Getting started
Enter your linkage geometry and desired control-surface travel. The calculator
solves arm lengths, pushrod length, and servo center angle, then updates the
diagram. Your settings are saved automatically in this browser.
Editing values
- Select the known arm in Known arm length, enter your geometry and travel values, then click Recalc.
- Only the selected known arm is shown in Geometry; the solved opposite arm appears in Results.
- A spinner appears while longer calculations run.
Common options
- Symmetric travel — one up-travel value applies to both directions.
- Servo arm / horn orientation — match how the parts are mounted on your model.
Results
- Servo arm angle at center — where the servo arm sits at 0% throw for this linkage.
- Servo at 0 deflection — the throw slider position (%) that fairs the surface to 0°; use this when setting subtrim or endpoint mix in the radio.
- Required pushrod length — cut length between the arm and horn at the solved center geometry.
- Actual up/down travel — surface travel achieved at nominal ±45° servo throw.
Diagram & throw slider
After each calculation the diagram moves to show the surface at 0° deflection.
Drag the throw slider to preview other servo positions within usable travel.
mm to degrees
Use the table below the main calculator to convert recommended surface throw in
millimeters to degrees for ailerons, flaps, elevator, and rudder.