Motor mount failure
The first revision of the custom motor and encoder brackets cracked at the fastener bosses. The failure showed up on a bench load test rather than in the field, which is the good version of this outcome. The more interesting problem is that the same bracket locates the encoder against the motor shaft, so the part degrades odometry as it goes soft, long before it visibly breaks. Any encoder data collected in the last two weeks has to be treated as suspect.
What we learned
- The first part we designed ourselves is the first part that failed. That is not a coincidence — it is the part with no service history behind it.
- A mount that holds a sensor is a sensor component. Its stiffness is a measurement specification, not a mechanical convenience.
- Compliance fails quietly. The bracket was degrading the encoder signal well before the crack was visible, and nothing in the data flagged it.
Next steps
- Redesign with thicker fastener bosses and re-evaluate material; machined aluminium is on the table for revision two.
- Discard encoder data collected before the replacement rather than trying to correct it.
- Add a bench load test to the checklist for every custom structural part before it goes on the platform.
Hardware referenced
- Motor and encoder mounts (custom)Designed and printed in-housePrinted brackets, revision 2 in design
- WAVE ROVER 4WDWaveshare4WD skid-steer base, integrated ESP32 driver board
Open challenges touched
Motor mount replacement
The first-revision printed motor brackets cracked at the fastener bosses under drivetrain load. Because the same bracket locates the encoder against the motor shaft, a compliant mount corrupts odometry well before it fails visibly. Revision two thickens the bosses and moves to a stiffer material; it has not yet been printed or loaded.
Decisions referenced
Design the motor and encoder mounts in-house
Encoder mounting was taken in-house to control encoder alignment. The first revision failed under load, and the approach is being re-examined rather than abandoned.
- Encoder alignment determines odometry quality; it is not a detail worth inheriting from a generic bracket.
- Printed parts can be iterated in a day, which suits an unresolved geometry.
- Machined aluminium brackets — Under consideration for revision two — stiffer, but a longer loop on a geometry that is still changing.
- Stock mounting with the encoder mounted separately — Rejected — decouples the encoder from the shaft it is measuring.
Outcome Revision one cracked at the fastener bosses. The iteration speed argument held; the material choice did not.
Images
Revision one bracket after the bench load test.
Thicker bosses and a wider load path into the chassis rail.