A major part of our progress constitutes the building of the “parallelogram mechanism”. This refers to the steering structure at the front of the vehicle, which allows the wheels to tilt around bends with all wheels on the ground. This mechanism makes use of 6 half-inch ball bearings and 2 five-eighth-inch ball bearings. The prototype is pretty sweet! Check out this video:
- Geometry choice: So far, we have just made a prototype of the steering mechanism. The reason why our design is a parallelogram is because we thought is the most apt geometry to utilize steering via tilting.
- Interface between parts: Today we thought deeper about how axel of wheel is to be joined to vehicle. Our prototype revealed some structural weaknesses in the initial design of our steering mechanism, thus we had to think deeper about the way in which this was connected. In the end, we chose the box joint to change the interface plane by 90degrees while maintaining structural rigidity
- Manufacturing methods: Currently, we are making a prototype by laser-cutting wood. However, our final vehicle will use water-jetted aluminum sheets as this would ensure that they are a lot stronger.
Our component choices have not differed much since Milestone 2:
- The SK3 motor was chosen, as it is a brushless motor that fit our budget. We chose the brushless motor for its power over its brushed counterpart. We are also purchasing $3.99 brake pads to make a custom brake mechanism, which will work together with the 65” brake cable we want to buy. We learned that a longer brake cable can always be shortened, but a brake cable that is too short would be useless!
- Appropriate wheels are really hard to find! We settled with 10”x2” side mount wheels – decently size for its price. Based on calculation, our optimal size of wheel was 14”, but we decided to work with 10” as it is the largest (affordable) side-mount wheel we could find.
- For now, we are using the provided 80/20 and aluminum plates to create the frame. Our strategy is first to purchase the major hardware, and then to make the frame around it. This would ensure that the spatial arrangement of each part does not clash with another.
So far, our prototype has revealed much about our preliminary design of the gold-kart. We received a comment that we can potentially include a torsion spring in our parallelogram so that the vehicle’s natural state is upright and not slanting to one side, which will make tilting smoother. We’re tweaking the joints and fastening methods along the way; for example – we want to decrease the width of the kart by another 15cm by changing the length of the parallelogram mechanism. We’re excited for the weeks to come!
- Without factoring in wind resistance and rolling resistance, goldkart can go at a maximum speed of 31kmh, which is under 35kmh. However, a more reasonable speed might be 27kmh.
- To prevent the acceleration from tapering off early in the race, we plan to use a 2P2S configuration that increases the current supplied by the batteries to 80A. In order to not exceed the current limit on the batteries, we need a controller that can perform current control. This means that the maximum acceleration we can get is approximately 2.3 m/s2.
- We are intending to keep the base wide and the CG of the go-kart system low, so the chances of flipping over even during max acceleration would be low.
- We’d love to use the belts for transmission but the budget might get a little tight since a belt will require additional parts that cost money to be mounted on the wheel. The gear ratio we are intending to use is 1:6, and a front wheel size of 16″.
Our vehicle will be a tilting tricycle. Our primary interest and consideration is to develop a smooth and functioning front steering mechanism. With the given 80/20 Aluminium extrusions, ball joints, shoulder screws, threaded studs and rods, we will be able to make a basic frame of this mechanism. Our intended construction is far simplified than existing designs found online, and will be much cheaper. These parts will be bought first so that we can test our theoretical design. Thereafter, we will employ the Turnigy brushless motor and Kelly controller to the system.
Our group has decided on a 3 wheeled vehicle that uses a tilting mechanism for support during turns. Here are some of the preliminary sketches!
Figuring out what a controller does, and the difference between brushed and brushless motors. In the end, we decided to go with brushless; previous teams had stated that brushless motors may perform better. We’ll see how it goes!
And so, the first sketch of our finalised design!