Quote:
Originally Posted by Richard Wallace
Events and pictures like this one create "teachable" moments, and that is a good thing. One of the best things about the FRC, I believe.
Three ways to take advantage if you have not already done so:
(1) get the lead mechanical engineering mentor on your team to explain how stresses on gear teeth are calculated, or
(2) seek help with (1) from one of the fine mechanical engineers who designed this gear [looks like VexPro to me], or
(3) seek advice from one of the many experts who follow CD.
After working through the stress analysis, try to understand the loading conditions that caused the 14T gear in your elevator drive to become over-stressed. Then (depending on the cause) you might look for design improvements to keep it from happening again.
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Our team actually does not have any mechanical engineers as mentors, in fact the entire robot was CADed, and manufactured by students (under the supervision of a few qualified parents.) We have addressed the issue by ordering a new gear, fashioned from steel instead of aluminum.
It seems that vex pro has already been notified of this issue, which is why they offer this gear in a steel variety.
Thanks for the wise words!
Quote:
Originally Posted by s_forbes
We did something similar during testing, but managed to get the same gear down to 3 teeth. 
We didn't put much concern into stall conditions given the lightweight gamepieces. Then we stuck a sturdy locking mechanism on the output side of our gearbox. Should have probably seen that one coming. |
It definitely was a stall condition that caused the failure! We'll have to be a little more careful this week in Wisconsin
Quote:
Originally Posted by audietron
Just curious, What strategy change caused a pinion gear to break? Your lifter at Northern Lights seemed pretty solid.
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What happened was our operator and driver were pushing for a faster cycle time, and I believe the operator had driven the elevator down and stalled the gearbox in this haste. It is powered by two CIM motors at a 9.52:1 reduction, with a stall torque hovering around 350lbs. Looking at the gear teeth it is apparent that they are a little wimpy for high load applications
. We'll have a steel replacement when we get to competition and replace it on Thursday.