What is the small bearing used for, and what is the large one used for? Could the small one be used for an arm? Can they be lubricated?
We used them the large bearings last year as pivot points so that our two bases could drive independently. You could spin either one of them 360 degrees.
The first 20 seconds or so or this video has some footage of us driving it around. This was one draft of our Innovate Video (not the one we submitted), so forgive me for the ridiculous cinematography in parts.
You can use them for pretty much anything, although I guess the name suggests that the upper part of the bot would rotate independent of the drive, like a turret or some kind of anti-aircraft installment. Last year, we used them on the arm at one point because the ratio was pretty much exactly what we needed. They’re somewhat hard to use on an arm, though, because they’re pretty large. I guess you could lubricate the gear teeth, I’ve never tried anything else.
People in our club use them to power bar lifts as well. They work ok. Not my favorite thing because they take up so much space and are somewhat difficult to mount, but they have a good gearing and are reliable once they are mounted.
There is no “correct” use for them, nor any other part of the VEX system. That’s the great part about a closed platform competition like VRC, finding unique uses for parts to give you a leg up on others.
Are they useful for arm mounting? Are there any applications where the large bearing would be better?
With the small turntable, the motor mounting is not as integrated and you need some more effort. With the big ones it’s fairly easy with a 12 tooth metal gear. Not sure if it is more or less stable or weighs less than a metal version. (sorry I do not have any pictures of the small turntable in use)
On the big ones, getting the center hole aligned is on the center holes typically so the potentiometer is aligned.
Team 81M using them on the middle joint of an arm
Team 90C using 4 of these back at the base of a 6 bar lift.