Scrambler (Division B) - 2026 Event Guide

1. Description

Teams design, build, and test a mechanical device which uses the energy from a falling mass to transport a Grade A hen's egg along a straight track as quickly as possible and stop as close to the center of a Terminal Barrier without breaking the egg.

2. Key Construction Rules

• Safety: Competitors must wear eye protection (ANSI Z87+) during setup and running.
• Energy Source:
  • Propulsion energy comes solely from a failing mass (max 2.00 kg).
  • The mass must be detachable for impound authentication.
  • No springs, rubber bands, electric/electronic devices (including laser pointers for aiming), or elastic energy for propulsion or braking.
• Device Dimensions:
  • The entire device (Launcher + Vehicle + Mass) must fit within a 100.0 cm x 50.0 cm base rectangular box and 100.0 cm height in the "Ready to Run" configuration.
  • Once the vehicle leaves the start box, it may extend beyond these dimensions (but must stay in the track lane).
• Egg Holder / Vehicle:
  • The vehicle must have a rigid, flat Backstop (nominal 5.0 cm x 5.0 cm, +/- 0.5 cm) to support the egg.
  • Backstop Material: One piece of solid, rigid, unpadded wood (thickness ≥ 1.1 cm). No Balsa.
  • Mounting: The egg rests on two 1/4" to 3/8" wooden dowels extending 3.0-4.0 cm from the backstop.
  • The Egg (Grade A Large) must be the foremost part of the vehicle.
  • No tape or adhesive may cover the front 1.0 cm or rear 1.0 cm of the egg.
  • The bottom of the dowels must be between 5.0 and 10.0 cm above the floor.
• Components & Propulsion:
  • Propulsion: Solely gravitational potential energy from falling mass (max 2.00 kg).
  • Braking/Other: Pre-loaded energy (e.g., rubber bands) IS allowed for braking or other non-propulsion functions.
  • Start: Actuated by a #2 unsharpened pencil (provided by ES).
  • The vehicle must separate from the launcher. All launcher parts must stay behind the Start Line.

3. The Competition

• Track Parameters:
  • Surface: Smooth, hard, level surface.
  • Lane Width: 2.0 m.
  • Timing/Target: Start Point and Target Point marked by tape.
  • Target Distance: Selected by ES, between 7.00 m and 10.00 m. (Intervals: 0.25m Regional, 0.10m State, 0.01m National).
  • Bucket Bonus: An empty 5-gallon bucket may be placed on the centerline at the midpoint.
• The Run:
  • Teams have 8 minutes to complete setup and 2 runs.
  • Runs are initiated by a non-electric trigger (e.g., pulling a pin with a pencil).
  • Run Time: Measured from vehicle actuation until it comes to a complete stop (includes recoil/oscillations).
• Scoring:
  • Final Score = Better of 2 Runs (Run Score + Penalties). Low Score Wins.
  • Run Score = 100 + Distance Score + Time Score + Bucket Bonus + Run Penalties
    • Distance Score: 2.0 points per cm from egg tip to Terminal Barrier.
    • Time Score: Run Time in seconds.
    • Bucket Bonus: -100 points if vehicle passes around the bucket (Bonus not available if bucket is moved).
    • Failed Run: Distance Score = 2500, Time Score = 0.
  • Penalties:
    • Run Penalties: Competition Violation (+150), Construction Violation (+300).
    • Final Score Penalty: Vehicle Not Impounded (+5000).
    • Egg Broken: Results in a Failed Run (cannot run 2nd time if broken on 1st).

4. Strategy Tips

1. Braking Mechanism: Use a threaded rod and wingnut (axle-based) or a string-wrap system to lock the wheels exactly at the target distance.
2. Aiming: The vehicle must travel straight. Adjustable axles or a steering alignment mechanism are crucial.
3. Egg Protection: While padding is usually not allowed on the egg front, a stable mount prevents pre-cracking.
4. Practice: Calibrate your braking system for every 10cm increment between 7m and 10m.

5. Recommended Design: The "Threaded Rod Brake" System

This design focuses on the two most critical aspects: Targeting Accuracy (Braking) and Straight Line Motion (Alignment).

A. The Vehicle (Car)

Concept: A 3-wheel "trike" design is easiest to verify alignment. The rear axle serves as the braking mechanism.

1. Braking Mechanism (Threaded Rod)

This is the industry standard for Scrambler. It uses a threaded axle to count the exact number of wheel rotations before locking the wheels.

• axle: 1/4"-20 Threaded Steel Rod.
• Wheels: ~3-4 inch lightweight wheels (e.g., CD wheels or 3D printed hubs with O-rings) used on the rear. Use a single caster or low-friction wheel in the front.
• The Nut: A wingnut is placed on the threaded axle.
• The Guide: A smooth rod or plate is mounted parallel to the axle. The "wings" of the wingnut slide along this guide, preventing the nut from rotating with the axle.
• Action: As the vehicle moves forward, the wheels turn the axle. Since the wingnut cannot rotate, it travels laterally along the threads.
• The Stop: A lock nut is placed at a specific position on the axle. When the traveling wingnut hits the lock nut, it jams the axle, locking the wheels instantly.

graph TD
    subgraph "Rear Axle Assembly (Top View)"
    W1[Left Wheel] --- Axle[==== Threaded Rod Axle ====] --- W2[Right Wheel]
    Wing[Wingnut] --Slides along--> Guide[Anti-Rotation Guide Rod]
    Wing --Travels toward--> Stop[Lock Nut]
    Axle --"Rotates with Wheels"--> Wing
    Stop -->|Collision| Brake[Wheels Lock Up]
    end

2. Chassis & Alignment

• Material: Carbon fiber square tubing or rigid T-slot aluminum. Wood is acceptable but harder to keep perfectly straight.
• Alignment: The front wheel usually controls steering. Use a simple screw adjustment to angle the front axle left/right.
• Egg Mount: A vertical plate bolted to the absolute front of the chassis. Ensure dowels are compliant (wood, 1/4"-3/8").

B. The Launcher (Propulsion)

Concept: A Simple Pulley Tower.

• Frame: Built from PVC pipe or 2x4 wood. Must fit within 50cm x 100cm base.
• Height: Max 100cm. Build the tower ~95cm tall to maximize potential energy.
• Mass: A 1.8-1.95 kg mass (leaving safety margin under 2.00 kg). A dense metal block or a sand-filled bottle worked well.
• String Path:
  1. Attached to Mass.
  2. Goes up to a top pulley.
  3. Goes down to a bottom pulley (redirection).
  4. Runs horizontally to the car.
• Release: The string attaches to the car via a small loop over a smooth pin. When the mass hits its bottom stop (cushion), the string goes slack or acts on a specific release geometry to let the loop slip off, allowing the car to coast.

Crucial Note: The rules state the mass cannot contact the floor. You must build a "catch shelf" or cushion inside your launcher tower about 5cm off the ground.

       [Pulley]
          O
         /|
        / |
       /  | [Falling Mass]
      /   |
     /    |
    /     |
   |      |
   |      |
   |      |
   O------|------------------ [Car] -> (Toward Target)
[Pulley]  [Cushion/Shelf]
   (Base stays behind line)

C. Run Logic

1. Calculate: Measure distance to target (e.g., 8.50 m).
2. Convert:
   • Circumference = Wheel Diameter * PI.
   • Rotations Needed = 850 cm / Circumference.
   • Thread Distance = Rotations Needed / Threads Per Inch (approx 20 for 1/4-20 rod, but measure it!).
3. Set Brake: Spin the wingnut back the calculated distance from the lock nut.
4. Launch: Trigger the mass. Car accelerates.
5. Coast: Mass stops, string detaches. Car coasts.
6. Brake: Wingnut hits stop. Wheels lock. Car slides to a halt just in front of the wall.