Clothesline Racers

What is a Clothesline Racer?

A Clothesline Racer is a vehicle that can start at one end of a clothesline or cable, and go to the other end and return. (This contest described here will use a 3/16 inch galvanized steel cable.)

Click here to learn how to build a timer for Clothes-Line Racers.

Click here to see the clothesline race event held on 3 March, 2012. Clothes-Line Racers.

You can also see a participant’s videos of the 2012 event on by searching one of these: EsCcoChoppa, speeduino wire.

ferret racer

The Races: Where and When

Where: ITT Technical Institute, 401 Mile of Cars Way, National City (Just South of downtown San Diego).

When: 1:00 pm, 28 May.

Directions: The school is just off of I-5, a few miles South of downtown San Diego.

1. From East San Diego County: I-8 West to South I-15 to South I-5. Once on I-5, look for one of the first exits in National City; Mile of Cars Way. (Go to Step 3. below.)

2. From North of San Diego: Head South for San Diego on whichever is closest to you: I-5 South or I-15 South.

a. If you took I-15: I-15 ends South of downtown San Diego, near the National City border. Take I-5 South for just a few exits to the Mile of Cars Way exit.   (Go to Step 3. below.)

b. If you took I-5, stay on I-5 South past downtown San Diego. (Go to Step 3. below.)

3. Exit I-5 South at Mile of Cars Way. Go left one block. When you see Denny’s on the right, look for ITT Technical Institute on the left. (401 Mile of Cars Way) Turn left into parking lot; use the South building entrance.

Contest Registration

To allow organizers to plan the events, all contestants must register. Nothing formal. For each robot entered, send the Class that the racer is entering (See “Vehicle Classes”: “Low Tech”; “High Tech” below), the name of the contact person and a contact email address to Richard Vannoy at

Deadline for registration is 26 May, 2016.

The Rules

Race hardware:

  • The ‘Clothesline’ will be 3/16 inch galvanized, woven steel cable.
  • Cable length will be approximately 100 feet. (When the location of the cable is confirmed, the exact length will be provided here.)
  • The cable will be suspended approximately four feet off the ground.
  • Near each end of the cable there will be a wood plate (called the STOP) one foot square. The stops will be approximately 3 feet from each end. This plate will either be painted white or be covered with white paper to make it reflective for racers using infrared or acoustic distance sensors. This plate serves two purposes:
      1. To act as a mechanical stop at each end to prevent the vehicle from hitting the cable suspension hardware.
      2. To allow vehicles so equipped to detect, either mechanically or electronically, each end of the cable.
      3. Notice in the photo below the dark gray, plywood, six-inch, diamond-shaped stop just behind the robot.

    robot setup

  • The desire is to design and build an electronic timing mechanism that can accurately (to one one-hundredth of a second)
    measure the time it takes a vehicle to travel the full length of the track and return. If an accurate electronic timer is not available, a human operated stop-watch will be used.

Race Track Details

This diagram shows the probable details of the track. This drawing is from a contest held several years ago, so is only an approximation until details for this track are finalized. The most important dimension is the three feet between the STOP and the electronic sensor. That three feet will be maintained at 36 inches plus or minus one inch. This allows all racers to be able to consistently and accurately know when they are approaching the sensor. Since the sensor must be triggered at the far end of the course BEFORE the racer begins traveling back to the start, it must always be in the assigned place. If the sensor is not available, a human will be placed at each end to verify that the robot travels to within three feet of each end. When details are known, an updated sketch will be provided.

Race Track Details

Vehicle Classes

There will be two separate classes of racer:

      Low Tech Vehicles

A low-tech vehicle is defined as any vehicle that does not use any form of computing. (microprocessor, microcontroller, PIC chip, CPU, computer program, etc.)

     High Tech Vehicles

A high-tech vehicle is any vehicle that uses any form of computer/microprocessor/microcontroller to read sensors, control speed or perform any other tasks for the race.


tweaking the racer

Each vehicle:

Must weigh less than five pounds.

Has no restriction on size.

Must be battery powered. (Later contests will allow any form of propulsion, but for this event, batteries only.)

Must begin the race within three feet of the Stop at the starting end, then proceed to within three feet of the far stop and return to the start.

Must be fully autonomous after the GO signal is issued. No form of human-to-robot communication can be used. (Any manual or remote trigger mechanism is allowed to start the vehicle at the beginnig of a run.)

Must be able to be quickly placed on the wire without requiring disconnecting either end of the wire. The wire will be fixed at the start of the event and remain fixed for the entire event.

May not damage or adulterate the wire or stops in any way (no residue, soot, char, rubber, goop, or anything else left behind, no
cutting or abrading, or smashing into so hard as to break, and yes, we expect things to bonk into the stops pretty hard.)

Must finish the race with all parts it started with.

Must be safe for racers and spectators alike. Any racer deemed unsafe by the contest judges will be disqualified.

closepin racer


At a minimum, there will be certificates for top finishers. Other prizes to be determined.

The Race

Each racer gets up to three attempts to complete the course. Racers may complete two runs, the best time being the score for that racer.

Failure to complete the course after three attempts disqualifies the racer.

Judges may rule that a racer is failing to make headway if a racer has not moved within a period of at least 30 seconds at any point.

clothesline racer photo

Online Sources

Sites with Clothes-Line Racer Information:
A set of race rules that became the first draft for our rules above. Search for clothesline race for photos