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Originally Posted by thefro526
Any advice or examples would be greatly appreciated. -Dustin
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First of all, this is only our second year, so take this for what it's worth, we're still new at this; that said:
1732 uses grippy (roughtop) 1.5"W x 6" dia, six wheel drive with the center wheels dropped. We use a kitbot chassis setup for a 13" wheelbase. With 2 CIMs per side we can turn from a standstill easily in Low gear (geared for 5 ft/s max), and reluctantly in High (geared for 11 ft/s max). (We use 36tooth wheel sprockets and 2 speed AndyMark shifters to achieve these 'gearings').
We 'totter' very slightly and our turning axis shifts between mid-front and mid -back depending on instantaneous force distribution between the front and rear wheels (longhand for 'which way we're tottering').
Ease of turning is a double edged sword. By managing the ratio of wheelbase to track (width between wheels)and lateral friction coefficient of the wheel, you can achieve the degree that works best for you.
A robot that is too difficult to turn wastes power in turns and handles 'clumsily' (or doesn't turn at all). However, that same robot drives straight much more easily, which is is often helpful for driving up ramps (especially when combined with the traction bonus of grippy wheels).
A robot that turns too readily can generally be easily ‘directionally reoriented’ by opposing robots, and often tends to oversteer (keeps turning even when you want to stop turning).
My thinking is the optimal lies somewhere in between these two extremes; at least for standard four and six wheel ‘tank style’ drive types.
But then, there are several teams that can change lateral mobility on the fly. Some have used casters that are only deployed for turns (341 and others?), or a perpendicular set of wheels to roll sideways (175), or use swerve drive.