NATCAR RULES

Objective:

Rules - Part A: The Car

1

The car must be electric powered, have four or fewer wheels (nothing else may touch the ground - i.e., no rollers or slides), rubber tires of less than 4.25" diameter and 2.5" width, and the wheel base must have: length ≤ 14 inches (axle to axle), width ≤ 14 inches (from outside of wheel or tire to outside of wheel or tire). In addition, the overall car (including any electronics, sensors and body) must have: height ≤ 9 inches (except for the flag noted in item 5 below), overall width ≤ 14 inches, overall length ≤ 3 feet. 

We have been using the chassis of a standard off-the-shelf 1/10 scale radio controlled electric car and recommend this as a fine starting point (the off-road vehicles do not work as well on the carpet - so you are better off with street cars).

Note that the tires must NOT be modified to improve traction (e.g., no studs, nails, sandpaper etc.); these things tear up the course. So, when we say rubber tires, we mean some kind of off-the-shelf rubber (or foam) tire.

2

The vehicle (including all electronics, servos and motors) must be powered by a single battery, which may not cost more than $30 (e.g., a standard 7.2 volt NiCd radio-controlled vehicle rechargeable battery).

3

Teams must build their own motor control and DC-to-DC converter circuitry using discrete components and IC's. In other words, commercially available speed control units and DC-to-DC converter subassemblies (e.g., "bricks") are not allowed. All other circuitry can be constructed from whatever components (e.g.,resistors, capacitors, transistors, LED's) or subsystems (e.g.,microprocessor development boards like the Adapt812 from www.technologicalarts.com) are available.

4

For safety, each vehicle must have a single off/on switch that can be easily operated while the car is in motion. A good option is to make the flag connect to a switch so that someone can simply swat the flag to turn the car off as it comes by. A remote control may be used to turn the car off and on, but if it is, IT MUST BE GIVEN TO THE RACE ORGANIZERS to operate while your car is on the course. If any remote control is used by anyone other than a race organizer while the car is on the course, the car will be disqualified.

5

Each car must have a single rigid opaque flag on top of the car. The flag must be at least 3" high and 6" long when viewed from the side, with it's bottom edge 9.5 inches above the floor. The location of the flag along the length of the car is not important so long as it does not move. (This flag is used to trigger the timer, so it must be rigid enough to maintain it's shape. The length is required because of the response time of the detector used for timing the cars.)

Rules - Part B: The Racecourse

1

The course will be marked with 1-inch-wide white duct tape (it has a shiny bright white surface) on top of dark colored carpet (it may not be a completely solid color). The tape marks the center of the course (i.e., the car is supposed to be positioned over the tape). The tape is put down on top of a wire which is formed in a complete circuit and driven by a 75 kHz sinusoidal 100 mA RMS current (+/- 10%).

In addition, small pylons will be placed at various points along the course no less than 15" away from the tape and no closer than 15" to each other. A penalty of two seconds will be added to the lap time for each pylon that is hit by a car. We do not have carpet samples or other information to give you; the best you can do to see the carpet used is look at the video clips from the past year. Also, please note that you cannot measure the current with a standard digital multi-meter; they don't work at 75 kHz!

2

The course may be of any length and configuration but all turns will have a radius greater than or equal to 3 feet. Typical courses in the past have been between 250 and 350 feet in overall length with at least one straight-away of 25 feet or more (see the race results to see the layouts used in previous years).

3

The course may cross itself, but the crossing will never occur at an angle less than 60 degrees, although the crossing may occur in the middle of a curve.

4

The course may have sections that are parallel to each other, but they will be at least 3 feet apart.

5

At least 3 feet into a straight section of the course, the track may make a right-angle jog to the left or right of no more than 6 inches provided that the course then continues straight and parallel to its original direction for at least 3 feet.

Rules - Part C: Running the Race

1

Depending on the number of schools competing in a given year and the number of teams each school has, we may need to limit the number of teams that can compete from each school; check with the organizers to find out.

2

There will be one official race course and two warm-up tracks. The team on the first warm-up track is said to be "in the hole" (i.e., they are 2^nd in line for the race course). The team on the second warm-up track is said to be "on deck" (i.e., they are 1^st in line for the race course). No matter what happens to preceding teams (e.g., they abort their runs), each team may, if desired, have a total of at least three minutes on the warm-up tracks before being called to race. When a team is called to the race course they must report to the course and start running within one minute. After one minute, the clock will start whether or not the team is ready to run. Each team will be allowed five minutes on the course. This time includes the time used to make any adjustments desired to the car (within the guidelines given below). The team may make as many attempts to run the course as desired within the five minutes, but may not begin a run with less than 30 seconds remaining. The car will be allowed to complete the last run even if takes longer than 30 seconds. The best time will be recorded.

Adjustments may be made to the cars in-between runs, but the car may not be programmed in any way with specific information about the course. In other words, the idea is that the car runs autonomously; you may adjust maximum or minimum speeds or fix small problems, but you may not enter the configuration of the course into memory. If the car is capable of memorizing the course for itself, you may switch it from a memorization mode to a racing mode in-between runs.

3

The car will be placed at the start of the course and turned on. The time will start when the flag on the car interrupts a light beam (the car is given a short running start). The time will stop when the flag interrupts the beam again at the end of the run. A team may pick up their car at any point during the run, but the run is deemed to be aborted the instant the car is touched.

4

The car does not need to stay over the tape at all times but will be penalized two seconds for each pylon it hits as noted above in B.1. If the car deviates from the course, the time will still count so long as the route the car takes is not shorter than the planned course. For example, a car can lose the course and come back and find it so long as it does not cut off part of the course in the process.

5

A team may abort their five-minute session ONCE so long as they have at least 30 seconds left. If they do, they will be assigned the next available start time on the course (i.e., after all other currently- scheduled competitors are done) and will either keep their remaining time or two minutes, whichever is less. Under no circumstance (e.g., if they are the last group) will they receive less than a five-minute break.

6

The initial start times will be determined by the organizers.

7

If none of the teams can successfully complete the course, a simpler course may be used at the discretion of the race organizers and if time permits.

8

Each team is responsible for providing their own batteries and chargers, but it is not guaranteed that you will have the time to recharge your batteries in between runs, so have them ready!

9

All cars must be given to the race organizers at the start of the day. They will be checked for conformity to the rules at that time and any car not in compliance will be ineligible for the competition. It may still be allowed to run, but the time logged will not count in the official race results.

Rules - Part D: Judging