Gear Train

Gears give a mechanical advantage of speed or torque ( turning- force).

There is always a trade-off.

They are also used to transfer power from one location to another,

change direction, or axis of rotation.

The gear ratio is the relative mechanical advantage.

• Gear Animation( Basic)
• MIT+K12: How to Win a Bike Race Using Gears
  http://k12videos.mit.edu/content/how-to-win-a-bike-race-using-gears

Terms:

• Driver, Follower
• Ratio of # of teeth between Driver and follower=Gear Ratio= speed/force ratio
• Gearing Up- increasing speed, decreasing torque
• Gearing Down- decreasing speed, increasing torque
• Compound Gearing: Overall Gear Ratio is product of each separate ratio
• Idler Gear- Changes Direction of rotation; driver and follower turn in same direction

Video: Gears ( October 2010)

Video: Gearing Up

Video: Gear Basics ( 10 min)

Assignment 1: Using Beam, build a gear train that gears UP at least 5:1

Assignment 2: Using Beam, build a gear train that gears DOWN at least 5:1

Assignment 3: Build Worm Gear

Assignment 3:

Gearing Down: 8 tooth Driver, 40 tooth follower

Gearing Up: 40 tooth Driver, 8 tooth follower

• Show power drill, hand drill, etc.
• Build 5:1 gear ratio



3-24T idler gears move power to a location; 40T:8T gear pair gears up 5 to 1- Geartrain video

• Attach gear train one-motor NxT Car; Can you use gears to get more speed?- compare performance on flat ground and on hill

Worm Gear:Cannot be back-driven; high gear reduction in one step

• Worm Gear Video
• Flash Animation of Worm Gear

Tuner on Bass Violin: Tension of string on main gear blocked by worm

Lego Worm Gear