uxcell GA12-N20 12V 100RPM DC Gear Motor with Encoder Speed Velocity Measurement for Mini Car Balance Motor Encoder DIY

"uxcell GA12-N20 12V 100RPM DC Gear Motor with Encoder Speed Velocity Measurement for Mini Car Balance Motor Encoder DIY" Purchased Early 2021 $16.99 I'm certain these units are difficult and costly to produce. To that point I believe uxcell should take far more care in shipping these items. I received both units (same order separate shipments) in a bubble clad plastic Amazon bag. One wrapped in light closed cell foam and tape. The other was packaged similarly but inside of another small uxcell branded bag. After unpackaging and quick look, I tried powering each unit up. Both required me to gently pull the magnetic coded disc away from the motor as they were both pressed tightly against the encoder circuit board, preventing operation. I've also had to slightly adjust the position of the hall effect sensors on the circuit board as they were pressed against this disc. These are not listed as to what brush type is used, I'd guess carbon brushes as I've not been able to locate a 12 volt version of the N20 motor that uses precious metal brushes. After adjusting the position of the disc on the rear of each motor, both operated but, one is produces much more noise. I believe the rear motor shaft is slightly bent. I've noted this particular unit also requires more current to operate at the same speed and, does not meet the +-5% RPM spec (~92 RPM @ 12.00 Volts DC). For my application, the feedback loop provided by shaft encoder (+software) will allow me to match the speed of the mechanical assembly this will be driving. I expect the lifetime will be reduced due to this damage. Be sure to apply light oil, mine were shipped dry. I've chosen to post this review in this manner rather than trying to contact uxcell for a return, hoping they properly package these for future buyers. These units are tiny, fragile and sensitive to shock received by shipping them in a plastic bag. I feel a perfect unit is worth the cost but, only if it arrives undamaged