Each of our component is integral in ensuring that the emergency brake system works as intended, with minimal damage and backlash inflicted with multiple uses. All components mentioned previuosly are described here in more detail.

In choosing our braking mechanism, we had to choose between a drum brake or a brake caliper. A drum brake would certainly work, however it requires a significant amount of space that we weren't sure if we had, and is also relatively expensive (upwards of $200). A brake caliper is much more compact and cheaper, but doesn't have as much braking force as a drum brake. Still, the cons of the drum brake heavily outweighed the pros, so we decided on using a brake caliper for our final design.

For the brake caliper mount, we had two main issues: the design of the brake caliper mount and the material required to build it. In terms of the design, the brake caliper needs to be parallel with the rotor so that the application of force is accurately. Additionally, the mount needs to be able to withstand upwards of 100N of force, so the mount needs to be secured properly. Therefore, the mount is attached to two axles at its bottom, as well as to an L-shaped bracket at its side to ensure the mount does not tilt.

The material of the brake caliper mount is important, since, as stated before, the mounts needs to be able to withstand 100N of force, but also needs to be generally common and available due to the open-source nature of this project. We ended up choosing aluminum as the material for our final design, as aluminum is more than strong enough to handle that kind of force, and the previous team had leftover blocks of aluminum we could use for machining the mount. We also used 3D-printed PLA versions of the brake caliper mount before fully machining it out of aluminum to verify the fitness the design.

The spring required for engaging the emergency brake had a couple of design constraints that required us to choose some specific springs. The spring needs to stretch between 25.4-203.2 mm (1-8 in), while also holding between 300-900N of force. We also needed to choose a spring without a high spring rate or high spring load, since a high spring rate makes adjusting the spring difficult, and a high spring load makes initially activating the emergency brake difficult. With these range of parameters, we compiled a table of viable springs for our purposes:

The first two springs have an unknown max deflection and spring, and the 3rd spring only has a 24.63 mm (0.97 in) max deflection. Therefore, we chose the last two springs for our emergency brake, as they fulfilled our max deflection and max load requirements, as well as having a relatively low spring rate.

The electromagnet is another integral part of the emergency brake, as it is what keeps the brake caliper activated or not. The electromagnet is connected to a lever arm that holds the brake caliper, and requires 222 N at optimal environmental conditions for it not to disconnect with the lever arm accidentally. It also needs to be able to maintain operation for upwards for 30 minutes, as it is turned on while the emergency brake is deactivated, and needs to continue to hold 222 N of force throughout the entire time, even when the electromagnet is heating up. It's important to note that a magnet works well only when it is completely flush with the material it is attracted to. Any deviation, i.e. the material is at an angle or isn't touching the magnet, will drastically reduce the pulling force of the magnet, as it is an exponential relationship.

For our final design, we chose the EM300-12-212 electromagnet despite being the more expensive option, primarily due to its high pulling force. As stated above, a magnet's pulling force decreases rapidly with any minute change between the location of the material and magnet, so buying a magnet with a pulling force 8.01x higher than what is needed helps in that aspect. The electromagnet is also continuous, meaning it is meant to be turned on for long periods of time, which is exactly what we need for a kart competition.

In terms of its temperature and overheating, the electromagnet will begin to lose its force once it reaches 55 degrees Celsius. The outside of the magnet in a vacuum will heat up to 60 degrees Celsius. However, once placed within the electromagnet mount and the heat is allowed to dissipate, the outside of the magnet will only heat up to 50 degrees Celsius. This is also without the metallic lever arm attached to the electromagnet, meaning even more heat will be dissipated while the emergency brake is in action.

The electromagnet mount, similar to the brake caliper mount, exists to ensure the electromagnet is able to sit flush with the lever arm. Again, the design and material of the electromagnet mount were the two main issues of this component. In terms of the design, the biggest challenge was ensuring the angle of the magnet was the same as the lever arm once it touched. The electromagnet needs to make full contact with the lever in order for the theoretical prediction of the force (222 N) to be accurate. Therefore, the mount needs to hold the electromagnet parallel with the lever, as well as in the correct angle so the electromagnet is fully contacting the lever.

The material of the electromagnet mount does not need to be as robust or strong as the brake caliper mount. In fact, an FEA analysis shows that the final design of the electromagnet mount deforms slightly at 5 MPa. Therefore, because the force on the electromagnet mount is so low, we chose to use 3D-printed materials, as 3D-printing is much easier and faster than machining out of aluminum. Specifically, we chose PLA-CF, or Carbon Fiber Reinforced PLA, as it has 36 MPa in the correct direction, while PLA only has 25 MPa, which gives a higher safety of factor. PLA-CF is also only slightly more expensive than PLA, while still being easy to print despite the carbon fiber.

The lever arm was fully manufactured by us using 3/16 inch steel. The correct design was first CADed in Solidworks, with multiple holes to allow for future adjustments. We then laser cut the steel based on the Solidworks drawing. Finally, we bent the steel using a pneumatic presser so the holes are aligned to each other and a bar goes through the holes. The end result is roughly 3.5:1 mechanical advantage with respect towards the electromagnet, which is why the electromagnet mount does not need to sustain as much force.

After testing the prototype emergency brake system for the first time, it became apparent that once the emergency brake disengages ie. is released from the magnet, the lever arm slams back into the frame at a significant amount of force.  The video below showcases visually how the frame moves a significant amount during the emergency brake activating:

Since the TritonAi team needs to continuously test the kart over the duration of years, it was very clear that we needed some way to lessen the impact of the blow. Our first idea was to use shock absorbers, and since the only requirement was to soften the force the lever will exert onto the frame, we felt it would suit our needs. However, one issue is the fact that traditional shock absorbers can be upwards of 25.4 cm (10 in), while we only had space for roughly 12.7 cm (5 in) to install the shock absorber.  While we were able to find some shock absorbers that fit the length requirement (specifically 1/10 RC shock absorbers), there weren't enough specs to know if it would be able to handle the force of the lever. After some more research, we came across a viscous dampener called a dashpot, which could go as small as 7.0104 cm (2.67 in), which perfectly suited our space constraint. Additionally, the energy capacity of the dashpot exceeded the energy capacity of the lever arm motion, meaning the shock absorber would have enough strength to stop the lever arm. While the dampener hasn't been attached to the kart yet, we believe that the use of a dashpot will certainly help stop the force of the lever and thus propose this as our solution for the shock absorber.

Engaging the emergency brake system, or in other words pushing the lever arm to connect it to the electromagnet, was also an issue that we later realized we needed to tackle. While the lever arm can be engaged manually, this method requires a tool to push the lever in, which isn't installed on the kart. Therefore, we devised a way to engage the lever arm without needing any additional requirements that can't already be found on the court. Our final solution is essentially a roller that slides along rails parallel to the lever arm. This way, by pushing the roller against the lever arm, the lever arm will naturally be forced to go towards the electromagnet, and once enough distance is covered, will automatically stick to the powered-on electromagnet. While it has not been officially installed onto the kart, we have a working prototype printed in PLA that is able to move the lever arm, however friction is still a large issue that is currently only solvable by using lube.

Our sponsor also urged us to create a motorized method to activate the mechanism, so we are using a worm gear motor as another option to actuating the emergency brake system. By using a spindle and attaching a cable through it, the motor is able to run normally as well as backdrive, allowing the lever arm to be set in place initially while still having the ability to disengage once the electromagnet turns off.