Wheeled Vehicle

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Wheeled Vehicle is a physics based build event in which students must construct a vehicle powered only by a non-metallic elastic solid device. The participants must be able to adjust the vehicle to travel a specified distance around an obstacle as chosen by the event supervisor as fast and as accurately as possible. It was last run in 2015 before being run in 2023 and 2024.

Event Description

Prior to the event, competitors must design, build, and test a vehicle which is only powered by a non-metallic, elastic material that can store potential energy. This potential energy is stored (for example stretching a rubber band) and then released to make the vehicle move from the potential and kinetic energy.

The main object of this event is to navigate through two cans and stop at or as near as possible to the specified distance while moving as fast as possible.

At the competition, the event supervisor will announce a track distance between 8 and 12 meters after impound is complete. The exact distance will be in different intervals for different levels of competition (see below). Competitors will be given a total time of 8 minutes to set up their vehicle and perform two runs. The vehicle must be triggered by actuating a release mechanism with a unsharpened No. 2 pencil supplied by the event supervisor.

Basic Construction Parameters

  • The vehicle should be designed to travel between 8 and 12 meters.
  • All energy used to propel the vehicle must be stored in a non-metallic, elastic device.
  • All wheels must fit in a ready to run configuration in a 30.0 cm x 70.0 cm space (no height restriction).
  • The vehicle must have a 1/4 inch wooden dowel attached to the front of the vehicle. This dowel serves as a measurement point for distance to the line, and also a method to trigger the photogate system (if used by the event supervisor). The bottom of the dowel needs to be within 1 cm. from the track.
  • The dowel also needs a paper flag, (5 cm x 5 cm), with the center height at 17.5 cm. It may be any color and decorated.
  • The vehicle must be started by a vertically-actuated trigger.

The calibration intervals are: Regionals and Invitationals: 0.50m(50 cm) States: 0.20 meters (20 cm) Nationals: 0.05 meters (5 cm)

Designs

The three main parts of a design will be the energy mechanism, the turning mechanism, and the braking system.

Body design is also important- consider what type of car is most suitable whether it be a lightweight, easy-to-move car, or perhaps something in the middle that won't do a wheelie as easily, or maybe something ridiculously heavy, powered by a very strong elastic solid. Most teams choose to go as light as possible. Try to find ways to shave down weight wherever possible.

Elastic Energy Mechanisms

Some of the popular energy mechanisms are:

  • rubber bands
  • fishing poles
  • carbon fiber poles
  • bungee cords

These can be harnessed in many ways, such as a string wrapped around an axle, and the elastic unwrapping the string. Another popular method is to simply wrap the rubber band around the axle, hold it in place, and have it unwind during the course of the run to spin the wheels.

For rubber bands FAI Tan Super Sport is your to go rubber. It can stretch up to 7 times its length and is very durable. If using rubber, using lubricant will also help. Your go to lubricant brand is Son of a Gun Rubber Protectant. This ensures that the rubber will unwind better, without possible damage, and will make the rubber stronger.

Braking Mechanism

A braking system is needed to stop accurately. Here are some things to think about:

  • It needs to be accurate.
  • It can be adjusted to whatever distance is announced at the competition.
  • Somewhat simple is better, so that there's not a whole lot of room for error.
  • It has to be very reliable, so it will work (near) perfectly every time.

Braking systems are built differently by each team to accommodate their vehicle. There are several systems that can easily be adapted into a device. (Scrambler, Mousetrap Vehicle, and many other Science Olympiad events include similar braking concepts.)

With this planned out, teams know what is needed and can start designing a mechanism. There are many different kinds of mechanisms online. However, teams can also come up with their own braking device.

Threaded Rod and Nut

An example of a Scrambler device utilizing the wingnut braking mechanism.

One of the mechanisms commonly used on a vehicle is the threaded rod and wingnut design. It has been used by many competitors in multiple vehicle events and is reliable. The details of how to build and implement it can be decided by teams themselves, but the general idea is the same. A threaded rod, a wingnut, and something to hold the wingnut are needed. It is important to know how many revolutions of the wheel it will take for the vehicle to reach the target distance. This can be done by dividing the target distance by the wheel circumference, showing the number of turns and axle length required.

First, start by looking at the blue line which in this case is our axle (which is the threaded rod). The green line is the rod that holds the wing nut in place. As the wheels and axle spin, the wingnut will move down towards the chassis between the wheel and the inner assembly. Eventually, this nut will hit the chassis and lock up the axle, preventing the car from traveling more. In order to use this system for calibration, all one would have to do is start the nut on the chassis and then wind it out to the distance needed. Teams should know how much distance is gained per turn of the wheel. This can easily be figured out using the circumference formula.

Ratchet Mechanism similar to the braking mechanism used.

Release Mechanism

A Release Mechanism should be something you can count on not releasing on accident or not releasing at all.

Ratchet Mechanism

A ratchet is a mechanical device that allows continuous linear or rotary motion in only one direction while preventing motion in the opposite direction. The release mechanism functions from a gear fixed onto the axle that is connected to the power source. When the wheel moves in the opposite direction, the ratchet prevents motion. If the ratchet is lifted, the axle is free to move in both directions.

This would what the release mechanism would actually look like on the vehicle.

Turning Mechanism

For the turning mechanism, there are a few options. Some will probably work better than others.

  • One option is to have the vehicle naturally turn one direction, then aim it the opposite way.
    • This would involve having one of the axles placed at an angle, and then starting the vehicle at an angle that allows it to start out to the side of the can and gradually return to the center.
    • Another option is building the chassis in two halves, and adjusting axle angle by moving a joint that connects the two halves.
    • Building one axle on a pivot point is another commonly used method. This is simple, but you must have a way to secure the axle in the same position once you find the right angle.
    • A more complicated option would be to use an Ackermann steering system.

Competition

Goggles are required for the competition. Also, any tools or computing device needed to assist in calculating distance/time are permitted. However, note that the rules prohibit the use of any electronic devices except calculators (e.g. laser pointers are not allowed). The vehicle must be impounded before competition starts, and the event supervisor may not announce the target distance until the last vehicle is impounded. The competition will be on a relatively smooth, level track (often a corridor or gym). For the two runs, there will be a total of 8 minutes of preparation time. However, once time expires, you will not be able to continue to conduct a second (or first) run. Vehicles are to be triggered only when the event supervisor has indicated one may do so. Do not chase after the vehicle; this will result in a Competition Violation. Wait until an event supervisor signals that the vehicle can be retrieved.

Scoring

In this event, competitors compete to get the lowest final score possible. The final score is from the best run. The equation for the score is:


Base score - {2 × ( Time of run )} + ( centimeters away from target ) + {can bonus) + (Log bonus)

  • Base score is 100 points
  • Can Bonus is optional
  • Log Bonus is optional
  • Can Bonus is: -0.5 x (110 - distance of cans, in cm.)
  • Log Bonus is -40 points


Example calculation:

A vehicle traveled between a can distance of 75 cm, and had a time of 6.23 seconds. They did not submit a log bonus. Their distance from the target distance was 11.48 cm.

Calculation:


Base score (100) + Distance (11.48) + Time (12.46) + Can Bonus (-17.5) + Log Bonus (0) = 106.44 points

(100 + 11.48 + 12.46 - 17.5 + 0) = 106.44 points

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