Quote:
Originally Posted by BJC
Our team has done a lot of personal testing and evaluation on the top teams in the league and we have found that the CoG and tortional stiffness is generally what sets their robot's drivetrain apart from most others.
CoG, contrary to popular belief we have found that setting the CoG far to one side on a 6wd is best. A 6wd performs best when it is actually a 4wd with 2 extra wheels. Placing the CoG in the middle generally results in the turning point of the robot changing in the middle of the turn as the robot accelerates/decelerates and the outer wheels alernating touching the ground. This is especially important because a 6wd does not turn about the middle wheels but rather between the middle wheels and whichever pair of outer wheels happens to be touching the ground. So by limiting rocking as much as possible performace greatly increases.
Tortional stiffness is absolutely critical to a good 6wd. In 2008 we discovered that without a very stiff chassis the opposite outer wheels will touch down essentially creating a long wheelbase while turning. This will also seriously limits turning.
Edit: I forgot to add, an 8wd has mathmatically much better turning characteristics than a 6wd provided the wheels are properly spaced.
But don't take my word for it, if you don't believe me run some experiments.
Regards, Bryan
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Yes, our 8WD drive from last year worked well for the most part. It had difficulty in an off-season game because the softer carpet allowed our front and rear wheels to make contact with the ground. We tried to alleviate that problem this year by increasing the drop of our center wheel.
With regards to method of using a 6WD as a short-base 4WD with 2 additional wheels, this is something that we've considered last year, but I believe we chose against it because it might've made aiming on one side of the robot, either the scoring grid or minibot tower, difficult (this was before we chose to use "alignment legs" at the bottom of the robot). In addition, if our robot's turning axis is biased to one side, other robots may have a large moment arm to turn our robot.