Difference between revisions of "DEWBOT IX Drive Train"
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;Changes | ;Changes | ||
*'''#35 to #25 Wheel Drive Chain:''' the wheel drive chain has been changed from #35 to #25, maintaining the same gear ratio. The #35 9T ''Transfer Axle Sprockets'' and 24T ''Wheel Drive Sprockets'' were changed to 12T and 32T, respectively. The maintained an integer #25 chain link distance and thus did not require any new machining. 1640 has never used #25 chain, but given the weight savings we're interesting in investigating its practicality. | *'''#35 to #25 Wheel Drive Chain:''' the wheel drive chain has been changed from #35 to #25, maintaining the same gear ratio. The #35 9T ''Transfer Axle Sprockets'' and 24T ''Wheel Drive Sprockets'' were changed to 12T and 32T, respectively. The maintained an integer #25 chain link distance and thus did not require any new machining. 1640 has never used #25 chain, but given the weight savings we're interesting in investigating its practicality. | ||
| − | *'''Bearing to Bushing Coaxial Drive Shaft:''' The 1" low-friction, high-durability ball bearings on the ''Coaxial Drive Shafts'' have been switched with bushings. (This did require remaking the cage top plate and module bottom plate.) The bearings have never failed on any generation of pivot, but at $18/ea (x8), they represent a major cost investment both in real dollars and Bill of Materials quota. (The entire FIRST competition generally cannot cost more than $3,500 + Kit of Parts). They're also represent a major weight-saving opportunity, as most of the rest of the module is running out of reasonable diet options. | + | *'''Bearing to Bushing Coaxial Drive Shaft:''' The 1" low-friction, high-durability ball bearings on the ''Coaxial Drive Shafts'' have been switched with bushings, one plastic-on-brass and the other plastic-on-plastic. (This did require remaking the cage top plate and module bottom plate.) The bearings have never failed on any generation of pivot, but at $18/ea (x8), they represent a major cost investment both in real dollars and Bill of Materials quota. (The entire FIRST competition generally cannot cost more than $3,500 + Kit of Parts). They're also represent a major weight-saving opportunity, as most of the rest of the module is running out of reasonable diet options. |
;Test Results | ;Test Results | ||
| − | *'''Coaxial Drive Shaft Bushing Failure:''' The 2 pivots were put to the test at driver practice on 18-Oct-2012, primarily in bridge-balancing and slalom runs (the shooter was malfunctioning). Unfortunately, one (the front left) steering motor failed catastrophically in less than a hour, smoking visibly for almost 10 minutes and getting hotter than any steering (or other) motor we have ever had. The other test pivot (front right) was the second hottest motor we've ever had, though it did not emit smoke. Though the motors were checked periodically throughout the practice, the heat seemed to spike from mid-high normal to catastrophic in a matter of minutes, albeit during a rather difficult slalom course. Initial assessment attributes the failure to additional friction from the ''Coaxial Drive Shaft'' bushing. | + | *'''Coaxial Drive Shaft Bushing Failure:''' The 2 pivots were put to the test at driver practice on 18-Oct-2012, primarily in bridge-balancing and slalom runs (the shooter was malfunctioning). Unfortunately, one (the front left, plastic-plastic bushing) steering motor failed catastrophically in less than a hour, smoking visibly for almost 10 minutes and getting hotter than any steering (or other) motor we have ever had. The other test pivot (front right, plastic-brass bushing) was the second hottest motor we've ever had, though it did not emit smoke. Though the motors were checked periodically throughout the practice, the heat seemed to spike from mid-high normal to catastrophic in a matter of minutes, albeit during a rather difficult slalom course. Initial assessment attributes the failure to additional friction from the ''Coaxial Drive Shaft'' bushing. |
| + | **'''Update''': Upon disassembly, the plastic-on-plastic bushing module's failure has been attributed to steering motor gearbox lockup. However, based on the observed plastic-plastic stiction, we have decided to terminate this option anyway. The plastic-on-brass bushing module's failure is due partially to a re-assembly error causing undue vibration in the steering motor. This has been remedied and the module will be re-tested. | ||
*We have not observed any issues with the wheel drive chain. | *We have not observed any issues with the wheel drive chain. | ||
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[[Category:Robot]][[Category:DEWBOT IX]][[Category:Drive-train]][[Category:Pivot Drive]][[Category:Photo Galleries]] | [[Category:Robot]][[Category:DEWBOT IX]][[Category:Drive-train]][[Category:Pivot Drive]][[Category:Photo Galleries]] | ||
Revision as of 19:13, 31 October 2012
October swerve module work
Over the past few weeks prior to 17-Oct-2012, we have been modifying DEWBOT VIII's swerve modules to test cost- and weight-saving design changes. Thus far we've made 2 changes each on 2 pivots and have begun testing them as the front (intake & bridge arm side) on DEWBOT VIII Prime.
- Changes
- #35 to #25 Wheel Drive Chain: the wheel drive chain has been changed from #35 to #25, maintaining the same gear ratio. The #35 9T Transfer Axle Sprockets and 24T Wheel Drive Sprockets were changed to 12T and 32T, respectively. The maintained an integer #25 chain link distance and thus did not require any new machining. 1640 has never used #25 chain, but given the weight savings we're interesting in investigating its practicality.
- Bearing to Bushing Coaxial Drive Shaft: The 1" low-friction, high-durability ball bearings on the Coaxial Drive Shafts have been switched with bushings, one plastic-on-brass and the other plastic-on-plastic. (This did require remaking the cage top plate and module bottom plate.) The bearings have never failed on any generation of pivot, but at $18/ea (x8), they represent a major cost investment both in real dollars and Bill of Materials quota. (The entire FIRST competition generally cannot cost more than $3,500 + Kit of Parts). They're also represent a major weight-saving opportunity, as most of the rest of the module is running out of reasonable diet options.
- Test Results
- Coaxial Drive Shaft Bushing Failure: The 2 pivots were put to the test at driver practice on 18-Oct-2012, primarily in bridge-balancing and slalom runs (the shooter was malfunctioning). Unfortunately, one (the front left, plastic-plastic bushing) steering motor failed catastrophically in less than a hour, smoking visibly for almost 10 minutes and getting hotter than any steering (or other) motor we have ever had. The other test pivot (front right, plastic-brass bushing) was the second hottest motor we've ever had, though it did not emit smoke. Though the motors were checked periodically throughout the practice, the heat seemed to spike from mid-high normal to catastrophic in a matter of minutes, albeit during a rather difficult slalom course. Initial assessment attributes the failure to additional friction from the Coaxial Drive Shaft bushing.
- Update: Upon disassembly, the plastic-on-plastic bushing module's failure has been attributed to steering motor gearbox lockup. However, based on the observed plastic-plastic stiction, we have decided to terminate this option anyway. The plastic-on-brass bushing module's failure is due partially to a re-assembly error causing undue vibration in the steering motor. This has been remedied and the module will be re-tested.
- We have not observed any issues with the wheel drive chain.
