A quick look at our Drive Train:
NOTE: the ground clearance you see is the actual ground clearance…after we put the wheels (mecanum) on the drive shafts, the bolts holding the robot up will be dremelled down as to not interfere with the field
perhaps the clearance will be a tiny tiny amount more but the wheel barely touches the ground with those bolts there
EDIT: sorry about the link, couldn’t get the embedding to work
I think we’re that low too. 4 inch wheels, 3 inch tube…
you could have big problems running it on carpet. i recommend flopping the bolt nut set up because the lock nuts extend further down than the bolt heads. also then you can still have enough length on the bolts to use lock nuts. its a small thing but it seems like it might help in your interaction with the carpet.
I think our bot has approximately .3 inches of ground clearance. I’d have to give a picture.
i am afraid we take the cake, we have less than .25 inches of ground clearance, somewhere between 1/8 and 3/16, apparently andymarks 6 inch omnis are more like 5.675 in diam, so our .5 inch clearance shrank quite a bit.
Yeah, we’re using 6" andy mark mecanum wheels and the KOP chasis as a base to build off of, so in terms of mounting, we made it as low as possible using ordered parts.
we originally had about 2-3 inches of clearance and then realized it was silly to mount the wheels that way.
using the bolts im sure we can get the clearance to be almost touching the ground, but that doesnt really change the robot significantly enough to justify trying for lowest ground clearance
…then again, since when have we ever needed a reason to compete in anything? 
I hope everyone is taking into account the area around the mini-bot towers. It is slightly higher then the rest of the field. If my few minutes on the field at kickoff are any indication, the carpeting covering that area will move and bunch up a bit. It is not necessarily going to be even the whole way around.
Also, the lane dividers at the the feeder stations have some support on the ground. I’ve forgotten the thickness of the portion resting on the ground, but it’s something that could possibly catch a bolt head.
Edit: A relevant section of the ‘Arena’ manual, 2.2.5.:
The BASE rests on a 48-inch by 76-inch floor protector made
of 3/16-inch HDPE. The floor protector is velcroed to the
FIELD surface, and covered with a piece of similar carpet.
The edges of the floor protector cover are taped to the FIELD
carpet. This taped seam forms a slight (approximately 1/4-
inch) ridge in the FIELD around the TOWER.