The smaller gear (torque setting) in our High Strength 393 motor lost a tooth. Has this happened to anyone else?
This has happened quite a few times to my team, and I know of many other teams who have experienced this problem. This is why there is this product: http://www.vexrobotics.com/products/accessories/motion/276-1842.html
I have just never seen it before and I was surprised that it happened.
No biggie, now you know about it =). Our team was pretty surprised too when our 393’s internal gears broke for the first time, so yeah. Good luck!
AURA has done this about 6 times this year, all on drive trains. So annoying 
Ouch! That must be a pain to replace; luckily ours was just on our arm.
Thats one of the risks of agressive drive train gearing.
This is a good reason to invent an inverted motor mount bracket, so you can fasten motors from the top or outer sides.
Actually, ours were because of a (somewhat) defective motor in which the plastic surface that the metal gear rested on was not flat which caused the gear to not mesh correctly with the others… It may not sound like much but when we compared it to another motor there was quite a noticeable difference in the smoothness of the rotation of the gears… It took us 5 broken gears to think “maybe it’s the motor?” when the other drive motors had never had a single issue once.
If this is the case, then this definitely qualifies as a manufacturing defect and we would love to get this one back. I will be in NZ for the Robot World Cup so get this back to the Massey guys and I will bring some motors with me to replace it.
Paul
In addition, for those of you who broke this gear on the HS motor, please tell me everything you can about the system and situation in which it broke. we have not been able to fail the HS motor in the manner in which you describe in this thread so really want to know what is causing this.
2:1 drive on 4" omnis (fast)
drive a full length of the field, and then suddenly jerk the joysticks full backwards
its insane gear ratios like that AND “poor” driving practices that gets the motors ending up like this…
We know better than to gear/drive like that 
We’ll try to get some photos taken of it to document what’s happening and send it along to vex technical support.
That’s bad…
We’ve done this numerous times and haven’t failed a 393…
Very weird… Were these old motors or fairly new ones? Any information would be helpful.
well, i think the weight of the robot matters too
did you test it with only a drive chassis?
or a full competition sized robot?
because the momentum of the robot itself would also help aid the motors being broken