our car using cardboard as our base due to its weight and durability as well as its convenience. If we were to 3D print the base/frame, it would take many hours. In our design, we used bearings with a bearing holder to reduce friction and hold its speed. For our axle, we used a straw with a wooden rod that goes through it but we are thinking of remaking our axle with a full wooden rod because the straw made our axle uneven which created lots of vibrations. For our gearing, we are planning on changing the drive gear to a larger gear and the axle gear to something smaller so that we can achieve a higher speed but we need to make sure that the motor has enough power to spin the bigger gear. We are still trying to figure out how to create a steering system. For our steering, we have 2 individual motors up front that are speed-controlled by our code in the MicroBit Program. With our program, we are able to use another Microbit to wirelessly steer the car. We can steer the car by making one motor spin faster than the other.
3. We have not used any design/ideas from any sources. All of our ideas come from our experience with these types of projects.
Our Results
With our designs ready to build, we quickly started to get parts cut up and printed. We made sure to keep the cart as lightweight as possible by using less dense materials such as cardboard and paper straws. We split up our roles and each focused on different parts such as the frame, the gears, and the programming. One of our main priorities was to keep the weight balanced as much as possible so that the small motor in the back could have every chance at moving the car. Some ways we did this was by mounting the battery and cricket directly in the middle so that the weight is distributed as the battery weighs a lot. We also used bearings to hold the rear axle so that we get as little friction as possible. Another thing that we made sure to do was make the axle fit perfectly into the bearings so that the axle would not move side to side which would disengage the gear or turn the vehicle in another direction. These bearings also reduced a lot of friction compared to other designs and we know that more friction would slow the car down. We added many aesthetic pieces onto the car that resemble real items on a car that would reduce drag/air resistance such as a front splitter, a wing, a rear diffuser, side skirts, as well as some pieces that would allow air to get trapped under the car causing resistance.
Our issues
Some of the issues that we faced were dimensions and sizing, when we printed our gears, we had issues with the fitment for the gear to mount onto the axle but we were able to overcome this issue by making the holes bigger with a Dremel. We had the exact same issue with our wheels as well so we had to dremel out the hole as well so that it would fit snugly onto the axle. In our original plan, we were planning on using a 1:8 gear ratio (motor: axle) which wasn’t the best since it was really slow so we ended up switching it to a 4:1 gear ratio which improved the speed of our car. We also ran into another issue with fitment since we changed the gears so they didn’t line up anymore so we used cardboard as spacers between the frame and the motor which worked out perfectly. When we were spacing out the gears, we made sure they weren’t pressed up against each other but were still able to spin the gears since we knew that there would be more friction, the tighter they were together.
Improvements
In our next design, something that we could do to make it much better would be more weight-focused. In our design, I think we had too many components on the actual cart, especially the batteries since it weighed the most. Next time I would try to make the car more basic by only having the essentials on the car and the rest held on the controller/switch. Next, I would try to make the frame as light as possible which would work perfectly with my idea above since the chassis would not have to be as sturdy due to the loss of weight. I would also switch the wheels to something a bit lighter and smaller as rotational weight has a big role in having the motor move the car. I also think that we should have taken off the rubber that was around the rear wheels since it was pretty grippy and heavy which most likely caused unneeded friction. Our design/aesthetics of the car were thought out but next time I would want to take it to the next level and paint every single part as well as use a different material so that it looks even better. In our next design, I would try to find another way to steer the car as in our current design, we used 2 motors that spun in different directions and turned the front end left and right which worked decent but there are better designs to turn the car.
Here are some images of our car attached below.
