Quote:
Originally Posted by cbale2000
As for lubrication, for external (not inside of a gearbox) gears we just spray on Teflon dry lubricant during assembly and don't worry about it again for the rest of the season. |
I was looking forward to switching to dry lube similar to this this year, given its the first time in many years that we are running open gearboxes. After bad signs of premature wear on the practice bot, we have played it safe by sticking with Red & Tacky, and adding covers to keep the grease from getting flung everywhere.
I'll have to make it a goal in the off-season to properly test a dry lube, so I can have confidence in it.
Quote:
Originally Posted by Joe Johnson
I agree with your diagnosis but you lost me there on the recommended treatment.
Are shafts somehow immune to problems? Live axles bring there own problems. Gear teeth are not infinitely strong. And so on.
Make sure you have a reliable drive train. That is the take away. There are a lot of ways to get there, but you really need to get there.
Dr. Joe J.
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Quote:
Originally Posted by cbale2000
I think the point he was trying to make was that typically having a direct drive wheel eliminates total drive failure due to a chain or belt breaking. I also think that for most teams, you're FAR more likely to have a failure in a chain or a belt than you will with a gearbox output shaft (if you do, you've done something terribly wrong).
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Chris pretty much has it dead on. Direct-drive of course does not eliminate all possible failure modes, but it at least eliminates one. If you are designing for live axles already then direct-drive is almost trivial.
Of course very reliable dead-axle drivetrains are possible without direct-drive.
Attention to design details, such as well-supported shafts, ridgid/robust frame construction, careful component selection (chain/belt type, sprocket/pulley diameter, etc.) and reliable method of chain tensioning are all still critical for success, no matter what drive style you choose. In this era where there are a selection of proven COTS gearboxes to choose from, I would generally agree with Chris that most teams will have more issues with assembly and implementation than with the gearbox components themselves.
We have run both live and dead-axle drivetrains, with varying degrees of success. In my time in FIRST, we have experienced:
- Bent drive shafts (2007, poor steel grade selection)
- Stripped gear teeth (2012, inadequate lubrication, fortunately happened post-season)
- Sheared shafts at poorly placed E-clip grooves
- Set screw failure (2007, never use set screws and D shafts in reversing load situations, and never in drive trains!)
- More chain tension issues than I can count
And many other drive failures ranging from nuisance maintenance items to crippling season-killers.
Experience can teach you what not to do, but it also proves that there are many ways to get it right.