Swingarm PTO
Power-take-off that swings between two outputs from a single motor — drive a wheel and a climb hook with the same power source. Reclaims a motor without sacrificing endgame.
Before you start
PTO design is a tradeoff: one motor doing the job of two means it can't do them simultaneously. Confirm your match strategy lets you finish driving before you engage the climb output.
1Identify the two outputs
Sketch the two output shafts side-by-side. Output 1 is usually a drive wheel; Output 2 is whatever endgame device you want — a winch, an arm, a hook.
Both outputs need their own bearing support — they don't depend on the motor for axial support.
2Place the motor on a pivot
Mount the motor on a swing armA pivoting bracket lets the motor's output gear physically translate between two mating gears. One position drives Output 1; the swing position drives Output 2. Mechanically clean — no electronics involved. that swings around a fixed pivot point. The pivot puts the motor's output gear in mesh with Output 1's gear at rest.
The arc length and gear positions determine how far the motor has to swing to disengage and re-engage.
3Add the actuator that swings it
A servo, a solenoid, or a manual cable can drive the swing. For FTC, a small servo with a pushrod is the cleanest — dual-mode holdUse a smart servo that can hold a position under load. Cheap servos drift; if the PTO drifts mid-match, you'll lose drive control or fail to climb. matters because the motor will try to push the swing arm back.
Add hard mechanical stops at both positions so the servo isn't fighting the motor torque.
4Design the engagement geometry
When the swing arm reaches its second position, the motor's output gear should mesh cleanly with Output 2. Use slightly tapered gear teeth or a dog clutch so the engagement self-aligns.
Test the engagement in Onshape — simulate the swing and verify the teeth mesh without tooth-on-tooth conflict at any angle.
5Verify the disengagement is clean
Most PTO failures aren't engagement — they're disengagement. When the swing arm leaves Output 1, the gear has to fully clear. Check that the swing radius is large enough.
Run the full swing in the assembly's Play view. The output 1 gear should free-spin in mid-swing, then output 2 should engage at the destination.
A working PTO frees up a motor for a different subsystem. Used right it's a force multiplier; used wrong it's the most fragile point on the robot — test the engagement transitions hard.