Quote:
Originally Posted by dtengineering
We have four 56mm BB trannies running our mecanum drive. The 8" AM mecanums are directly mounted to the BB drive shaft which is supported on the outboard end quite securely. (photos at http://www.chiefdelphi.com/forums/sh...highlight=1346 )We "broke in" the gearboxes for at least 30 minutes of continuous operation before installing them.
We have been running our robot for... well... less than 30 minutes and noticed one or two of the trannies were beginning to show significant backlash.
We took the transmission apart and noticed that while the final drive plate had not failed completly it was very close to failure as discussed in this thread.
This is after very low use with ONE CIM in a relatively low dynamic loading (no chain to snap) environment.
We have noticed that the two BB's that came in the KOP have less backlash. They also fit much more nicely onto the CIMs than the two we bought in early January. Perhaps there is variation from batch to batch to deal with as well.
In any case, here is one more report of BB 56mm failing (or at least coming close enough to failure to count) under ONE CIM load... and at extremely low cycles, too.
We are also pondering solutions, but it seems manufacturing a new plate, or having one manufactured is what we are going to have to do if we want to use these trannies.
Jason |
This is a very strong case that the gearboxes will indeed fail in the field.
As to the low cycles, I have not observed this particular robot in action but based on other mechanum wheel robots I have seen (I can't get to YouTube from this PC), I am not sure that the loading was infact "low cycles"*
In these types of drives, even though the motion of the robot is smooth and continous, the voltages commanded to the motors are often rapid step changes from Full Forward to Full Reverse back to Full Forward -- Again, I am not denying that there is an issue, I am just saying that even though it is direct drive and only 30minutes, it may infact be many many high impact loadings on the gearbox.
For what it is worth.
Joe J.
*Don't jump on me here for burrying my head in the sand. I am have been working this issue since I first saw the joint the day after kickoff. It is only recently that I have been able to get others to join me.