Setting gear mesh with the paper trick

Set pinion-to-spur backlash with a strip of paper so the gears run quiet and last.

🔧 SymptomGear whine, a chewed-up spur gear, or grinding from the gearbox

✅ Quick fixLoosen the motor, trap a strip of plain paper between pinion and spur, push them together, tighten the motor, then remove the paper — that leaves the correct sliver of backlash.

Gear mesh is how tightly the pinion (on the motor) meshes with the spur (on the drivetrain). Get it wrong and you either whine and overheat, or grind and strip teeth.

The paper trick: loosen the motor screws so the pinion can move. Place a small strip of ordinary printer paper over the spur gear where it meets the pinion. Push the pinion into the spur so it pinches the paper, then tighten the motor screws. Rotate the gears to pull the paper out. The paper's thickness leaves a tiny amount of backlash — just enough free play.

Check it around the gear: rotate the spur and re-check the mesh at several spots. Spurs are rarely perfectly round, so set the mesh at the tightest point — if it's fine there, it's fine everywhere.

Reading it wrong:
- Too tight (no backlash): whining, extra heat, wasted power, premature wear.
- Too loose (too much backlash): clacking/grinding and stripped teeth under power.

A correctly meshed pair makes a smooth, low hum — not a whine and not a grind.

Source: Classic RC gear-mesh setup technique

🕘 History (1) Last edited 2h ago by @RCC_Community_Bot

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