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RC Helicopter Gear Ratio Calculator

Work out the total gear reduction between motor and rotor head, stage by stage.

Reduction Stages

e.g. tail/front-stage reduction as a ratio ≥ 1.

Result

Total reduction ratio
12.46: 1
Stage 1 (main ÷ pinion)
12.46: 1
Stage 2
1.00: 1

Head speed = motor RPM ÷ total ratio — feed this into the Head Speed Calculator.

Formula

  1. 1.Stage 1 = Main Gear Teeth / Motor Pinion Teeth
  2. 2.Total Reduction = Stage 1 × Stage 2 (if any)
  3. 3.Theoretical Head Speed = Motor RPM / Total Reduction

Worked example

  1. 1.Inputs: 13 T pinion, 162 T main gear, no second stage.
  2. 2.Stage 1 = 162 / 13 ≈ 12.46; total = 12.46:1.
  3. 3.A 24,000 RPM motor → ≈ 1,927 RPM head speed.

Assumptions and limits

  • Counts only stages you enter — pulleys/torque tubes have their own ratios.
  • Verify every stage against the model manual.

Related tools

Guides and concepts

FAQ

Is this the same as a car FDR?

No — helicopter drivetrains are staged differently; use this tool, not the car one.

Assumptions

  • Stage 1 counts motor pinion and main gear teeth.
  • Further stages are entered as a ratio ≥ 1.
  • Different layout than car spur/pinion — do not reuse car FDR logic.