Quote:
Originally Posted by GeeTwo
I never heard of anyone treating motors with liquefied gasses in 2015. My understanding is that the 2011 minibot arms race was steeper than the 2015 grabbers. What surprised me when I went back and read about it was that no one (as far as I found) had implemented an ultra-simple CVT (continuously variable transmission) nor taken advantage of the ability of the minibot to have a mobile center of gravity.
Wait, what? Ultra-simple CVT? That can't be!
Actually, for a short, drag-race type run, there IS an ultra-simple CVT design. Don't think of doing this in gears, but in the diameter of the wheel. That is, start with a rather small wheel engaging the climb shaft, but with a bit of tread wrapped around it so that the wheel diameter increases (and therefore the effective gear ratio decreases) as the mini-bot completes its run. With proper design of the initial wheel shape, this transition can be continuous.
Mobile Center of Gravity? Whachu Talkin' 'bout, Willis? While it was a while back that I looked at the mini-bot rules, it seemed to me that a mini-bot was allowed to be about three times as tall as it actually had to be. So -- build the mini-bot to the shortest length possible, then stand it on a "rack" which raises it to the highest initial altitude allowed. As the robot climbs, the "rack" automatically climbs relative to the robot weight, until, at the top of the climb, the rack reaches the roof to signal contact, though the "real minibot" is still several inches lower.
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With the minibot drag races it came down to reducing drag and weight as much as possible. Once FIRST said the transmissions could be modified it was quickly figured out how to remove stages, both to reduce the power loss in the transmission and allow smaller diameter wheels with less rotational inertia and overall weight. Then once FIRST clarified that you could toss the transmission that weight went out the window and the wheels became aluminum rod with some sort of tread, my team used the black surgical tubing turned inside out and carefully cleaned on 1/4" rod drilled and pressed onto the shaft. Then to get it in the power band off the line as quick as possible launch it horizontally so it wasn't fighting gravity and create a ramp so it hit the pole at peak power. Anything that added more than a couple of ounces beyond the battery, motors and the switch to turn it off at the top was at a big disadvantage.