[dtengineering]

Following up on my earlier post, I have had a chance to pull one of the carrier plates, clean it up and get a photo to post.

This is similar to what I saw in the transmission I opened up last night... and is from one of the transmissions exhibiting about 25 degrees of backlash.

A couple of things to note:

The hardness test indentations: Although my hardness tester is old and uncalibrated, the two tests in the deformed area showed "Rc 40" (uncalibrated... not likely the real value) while the tests in the base metal showed closer to "Rc 30", again uncalibrated, sorry... these should not be taken as absolute values, but rather the difference between them should be sufficient to back up the concept of work hardening.

The crack formation: unfortunately this does not show up particularly well, however if you follow the radius of the double d you can see a faint line beginning to trace out a circle on three of the corners. I suspect this will be the ultimate failure mode.

The mecanum may subject the drivetrain to extra cycles, and certainly when the robot was up on blocks and the programmers were testing their drive code we would do many, many, many forward and reverse max to max cycles. With the AM mecanums, that is a fair bit of impact... while they might be lightweight for mecanum wheels, they sure pack more rotational momentum than a standard wheel.

In any case, we're really good at ripping the trannies apart and throwing them back together, and will be packing a 2.5mm hex key with us to Portland.

Jason

P.S. The deformation extends about 80%-90% of the way through the carrier plate, so it is pretty obvious that the shaft does not fully engage the plate... a condition noted elsewhere already that may or may not contribute to the potential failure.