Plan before you build
The gearbox position, wheel clearance, axle alignment, battery access and body shape affect one another.
Interactive construction document
Build your Scorpio vehicle, one clear step at a time.
This guide combines the vehicle and multi-ratio gearbox instructions into one build pathway. It helps you assemble the car without choosing your design decisions for you.
✓ Saved progress
✓ Gear setup selector
✓ Wiring walkthrough
✓ Troubleshooting
Start here: understand the build pathway
Read the whole sequence once before cutting, gluing, drilling or soldering anything.
Workshop safety comes first
Follow your teacher’s instructions for PPE and tool use. Soldering irons, hot glue guns, drills, cutters and hammers must only be used when your teacher has approved the task.
Test before decorating
Get the drive system working first. Decorative body parts should be added only after the vehicle runs reliably.
Ask before forcing parts
Press-fit gears are meant to be firm, but forcing a gear, motor or shaft can permanently damage it.
Before continuing
Check your kit before building
Identify each component now. A missing part discovered halfway through assembly is a spectacularly annoying plot twist.
Stop and tell your teacher
Report missing, damaged or mismatched parts before assembly. Do not substitute a gear or shaft without checking.
Plan the vehicle layout
Place the real components on the base before marking holes. Your body design must fit around the working system.
Place the four wheels
Check the full sweep of each wheel. Nothing should rub against the body or base.
Position the gearbox
Decide which end will be driven and which side the motor will sit on.
Position the battery and switch
Keep them accessible and away from moving wheels and gears.
Plan the wire route
Wires must be secure, short enough to stay tidy and long enough not to pull on solder joints.
Check the body envelope
Your CAD or manufactured body must fit the supplied base and preserve all clearances.
Layout checkpoint
Prepare the chassis
Measure twice, mark clearly and drill only after the component layout has been checked.
Confirm the actual base dimensions and component locations.
Use a ruler and pencil to mark axle lines and mounting holes.
Use only teacher-approved tools and methods.
Remove sharp edges and loose material.
Place the components back on the base before gluing or screwing.
Do not guess hole positions
Use the actual gearbox as a template. Mounting holes should match diagonally opposite corner holes in the gear case.
Chassis preparation check
Cut and fit the axle guide
The plastic tube guides the free axle. It must be straight, parallel and slightly wider than the chassis.
Measure the chassis width
Cut the guide tube about 2–3 mm longer than the width it crosses.
Deburr the tube
Remove rough edges so the axle cannot scrape or bind.
Slide a shaft through it
Leave a steel shaft inside the tube while positioning and hot gluing. This keeps the tube straight and protects it from bending under heat.
Glue on the marked axle line
Hold only the cool ends of the steel shaft. Keep fingers away from hot glue.
Test rotation
After cooling, the axle should slide and rotate freely without wobbling.
Axle guide check
Choose a gearbox arrangement
You are choosing a design trade-off, not hunting for one secretly “correct” answer.
Fewer gear stagesGenerally more wheel speedGenerally less turning force
More gear stagesGenerally more turning forceGenerally less wheel speed
Your design decision
Consider towing, acceleration, traction, wheel size and your intended testing. The guide shows how to assemble each option but does not select one for you.
No arrangement selected yet.
Choose an option above to reveal its parts and assembly pathway.
Gear decision check
Build the selected gearbox
The panel below updates to match the arrangement chosen in Step 05.
Select a gearbox arrangement first.
Return to Step 05 and choose the option you plan to build.
White gears are press-fit
Their smaller hole grips the 2.5 mm steel shaft. Support the shaft and press carefully.
Yellow gears spin freely
Their slightly larger hole lets them act as intermediate gears.
12-tooth gears act as locators
They help hold the outer gear stack in position.
The washer prevents rubbing
Place it between the gear case and the first outer gear shown in the selected pathway.
Do not force a jammed gear train
If the gears do not rotate by hand, stop. Check hole A/B placement, white versus yellow gears, washer location, shaft straightness and gear spacing.
Gearbox assembly check
Attach the motor to the gearbox
The small 10-tooth pinion must be pressed onto the motor shaft without loading the motor body.
Ask for the approved pressing setup
The motor and gear must be supported so force goes through the shaft, not the motor casing.
Press the 10-tooth pinion onto the shaft
Leave a small gap between the gear and motor body so the gear does not rub.
Check the pinion is straight
A tilted gear will bind and damage the larger gear.
Secure the motor to the case
Use the two correct self-tapping screws. Do not overtighten.
Check the mesh by hand
Turn the output shaft gently. The motor pinion and first large gear should mesh without skipping.
Motor attachment check
Mount the gearbox to the chassis
The output shaft must sit square to the chassis so the driven wheels remain aligned.
- Return the gearbox to the dry-fit position from your plan.
- Confirm wheel clearance on both ends of the output shaft.
- Use two diagonally opposite gear-case corner holes as the mounting points.
- Drill the teacher-approved pilot holes using the gearbox as the template.
- Insert the self-tapping screws from the top of the gear case into the chassis.
- Tighten until secure, then stop. The case should not distort.
- The output shaft is square to the centreline.
- The shaft ends extend far enough for both driven wheels.
- The motor does not touch the chassis or body.
- The gears remain free after the mounting screws are tightened.
- The gearbox cannot rock or twist under light hand pressure.
Gearbox mounting check
Install the axles and wheels
Wheel alignment and friction can make or break the vehicle’s performance.
✓Good alignment
Wheels are parallel, clear of the chassis and seated evenly.
×Wheel rubbing
A wheel pushed hard against the chassis creates drag.
×Crooked axle
Misaligned axle guides make the vehicle curve and waste energy.
Fit the free axle
Slide the shaft through the guide tube. It should rotate and move without scraping.
Fit the free wheels
Press them on evenly. Leave a tiny clearance so they do not clamp against the tube or chassis.
Fit the driven wheels
Press the wheels onto the gearbox output shaft. Keep both wheels square to the shaft.
Spin-test each wheel
Look for wobble, rubbing, slipping or unequal spacing.
High-load builds
If your driven wheels slip on the shaft, ask your teacher about the approved method for improving the shaft-to-wheel grip. Do not damage the shaft or wheel hub without permission.
Wheel system check
Wire the motor, switch and battery holder
The six-terminal, centre-off switch reverses the motor by reversing the polarity supplied to it.
Disconnect the batteries before soldering
Complete and inspect all solder joints before inserting batteries. Wear eye protection and use the soldering iron only under teacher supervision.
Prepare the wire lengths
Keep wires clear of wheels and axles, but leave enough slack to avoid pulling on joints.
Connect the motor
Connect the two motor leads to the centre terminals: 2 and 5.
Connect battery positive
Connect the positive lead to terminal 3, then add a jumper from 3 to 4.
Connect battery negative
Connect the negative lead to terminal 6, then add a jumper from 6 to 1.
Inspect and secure
Check for loose strands, solder bridges and wires that could enter moving parts.
Switch orientation matters
Hold the six terminals in two rows of three exactly as shown. If your physical switch is different, stop and ask your teacher before soldering.
Wiring check
Complete the first test and diagnose problems
Start with the driven wheels lifted off the bench. Test briefly before placing the vehicle on the floor.
Support the chassis so the powered wheels can rotate freely.
Check polarity in the holder and keep hands clear of gears.
Move the switch briefly. Watch and listen for rubbing, skipping or jamming.
Stop immediately if the motor stalls or the gears cannot rotate.
Confirm the switch reverses the driven wheels.
Only continue when the lifted-wheel test is smooth and reliable.
Interactive troubleshooting
What is your vehicle doing?
Select a symptom to see the most useful checks.
First test check
Complete the final build check
Only add or finalise decorative body parts after the working system passes this check.
Build status
Keep working through the checklist.
Your progress bar will update as each item is completed.