Quote:
Originally Posted by ThaddeusMaximus
Great, now I'm thinking about lawyering the rules to use differently-sized pool noodles which make wedged bumpers...
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I've seen this done before, and it provides little to no real world advantage - ignoring the fact that this is illegal. Bumpers don't seem to be rigid enough to act as an effective wedge, which seems to lead to minimal weight transfer.
As others have noted before, low (literally, the bottom of the bumper zone) bumpers are pretty much all you need if you want to build a drivetrain that's effective at holding it's ground and/or moving objects.
If you really want to have fun, you can start playing with the center wheel spacing relative to the outer wheels, a larger center wheel base will lead to a drive train that has more of a tendency to drive straight while a shorter wheel base will lead to better agility at the expense of straight tracking.
I personally am an advocate for minimal drop on 8 wheel drives. The last two I had direct involvement with had .090" drop (2013) and .060" drop (2014). The difference in drop were due to different strategic objectives and robot configurations but each was somewhat optimized for the role. The 2013 drive train was optimized to sit on the back 6 wheels when in shooting position to provide a stable platform and while in transit position it rocked forward to "tip" the whole robot back for more stable driving and a slightly angled leading edge, helping to get "under" other robots. 2014 was designed to "Squat" when pushing, digging all 8 wheels into the carpet while also providing good stability at speed.
A couple things to remember when chasing high traction performance:
-Wheels sink into the carpet, sometimes as much as 1/8". A drive with minimal drop may not ever have it's wheels leave the carpet, nor does it truly rock, instead the force on each wheel changes depending on the conditions.
-Traction on carpet is a bit more complicated than F=CoF x Fn. There are a series of factors such as carpet wear, tread geometry and tread hardness to consider as some wheels actually "Dig" into the carpet, creating additional mechanical forces that appear to increase traction.
-When working with 6 CIM drive trains, you have to be extremely conscious of current draw, especially when pushing. Once you're pushing another robot, if it's weight begins to transfer to your machine, suddenly a traction limited machine may no longer be traction limited, which usually doesn't end well.