My team is using 6 motor drive with custom drop center wheels (i.e. slightly larger than the 3.25" omnis). The ratio is a standard 36/60 with blue cartridges for 360 rpm. The bot weights between 15 and 20lb.
Yet, we find in our scrimmages and tournaments that our pushing power is below what we would expect. Against a well designed robot we will often lose a pushing match. For example, our sister team using 4 motor drive, no traction wheels, old 4" omnis on 257 RPM can push us when driving head to head, despite their weight being close to ours or even lesser.
We experimented with the new 3.25" traction wheels, which we found to be worse than our custom wheels. All 6 motors on the drivetrain are actually running, on hold brake mode too. Against an immovable obstacle, our wheels will spin out rather than max out our motors. For this reason I suspect a lack of traction is at fault.
It seems as though our wheel choice is already optimal. Have teams found other wheels to be superior to the new 3.25" omnis, or even custom traction wheels? Is it worth it to add ballast to the robot or will the driving just feel sluggish? Basically, what is the state-of-the-art in vex robot traction maximizing?
adding weight is one solution but not a very good one. If i were yuo i would look into building a wedge which will allow you to lift some of your opponents wheels of the ground making it much easier to push them around.
One thing we found to be very important is using velocity mode to command the motors so that the brakemode can prevent the motors being back-driven by external loads.
(Where limiting is the minimum force needed to begin moving the bot and dynamic is the maximum force which the bot can exert in motion at 22.4 lb weight)