Harmonic Drive LLC | 42 Dunham Ridge, Beverly, MA 01915 | 800-921-3332
Harmonic Drive and Harmonic Planetary are registered trademarks of Harmonic Drive LLC.

Series Size Version Ratio Type
HPG 20 A 21 U1
  • High Efficiency
  • Low Backlash
  • High load capacity output bearing
**Drawing does not include modified features for mounting the selected motor.

Gear Model Number
Gear Dimensions (see drawing)
Flange Dim A - Motor Adapter Flange Bore Dia. {{foundMotor.flangeDimA}} mm
Flange Dim B - Motor Adapter Flange Bore Depth {{foundMotor.flangeDimB}} mm
Motor Dim C - Motor Bolt Circle Dia. {{foundMotor.dimC}} mm
Flange Dim D - Bolt Size {{foundMotor.flangeDimD}}
Coupling Dim F - Motor Coupling Bore Dia. {{foundMotor.couplingDimF}} mm
Mass kg
Gear Performance Data
Rated Torque L10 25 Nm
Rated Torque L50 58 Nm
Limit for Average Torque 55 Nm
Limit for Repeated Peak Torque 107 Nm
Limit for Momentary Peak Torque 217 Nm
Starting Torque 24 Ncm
Backdriving Torque 5.1 Nm
Max. Input Speed 6,000 rpm
Ave. Input Speed 3,000 rpm
Standard Accuracy 4 arc min
Gear Backlash < 3 arc min
Input Inertia 0.23 kg-cm^2
Mass 2.1 kg
Torsional Stiffness
K1 1.8 10^4 Nm / rad
Output Bearing
Pitch Circle Diameter (dp) 0.06 m
Basic Dynamic Rated Load (C) 106 10^2 N
Basic Static Rated Load (Co) 173 10^2 N
Allowable Moment Load (Mc) 183 Nm
Moment Stiffness (Km) 16.8 10^4 Nm / rad
Permissible Radial Load 1,510 N
Permissible Axial Load 2,250 N


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