HD20 20:1 harmonic drive: output spline torque test

Elliptical wave generator · PETG flex spline · FOC · 100 mm lever arm. Gearbox 1 is the 260704/260705 unit (tightened, then further super-tightened output spline). Gearbox 2 is a second printed unit (white filament) tested fresh off the printer, then again ("notfresh") after further running-in, at both 0.7 A and 1.4 A. The no-gearbox baseline is shared across all runs. Raw load-cell counts scaled ×980.7 to N·m (same factor as prior reports).

58%
best efficiency so far: gearbox 1, super-tightened, 0.7 A
53% → 48%
gearbox 2 efficiency, fresh → notfresh @ 0.7 A (-10.2% steady-state torque)
-18.4%
gearbox 2 (notfresh) vs gearbox 1 (super-tightened) @ 0.7 A
+9.3%
gearbox 2 (notfresh) vs gearbox 1 (tightened) @ 1.4 A

Summary table

ConfigurationSteady-state (N·m)Peak (N·m) 10–90% rise (s)Duration (s)Samples
No gearbox, 0.7 A0.219 ± 0.0040.2240.2730.03000
Gearbox 1, tightened spline (260704), 0.7 A2.372 ± 0.0462.5950.0317.91794
Gearbox 1, super-tightened spline (260705), 0.7 A2.552 ± 0.0432.8330.0318.61860
Gearbox 2, fresh, 0.7 A2.320 ± 0.0372.5950.0321.92186
Gearbox 2, notfresh, 0.7 A2.083 ± 0.0372.2820.0329.12914
Gearbox 1, tightened spline (260704), 1.4 A3.009 ± 0.0593.3080.1020.62059
Gearbox 2, notfresh, 1.4 A3.288 ± 0.0623.5280.0814.91497

Steady-state = median of samples above 50% of peak; ± is one standard deviation over that plateau. Torque multiplication and efficiency are each computed against the shared no-gearbox 0.7 A baseline (ideal ratio 20:1).