- Complete the guided VEX mechanism build.
- Check spacing, fastening, axle support, alignment, and structural rigidity.
- Correct any build-quality problems before submitting.
POE Unit 1 • Lesson 1.7
Guided VEX Gear & Sprocket Drive Systems
Focus question: How do we correctly build gear and sprocket drive systems so that calculated mechanical relationships work in a physical VEX mechanism?
Start Here
What You Need to Do
Use this section as your checklist before moving through the lesson resources below.
- Completed VEX build
- VEX mechanism build-quality checklist
The mechanism moves freely, stays aligned, and does not rely on loose or unsupported components.
Lesson Snapshot
What You Will Be Able to Do
This is a training-wheels-on lesson before later open-ended mechanism challenges.
Build a gear reduction
Construct a 12T driver gear meshed with a 36T driven gear and test smooth rotation.
Add an idler gear
Use an idler to change direction or transfer motion across more distance while tracking the overall ratio.
Build a chain drive
Connect a 12T driver sprocket to a 24T driven sprocket using chain, proper alignment, and good tension.
Today’s Flow
How the Lesson Moves
Parts checkGuided gear buildStop and checkIdler gear buildGuided chain buildMini modificationExit ticket
Learning Target
Main Objective and Evidence
I can build functional VEX gear and sprocket drive systems using correct shaft support, spacing, alignment, collars, spacers, and chain tension.
Guided VEX Gear & Sprocket Drive Systems Build Guide with calculations, stop-and-check boxes, troubleshooting notes, and photos.
Your mechanisms spin freely by hand, the gears do not skip, the chain stays on, and your team can explain speed, torque, and direction changes.
Build Sequence
Copy - Build - Test - Understand - Modify
Follow the build guide exactly until both drive systems work. Open-ended design comes later.
| Part | System | Required Evidence |
|---|---|---|
| A | Identify drive-system parts | Parts checklist and vocabulary table |
| B-C | 12T gear driver to 36T gear driven | Gear ratio calculation and motion observations |
| D | Idler gear system | Direction tracking and explanation of what the idler changes |
| E-F | 12T sprocket driver to 24T sprocket driven | Sprocket ratio calculation and chain-quality check |
| G | Mini modification challenge | One small change to make output rotate faster than input |
Build Checks
Stop Before You Continue
Do not keep building on top of a problem. If a shaft binds, a gear skips, or the chain climbs off the sprocket, stop and fix alignment, spacing, collars, or chain tension before moving to the next step.
Gear drive should...
- Spin freely by hand
- Mesh without jamming
- Show slower output with more ideal torque
- Reverse direction with one external mesh
Idler gear should...
- Mesh smoothly with both gears
- Change the direction pattern
- Transfer motion across more distance
- Keep the overall simple-train ratio based on first and last gears
Chain drive should...
- Have aligned sprockets
- Use chain that is not too tight or too loose
- Keep the chain on the teeth
- Rotate input and output in the same direction
Resources
Lesson Resources
Use the guided build packet during class. It is designed to print cleanly in black and white.
Guided VEX Gear & Sprocket Drive Systems Build Guide
Step-by-step build instructions, parts-and-tools checklist, calculation boxes, stop-and-check tables, troubleshooting guide, mini modification challenge, and exit ticket.
VEX Rover Mechanisms Challenge
Use this guided practice to prepare for later open-ended mechanism design, testing, and presentation work.