Here ya go with some juicy material to chew on. Hopefully it makes up in quality, for the lack of quantity of reply posts here in the thread so far.
We have build what is likely to be one of the most robust, 3-wheeled Kiwi drives ever seen at FTC competition.
With the new rules allowing sturdier materials in greater variety, we designed some super compact, linearly aligned motor-wheel modules, assembled along a joined pair of slotted AL framing pieces. The clearances are all engineered to be very close.
The omni-wheels are chain driven via direct mounted sprockets, and they free spin on fixed, case hardened (no-flat) axles. The drive sprockets are isolated on their own shafts with double bearing support via Tetrix sleeve bearings set in a one-unit doubled/nested Tetrix "channel block". This scheme prevents any chain tension shaft-bending torque from transferring onto the motor's shaft.
The motor is coupled to the sprocket drive shaft via a urethane rubber flexible coupling that handles any minor misalignment of the shafts, and isolates the motor from any loading, other than rotational torque. Motor shafts are set to bottom dead center in the clamps, and the clamps are then shimmed up slightly to the Tetrix sleeve bearing module centerline heights.
All of the driven (wheel) sprockets and the drive shaft sprockets have bearing support immediately adjacent to them, with absolute minimum axle/shaft overhang, to minimize the bending forces on the axles/shafts from chain tension and impacts.
We are currently at one-to-one on the sprocket ratio, but may go to 1.5 to 1 as we gain confidence with our driving skills. Each of the three drive/wheel modules are completely removable by just loosening three slot T-nut screws, unplugging the motor and encoder, and sliding the framing piece radially from the bot. We have a 4th module ready to go if there is any problem.
We handle rings with two gripper modules mounted adjacent on a horizontal conveyor belt. The conveyor is sandwiched between two vertical elevator assemblies that extend up to 28" from initial level 1 height. The conveyor pushes the grippers past the sides of the rings and they snap into flexible plastic U-shaped channels in a little over 1 second. Reversing the conveyor takes them off the dispenser and to the rear of the bot in another 1-2 seconds
With the front of the bot pushing against the scoring rack PVC pipe base bar, we can move laterally along it to align with scoring columns (Kiwi drive).
Our conveyor sits below the level 1 scoring pegs, and nothing will hit the pegs or hanging rings as we move laterally.
Once we have column alignment established, the conveyor pushes the rings forward onto the scoring peg. We can score one or two rings on a peg in under 2 seconds
If we raise the elevator to level 2 or 3, we can still move laterally between the columns without hitting pegs or rings, since the conveyor remains just below them at each level, and since the elevator columns are set far enough back, near the rear of the bot.
We are just starting to practice driving and scoring this week. Our qualifying competition is this coming Sat. We are using shorter elevator columns that only allow reaching level 2 for qualifying, and will upgrade them for longer ones for the state competition. We spent so much time on the drive setup, we fell behind on our build schedule for the other modules, but we are starting to catch up now.
