Lesson #4

Introduction to Gears

Prep: Sample gear-driver cars with spur gear, crown gear

The one-motor car:

  • Demonstrate by connecting two motors together with a wire that turning a motor can make electricity that can turn another motor.
  • Show two sample one-motor cars

Gear-Wall:

  • Demonstrate how a simple gear train can be constructed to get more power to motor.
  • If gears do not mesh, move over one stud and/or add plates
  • Discourse on Gears and Gear Ratios;
  • Show Robotics Educator Introduction to Gears slideshow

Gears:

    • The speed with which the crank rotates depends upon the gear ratio of the driver gear and follower gear.
    • If the driver gear has more teeth than the driven gear, the follower gear goes faster than the driver, but with less torque. This is termed gearing up.
    • If the driver gear has fewer teeth than the driven gear, the follower gear goes slower than the driver gear, but with greater torque. This is called gearing down.
    • There is always a trade-off of speed and torque(turning-force).

CHALLENGE: Build a one-motor car which will go up a 30% incline.

Typical problem: Car is built with large drive wheels- goes fast on level, will not go up hill.

Explanation: It takes a certain force to push car up hill. Torque/wheel radius= force. So the large the wheel, the smaller available pushing-force.

Extra Credit: Build merry-go-round.
Draw Lego Pins on Board
Build worm gear sample
Build Gear train sample

Technology: Types of pins

  • Gray round/round- snap into round holes, spin easily
  • Black round-round: Form tight connection
  • Gray or brown round/cross: Link two types of holes
  • Brown short/round: Connect RCX to Beams


To extend angle beam, attach regular beam with two black pins.

Mechanism: Crank

Challenge 3: Build gear-driven claw. Try interchanging gears.

Bioengineering Aside:

Orthotic: An assistive device, such as:

  • Eyeglasses
  • Walker, Cane
  • Leg Braces
  • Functional Electrical Stimulation
  • Wheelchair Ramp
  • Wheelchair

Orthosis: Custom designed and/or fitted anatomical devices applied externally on the human body which are intended to provide support and/or control of disorders associated with neuromuscular and/or musculoskeletal dysfunctions.

Prosthetic: A device that replaces a normal body part or organ, such as:

  • Artificial limb
  • Artificial kidney
  • Artificial heart valve

 

 

Prosthetic

Photos from Technology Review Magazine

* Extra Credit or alternative: Build tilt-a-whirl;
Gear Train; worm gear