Looking for the dimensions or CAD model of the small front motor shaft and 10-tooth pinion of the Pololu 20D 25:1 gearmotor.

Support Motor controllers/drivers and motors
1

Hi, I’m designing a custom gearbox for the Pololu 20D 25:1 Metal Gearmotor, 6V (#3450).

I need the dimensions or CAD model of the small front motor shaft and the 10-tooth pinion gear directly attached to it.

I am not looking for the large 4 mm D-shaped gearbox output shaft or the rear encoder shaft.

The official STEP model only shows the complete assembled gearmotor, so I cannot isolate the bare motor/pinion geometry.

Specifically, I’m looking for:

  • motor shaft diameter
  • shaft protrusion from the motor
  • 10T pinion outside diameter
  • pinion width
  • pinion position relative to the motor face
  • module/pressure angle, if known
  • preferably a STEP/CAD model

I want to reuse the original gears and build my own gearbox while keeping the 25:1 ratio.

If anyone has disassembled a 20D gearmotor and can provide measurements or a CAD model of the motor + pinion, I would really appreciate it. Thanks!

2

Hello.

We do not have a 3D model for the 20D motor’s pinion gear. What are you aiming to change about the gearbox design?

By the way, perhaps you are accidentally referencing another motor, but our 20D gearmotors do not use 10-tooth pinion gears.

- Patrick

3

I’d check the motor identification first. In Patrick’s reply, he mentions that the 20D gearmotors don’t use a 10-tooth pinion and that Pololu doesn’t have a pinion CAD model. A close-up photo would help resolve that before you start modelling around it.

If you’re reusing the complete original gear train, keeping the same gears meshing in the same sequence preserves the ratio. For the new housing, I’d concentrate on measuring the shaft centre distances, shaft support diameters, and each gear’s axial position. You’ll also need enough end clearance that tightening the housing doesn’t bind the gears.

For housing design, simplified gear models showing the outside diameters and widths can be enough to check clearances, provided the shaft locations are accurate.

If you eventually use PCBWay’s CNC machining service for the housing, include a dimensioned drawing specifying the critical shaft positions and bearing or bushing fits alongside the STEP file.

What are you hoping to change about the original gearbox—its shape, mounting arrangement, or output shaft position?